Signalling in Coordinated Multi-Point Transmission and Reception (CoMP)

[0001] This application claims the benefit of

U.S. Provisional Application No. 62/055,381, entitled "Signalling for Inter-eNB CoMP," filed on September 25, 2014,

U.S. Provisional Application No. 62/056,095, entitled "Signalling for Inter-eNB CoMP," filed on September 26, 2014,

U.S. Provisional Application No. 62/076,221, entitled "CSI Exchange for Inter-eNB CoMP," filed on November 6, 2014,

U.S. Provisional Application No. 62/076,873, entitled "CSI Exchange for Inter-eNB CoMP," filed on November 7, 2014,

U.S. Provisional Application No. 62/110,006, entitled "CSI Exchange for Inter-eNB CoMP," filed on January 30, 2015,

U.S. Provisional Application No. 62/145,251, entitled "Efficient CSI and e-RNTP Exchange for

Inter-eNB CoMP," filed on April 9, 2015,

U.S. Provisional Application No. 62/145,580, entitled "Efficient CSI and e-RNTP Exchange for

Inter-eNB CoMP," filed on April 10, 2015,

U.S. Provisional Application No. 62/150,178, entitled "CSI Exchange for Inter-eNB CoMP," filed on April 20, 2015,

U.S. Provisional Application No. 62/151,796, entitled "Subband Definitions and eRNTP enhancements," filed on April 23, 2015,

U.S. Provisional Application No. 62/161,804, entitled "On the Subband Definition in CSI Signaling," filed on May 14, 2015,

U.S. Provisional Application No. 62/162,285, entitled "eRNTP Signalling for Inter-eNB CoMP," filed on May 15, 2015,

U.S. Provisional Application No. 62/204,541, entitled "Subband definition in CSI Signaling," filed on August 13, 2015,

the contents of all of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION [0002] The present invention relates to coordinated multi-point transmission and reception (CoMP) in wireless or mobile communications and, more particularly, to signalling in inter-eNB (E-UTRAN

NodeB or eNodeB) CoMP.

[0003] Referring now to FIG. 1, a CoMP mobile communications system 400 comprising a CoMP coordination zone or area or CoMP cooperating set 402 in which the embodiments may be implemented is illustrated. One or more user equipments (UEs) 410 are served by one or more TPs or cells 404 to 408. TPs 404 to 408 can be base stations or eNBs. Each of the user equipments includes e.g. a transmitter and a receiver, and each of the base stations or eNBs 104 includes e.g. a transmitter and a receiver.

[0004] Transmission layers are sometimes called "transmit layers" or "layers." The number of transmission layers is known as "transmission rank" or "rank." A codebook is a set of precoding matrices or precoders. A precoding matrix is also known as a codeword.

[0005] Reference

[0006] [1] RP-141032, "New Work Item on Enhanced Signaling for Inter-eNB CoMP," June 2014.

[0007] [2] R3-142582, "Way forward on WI: Enhanced signalling for inter-eNB CoMP," October 2014.

[0008] [3] Rl-141206, "Signaling Considerations for Inter-eNB CoMP", NEC, March 2014.

[0009] [4] R3-151209, Change Request, May 2015.

BRIEF SUMMARY OF THE INVENTION

[0010] An objective of the present invention is to provide efficient channel state information (CSI) and/or relative narrowband Tx (transmit) power (RNTP) exchanges between eNBs.

[0011] An aspect of the present invention includes, in a wireless communications system including a first base station and a second base station, a wireless communications method implemented in the first base station supporting coordinated multi-point transmission and reception (CoMP). The wireless communications method comprises, for a given user equipment (UE) identification (ID) and a given channel state information (CSI) process, receiving from the second base station a plurality of CSI reports each of which comprises a rank indication (RI) and a channel quality indicator (CQI), wherein the second base station receives from one or more user equipments (UEs) RI and CQI information.

[0012] Another aspect of the present invention includes, in a wireless communications system including a first base station and a second base station, a wireless communications method implemented in the second base station supporting coordinated multi-point transmission and reception (CoMP). The wireless communications method comprises receiving from one or more user equipments (UEs) rank indication (RI) and channel quality indicator (CQI) information, and for a given user equipment (UE) identification (ID) and a given channel state information (CSI) process, transmitting to the first base station a plurality of CSI reports each of which comprises an RI and a CQI.

[0013] Still another aspect of the present invention includes a first base station supporting coordinated multi-point transmission and reception (CoMP) and used in a wireless communications system. The first base station comprises a receiver to receive from a second base station, for a given user equipment (UE) identification (ID) and a given channel state information (CSI) process, a plurality of CSI reports each of which comprises a rank indication (RI) and a channel quality indicator (CQI), wherein the second base station receives from one or more user equipments (UEs) RI and CQI information.

[0014] Still another aspect of the present invention includes a second base station supporting

coordinated multi-point transmission and reception (CoMP) and used in a wireless communications system. The second base station comprises a receiver to receive from one or more user equipments (UEs) rank indication (RI) and channel quality indicator (CQI) information, and a transmitter to transmit to a first base station, for a given user equipment (UE) identification (ID) and a given channel state information (CSI) process, a plurality of CSI reports each of which comprises an RI and a CQI.

[0015] Still another aspect of the present invention includes a wireless communications method implemented in a wireless communications system supporting coordinated multi-point transmission and reception (CoMP) and including a first base station and a second base station. The wireless

communications comprises transmitting from one or more user equipments (UEs) to the second base station rank indication (RI) and channel quality indicator (CQI) information, and for a given user equipment (UE) identification (ID) and a given channel state information (CSI) process, transmitting from the second base station to the first base station a plurality of CSI reports each of which comprises an RI and a CQI.

[0016] Still another aspect of the present invention includes a wireless communications system supporting coordinated multi-point transmission and reception (CoMP). The wireless communications system comprises a first base station, a second base station transmitting to the first base station, for a given user equipment (UE) identification (ID) and a given channel state information (CSI) process, a plurality of CSI reports each of which comprises a rank indication (RI) and a channel quality indicator (CQI), and one or more user equipments (UEs) transmitting to the second base station RI and CQI information. [0017] An aspect of the present invention includes, in a wireless communications system including a first base station and a second base station, a wireless communications method implemented in the first base station supporting coordinated multi-point transmission and reception (CoMP). The wireless communications method comprises receiving from the second base station an information element (IE) indicating multiple relative narrowband Tx (transmit) power (RNTP) thresholds, and performing interference aware scheduling.

[0018] Another aspect of the present invention includes, in a wireless communications system including a first base station and a second base station, a wireless communications method implemented in the second base station supporting coordinated multi-point transmission and reception (CoMP). The wireless communications method comprises transmitting to the first base station an information element (IE) indicating multiple relative narrowband Tx (transmit) power (RNTP) thresholds, wherein the first base station performs interference aware scheduling.

[0019] Still another aspect of the present invention includes a first base station supporting coordinated multi-point transmission and reception (CoMP) and used in a wireless communications system. The first base station comprises a receiver to receive from the second base station an information element (IE) indicating multiple relative narrowband Tx (transmit) power (RNTP) thresholds, and a controller to perform interference aware scheduling.

[0020] Still another aspect of the present invention includes a second base station supporting

coordinated multi-point transmission and reception (CoMP) and used in a wireless communications system. The second base station comprises a transmitter to transmit to the first base station an information element (IE) indicating multiple relative narrowband Tx (transmit) power (RNTP) thresholds, wherein the first base station performs interference aware scheduling.

[0021] Still another aspect of the present invention includes a wireless communications method implemented in a wireless communications system supporting coordinated multi-point transmission and reception (CoMP) and including a first base station and a second base station. The wireless

communications comprises transmitting from the second base station to the first base station an information element (IE) indicating multiple relative narrowband Tx (transmit) power (RNTP) thresholds, and performing at the first base station interference aware scheduling.

[0022] Still another aspect of the present invention includes a wireless communications system supporting coordinated multi-point transmission and reception (CoMP). The wireless communications system comprises a first base station, and a second base station transmitting to the first base station an information element (IE) indicating multiple relative narrowband Tx (transmit) power (RNTP) thresholds, wherein the first base station performs interference aware scheduling.

[0023] An aspect of the present invention includes, in a wireless communications system including a first base station and a second base station, a wireless communications method implemented in the first base station supporting coordinated multi-point transmission and reception (CoMP). The wireless communications method comprises receiving, from the second base station, a user equipment (UE) identification (ID) for a UE in a reference signal received power (RSRP) report, and using the UE ID to link the RSRP report with another measurement result for the UE.

[0024] Another aspect of the present invention includes, in a wireless communications system including a first base station and a second base station, a wireless communications method implemented in the second base station supporting coordinated multi-point transmission and reception (CoMP). The wireless communications method comprises transmitting, to the first base station, a user equipment (UE) identification (ID) for a UE in a reference signal received power (RSRP) report, wherein the first base station uses the UE ID to link the RSRP report with another measurement result for the UE.

[0025] Still another aspect of the present invention includes a first base station supporting coordinated multi-point transmission and reception (CoMP) and used in a wireless communications system. The first base station comprises a receiver to receive, from the second base station, a user equipment (UE) identification (ID) for a UE in a reference signal received power (RSRP) report, and a controller to use the UE ID to link the RSRP report with another measurement result for the UE.

[0026] Still another aspect of the present invention includes a second base station supporting

coordinated multi-point transmission and reception (CoMP) and used in a wireless communications system. The second base station comprises a transmitter to transmit to the first base station, a user equipment (UE) identification (ID) for a UE in a reference signal received power (RSRP) report, wherein the first base station uses the UE ID to link the RSRP report with another measurement result for the UE.

[0027] Still another aspect of the present invention includes a wireless communications method implemented in a wireless communications system supporting coordinated multi-point transmission and reception (CoMP) and including a first base station and a second base station. The wireless

communications comprises transmitting, from the second base station to the first base station, a user equipment (UE) identification (ID) for a UE in a reference signal received power (RSRP) report, and using at the first base station the UE ID to link the RSRP report with another measurement result for the UE.

[0028] Still another aspect of the present invention includes a wireless communications system supporting coordinated multi-point transmission and reception (CoMP). The wireless communications system comprises a first base station, and a second base station transmitting to the first base station, a user equipment (UE) identification (ID) for a UE in a reference signal received power (RSRP) report, wherein the first base station uses the UE ID to link the RSRP report with another measurement result for the UE.

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] FIG. 1 depicts a block diagram of a CoMP system.

DETAILED DESCRIPTION

[0030] Embodiment A

[0031] Al. Introduction

[0032] In the following we provide our views on channel state information (CSI) and enhanced relative narrowband Tx (transmit) power (eRNTP) exchange as well as proposals containing the required message structure.

[0033] A2. Discussion

[0034] A2.1 CSI exchange

[0035] One eNB can send CSI report pertaining to one or more of its users to a neighboring eNB.

[0036] For each UE the CSI that the eNB sends can comprise:

[0037] CQI (channel quality indication): up-to 2 CQIs, each including a wideband CQI or component and possible sub-band differential CQIs or components

[0038] RI: wideband component

[0039] We note that the PMI was excluded from the CSI exchange report. The justification for this exclusion was to minimize the overhead and the fact that PMI can depend on fast changing channel information, thus reducing its utility over non ideal backhaul with a higher latency. However, in the absence of PMI the use of RI is limited. Indeed, any rank greater than 1 will convey only 2 CQIs, one for each of the two codewords. No further information about the (average) spatial directions seen by that user can be deduced by the eNB receiving the report. As a result, reporting the RI should be made optional. Moreover, the eNB requesting the CSI report should be able to able to specify whether or not it would like to receive RI reports. This can be achieved by setting a bit (for instance in the CSI Measurement Report type field) to be 0 if rank is not requested and 1 otherwise. Similarly, the eNB requesting the CSI reports should be able to specify whether or not it requires subband specific CQI reports. Another bit can be set to 0 if subband CQIs are not requested and 1 otherwise. The response of the eNB receiving the request can be mandated to comply with this request, i.e., that eNB can decide to include a rank indication in its response only if it is requested in the CSI measurement report type field of the corresponding request. Further, the subband specific CQI can be included only if they are requested in the CSI measurement report type field of the corresponding request.

[0040] In this context, we note that a CSI process can be defined to be the reference process for another one. In that case the latter process will reuse the rank determined for its reference process. It can be beneficial to exploit reference rank in the X2 signalling as well. One way to achieve this is to include another bit in the CSI Measurement Report type field which specifies whether or not a single rank is requested. In particular, this bit can be set to 1 only if the rank request bit is also set to 1. In that case the eNB receiving the request should understand that the requesting eNB is requesting CSI reports where only one rank is reported for each user. The response of the eNB receiving the request can be mandated to comply with this request, i.e., if the eNB decides to include a rank indication in its response then it has to be one indication per user.

[0041] Alternatively, no such mandate can be enforced, in which case it is up-to the eNB whether or not to include a rank indication in the CSI corresponding to each CSI-process of each user and the ranks indicated for a particular user need not be identical.

[0042] One of the goals of CSI exchange was to facilitate centralized RRM. In a scenario with centralized RRM, the central node receiving the CSI reports should be able to keep track of the CSI information received for each particular UE, over all the received CSI reports. This can be achieved by including a UE identifier in each CSI report for each UE whose CSI is conveyed in that report.

[0043] Moreover, for each CSI in the report, the CSI process configuration information should be included in order to convey the conditions under which the CSI was measured by the UE. This configuration information includes non-zero power CSI-RS information and IMR information (including, for example, the sub frame indices and zero-power CSI-RS information). Since this configuration is anyway informed to the UE via higher layer signaling, for instance CSI-RS in tables 7.2.6 of TS36.213, and tables 6.10.5.2-1, 6.10.5.2-2 of TS36.211 and subframe indices in tables 7.2.6 of TS36.213, and table 6.10.5.3-1 of TS36.211, the same signaling can be reused to convey the configuration to the neighboring eNB. Another way of conveying this configuration information is through a look-up-table. A look-up-table mapping an index to each distinct applied CSI process configuration can be constructed for each eNB. Here, by an applied CSI process we mean a process that is used by at-least one served UE to measure its CSI. Such a table can be conveyed beforehand by it to eNBl, and then each report can include an index which will inform. Such a table can also be exchanged among neighbor eNBs first, and then the configuration information can be exchanged via indices.

[0044] We note that the period specified in the request by eNBl to a neighboring eNB2 (via the

Reporting Periodicity of CSI Measurement Report field) can be different from the periodicity with which the CSI is measured by a UE as per a CSI process, and then reported (over the air) to eNB2. To address such scenarios, eNB2 can either subsample (for example select the most recently received CSI) or average (over all CSIs received after those considered while determining the previous response) and send its response to eNBl, for example, about the CSI process configuration information. Note that the averaging can be done over the CQIs for a given codeword, given rank and given subband. The most recent received rank can be used for averaging.

[0045] A2.2 eRNTP exchange

[0046] Our view on eRNTP exchange is captured in a corresponding proposal.

[0047] We note that the RNTP for the first subframe is always conveyed. If no information about the downlink (DL) power restriction on any subsequent subframe is conveyed, then the one conveyed for the first subframe can be assumed to remain static (i.e., applicable over subsequent subframes).

[0048] A3. Conclusion

[0049] We discussed the necessary X2 message to support CSI and eRNTP exchange for inter-eNB CoMP and presented corresponding proposals.

[0050] Proposals

[0051] 9.1.2.1 LOAD INFORMATION

[0052] This message is sent by an eNB to neighbouring eNBs to transfer load and interference co-ordination information.

[0053] Direction: eNBi→ eNB ₂ . Table Al

»lntended 0 ENUMER One of the YES ignore UL-DL ATED UL-DL

Configuration (saO, sal , configuration

sa2, sa3, s defined in

sa4, sa5, TS 36.21 1

sa6, ...) [10]. The UL

subframe(s)

in the

indicated

configuration

is subset of

those in

SIB1 UL-DL

configuration

This IE

applies to

TDD only.

»Extended UL 0 9.2.67 This IE YES ignore

Interference applies to

Overload Info TDD only.

»Enhanced 0 9.2.X2 YES ignore Relative

Narrowband Tx

Power (eRNTP)

[0054] 9.1.2.11 RESOURCE STATUS REQUEST

[0055] This message is sent by an eNBi to a neighbouring eNB ₂ to initiate the requested measurement according to the parameters given in the message.

[0056] Direction: eNBi→ eNB ₂ . Table A2

1 ,

Fifth Bit = ABS

Status Periodic,

Xth Bit = UE-CSI

Periodic.

Other bits shall be

ignored by the

eNB ₂ .

Cell To Report 1 Cell ID list for YES ignore which

measurement is

needed

>Cell To Report 1 .. EACH ignore Item <maxC

ellineN

B>

»Cell ID M ECGI

9.2.14

Reporting Periodicity 0 ENUMERA YES ignore

TED(1000

ms,

2000ms,

5000ms, 10

000ms, ...)

Partial Success 0 ENUMERA Included if partial YES ignore Indicator TED(partia success is allowed

I success

allowed, ...

)

CSI Measurement 0 BITSTRIN Each position in YES ignore Report type G the bitmap

(SIZE(2)) indicates the type of CSI

measurement to

report.

First bit=Rank,

Second

bit=subband CQI.

Reporting Periodicity 0 ENUMERA Periodicity for CSI YES ignore of CSI Measurement TED(5ms, Measurement

Report 10ms, Report Periodic

20ms,40m

s, 80ms,

aperiodic, .

^■■ )

[0057] 9.1.2.14 RESOURCE STATUS UPDATE

[0058] This message is sent by eNB ₂ to neighbouring eNBi to report the results of the requested measurements.

[0059] Direction: eNB ₂ → eNBi .

Table A3

[0060] 9.2.xl UE-CSI Report

[0061] This information element (IE) provides UE-CSI information for a subset or set of UEs served by eNB ₂ .

Table A4

(2))

»UE-CSI process M INTEGER(0..3 CSI process

Configuration information 1 ) or FFS configuration

information.

[0062] maxUEsubsetCSIReport can alternatively be set to 16, 20, 30, 35, or 40.

[0063] 9.2.x2 Enhanced Relative Narrowband Tx Power (E-RNTP)

[0064] This IE (infromation element) provides an indication on DL power restriction per PRB (physical resource block) per subframe in a cell and other information needed by to a neighbour eNB for interference aware scheduling.

Table A5

IE/Group Presence Range IE type and Semantics Criticality Assigned Name reference description Criticality

RNTP Per M BIT STRING Each position

PRB (6..1 10, ...) in the bitmap

represents a

n value

(i.e. first

bit=PRB 0

and so on),

for which the

bit value

represents

RNTP (n _PRB ),

defined in TS

36.213 [1 1].

Value 0

indicates "Tx

not

exceeding

RNTP

threshold".

Value 1

indicates "no

promise on

the Tx power

is given".

This IE is

used to

indicate DL

power

restriction per

PRB for the

first

subframe. In

case the DL

power

restriction is static, the indicated DL power restriction is maintained over the subsequent subframes.

RNTP M ENUMERAT RNTPthreshold Threshold ED (-∞, -1 1 , is defined in

-10, -9, -8, TS 36.213 -7, -6, -5, -4, [1 1 ].

-3, -2, -1 , 0,

1 , 2, 3, ...)

Number Of M ENUMERAT P (number of Cell-specifi ED (1 , 2, 4, antenna ports c Antenna ^■■■ ) for

Ports cell-specific reference signals) defined in TS 36.21 1 [10]

P_B M INTEGER P _B is defined

(0..3, ...) in TS 36.213

[1 1 ].

PDCCH M INTEGER Measured by Interferenc (0..4, ...) Predicted e Impact Number Of

Occupied PDCCH OFDM

Symbols (see TS 36.21 1 [10]).

Value 0 means "no prediction is available".

Starting M INTEGER Number of SFN (0..1023, ...) the first system frame from which the RNTP Per PRB Per Subframe IE is valid.

Starting M INTEGER Index of the

Subframe (0..9, ...) first subframe

Index from which the RNTP Per PRB Per Subframe IE is valid.

RNTP List 0 2 .. The first item

<maxno in the list ofSubfra corresponds mes> to the second subframe, the second to the third subframe, and so on. The DL power restrictions conveyed for the first subframe and the ones conveyed for the subsequent subframes in the list, are together applied repeatedly.

>RNTP M BIT STRING Each position Per PRB (6..1 10, ...) in the bitmap Subframe represents a -Specific n value

(i.e. first bit=PRB 0 and so on), for which the bit value represents RNTP (n _PRB ), defined in TS 36.213 [1 1]. Value 0 indicates "Tx not exceeding RNTP

threshold". Value 1 indicates "no promise on the Tx power is given". This IE is used to

indicate DL

power

restriction per

PRB for the

correspondin

g subframe.

[0065] Embodiment B

[0066] Bl. Introduction

[0067] In the following we provide our views on CSI and eRNTP exchange, as well as proposals containing the required message structures.

[0068] B2. Discussion

[0069] B2.1 CSI exchange: Configuring CSI processes

[0070] The concept of CSI processes was defined in Rel. l 1 to enable CSI feedback from a UE to its serving eNB. The CSI feedback is determined for each CSI process according to the serving TP and interference hypothesis configured in that process. . Each CSI process that is configured for a UE, comprises a set of resource elements on which non-zero power CSI-RSs are sent and a channel estimate is obtained by that UE using observations received on those resource elements.

[0071] In addition, a set of resource elements is also indicated by the CSI process (referred to as interference measurement resources (IMRs)) on which the UE estimates the covariance of the interference it observes. The channel and covariance estimates are together used by the UE to determine and send its feedback report corresponding to that CSI process. Multiple such CSI processes (up-to 4) can be configured for a UE, each process corresponding to a different choice of signal or interference hypothesis. Moreover, in the scenario in which fast switching of the serving TP is not possible, different CSI processes that are configured for any given UE typically correspond to different choices of interference hypothesis.

[0072] Note from the brief discussion above that in the event the interference hypothesis of a configured CSI process presumes muting from a TP (that is a dominant interferer for the UE of interest) which is controlled by the neighboring eNB, coordination among the eNBs is required in order to ensure that the interference estimated by the UE on the constituent IMRs is consistent with the assumed hypothesis. Another similar event that requires coordination is if the non-zero power CSI-RSs indicated in the CSI process must be interference protected in order to ensure reliable channel estimation at the UE. In both these events, the dominant interferer that is controlled by the neighboring eNB must be muted on certain resource elements. Thus, a mechanism (with appropriate signaling) should be available to share the CSI-RS (comprising non-zero power CSI-RSs and IMRs) configurations between eNBs, which would facilitate configuration of CSI processes across multiple eNBs.

[0073] Once the CSI processes are configured, the CSI exchanged among eNBs over the backhaul should include the respective CSI process configuration information, in order to convey the conditions under which the CSI was measured by the UE. This configuration information includes non-zero power CSI-RS information and IMR information (comprising the subframe indices and zero-power CSI-RS information). Since this configuration is anyway informed to the UE via RRC (or higher layer) signaling, the same information can be reused as a container to convey the configuration to the neighboring eNB.

[0074] Another way of conveying this configuration information is through a look-up-table. A look-up-table mapping an index to one or more distinct applied CSI process configurations can be constructed for each eNB. Here, by an applied CSI process we mean a process that is used by at-least one UE served by that eNB to measure its CSI. Such a table can be exchanged among neighbors first and from then on the configuration information can be exchanged via indices. The total number of configurations in the table can be limited in order to limit signaling overhead.

[0075] Suitable values for the number of configurations in this table are either 8 or 16 or 32.

[0076] B2.2 CSI exchange: Contents

[0077] One eNB can send CSI report pertaining to one or more of UEs to a neighboring eNB. For each UE, the CSI that the eNB sends to a neighbor can comprise:

[0078] (i) CQI: up-to 2 CQIs, each including a wideband component and possible sub-band differential components

[0079] (ii) RI (rank indicator): one wideband component

[0080] We note that the PMI was excluded from the CSI exchange report [1 ]. The justification for this exclusion was to minimize the overhead and the fact that PMI can depend on fast changing channel information, thus reducing its utility over non ideal backhaul with a higher latency. However, in the absence of PMI the use of RI is limited. Indeed, any rank greater than 1 will convey only 2 CQI(s), one for each of the two codewords. No further information about the (average) spatial directions seen by that UE can be deduced by the eNB receiving the report. As a result, reporting the RI should be made optional. Moreover, the eNB requesting the CSI report should be able to specify whether or not it would like to receive RI reports. Similarly, the eNB requesting the CSI reports should be able to specify whether or not it requires subband specific CQI reports. This can be achieved by setting a bit (in the measurement request) to be 0 if rank is not requested and 1 otherwise. Another bit can be set to 0 if subband CQIs are not requested and 1 otherwise.

[0081] Processing (filtering or subsampling) of the short-term CSI (received via over-the-air signaling) at an eNB prior to exchange should be permitted.

[0082] One use case for this is when the periodicity of the CSI report that is requested by eNBl to its neighbor eNB2, is larger than the over-the-air CSI signaling periodicity configured by eNB2. In this case eNB2 has to do some processing (such as subsampling or averaging) of the reports it receives before it sends it to eNBl . In this context, we note that the subsampling employed by eNB2 should be understood by eNBl (if needed additional signaling can be added to ensure this). One possible way this can be accomplished (without any signaling overhead) is for eNB2 to use the subsampling factor determined by a pre-determined rule (known to or configured for all eNBs in advance) that outputs a subsampling factor, given the requested periodicity and CSI process configuration as inputs. On the other hand, averaging or scaling or filtering employed by eNB2 can be transparent to the receiving eNB 1.

[0083] One of the goals of CSI exchange is to facilitate centralized RRM [3]. In a scenario with centralized RRM, the central node receiving the CSI reports should be able to keep track of the CSI information received for each particular UE, over all the received CSI reports. This can be achieved by including a UE identifier in each CSI report for each UE whose CSI is conveyed in that report. We want to include a unique ID (identification or identifier) for each user so that the receiving node knows which ones among all the reports that it receives, belong that user. This will be useful for RRM. Otherwise the receiving eNB will regard each received report as belonging to a distinct user. This can lead to sub-optimal resource allocation.

[0084] B2.3 eRNTP exchange

[0085] Our view on eRNTP exchange is captured in a corresponding proposal attached in the end of this embodiment.

[0086] We note that the RNTP (i.e., downlink (DL) power restriction) for the first subframe is always conveyed. If no information about the DL power restriction on any subsequent subframe is conveyed, then the one conveyed for the first subframe can be assumed to remain static (i.e., applicable over subsequent subframes).

[0087] We also present several variations, one of which includes the use of multiple thresholds

[0088] B3. Conclusion

[0089] We discussed the necessary X2 message to support CSI and eRNTP exchange for inter-eNB CoMP and presented corresponding proposals.

[0090] Proposals

[0091] 9.1.2.11 RESOURCE STATUS REQUEST

[0092] This message is sent by an eNBi to a neighbouring eNB ₂ to initiate the requested measurement according to the parameters given in the message.

[0093] Direction: eNBi→ eNB ₂ .

Table Bl IE/Group Name Presenc Range IE type Semantics Criticalit Assigned e and description y Criticality referenc

e

Message Type M 9.2.13 YES reject eNB1 M INTEGE Allocated by YES reject

Measurement ID R eNB-i

(1..4095,

■ ^■■ )

eNB2 C-ifRegi INTEGE Allocated by YES ignore

Measurement ID strationR R eNB ₂

equestSt (1..4095,

op ^■■■ )

Registration M ENUME A value set to YES reject Request RATED( "stop",

start, indicates a

stop, request to

^■■■ ) stop all cells

measuremen

ts.

Report 0 BITSTRI Each position YES reject

Characteristics NG in the bitmap

(SIZE(32 indicates

)) measuremen

t object the

eNB ₂ is

requested to

report.

First Bit =

PRB

Periodic,

Second Bit =

TNL load Ind

Periodic, Third Bit =

HW Load Ind

Periodic,

Fourth Bit =

Composite

Available

Capacity

Periodic, this

bit should be

set to 1 if at

least one of

the First,

Second or

Third bits is

set to 1 ,

Fifth Bit =

ABS Status

Periodic, Xth

Bit = UE-CSI

Periodic.

Other bits

shall be

ignored by

the eNB ₂ .

Cell To Report 1 Cell ID list for YES ignore which

measuremen

t is needed

>Cell To 1 .. EACH ignore Report Item <maxC

ellineN

B>

»Cell ID M ECGI

9.2.14 Reporting 0 ENUME YES ignore

Periodicity RATED(

1000ms,

2000ms,

5000ms,

10000ms

, ...)

Partial Success 0 ENUME Included if YES ignore

Indicator RATED( partial

partial success is

success allowed

allowed,

■ ^■■ )

CSI 0 BITSTRI Each position YES ignore

Measurement NG in the bitmap

Report type (SIZE(2)) indicates the

type of CSI

measuremen

t to report.

First

bit=Rank,

Second

bit=subband

CQI.

((Reporting 0 ENUME Periodicity YES ignore

Periodicity of CSI RATED( for CSI

Measurement 5ms, Measuremen

Report 10ms, t Report

20ms,40 Periodic

ms,

80ms,

aperiodic

, ...) Range bound Explanation maxCellineNB Maximum no. cells that can be served by an eNB. Value is

256.

Condition Explanation ifRegistrationRequestStop This IE shall be present if the Registration Request IE is

set to the value "stop".

[0094] 9.1.2.14 RESOURCE STATUS UPDATE

[0095] This message is sent by eNB2 to neighbouring eNBl to report the results of the requested measurements.

[0096] Direction: eNB ₂ → e Bi .

Table B2

IE/Group Name Presen Range IE type Semantics Criticality Assigned ce and description Criticality reference

Message Type M 9.2.13 YES ignore eNB1 M INTEGER Allocated by YES reject

Measurement ID (1..4095,... eNB-i

)

eNB2 M INTEGER Allocated by YES reject

Measurement ID (1..4095,... eNB ₂

)

Cell 1 YES ignore

Measurement

Result

>Cell 1 .. EACH ignore

Measurement <maxCelline

Result Item NB>

»Cell ID M ECGI

9.2.14

»Hardware 0 9.2.34

Load Indicator

»S1 TNL 0 9.2.35

Load Indicator

» Radio 0 9.2.37

Resource

Status

»Composite 0 9.2.44 YES ignore Available

Capacity Group

»ABS Status 0 9.2.58 YES ignore

» UE-CSI 0 9.2.X1 YES ignore Report Range bound Explanation maxCellineNB Maximum no. cells that can be served by an eNB. Value is 256.

[0097] 9.2.xl UE-CSI Report

[0098] This IE provides UE-CSI information for a set of UEs served by eNB ₂ .

Table B3

IE/Group Name Presence Range IE type and Semantics reference description

UE subset CSI 1 ..

Report <maxUEsubs

etCSIReport

>

>(C-RNTI) UE ID M BIT STRING (SIZE ID of the UE served by

(16)) the cell in eNB ₂ .

Defined in TS 36.331.

>UE-CSI process 1 ..

information <maxUE-CSI

process>

»Rank 0 BIT STRING (SIZE The rank indicator IE is Indicator (3)) present only if it is requested in the associated request. In that case Cf. TS 36.213 [7.2.3].

»Wideband M BIT STRING (SIZE Cf. TS 36.213 [7.2.3]. CQI For (4))

Codeword 0

»Wideband 0 BIT STRING (SIZE Cf. TS 36.213 [7.2.3]. CQI For (4))

Codeword 1

»Subband CQI 0..<maxCQI 0 indicates no subband List Subbands > CQI, which is always chosen if associated request does not want subband CQI, or this IE is present only if associated request wants subband CQI »>Subband 0 BIT STRING (SIZE Cf. TS 36.213 [7.2.3].

CQI for (2))

codeword 0

»>Subband 0 BIT STRING (SIZE Cf. TS 36.213 [7.2.3].

CQI for (2))

codeword 1

»UE-CSI M FFS CSI process

process configuration

Configuration information.

information

[0099] Alternatively, the parameter maxUEsubsetCSIReport can be 8, 16, 32, 48, 64, or 256. Further, optionally, the UE-ID can have a more compact representation using say 8bits or 6bits or 5 bits (equivalently 256 or 64 or 32 possible indices from a configurable table).

[00100] Next, we consider the case when subband indices have to be indicated. This is important to accommodate feedback modes that involve UE selected subband feedback.

Table B4 IE/Group Name Presence Range IE type and Semantics reference description

UE subset CSI Report 1 ..

<maxUEsubset

CSIReport>

>C-RNTI M BIT STRING ID of the UE served by

(SIZE (16)) the cell in eNB ₂ .

Defined in TS 36.331.

>UE-CSI process 1 ..

information <maxUE-CSIpr

ocess>

»Rank Indicator 0 BIT STRING The rank indicator IE is

(SIZE (3)) present only if it is requested in the associated request. In that case Cf. TS 36.213 [7.2.3].

»Wideband CQI For M BIT STRING

Codeword 0 (SIZE (4))

»Wideband CQI For 0 BIT STRING

Codeword 1 (SIZE (4))

»Subband CQI List 0..<maxCQISub This IE is present only bands > if associated request wants subband CQI

»>Subband CQI 0 BIT STRING

for codeword 0 (SIZE (4))

»>Subband CQI 0 BIT STRING

for codeword 1 (SIZE (4))

»>Subband index O INTEGER Included in case of UE

(0..27, ...) selected subband CQI reporting.

[00101] Note that as an alternative in the above tables, for each CQI the bit string field of 4 bits (2 bits) can be replaced by INTEGER (0..15, ...) (INTEGER (0..7, ...)).

[00102] In another alternative the sub band indices can be conveyed by means of a combinatorial index which is described next.

[00103] The idea here is that depending on the number of PRBs (or RBs (resource blocks) for short) in the downlink available at sending eNB2 (a parameter which is known or conveyed separately to the receiving eNBl) , the set of all possible subband selections that can be made together with the subband size, for all feedback modes, can be deduced by eNBl .

[00104] For example when 110 RBs are available at eNB2 (and this number is conveyed to eNBl) eNBl can deduce that for a UE configured under:

[00105] Aperiodic, Mode 2-*: 6 UE selected subband indices

[00106] A subframe is composed of 28 subbands. Among 28 subbands, 6 subbands are selected by the UE. The number of PRBs in the subbands is 4 except for the last one; the number of PRBs in the last subband is 2 (4*27 + 2 = 110).

[00107] For Aperiodic, Mode 3-* : 14 higher layer-configured sub bands

[00108] A subframe is composed of 14 subbands. The number of PRBs in the subband is 8 except for the last one; the number of PRBs in the last subband is 6 (8* 13 + 6 = 1 10).

[00109] For Periodic, Mode 2-*: 4 UE selected subband indices (with an additional constraint on choosing one sub band per bandwidth portion or part)

[00110] A subframe is composed of 14 subbands. Among 14 subbands, 4 subbands are selected by the UE. The number of PRBs in the subbands is 8 except for the last one; the number of PRBs in the last subband is 6 (8* 13 + 6 = 110).

[00111] Then, considering all possible feasible subband selections under all the aforementioned feedback modes, it is possible to assign a unique label to each distinct feasible selection of sub bands. All possible such labels together decide the range of a combinatorial index R. As a result, knowing the value of R the receiving eNBl can deduce the subband selection. The associated CQIs (one for each subband in the indicated selection) can be ordered in the increasing order of the frequency range represented by the indicated subbands. Each such CQI can be conveyed using full representation (i.e., using 16 possibilities) which can then be directly used by the receiving eNBl .

Table B5 IE/Group Name Presence Range IE type and Semantics reference description

UE subset CSI Report 1 ..

<maxUEsubsetC

SIReport>

>C-RNTI M BIT STRING ID of the UE

(SIZE (16)) served by the cell in eNB ₂ .

Defined in TS 36.331.

>UE-CSI process 1 ..

information <maxUE-CSIpro

cess>

»Rank Indicator 0 BIT STRING The rank indicator

(SIZE (3)) IE is present only if it is requested in the associated request. In that case Cf. TS 36.213 [7.2.3].

»Wideband CQI For M BIT STRING

Codeword 0 (SIZE (4))

»Wideband CQI For 0 BIT STRING

Codeword 1 (SIZE (4))

» combinatorial O Integer FFS This IE is present index only if associated request wants subband CQI

»>Subband CQI List 0..<maxCQISubb The number of ands > subbands in the list as well as their respective indices and sizes are deduced from the

combinatorial index.

»»Subband CQI M BIT STRING

for codeword 0 (SIZE (4))

»»Subband CQI 0 BIT STRING

for codeword 1 (SIZE (4))

»UE-CSI process M FFS CSI process

Configuration configuration

information information.

[00112] UE configuration independent coding structure

[00113] A coding structure for signaling CSI over X2 in a UE-configuration independent way is shown in Table II . In this structure, a subband is defined as a set of contiguous PRBs having the same CQI value. The subband partitioning is left to the sending eNB2 implementation, and is not restricted by the UE's CSI reporting configuration. Each indicated CQI follows the definition of a 4 bit CQI (Cf. TS 36.213). This allows for the sending eNB2 to process the CSI it receives from the UE in any manner as long as each indicated CQI is consistent with the basic CQI definition. The receiving eNBl can directly use these CQIs while being agnostic to how they were procured and processed by eNBl .

Table B6 UE configuration independent coding structure

IE/Group Name Presence Range IE type and Semantics description reference

CSI per UE 1..<maxnoofUE-C

Sl>

>C-RNTI M BIT STRING

(SIZE (16))

>CSI per Interference 1..<maxnooflnterfe

Hypotheses renceHypothesis >

»lnterference Hypothesis M [FFS]

Information

»Wideband CQI for M INTEGER(0..15,

Codeword 0 ...)

»Wideband CQI for O INTEGER(0..15,

Codeword 1 ...)

»Rank Indication M INTEGER(1..8,..) Defined in TS 36.213 [1 1 ].

»Subband CQI List 0.. Subbands are listed in the

<maxnoofSubband order of increasing > frequency.

»>Subband Start O INTEGER(0..109 PRB number of the first

, ... ) PRB in the subband. If this

IE is not present, the subband is contiguous with the previous subband in the list, or starts with PRB 0 if this is the first subband in the list.

»>Subband Size O INTEGER(1..1 10 Number of contiguous

, ... ) PRBs in the subband. If this

IE is not present, the value is the same as the previous subband in the list.

»>Subband CQI for M INTEGER(0..15,

Codeword 0 ...)

»>Subband CQI for O INTEGER(0..15,

[00114] We note here that reporting full (complete) CQI (with 16 possibilities) for each indicated subband CQI instead of differential CQI is useful since otherwise the receiving eNBl may not know how to combine a corresponding wideband CQI and differential sub-band CQI (with fewer than 16 possibilities) in order to obtain the full CQI for that subband, for instance, in the case that the precise feedback mode configured for the UE of interest under that CSI process is not conveyed to the receiving eNBl . We note here also that it might be desirable to not impose restrictions on sending eNB2 on how it combines reports from multiple different feedback modes configured for that UE under the same CSI process. Then, note that when aperiodic feedback mode 3-1 is configured for the UE (by eNB2), the UE reported sub band CQI is encoded differentially with respect to the corresponding wideband CQI using 2 bits representing differential values {-2, 0, 1, 2} . On the other hand, in the case of aperiodic feedback mode 2-0 or 2-2, only the best M-average is reported by the UE by differentially encoding it with respect to a corresponding wideband CQI using 2 bits representing differential values { 1 , 2, 3, 4} . Further, in case of periodic feedback mode 2-1 the CQI corresponding to codeword- 1 for each UE selected subband within a bandwidth part can itself be of 4 bits, whereas that of codeword-2 (when RI>1) is differentially encoded with respect to CQI of codeword- 1 using 3 bits.

[00115] It becomes apparent from the above discussion that a transparent way of conveying CQI

(without having to convey all details regarding to one or more feedback modes configured under that CSI process for that UE) is to allow for full (complete) CQI for each indicated subband.

[00116] Another issue that is important, is to ensure that the RI and CQIs conveyed by eNB2 to eNBl in a UE CSI report are mutually consistent, i.e., all the reported CQIs are computed by the UE for the same RI (which is identical to the one in the Rank Indication IE when the latter is present). This issue is important to address because under certain feedback modes (such as periodic mode 2-1) the RI and the wideband CQI(s) as well as the subband CQI(s) for one or more bandwidth portions can be reported by the UE on different subframes. Thus, depending on the periodicity defined by eNBl in its CSI request, it can happen that the latest RI available for the UE under the CSI process, can be different from the one for which the most recent CQI(s) are computed. In such a case, the sending eNB2 should ensure that its CSI report is consistent, for instance by using the RI value for which the most recently available CQI(s) have been computed.

[00117] The variation (which allows the requesting eNB to specify whether or not it wants to receive subband CQI(s) or Rank Indication is provided below. In this context, we note that since the requesting eNBl has no control over how eNB2 configures CSI processes (and constituent feedback modes) for its users, it should be in any case able to exploit different type of CSI reports (wideband only or wideband and subband).

Table B7

IE/Group Name Presence Range IE type and Semantics description reference

CSI per UE 1..<maxnoofUE- CSI>

>C-RNTI M BIT STRING

(SIZE (16))

>CSI per Interference 1..<maxnooflnte

Hypotheses rferenceHypoth

esis >

»lnterference M [FFS]

Hypothesis Information

»Wideband CQI for M INTEGER(0..1

Codeword 0 5, ...)

»Wideband CQI for 0 INTEGER(0..1

Codeword 1 5, ...)

»Rank Indication 0 INTEGER(1..8 The rank indication IE is

-) present only if it is requested in the associated request. In that case it follows the definition in TS 36.213

[1 11-

»Subband CQI List 0.. Th is IE is present only if

<maxnoofSubb associated request and> wants subband CQI. In that case subbands are listed in the order of increasing frequency.

»>Subband Start 0 INTEGER(0..1 PRB number of the first

09, ...) PRB in the subband. If this IE is not present, the subband is contiguous with the

previous subband in the

list, or starts with PRB 0

if this is the first

subband in the list.

»>Subband Size 0 INTEGER(1..1 Number of contiguous

10, ...) PRBs in the subband. If

this IE is not present,

the value is the same as

the previous subband in

the list.

»>Subband CQI for M INTEGER(0..1

Codeword 0 5, ...)

»>Subband CQI for 0 INTEGER(0..1

Codeword 1 5, ...)

[00118] Another variation which allows for further simplification at the expense of not being bit efficient is as follows. Here the full CQIs for all possible subbands (which can be determined by the number of PRBs in the downlink available at eNB2) are always conveyed for a UE under the CSI process. In case the sub band CQI is not reported by a UE under the configured feedback mode for a subband, the sending eNB2 simply uses the corresponding wideband CQI value for that subband. Then, note that there is no need to include the wideband CQI(s) in case the associated request wants subband CQI.

[00119] 9.2.19 Relative Narrowband Tx Power (RNTP)

[00120] This IE provides an indication on DL power restriction per PRB in a cell and other information needed by a neighbour eNB for interference aware scheduling.

Table B8 IE/Group Presence Range IE type Semantics Criticality Assigned Name and description Criticality reference

RNTP Per M BIT Each position in

PRB STRING the bitmap

(6..1 10, represents a n _PRB

^■■■ ) value (i.e. first

bit=PRB 0 and so

on), for which the

bit value

represents RNTP

(npRB), defined in

TS 36.213 [1 1].

Value 0 indicates

"Tx not exceeding

RNTP threshold".

Value 1 indicates

"no promise on the

Tx power is

given".

This IE is used to

indicate DL power

restriction per

PRB for the first

subframe. In case

the DL power

restriction is static,

the indicated DL

power restriction

is maintained over

the subsequent

subframes.

RNTP M ENUMER RNTPthreshold ' ^s

Threshold ATED (-∞, defined in TS

-1 1 , -10, 36.213 [1 1].

-9, -8, -7, -6, -5, -4,

-3, -2, -1 ,

0, 1 , 2, 3,

■ ^■■ )

Number Of M ENUMER P (number of Cell-specific ATED (1 , antenna ports for Antenna 2, 4, ...) cell-specific Ports reference signals) defined in TS 36.21 1 [10]

P_B M INTEGER P _B is defined in TS

(0..3, ...) 36.213 [1 1].

PDCCH M INTEGER Measured by

Interference (0..4, ...) Predicted Number

Impact Of Occupied

PDCCH OFDM

Symbols (see TS 36.21 1 [10]).

Value 0 means "no prediction is available".

Extended M or O BIT Each position in RNTP Per STRING the bitmap PRB (6..4290, represents a PRB

^■■■ ) in a subframe, for which value "1 " indicates 'interference protected resource' or 'no promise on the Tx power is given' and value "0" indicates 'resource with no utilization constraints' or 'Tx not exceeding RNTP threshold.' The first bit corresponds to PRB 0 of the second or first subframe for which the extended RNTP per PRB IE is valid, the second bit corresponds to PRB 1 of the second or first subframe for which the extended RNTP per PRB IE is valid, and so on. The length of the bit string is an integer (maximum 39) multiple of

N _m ■ N _m is defined in TS 36.21 1 [10]. The bit string may span across multiple contiguous subframes.

The pattern across contiguous subframes (formed by RNTP per PRB and extended RNTP per PRB) is continuously repeated.

RNTP per 0..1

PRB start

time

>Starting M or 0 INTEGE Number of the first SFN R system frame from

(0..1023, which the RNTP Per ■ ^■■ ) PRB {Per Subframe)

IE is valid or SFN of the radio frame containing the first subframe when the RNTP Per PRB IE is valid.

>Starting M or 0 INTEGE Index of the first Subframe R (0..9, subframe from Index ^■■■ ) which the RNTP Per

PRB {Per Subframe) IE is valid or

Subframe number, within the radio

frame indicated by the Start SFN IE, of the first subframe when the RNTP Per PRB IE is valid. 121] An alternate Table for RNTP enhancement is given below.

Table B9

IE/Group Presence Range IE type Semantics Criticality Assigned Name and description Criticality referenc

e

RNTP per M BIT Each position in

PRB STRING the bitmap

(6..1 10, represents a n _PRB

■ ^■■ ) value (i.e. first

bit=PRB 0 and so

on), for which the

bit value

represents RNTP

(n _PRB ), defined in

TS 36.213 [1 1].

Value 0 indicates

"Tx not exceeding

RNTP threshold".

Value 1 indicates

"no promise on the

Tx power is

given".

This IE is ignored

if the RNTP per

PRB per subframe

IE is present.

RNTP M ENUME RNTPthreshold I ^s

Threshold RATED defined in TS

(- ^» , -1 1 , 36.213 [1 1].

-10, -9,

-8, -7, -6,

-5, -4, -3,

-2, -1 , 0,

1 , 2, 3,

^■■■ ) Number Of M ENUME P (number of Cell-specific RATED antenna ports for Antenna (1 , 2, 4, cell-specific Ports ^■■■ ) reference signals) defined in TS 36.21 1 [10]

P_B M INTEGE P _B is defined in TS

R (0..3, 36.213 [1 1].

^■■■ )

PDCCH M INTEGE Measured by

Interference R (0..4, Predicted Number

Impact ^■■■ ) Of Occupied

PDCCH OFDM

Symbols (see TS 36.21 1 [10]).

Value 0 means "no prediction is available".

RNTP Per O BIT Each position in PRB per STRING the bitmap subframe (6..4400, represents a PRB in a subframe, for which value "1 " indicates 'no promise on the Tx power is given' and value "0" indicates Tx not exceeding RNTP threshold.' The first bit corresponds to PRB 0 of the first subframe for which the RNTP per PRB per subframe IE is valid, the second bit corresponds to PRB 1 of the first subframe for which the RNTP per PRB per subframe IE is valid, and so on. The length of the bit string is an integer (maximum 40) multiple of defined in TS 36.21 1 [10]. The bit string may span across multiple

contiguous

subframes.

The pattern

across contiguous

subframes formed

by RNTP per PRB

per subframe IE is

continuously

repeated.

RNTP per 0..1

PRB per

subframe

start time

>Starting M INTEGE SFN of the radio

SFN R frame containing the

(0..1023, first subframe when

■ ^■■ ) the RNTP Per PRB

Per Subframe IE is

valid.

>Starting M INTEGE Subframe number,

Subframe R (0..9, within the radio

Index ^■■■ ) frame indicated by

the Start SFN IE, of

the first subframe

when the RNTP Per

PRB Per Subframe

IE is valid. 122] Another alternate Table for RNTP enhancement is given below.

Table BIO IE/Group Presence Range IE type Semantics Criticality Assigned Name and description Criticality referenc

e

RNTP per M BIT Each position in

PRB STRING the bitmap

(6..1 10, represents a n _PRB

■ ^■■ ) value (i.e. first

bit=PRB 0 and so

on), for which the

bit value

represents RNTP

(n _PRB ), defined in

TS 36.213 [1 1].

Value 0 indicates

"Tx not exceeding

RNTP threshold".

Value 1 indicates

"no promise on the

Tx power is

given".

This IE is ignored

if the RNTP per

PRB per subframe

IE is present.

RNTP M ENUME RNTPthreshold I ^s

Threshold RATED defined in TS

(- ^» , -1 1 , 36.213 [1 1].

-10, -9,

-8, -7, -6,

-5, -4, -3,

-2, -1 , 0,

1 , 2, 3,

^■■■ ) Number Of M ENUME P (number of Cell-specific RATED antenna ports for Antenna (1 , 2, 4, cell-specific Ports ^■■■ ) reference signals) defined in TS 36.21 1 [10]

P_B M INTEGE P _B is defined in TS

R (0..3, 36.213 [1 1].

^■■■ )

PDCCH M INTEGE Measured by

Interference R (0..4, Predicted Number

Impact ^■■■ ) Of Occupied

PDCCH OFDM

Symbols (see TS 36.21 1 [10]).

Value 0 means "no prediction is available".

RNTP Per O BIT Each position in PRB per STRING the bitmap subframe (6..4400, represents a PRB ■ ^■■ ) in a subframe, for which value "1 " indicates resource with no utilization constraints' and value "0" indicates 'interference protected resource.' The first bit corresponds to PRB 0 of the first subframe for which the RNTP per PRB per subframe IE is valid, the second bit corresponds to PRB 1 of the first subframe for which the RNTP per PRB per subframe IE is valid, and so on. The length of the bit string is an integer (maximum 40) multiple of

Ni defined in TS 36.21 1 [10]. The bit string may span across multiple contiguous

subframes.

The pattern

across contiguous

subframes formed

by RNTP per PRB

per subframe IE is

continuously

repeated.

RNTP per 0..1

PRB per

subframe

start time

>Starting M INTEGE SFN of the radio

SFN R frame containing the

(0..1023, first subframe when

■ ^■■ ) the RNTP Per PRB

Per Subframe IE is

valid.

>Starting M INTEGE Subframe number,

Subframe R (0..9, within the radio

Index ^■■■ ) frame indicated by

the Start SFN IE, of

the first subframe

when the RNTP Per

PRB Per Subframe

IE is valid. 123] Another alternative using multiple thresholds conveyed via 2 bits is given below.

Table Bll IE/Group Presence Range IE type Semantics Criticality Assigned

Name and description Criticality referenc

e

ERNTP Per M BIT Each position in - -

PRB and STRING the bitmap

subframe (12..220, represents a PRB

■ ^■■ ) in a subframe, for

which the value

"xx" indicates how

the transmission

power in a

resource block is

mapped relative to

the two power

thresholds:

00 - power level

not exceeding the

LPTH

01 - power level

between LPTH

and MPTH;

10 - power level

between MPTH

and HPTH;

1 1 - no promise

on the Tx power is

given.

The first 2 bits

correspond to

PRB 0 of the first

subframe for

which the IE is

valid, the following

2 bits correspond to PRB 1 of the first subframe for which the IE is valid, and so on. The bit string may span across multiple contiguous subframes. The length of the bit string is an integer (maximum 40) multiple of

N^ . The parameter is defined in TS 36.21 1 [10]. The ERNTP pattern is continuously repeated with a periodicity indicated in Periodicity.

Transmitted

power levels

LPTH (Low M ENUME Lower RNTP

Power RATED power threshold,

Threshold) (- ^» , -1 1 , using the

-10, -9, RNTPthreshold -8, -7, -6, defined in TS -5, -4, -3, 36.213 [1 1]. -2, -1 , 0,

1 , 2, 3,

^■■■ ) MPTH M ENUME Medium RNTP (Medium RATED power threshold, Power (- ^» , -11, using the Threshold) -10, -9, RNTPthreshold

-8, -7, -6, defined in TS -5, -4, -3, 36.213 [11]. -2, -1, 0,

1,2, 3,

^■■■ )

HPTH (High M ENUME Higher RNTP

Power RATED power threshold,

Threshold) (-∞, -11, using the

RNTPthreshold

-10, -9,

defined in TS -8, -7, -6,

36.213 [11]. -5, -4, -3,

-2, -1, 0,

1,2, 3,

^■■■ )

Subframe

sequence

definition

>Start SFN M INTEGE SFN of the radio

R frame containing

(0..1023) the first subframe where the RNTP Per PRB Per Subframe IE is valid.

>Start M INTEGE Subframe

Subframe R(0..39) number, within the

Number radio frame

indicated by the Start SFN\E, of the first subframe when the RNTP

Per PRB Per

Subframe IE is

valid.

No. of M 1 ...40 No. of subframes

subframes for which is

defined the

bitstream

Periodicity 1 ...40 The number of

subframes after

which the bit

pattern is

repeated

Number Of M ENUME P (number of

Cell-specific RATED antenna ports for

Antenna (1 , 2, 4, cell-specific

Ports ^■■■ ) reference signals)

defined in TS

36.21 1 [10]

P B M INTEGE P _B is defined in

R (0..3, TS 36.213 [1 1].

^■■■ )

[00124] The point in the table given above is that since the choice ' 11 ' already indicates no promise on the power level (which covers the case of transmit power being arbitrarily high) we can use three thresholds (instead of two) since there is no need to convey that the power level is greater than HPTH (as this is subsumed by ' 11 ').

[00125] However, one problem with indicating multiple thresholds is that the current CoMP hypothesis (implicitly) assumes just one threshold. In this sense there is a mismatch between using multiple thresholds in eR TP and not in the CoMP hypothesis. Consequently, the full potential of multiple thresholds may not be realized inspire of the additional overhead.

[00126] Embodiment C

[00127] CI. Introduction [00128] In the following we provide our views on CSI exchange, as well as proposals containing the required message structures.

[00129] C2. Discussion

[00130] C2.1 CSI exchange: Configuring CSI processes

[00131] From previous discussion it is evident that coordination among the eNBs is required in order to define a set of assignable CSI processes that have a consistent meaning. Once the set of these CSI processes is defined, the CSI exchanged among eNBs should include the respective CSI process configuration information, in order to convey the conditions under which the CSI was measured by the UE. This configuration information should include CSI-RS-ConfigNZP [36.331b, Section 6.3.2] and CSI-IM-Config [36.331b, Section 6.3.2]. We note here that doing so would enable exchange of per-point CSI process (under which the UE estimates RS from any one point in its measurement set (or CoMP set) while the associated IMR measures the out of CoMP set or out of cluster interference) configuration. If one such process is sent to a receiving eNB for each point in that UE's measurement set, any interference hypothesis for that UE can be emulated by receiving eNB. This can indeed mitigate the bottleneck in terms defining enough CSI processes to cover sufficiently many interference hypotheses. One way of conveying this configuration information is through a look-up-table. A look-up-table mapping an index to each possible distinct CSI process configuration can be constructed (possibly separately for each eNB). Here, by a possible CSI process we mean a process that can be assigned to a served UE to measure its CSI. Such a table can be exchanged among neighbors first and from then on the configuration information can be exchanged via indices. The total number of defined processes (including their configuration information) in each table can be limited in order to limit signaling overhead. For instance, this number could be one of {7,8, 9,16,32} . As an option, the configuration information for a process can also include power offset value Pc and/or offsets Pa and Pb, that were configured for that process. Further optionally, it can also indicate for which (if any) among the other processes, that process was set to be reference rank process. As an additional option, the configured feedback mode information (such as periodic or aperiodic) can also be included.

[00132] C2.2 CSI exchange: Contents

[00133] One eNB can send CSI reports pertaining to one or more of its UEs to a neighboring eNB.

For each UE, the CSI that the eNB sends to a neighbor can comprise:

[00134] CQI: up-to 2 CQIs, each including a wideband component and possible sub-band components

[00135] RI: one wideband component [00136] We note that the PMI was excluded from the CSI exchange report [1]. The justification for this exclusion was to minimize the overhead and the fact that PMI can depend on fast changing channel information, thus reducing its utility over non ideal backhaul with a higher latency. However, in the absence of PMI the use of RI is limited. Indeed, any rank greater than 1 will convey only 2 CQI(s), one for each of the two codewords. No further information about the (average) spatial directions seen by that UE can be deduced by the eNB receiving the report. As a result, reporting the RI should be made optional. Moreover, the eNB requesting the CSI report (eNBl) should be able to specify whether or not it would like to receive RI reports. Similarly, the eNB requesting the CSI reports should be able to specify whether or not it requires subband specific CQI reports. This can be achieved by setting a bit (in the measurement request) to be 0 if rank is not requested and 1 otherwise. Another bit can be set to 0 if subband CQIs are not requested and 1 otherwise. In this context, we note that since the requesting eNB has no control over how the sending eNB (eNB2) configures CSI processes (and constituent feedback modes) for its users, it should be in any case able to exploit different type of CSI reports (wideband only or wideband and subband).

[00137] Proposal: Include optional IE in resource status request indicating whether RI and/or subband CQI should be sent in the the resource status response message.

[00138] Implementation based processing of the short-term CSI (received via over-the-air signaling) by the sending eNB, prior to CSI exchange has been agreed. In this context, we believe that reporting full (complete) CQI (with 16 possibilities), where each such CQI follows the definition of a 4 bit CQI (Cf. TS 36.213), for each indicated subband instead of differential CQI is useful. This has main two advantages. It allows the sending eNB full freedom in obtaining these CQIs. Indeed, it is desirable to not impose restrictions on sending eNB2 on how it processes or combines reports from multiple different feedback modes configured for a UE under the same CSI process. Secondly, the receiving eNB can be agnostic to the configured feedback modes. This latter point is important because when aperiodic feedback mode 3-1 is configured for the UE (by eNB2), the UE reported sub band CQI is encoded differentially with respect to the corresponding wideband CQI using 2 bits representing differential values {-2, 0,1,2} . On the other hand, in the case of aperiodic feedback mode 2-0 or 2-2, only the best M-average CQI is reported by the UE by differentially encoding it with respect to a corresponding wideband CQI, using 2 bits representing differential values {1,2,3,4} . Further, in case of periodic feedback mode 2-1 the CQI corresponding to codeword- 1 for each UE selected subband within a bandwidth part can itself be of 4 bits, whereas that of codeword-2 (when RI>1) is differentially encoded with respect to CQI of codeword- 1 using 3 bits.

[00139] It becomes apparent from the above discussion that a transparent way of conveying CQI

(without having to convey all details regarding to one or more feedback modes configured under that CSI process for that UE) is to allow for full (complete) CQI for each indicated subband.

[00140] Proposal: Convey each subband CQI using full representation (4bits or 16 possibilities)

[00141] Next, we consider subband indexing and propose an alternative in which the subband selection (including their sizes, indices) is conveyed by means of a combinatorial index which is described next.

[00142] This idea is a simple extension of that used in TS 36.213 for aperiodic feedback mode 2-*.

In particular, depending on the number of PRBs (or RBs for short) in the downlink available at sending eNB2 (a parameter which is known or conveyed separately to the receiving eNBl) , the set of all possible subband selections that can be made together with the subband sizes for all feedback modes can be deduced by eNBl .

[00143] For example when 110 RBs are available at eNB2 (and this number is conveyed to eNBl) eNBl can deduce that for a UE configured under:

[00144] Aperiodic, Mode 2-*: 6 UE selected subband indices [00145] A subframe is composed of 28 subbands. Among 28 subbands, 6 subbands are selected by the UE. The number of PRBs in the subbands is 4 except for the last one; the number of PRBs in the last subband is 2 (4*27 + 2 = 110).

[00146] For Aperiodic, Mode 3-* : 14 higher layer-configured sub bands

[00147] A subframe is composed of 14 subbands. The number of PRBs in the subband is 8 except for the last one; the number of PRBs in the last subband is 6 (8* 13 + 6 = 1 10).

[00148] For Periodic, Mode 2-*: 4 UE selected subband indices (with an additional constraint on choosing one sub band per bandwidth portion or part)

[00149] A subframe is composed of 14 subbands. Among 14 subbands, 4 subbands are selected by the UE. The number of PRBs in the subbands is 8 except for the last one; the number of PRBs in the last subband is 6 (8* 13 + 6 = 110).

[00150] Then, considering all possible feasible subband selections under all the aforementioned feedback modes, it is possible to assign a unique label to each distinct feasible selection of sub bands. All possible such labels together decide the range of a combinatorial index R. As a result, knowing the value of R the receiving eNB can deduce the subband selection. The associated CQIs (one for each subband in the indicated selection) can be ordered in the increasing order of the frequency range represented by the indicated subbands. Each such CQI can be conveyed using full representation (i.e., using 16 possibilities) which can then be directly used by the receiving eNBl .

[00151] Proposal: Convey subband indexing and size information via a combinatorial index.

[00152] Another issue that is important, is to ensure that the RI and CQIs conveyed by eNB2 to eNBl in a UE CSI report are mutually consistent, i.e., all the reported CQIs are computed by the UE for the same RI (which is identical to the one in the Rank Indication IE when the latter is present). This issue is important to address because under certain feedback modes (such as periodic mode 2-1) the RI and the wideband CQI(s) as well as the subband CQI(s) for one or more bandwidth portions can be reported by the UE on different subframes. Thus, depending on the periodicity defined by eNBl in its CSI request, it can happen that the latest RI available for the UE under the CSI process, can be different from the one for which one or more of the most recently available CQI(s) are computed. In such a case, the sending eNB2 should ensure that its CSI report is consistent, for instance by using the RI value for which the most recently available CQI(s) have been computed.

[00153] Proposal: Sending eNB must ensure RI and CQI(s) conveyed in a CSI report are mutually consistent. [00154] One of the goals of CSI exchange is to facilitate centralized RRM. In a scenario with centralized RRM, the central node receiving the CSI reports should be able to keep track of the CSI information received for each particular UE, over all the received CSI reports. In order to ensure this, it has been agreed that a UE identifier will be included in each CSI report for each UE whose CSI is conveyed in that report. This ID should enable the receiving node to deduce which ones among all the reports that it receives, belongs to that user, thereby facilitating RRM. Including a similar UE ID in the reference signal received power (RSRP) reports will also be beneficial and allow the receiving eNB to combine or jointly exploit these two sets of reports.

[00155] Proposal: Include UE ID in RSRP measurement report

[00156] Proposals:

[00157] 9.1.2.11 RESOURCE STATUS REQUEST

[00158] This message is sent by an eNBi to a neighbouring eNB ₂ to initiate the requested measurement according to the parameters given in the message.

[00159] Direction: eNB i→ eNB ₂ .

Table CI

Periodic,

Third Bit =

HW Load Ind

Periodic,

Fourth Bit =

Composite

Available

Capacity

Periodic, this

bit should be

set to 1 if at

least one of

the First,

Second or

Third bits is

set to 1 ,

Fifth Bit =

ABS Status

Periodic, Xth

Bit = UE-CSI

Periodic.

Other bits

shall be

ignored by the

eNB ₂ .

Cell To 1 Cell ID list for YES ignore Report which

measurement

is needed

>Cell To 1 .. EACH ignore Report Item <maxCellin

eNB> »Cell ID M ECGI 9.2.14

Reporting 0 ENUMERA YES ignore Periodicity TED(1000m

s, 2000ms,

5000ms, 10

000ms, ...)

Partial 0 ENUMERA Included if YES ignore

Success TED(partial partial

Indicator success success is

allowed, ...) allowed

CSI 0 BITSTRING Each position YES iqnore

Measurement (SIZE(2)) in the bitmap

Report type indicates the

type of CSI

measurement

to report.

First

bit=Rank,

Second

bit=subband

CQI.

Reporting 0 ENUMERA Periodicity for YES ignore Periodicity of TED(5ms, CSI

CSI 10ms, Measurement

Measurement 20ms,40ms, Report

Report 80ms, Periodic

aperiodic,

^■■■ ) Condition Explanation ifRegistrationRequestStop This IE shall be present if the Registration Request IE is

set to the value "stop".

Range bound Explanation maxCellineNB Maximum no. cells that can be served by an eNB. Value

is 256.

[00160] 9.1.2.14 RESOURCE STATUS UPDATE

[00161] This message is sent by eNB ₂ to neighbouring eNBi to report the results of the requested measurements.

[00162] Direction: eNB ₂ → eNB i .

[00163] 9.2.aa UE-C SI Report

[00164] This IE provides UE-CSI information for a set of UEs served by eNB ₂ .

Table C2

combinatorial index.

Subband COIs are

sorted in the order of

increasing

frequency.

»»Subband CQI M INTEGER

for codeword 0 (0..15, ...)

»»Subband CQI 0 INTEGER

for codeword 1 (0..15, ...)

»UE-CSI process M FFS CSI process

Configuration configuration

information information.

[00165] We now consider eR TP exchange.

[00166] It has been agreed that eRNTP will be delivered with the Load Information message.

[00167] In the following, we provide our views on content of this message, as well as a proposal.

[00168] C3. Discussion

[00169] C3.1 eRNTP exchange

[00170] One concern is that a receiving eNB does not have the means to differentiate the

"meaning" of the CoMP hypothesis. In particular, a potential issue is that the signaled hypothesis could be a "suggestion" by the sender or an "action" which implies that the pattern in the hypothesis will be applied. A proposed solution to this issue is to introduce an indicator IE in the CoMP Information IE to convey that the constituent resource allocation is an action. This proposal can be useful if a common pre-configured threshold is used (or implicitly assumed) with or with our this indicator IE. In other words, the "suggestion for" as well as the "action" by an eNB (or cell) are based on a common threshold (pre-configured for that eNB or cell and known to its neighbors). Another slightly more preferable option is to enhance and use the existing RNTP in order to convey the "action". The enhancements can be done in two ways. The contents are captured in two corresponding proposals attached in the sequel.

[00171] The first presented proposal is based on a single threshold and exploits that fact that the

RNTP (i.e., downlink (DL) power restriction) for the first subframe (subframe #0) is always conveyed. Then, if no information about the DL power restriction on any subsequent subframe is conveyed, the one conveyed for the first subframe can be assumed to remain static (i.e., applicable over subsequent sub frames).

[00172] The second proposal is based one multiple thresholds. The point here is that since the choice ' 11 ' already indicates no promise on the power level (which covers the case of transmit power being arbitrarily high) we can use three thresholds (instead of two), since there is no need to convey that the power level is greater than HPTH (as this is subsumed by ' 11 ')

[00173] Proposal:

[00174] 9.2.19 Relative Narrowband Tx Power (RNTP)

[00175] This IE provides an indication on DL power restriction per PRB in a cell and other information needed by a neighbour eNB for interference aware scheduling.

Table C3

subframes.

RNTP M ENUME AT RNTPtiires oid is Threshold ED (-∞, -11, defined in TS

36.213 [11].

-10, -9, -8, -7,

-6, -5, -4, -3,

-2, -1, 0, 1, 2,

3, ...)

Number Of M ENUMERAT P (number of Cell-specific ED (1, 2, 4, antenna ports for Antenna Ports ...) cell-specific reference signals) defined in TS 36.211 [10]

P_B M INTEGER P _B is defined in TS

(0..3, ...) 36.213 [11]. PDCCH M INTEGER Measured by

Interference (0..4, ...) Predicted Number

Impact Of Occupied

PDCCH OFDM

Symbols (see TS 36.211 [10]).

Value 0 means "no prediction is available".

Extended O BIT STRING Each position in RNTP Per (6..4290, ... the bitmap PRB represents a PRB in a subframe, for which value " 1 " indicates 'no promise on the Tx power is given' and value "0" indicates 'Tx not exceeding RNTP threshold.'

The first bit corresponds to PRB 0 of the first subframe for which the extended RNTP per PRB IE is valid, the second bit corresponds to PRB 1 of the first sub frame for which the extended RNTP per PRB IE is valid, and so on.

The length of the bit string is an integer (maximum 39) multiple of nDLRB, which is defined in TS 36.211 Γ101.

The bit string may span across multiple contiguous subframes.

The pattern across contiguous subframes (formed bv RNTP per PRB and extended RNTP per PRB) is continuously repeated

RNTP per 0..1

PRB start time

>Starting SFN M INTEGER SFN of the radio

(0..1023, ...) frame containing the first subframe when the RNTP Per PRB IE is valid.

>Starting M INTEGER Subframe number, Sub frame (0..9, ...) within the radio Index frame indicated by the Start SFN IE, of the first subframe when the RNTP Per PRB IE is valid.

[00176] The second alternative is given below.

Table C4

01 - power level between LPTH and MPTH;

10 - power level between MPTH and HPTH;

1 1 - no promise on the Tx power is given.

The first 2 bits correspond to PRB 0 of the first subframe for which the IE is valid, the following 2 bits correspond to PRB 1 of the first subframe for which the IE is valid, and so on. The bit string may span across multiple contiguous subframes. The length of the bit string is an integer

(maximum 40) multiple of nDLRB. The parameter is defined in TS 36.21 1 [101. The ERNTP pattern is continuously repeated with a periodicity indicated in Periodicity.

Transmitted

power levels

LPTH (Low M ENUMERAT Lower RNTP

Power ED power threshold,

Threshold) usinq the

RNTPthreshnlH defined in TS

MPTH M ENUMERAT Medium RNTP (Medium ED ί power threshold, Power usinq the Threshold) RNTPthrPihnlrl defined in TS

HPTH (Hiah M ENUMERAT Hiaher RNTP

Power ED (-∞, power threshold,

Threshold) usinq the

RNTPthreshnlH defined in TS

Subframe

sequence

definition

>Start SFN M INTEGER SFN of the radio frame containing the first subframe where the RNTP Per PRB Per Subframe IE is valid.

>Start M INTEGER Subframe

Subframe (0..39) number, within

Number the radio frame indicated by the Start SFN \E, of the first subframe when the RNTP Per PRB Per Subframe IE is valid.

No. of M 1 ...40 No. of subframes subframes for which is defined the bitstream

Periodicity 1 ...40 The number of subframes after which the bit pattern is repeated

Number Of M ENUMERAT P (number of Cell-specific ED (1 , 2, 4, antenna ports for Antenna Ports ^■■■ ) cell-specific reference signals) defined in TS 36.21 1 [10]

P B M INTEGER P _B is defined in

(0..3, ...) TS 36.213 [1 1].

[00177] Embodiment D [00178] Dl. Introduction

[00179] In the following we provide our views on CSI and eRNTP exchange, as well as proposals containing the required message structures.

[00180] D2. Discussion

[00181] D2.1 CSI exchange: Configuring CSI processes

[00182] The concept of CSI processes was defined in Rel.11 to enable CSI feedback from a UE to its serving eNB. The CSI feedback is determined for each CSI process according to the serving TP and interference hypothesis configured in that process. . Each CSI process that is configured for a UE, comprises a set of resource elements on which non-zero power CSI-RSs are sent and a channel estimate is obtained by that UE using observations received on those resource elements.

[00183] In addition, a set of resource elements is also indicated by the CSI process (referred to as interference measurement resources (IMRs)) on which the UE estimates the covariance of the interference it observes. The channel and covariance estimates are together used by the UE to determine and send its feedback report corresponding to that CSI process. Multiple such CSI processes (up-to 4) can be configured for a UE, each process corresponding to a different choice of signal or interference hypothesis. Moreover, in the scenario in which fast switching of the serving TP is not possible, different CSI processes that are configured for any given UE typically correspond to different choices of interference hypothesis.

[00184] Note from the brief discussion above that in the event the interference hypothesis of a configured CSI process presumes muting from a TP (that is a dominant interferer for the UE of interest) which is controlled by the neighboring eNB, coordination among the eNBs is required in order to ensure that the interference estimated by the UE on the constituent IMRs is consistent with the assumed hypothesis. Another similar event that requires coordination is if the non-zero power CSI-RSs indicated in the CSI process must be interference protected in order to ensure reliable channel estimation at the UE. In both these events, the dominant interferer that is controlled by the neighboring eNB must be muted on certain resource elements. Thus, a mechanism (with appropriate signaling) should be available to share the CSI-RS (comprising non-zero power CSI-RSs and IMRs) configurations between eNBs, which would facilitate configuration of CSI processes across multiple eNBs.

[00185] Once the CSI processes are configured, the CSI exchanged among eNBs over the backhaul should include the respective CSI process configuration information, in order to convey the conditions under which the CSI was measured by the UE. This configuration information includes non-zero power CSI-RS information and IMR information (comprising the subframe indices and zero-power CSI-RS information). Since this configuration is anyway informed to the UE via RRC (or higher layer) signaling, the same information can be reused as a container to convey the configuration to the neighboring eNB. [00186] Another way of conveying this configuration information is through a look-up-table. A look-up-table mapping an index to one or more distinct applied CSI process configurations can be constructed for each eNB. Here, by an applied CSI process we mean a process that is used by at-least one UE served by that eNB to measure its CSI. Such a table can be exchanged among neighbors first and from then on the configuration information can be exchanged via indices. The total number of configurations in the table can be limited in order to limit signaling overhead.

[00187] Suitable values for the number of configurations in this table are either 8 or 16 or 32.

[00188] D2.2 CSI exchange: Contents

[00189] One eNB can send CSI report pertaining to one or more of UEs to a neighboring eNB.

For each UE, the CSI that the eNB sends to a neighbor can comprise:

[00190] CQI: up-to 2 CQIs, each including a wideband component and possible sub-band differential components

[00191] RI: one wideband component

[00192] We note that the PMI was excluded from the CSI exchange report [1]. The justification for this exclusion was to minimize the overhead and the fact that PMI can depend on fast changing channel information, thus reducing its utility over non ideal backhaul with a higher latency. However, in the absence of PMI the use of RI is limited. Indeed, any rank greater than 1 will convey only 2 CQI(s), one for each of the two codewords. No further information about the (average) spatial directions seen by that UE can be deduced by the eNB receiving the report. As a result, reporting the RI should be made optional. Moreover, the eNB requesting the CSI report should be able to specify whether or not it would like to receive RI reports. Similarly, the eNB requesting the CSI reports should be able to specify whether or not it requires subband specific CQI reports. This can be achieved by setting a bit (in the measurement request) to be 0 if rank is not requested and 1 otherwise. Another bit can be set to 0 if subband CQIs are not requested and 1 otherwise.

[00193] Processing (filtering or subsampling) of the short-term CSI (received via over-the-air signaling) at an eNB prior to exchange should be permitted. [00194] One use case for this is when the periodicity of the CSI report that is requested by eNBl to its neighbor eNB2, is larger than the over-the-air CSI signaling periodicity configured by eNB2. In this case eNB2 has to do some processing (such as subsampling or averaging) of the reports it receives before it sends it to eNB 1. In this context, we note that the subsampling employed by eNB2 should be understood by eNBl (if needed additional signaling can be added to ensure this). One possible way this can be accomplished (without any signaling overhead) is for eNB2 to use the subsampling factor determined by a pre-determined rule (known to or configured for all eNBs in advance) that outputs a subsampling factor, given the requested periodicity and CSI process configuration as inputs. On the other hand, averaging or scaling or filtering employed by eNB2 can be transparent to the receiving eNBl .

[00195] One of the goals of CSI exchange is to facilitate centralized RRM [3]. In a scenario with centralized RRM, the central node receiving the CSI reports should be able to keep track of the CSI information received for each particular UE, over all the received CSI reports. This can be achieved by including a UE identifier in each CSI report for each UE whose CSI is conveyed in that report. We want to include a unique ID for each user so that the receiving node knows which ones among all the reports that it receives, belong that user. This will be useful for RRM. Otherwise the receiving eNB will regard each received report as belonging to a distinct user. This can lead to sub-optimal resource allocation.

[00196] D2.3 eRNTP exchange

[00197] Our view on eRNTP exchange is captured in a corresponding proposal attached in the end of this embodiment.

[00198] We note that the RNTP (i.e., downlink (DL) power restriction) for the first subframe is always conveyed. If no information about the DL power restriction on any subsequent subframe is conveyed, then the one conveyed for the first subframe can be assumed to remain static (i.e., applicable over subsequent subframes).

[00199] We also present several variations, one of which includes the use of multiple thresholds

[00200] D3. Conclusion

[00201] We discussed the necessary X2 message to support CSI and eRNTP exchange for inter-eNB CoMP and presented corresponding proposals.

[00202] Proposal: [00203] 9.1.2.11 RESOURCE STATUS REQUEST

[00204] This message is sent by an eNBi to a neighbouring eNB ₂ to initiate the requested measurement according to the parameters given in the message.

[00205] Direction: eNBi→ eNB ₂ .

Table Dl

Periodic, this bit

should be set to

1 if at least one

of the First,

Second or Third

bits is set to 1 ,

Fifth Bit = ABS

Status

Periodic, Xth Bit

= UE-CSI

Periodic.

Other bits shall

be ignored by

the eNB ₂ .

Cell To 1 Cell ID list for YES ignore Report which

measurement is

needed

>Cell To 1 .. EACH ignore Report Item <maxCelli

neNB>

»Cell ID M ECGI

9.2.14

Reporting 0 ENUMERA YES ignore Periodicity TED(1000m

s, 2000ms,

5000ms, 10

000ms, ...)

Partial 0 ENUMERA Included if YES ignore

Success TED(partial partial success

Indicator success is allowed

allowed, ...)

CSI 0 BITSTRING Each position in YES ignore

Measurement (SIZE(2)) the bitmap Report type indicates the

type of CSI

measurement to

report.

First bit=Rank,

Second

bit=subband

CQI.

((Reporting 0 ENUMERA Periodicity for YES ignore

Periodicity of TED(5ms, CSI

CSI 10ms, Measurement

Measurement 20ms,40ms, Report Periodic

Report 80ms,

aperiodic,

^■■■ )

[00206] 9.1.2.14 RESOURCE STATUS UPDATE

[00207] This message is sent by eNB ₂ to neighbouring eNBi to report the results of the requested measurements.

[00208] Direction: eNB ₂ → eNB i . Table D2

Group

»ABS 0 9.2.58 YES ignore Status

» UE-CSl 0 9.2.X1 YES ignore Report

[00209] 9.2.xl UE-CSI Report

[00210] This IE provides UE-CSI information for a set of UEs served by eNB ₂ .

Table D3

»>Subba 0 BIT STRING Cf. TS 36.213

nd CQI for (SIZE (2)) [7.2.3].

codeword

1

»UE-CSI M FFS CSI process

process configuration

Configuratio information.

n

information

[00211] Alternatively, the parameter maxUEsubsetCSIReport can be 8 or 64. Further, optionally, the UE-ID can have a more compact representation using say 8bits or 6bits or 5 bits (equivalently 256 or 64 or 32 possible indices from a configurable table).

[00212] Next, we consider the case when subband indices have to be indicated. This is important to accommodate feedback modes that involve UE selected subband feedback.

Table D4

codeword 1 (SIZE (4))

>»Subband index O INTEGER Included in case of

(0..27, ...) UE selected

subband CQI

reporting.

»UE-CSI process M FFS CSI process

Configuration configuration

information information.

[00213] Note that as an alternative in the above tables, for each CQI the bit string field of 4 bits (2 bits) can be replaced by INTEGER (0..15, ...) (INTEGER (0..7, ...)).

[00214] In another alternative the sub band indices can be conveyed by means of a combinatorial index which is described next.

[00215] The idea here is that depending on the number of PRBs (or RBs for short) in the downlink available at sending eNB2 (a parameter which is known or conveyed separately to the receiving eNBl) , the set of all possible subband selections that can be made together with the subband size for each feedback mode can be deduced by eNBl .

[00216] For example when 110 RBs are available at eNB2 (and this number is conveyed to eNBl) eNBl can deduce that for a UE configured under:

[00217] Aperiodic, Mode 2-*: 6 UE selected subband indices

[00218] A subframe is composed of 28 subbands. Among 28 subbands, 6 subbands are selected by the UE. The number of PRBs in the subbands is 4 except for the last one; the number of PRBs in the last subband is 2 (4*27 + 2 = 110).

[00219] For Aperiodic, Mode 3-*: 14 higher layer-configured sub bands

[00220] A subframe is composed of 14 subbands. The number of PRBs in the subband is 8 except for the last one; the number of PRBs in the last subband is 6 (8* 13 + 6 = 1 10).

[00221] For Periodic, Mode 2-*: 4 UE selected subband indices (with an additional constraint on choosing one sub band per bandwidth portion or part)

[00222] A subframe is composed of 14 subbands. Among 14 subbands, 4 subbands are selected by the UE. The number of PRBs in the subbands is 8 except for the last one; the number of PRBs in the last subband is 6 (8* 13 + 6 = 110). [00223] Then, considering all possible feasible subband selections under all the aforementioned feedback modes, it is possible to assign a unique label to each distinct feasible selection of sub bands. All possible such labels together decide the range of a combinatorial index R. As a result, knowing the value of R the receiving eNB can deduce the subband selection. The associated CQIs (one for each subband in the indicated selection) can be ordered in the increasing order of the frequency range represented by the indicated subbands. Each such CQI can be conveyed using full representation (i.e., using 16 possibilities) which can then be directly used by the receiving eNBl .

Table D5

Codeword 1 (SIZE (4))

» combinatorial O Integer FFS This IE is present

index only if associated

request wants

subband CQI

»>Subband CQI List 0..<maxCQISubb The number of

ands > subbands in the list

as well as their

respective indices

and sizes are

deduced from the

combinatorial index.

»»Subband CQI M BIT STRING

for codeword 0 (SIZE (4))

»»Subband CQI 0 BIT STRING

for codeword 1 (SIZE (4))

»UE-CSI process M FFS CSI process

Configuration configuration

information information.

[00224] UE configuration independent coding structure

[00225] A coding structure for signaling CSI over X2 in a UE-configuration independent way is shown in Table II . In this structure, a subband is defined as a set of contiguous PRBs having the same CQI value. The subband partitioning is left to the sending eNB2 implementation, and is not restricted by the UE's CSI reporting configuration. Each indicated CQI follows the definition of a 4 bit CQI (Cf. TS 36.213). This allows for the sending eNB2 to process the CSI it receives from the UE in any manner as long as each indicated CQI is consistent with the basic CQI definition. The receiving eNBl can directly use these CQIs while being agnostic to how they were procured and processed by eNBl . Table D6 UE configuration independent coding structure

the list.

»>Subband Size 0 INTEGER(1..1 Number of

10, ...) contiguous PRBs in the subband. If this IE is not present, the value is the same as the previous subband in the list.

»>Subband CQI for M INTEGER(0..1

Codeword 0 5, ...)

»>Subband CQI for 0 INTEGER(0..1

Codeword 1 5, ...)

[00226] We note here that reporting full (complete) CQI (with 16 possibilities) for each indicated subband CQI instead of differential CQI is useful since otherwise the receiving eNBl may not know how to combine a corresponding wideband CQI and differential sub-band CQI (with fewer than 16 possibilities) in order to obtain the full CQI for that subband, for instance, in the case that the precise feedback mode configured for the UE of interest under that CSI process is not conveyed to the receiving eNBl . We note here also that it might be desirable to not impose restrictions on sending eNB2 on how it combines reports from multiple different feedback modes configured for that UE under the same CSI process. Then, note that when aperiodic feedback mode 3-1 is configured for the UE (by eNB2), the UE reported sub band CQI is encoded differentially with respect to the corresponding wideband CQI using 2 bits representing differential values {-2, 0,1,2} . On the other hand, in the case of aperiodic feedback mode 2-0 or 2-2, only the best M-average is reported by the UE by differentially encoding it with respect to a corresponding wideband CQI using 2 bits representing differential values {1, 2,3,4} . Further, in case of periodic feedback mode 2-1 the CQI corresponding to codeword- 1 for each UE selected subband within a bandwidth part can itself be of 4 bits, whereas that of codeword-2 (when RI>1) is differentially encoded with respect to CQI of codeword- 1 using 3 bits.

[00227] It becomes apparent from the above discussion that a transparent way of conveying CQI

(without having to convey all details regarding to one or more feedback modes configured under that CSI process for that UE) is to allow for full (complete) CQI for each indicated subband.

[00228] Another issue that is important, is to ensure that the RI and CQIs conveyed by eNB2 to eNBl in a UE CSI report are mutually consistent, i.e., all the reported CQIs are computed by the UE for the same RI (which is identical to the one in the Rank Indication IE when the latter is present). This issue is important to address because under certain feedback modes (such as periodic mode 2-1) the RI and the wideband CQI(s) as well as the subband CQI(s) for one or more bandwidth portions can be reported by the UE on different subframes. Thus, depending on the periodicity defined by eNBl in its CSI request, it can happen that the latest RI available for the UE under the CSI process, can be different from the one for which the most recent CQI(s) are computed. In such a case, the sending eNB2 should ensure that its CSI report is consistent, for instance by using the RI value for which the most recently available CQI(s) have been computed. [00229] The variation (which allows the requesting eNB to specify whether or not it wants to receive subband CQI(s) or Rank Indication is provided below. In this context, we note that since the requesting eNBl has no control over how eNB2 configures CSI processes (and constituent feedback modes) for its users, it should be in any case able to exploit different type of CSI reports (wideband only or wideband and subband).

Table D7

nd> request wants subband CQI. In that case subbands are listed in the order of increasing frequency.

»>Subband Start 0 INTEGER(0..1 PRB number of the

09, ...) first PRB in the subband. If this IE is not present, the subband is contiguous with the previous subband in the list, or starts with PRB 0 if this is the first subband in the list.

»>Subband Size 0 INTEGER(1..1 Number of

10, ...) contiguous PRBs in the subband. If this IE is not present, the value is the same as the previous subband in the list.

»>Subband CQI for M INTEGER(0..1

Codeword 0 5, ...)

»>Subband CQI for 0 INTEGER(0..1

Codeword 1 5, ...) [00230] Another variation which allows for further simplification at the expense of not being bit efficient is as follows. Here the full CQIs for all possible subbands (which can be determined by the number of PRBs in the downlink available at eNB2) are always conveyed for a UE under the CSI process. In case the sub band CQI is not reported by a UE under the configured feedback mode for a subband, the sending eNB2 simply uses the wideband CQI value for that subband.

[00231 ] 9.2.19 Relative Narrowband Tx Power (RNTP)

[00232] This IE provides an indication on DL power restriction per PRB in a cell and other information needed by a neighbour eNB for interference aware scheduling.

Table D8

This IE is used to indicate DL power restriction per PRB for the first subframe. In case the DL power restriction is static, the indicated DL power restriction is maintained over the subsequent subframes.

RNTP M ENUMERA RNTPthreshold IS Threshold TED (-∞, defined in TS

-1 1 , -10, -9, 36.213 [1 1]. -8, -7, -6, -5,

-4, -3, -2, -1 ,

0, 1 , 2, 3,

■ ^■■ )

Number Of M ENUMERA P (number of Cell-specific TED (1 , 2, 4, antenna ports Antenna ^■■■ ) for cell-specific Ports reference

signals) defined in TS 36.21 1 [10]

P_B M INTEGER P _B is defined in

(0..3, ...) TS 36.213 [1 1]. PDCCH M INTEGER Measured by

Interference (0..4, ...) Predicted

Impact Number Of

Occupied PDCCH OFDM

Symbols (see TS 36.21 1 [10]).

Value 0 means "no prediction is available".

Extended O BIT Each position in RNTP Per STRING the bitmap PRB (6..4290, represents a

■ ^■■ ) PRB in a

subframe, for which value "1 " indicates 'no promise on the Tx power is given' and value "0" indicates Tx not exceeding RNTP

threshold.' The first bit corresponds to PRB 0 of the first subframe for which the extended RNTP per PRB IE is valid, the second bit corresponds to PRB 1 of the first subframe for which the extended RNTP per PRB IE is valid, and so on. The length of the bit string is an integer (maximum 39) multiple of is defined in TS

36.21 1 [10]. The bit string may span across multiple contiguous subframes. The pattern across contiguous subframes (formed by RNTP per PRB and extended RNTP per PRB) is continuously repeated.

RNTP per 0..1

PRB start

time

>Starting M INTEGER SFN of the radio SFN (0..1023, frame containing

^■■■ ) the first subframe when the RNTP Per PRB IE is valid.

>Starting M INTEGER Subframe

Subframe (0..9, ...) number, within

Index the radio frame indicated by the Start SFN IE, of the first subframe when the RNTP Per PRB IE is valid. [00233] An alternate Table for RNTP enhancement is given below.

Table D9

RNTP M ENUMERA RNTPthreshold IS Threshold TED (-∞, defined in TS

-11,-10, -9, 36.213 [11]. -8, -7, -6, -5,

-4, -3, -2, -1,

0, 1, 2, 3,

■ ^■■ )

Number Of M ENUMERA P (number of Cell-specific TED (1,2, 4, antenna ports Antenna Ports ^■■■ ) for cell-specific reference signals) defined in TS 36.211 [10]

P_B M INTEGER P _B is defined in

(0..3, ...) TS 36.213 [11].

PDCCH M INTEGER Measured by

Interference (0..4, ...) Predicted

Impact Number Of

Occupied PDCCH OFDM

Symbols (see TS 36.211 [10]).

Value 0 means "no prediction is available".

RNTP Per O BIT Each position in PRB per STRING the bitmap subframe (6..4400, represents a ■ ^■■ ) PRB in a

subframe, for which value "1 " indicates 'no promise on the Tx power is given' and value "0" indicates Tx not exceeding RNTP

threshold.' The first bit corresponds to PRB 0 of the first subframe for which the RNTP per PRB per subframe IE is valid, the second bit corresponds to PRB 1 of the first subframe for which the RNTP per PRB per subframe IE is valid, and so on.

The length of the bit string is an integer (maximum 40) multiple of ■ ^ ^L is

defined in TS 36.21 1 [10]. The bit string may span across multiple contiguous subframes. The pattern across contiguous subframes formed by RNTP per PRB per subframe IE is continuously repeated.

RNTP per 0..1

PRB per

subframe

start time

>Starting M INTEGER SFN of the radio SFN (0..1023, frame containing

^■■■ ) the first subframe when the RNTP Per PRB Per Subframe IE is valid.

>Starting M INTEGER Subframe

Subframe (0..9, ...) number, within

Index the radio frame indicated by the Start SFN IE, of the first subframe when the RNTP Per PRB Per

Subframe IE is

valid.

[00234] Another alternate Table for RNTP enhancement is given below.

Table D10

is present.

RNTP M ENUMERA RNTPthreshold IS Threshold TED (-∞, defined in TS

-11,-10, -9, 36.213 [11]. -8, -7, -6, -5,

-4, -3, -2, -1,

0, 1, 2, 3,

■ ^■■ )

Number Of M ENUMERA P (number of Cell-specific TED (1,2, 4, antenna ports Antenna Ports ^■■■ ) for cell-specific reference signals) defined in TS 36.211 [10]

P_B M INTEGER P _B is defined in

(0..3, ...) TS 36.213 [11]. PDCCH M INTEGER Measured by

Interference (0..4, ...) Predicted

Impact Number Of

Occupied PDCCH OFDM

Symbols (see TS 36.21 1 [10]).

Value 0 means "no prediction is available".

RNTP Per O BIT Each position in PRB per STRING the bitmap subframe (6..4400, represents a

PRB in a subframe, for which value "1 " indicates resource with no utilization constraints' and value "0" indicates 'interference protected resource.' The first bit corresponds to PRB 0 of the first subframe for which the RNTP per PRB per subframe IE is valid, the second bit corresponds to PRB 1 of the first subframe for which the RNTP per PRB per subframe IE is valid, and so on.

The length of the bit string is an integer (maximum 40) multiple of

■ is defined in TS 36.21 1 [10]. The bit string may span across multiple contiguous subframes. The pattern across contiguous subframes formed by RNTP per PRB per subframe IE is continuously repeated.

RNTP per 0..1

PRB per

subframe

start time

>Starting M INTEGER SFN of the radio SFN (0..1023, frame containing

^■■■ ) the first subframe when the RNTP Per PRB Per Subframe IE is valid.

>Starting M INTEGER Subframe

Subframe (0..9, ...) number, within

Index the radio frame indicated by the Start SFN IE, of the first subframe

when the RNTP

Per PRB Per

Subframe IE is

valid.

[00235] Another alternative using multiple thresholds conveyed via 2 bits is given below.

Table Dll

1 1 - no promise on the Tx power is given.

The first 2 bits correspond to PRB 0 of the first subframe for which the IE is valid, the following 2 bits correspond to PRB 1 of the first subframe for which the IE is valid, and so on.

The bit string may span across multiple contiguous subframes. The length of the bit string is an integer (maximum 40) multiple of . The parameter is defined in TS 36.21 1 [10]. The ERNTP pattern is continuously repeated with a periodicity indicated in Periodicity. Transmitted

power levels

LPTH (Low M ENUMERA Lower RNTP

Power TED (-∞, power

Threshold) -11,-10, -9, threshold, using

-8, -7, -6, -5, the

-4, -3, -2, -1, RNTPthreshold 0, 1, 2, 3, defined in TS ■ ^■■ ) 36.213 [11].

MPTH M ENUMERA Medium RNTP (Medium TED (-∞, power

Power -11,-10, -9, threshold, using Threshold) -8, -7, -6, -5, the

-4, -3, -2, -1, RNTPthreshold 0, 1, 2, 3, defined in TS ■ ^■■ ) 36.213 [11].

HPTH (High M ENUMERA Higher RNTP

Power TED (-∞, power

Threshold) threshold, using

-11,-10, -9,

the RNTP _thresh0 | _d -8, -7, -6, -5,

defined in TS -4, -3, -2, -1,

36.213 [11]. 0, 1, 2, 3,

^■■■ )

Subframe

sequence

definition

>Start SFN M INTEGER SFN of the radio

(0..1023) frame

containing the first subframe where the RNTP Per PRB Per Subframe IE is valid.

>Start M INTEGER Subframe

Subframe (0..39) number, within

Number the radio frame indicated by the Start SFN \E, of the first subframe when the RNTP Per PRB Per Subframe IE is valid.

No. of M 1 ...40 No. of subframes subframes for which is defined the bitstream

Periodicity 1 ...40 The number of subframes after which the bit pattern is repeated

Number Of M ENUMERA P (number of Cell-specific TED (1 , 2, antenna ports Antenna Ports 4, ...) for cell-specific reference signals) defined in TS 36.21 1 [10]

P B M INTEGER P _B is defined in

(0..3, ...) TS 36.213 [1 1]. [00236] The point in the table given above is that since the choice Ί Γ already indicates no promise on the power level (which covers the case of transmit power being arbitrarily high) we can use three thresholds (instead of two) since there is no need to convey that the power level is greater than HPTH (as this is subsumed by Ί 1 ').

[00237] However, one problem with indicating multiple thresholds is that the current CoMP hypothesis (implicitly) assumes just one threshold. In this sense there is a mismatch between using multiple thresholds in eRNTP and not in the CoMP hypothesis. Consequently, the full potential of multiple thresholds may not be realized inspire of the additional overhead.

[00238] Suppose that there are L subband selection types denoted by {(Ni, q- ), ^■■■ , (N _L , ¾)}, where the I ^th selection type is defined by N _b q _t which denote the total number of subbands and the number of subbands that must be selected, respectively, under that type. Note that under each selection type the size of each subband is fixed and known a-priori. Further, suppose that there are / bandwidth portions, each portion comprising Sj, 1 < j≤ J subbands. Only one subband is selected from the Sj subbands in each bandwidth portion j E {1, ·· · ,/}. Further since the user sequentially reports its CSI report for the bandwidth portions, we can impose a nested structure on the corresponding exchange of CSI from sending eNB2 to receiving eNBl . In particular, we impose the structure under which the CSI of any subband in the j ^th portion is sent only if the CSI of a suband in each of the preceeding j— 1 bandwidth portions are sent. This structure enables efficient exchange of CSI without any loss of generality. Thus, overall there are L + J different selection types possible (with the last / types associated with the selctions from bandwidth portions). Then, each selection in the total number of distinct subband selections can be identified by a combinatorial index R whose range is given by

' ^A " ^{*i = 1} t-i ) . We next discuss the generation of the index at the sending eNB followed by the determination of the particular selection from the index at the receiving eNB. Towards this end, we define a set of offsets as follows:

Oi = 0 _/ _ _! -h ^-'V / = 2, . . - , L -h l

V ^{qi~ l} J and 0 ₁ = 0. Further, we set O _l = +

[00239] Generation of index at sending eNB

[00240] · At the sending eNB, first identify the selection type I. [00241] · If I E {1, ^■■■ ,L} then q _t subbands are selected from N _t total subbands. Let

■ ^■■ , m _{g !} be the selected subband indices that are ordered, i.e., m ₀ < m ₁ < ··· < m _qi -i and all lie

[00242] · Else I E {L + 1, ··· , L +/}. Let m , ^■■■ , m.i_ _L denote the chosen subband indices, one from each of the first I— L bandwidth portions, and where rrij E {1 ··· , Sj},j = 1, ^■■■ . I— L. Set

R = O _t + Π¾ j - 1.

[00243] Retrieving subband selection from index at receiving eNB

[00244] · At the receiving eNB, find the greatest / such that O _l < R.

[00245] · If I E {1, ···,!} then q _t subbands have been selected from N _t total subbands. Let m ₀ , ^■■■ , m _qi -i be the ordered subband indices that need to be determined. Initialize a = l,r = R— O _t .

• For k = 0, ^■■■ , q _t — 1 Do

- While Q > r Do: b = b + 1 and : EndWhile

[00249] - m _k = b, a = b + 1, r = r-Q.

[00250] · Else I E {L + 1, ··· , L +/}. Let m , ^■■■ , m.i_ _L denote the subband indices that need to be determined, one from each of the first I— L bandwidth portions, and where rrij E {1 ··· , Sj},j = 1, ^■■■ .1— L. Set r = R- 0 ₀ B = l-L and A =S ₁ x ··· xS _B .

[00251] • For k Ι,-,Β- l Do

[00252] - A A/S _k , in = l _^ -J and m _k = in + 1.

[00253] - Update r = r— fhS _k

[00254] . m _B = r + 1

[00255] Embodiment E

[00256] El Introduction

[00257] We summarize the 3 options for subband definition, and provide enhancements for them, together with an enhancement for eRNTP (enhanced Relative Narrowband Tx Power).

[00258] E2 Summary of solutions

[00259] General notes: [00260] - All the following options allows eNB to "process" CQI (channel quality indication) values (implementation based manner) before sending over X2.

[00261] - Some of the main differentiators between the options are:

[00262] 1) Simplicity, if sending eNB implementation only sends "raw" CSI (Channel State

Information) Option A, C (albeit only with the respective enhancements)

[00263] 2) Flexibility, if sending eNB implementation processes CSI (e.g. combines or merges overlapping Periodic and Aperiodic reports) Option B, C

[00264] Option A: Subband Index + Report Type

Table El

[00265] Notes for Option A:

[00266] - Primary Motivation: Allows serving eNB to send CSI reports over X2 with as little processing as possible

[00267] - Description: The subband partitioning is fixed, based on the UE's CSI reporting configuration. The Report Type and Subtend Index IEs are used by the receiving eNB to derive the subband positions and their size and total number of subbands. The latter information is also important since it will enable receiving eNB to determine what the differential CQI conveyed for that subband means. This is because in aperiodic mode 3-0 (or 3-1) and aperiodic mode 2-0 (or 2-2) the same differential value can be mapped to different offsets, respectively. Thus, the only way the receiving eNBl can deduce the right offset value to use is to utilize the fact that for the given system bandwidth (or given total number of PRBs (physical resource blocks) available at sending eNB2 (which is known or conveyed separately to eNBl)) the number of sub bands for which CQIs are reported is distinct under those two aperiodic modes, respectively. Another alternative is to convey the exact configured feedback mode (such as aperiodic 3-1 etc) under the Report type IE (infromation element).

[00268] - Allows sending "raw" CQI over X2, in a format similar to what is received from the UE (i.e. Subband Index)

[00269] - Allows sending both Periodic and Aperiodic reports in the same X2 message; in case of overlapping Aperiodic and Periodic CSI reports, the handling is left to receiving eNB

implementation (e.g. merge, discard, etc). We note that sending two reports in the same message is beneficial since otherwise several reports may need to be dropped by the sending eNB in order to comply with the one report per X2 message constraint and the periodicity configured for the X2 messages.

[00270] However, a problem in sending both aperiodic and periodic subband reports together in the same X2 message as per the aforementioned structure, is that the associated reference wideband reports that are used to compute them can be different. In particular, the wideband rank indicators (RIs) that are determined by the UE under the configured aperiodic mode and the configured periodic mode can be different. Similarly, the wideband CQIs determined by the UE under the configured periodic mode and the configured aperiodic mode can be different. Furthermore, each subband CQI determined under the aperiodic mode is reported by the UE (over PUSCH (physical uplink shared channel)) as a differential value with respect to the corresponding wideband CQI. For example, suppose aperiodic feedback mode 2-2 and periodic feedback mode 2-1 are configured. Then, under the aperiodic mode 2-2 the UE will report one wideband CQI (per codeword) as well as one subband CQI (per codeword) for the selected best-M feedback as a differential value (using 2 bits) with respect to the wideband CQI corresponding to that codeword. On the other hand, under the periodic 2-1 mode the UE will report (over PUCCH (physical uplink control channel)) one wideband CQI (per codeword), with the wideband CQI of the second codeword being reported as a differential value with respect to the wideband CQI of the first one. In addition the UE will report one subband CQI for the first codeword and the second CQI as a differential value with respect to the subband CQI of the first one.

[00271] Therefore it becomes clear that we need to have separate sets of RIs and wideband CQIs in the X2 message whenever that message contains both aperiodic and periodic subband reports. If such separate sets of wideband components are not included then the receiving eNB will use the same wideband RI or CQI(s) for both aperiodic and periodic information. This defeats the purpose of conveying separate aperiodic and periodic subband reports in the same X2 message.

[00272] We propose an optimized structure in the following as a remedy to this issue.

Table E2

CSI Report per UE 1 ..

<maxUERepo

rt>

>UE ID M BIT STRING ID of the UE served

(SIZE(16)) by the cell in eNB ₂ .

>CSI Report per 1 ..

CSI Process <maxCSIProc

ess>

» Report type per 0..1

CSI process

»>Report Type M ENUMERATED

(periodic,

aperiodic, ...)

»>RI M INTEGER (1..8, ...) Defined in TS

36.213 [1 1].

»>Wideband M 9.2. bb

CQI

»>Subband 0 ..

CQI List <maxSubban

d>

»»Subband M 9.2.CC

CQI

»»Subband INTEGER (0..27, Included in the case Index ^■■■ ) of UE selected subband CQI reporting.

Range bound Explanation maxUEReport Maximum number of UE measurement reports. Value is

128. maxCSIProcess Maximum number of CSI processes. The value is 4. maxSubband Maximum number of subbands. The value can be 14 or 15

or 16 or 17 or 18 or 28

[00273] The value of 15 for the maxSubband is computed as 14 + 1, where 14 is the number of subbands in an aperiodic mode 3-0 or 3-1 assuming 110 DL (downlink) RBs (resource blocks) and 1 other subband is for periodic mode 2-0 or 2-1 assuming subband report for one bandwidth portion is allowed in the X2 message. Similarly, values 16,17,18 are computed assuming subband report for 2,3,4 bandwidth portions, respectively, are allowed in the same X2 message.

[00274] The same problem identified above can also arise when the sending eNB sends two different reports (corresponding to a configured periodic mode or corresponding to a configured aperiodic mode). The presented optimized structure addresses even such cases since it allows for two reporting types per CSI process of each UE. Each one of those two reporting types can be both periodic or both aperiodic.

[00275] In this context, we note that the value of maxSubband equal to 28 arises when we allow for two aperiodic reports, for example 28= 14 + 14, where 14 is the number of subbands in an aperiodic mode 3-0 or 3-1 assuming 110 DL RBs.

[00276] Moreover, to provide further flexibility the range of the "Report type per CSI process" can be increased from two to a larger value such as 3 or 4 or 5.

[00277] 9.2.bb Wideband CQI

[00278] This IE indicates the Wideband CQI as defined in TS 36.213.

Table E3

Wideband absolute CQl M INTEGER (0..15, ...) Encoded in

Codeword 0 TS 36.213

[1 1 ].

CHOICE Wideband CQl 0

Codeword 1

>Wideband absolute CQl M INTEGER (0..15, ...) Encoded in

Codeword 1 TS 36.213

[1 1 ].

>Wideband differential CQl M INTEGER (0..7, ...) Encoded in

Codeword 1 TS 36.213

[1 1 ].

[00279] 9.2.CC Subband CQl

[00280] This IE indicates the Subband CQl as defined in TS 36.213.

Table E4

>Subband M INTEGER (0..15, Encoded in TS 36.213 [1 1].

absolute CQI ^■■■ )

Codeword 0

>Subband M INTEGER (0..3, ...) Encoded in TS 36.213 [1 1].

differential CQI

Codeword 0

CHOICE Subband 0

CQI Codeword 1

>Subband M INTEGER (0..15, Encoded in TS 36.213 [1 1].

absolute CQI ^■■■ )

Codeword 1

>Subband M INTEGER (0..7, ...) Encoded in TS 36.213 [1 1].

differential CQI

Codeword 1

>Subband M INTEGER (0..3, ...) Encoded in TS 36.213 [1 1].

differential CQI

Codeword 1

[00281] Other equivalent variations of the optimized structure are possible with the common theme being that a separate wideband component (comprising RI and wideband CQI(s)) is conveyed for the aperiodic and the periodic reports, respectively, and where the structure should allow the receiving eNB to unambiguously associate the periodic and aperiodic subband components with their respective wideband counterparts. Notice that under the optimized structure if only one of the aperiodic or periodic subband information is reported in the X2 message, it will include only the corresponding wideband information.

[00282] Notice also that under the aperiodic feedback modes (2-0 and 2-1) the UE reports common subband information for all the best-M subbands, thus in the structure presented above the sender eNB will repeat the same subband CQI for all the best-M indicated subbands. This repetition can be avoided by modifying the structure as follows. [00283] The subband CQI IE is made optional with the understanding that if this IE is not present the CQI for that subband is taken to be the same as that of the subband (closest to it in frequency and of the same reporting type) with a lower index for which the CQI has been conveyed in that message, with the restriction that the latter CQI must have been indicated.

[00284] Option B: Subband Start + Subband Size

Table E5

[00285] Notes for Option B:

[00286] - Primary Motivation: Enables greater implementation flexibility for sending

"processed" CQI in alignment with the RAN3 agreement that "the serving eNB can process CSI (implementation)", particularly for the case where UE is configured for both Aperiodic and Periodic CSI reporting [00287] - Description: The Subband Start and Subband Size IEs are used to explicitly

¾·» ⁽ · indicate the subbands. The subbands are restricted to those defined for the system bandwidth >«> .

[00288] - Allows sending "raw" CQI over X2, but in a different format than used by the UE

(i.e. Subband Start)

[00289] - Allows sending both Periodic and Aperiodic reports in the same X2 message; in case of overlapping Aperiodic and Periodic CSI reports, the sending eNB can process (e.g. merge) according to implementation-specific algorithms

[00290] We note that in this structure given for option-B since only one set of wideband components are included, the sending eNB must harmonize RIs and wideband CQIs that are received from a periodic and aperiodic reports or two different periodic reports or two different aperiodic reports, respectively. In this context, using absolute value for the subband CQIs is particularly beneficial since then such CQIs can be directly used without matching them to any sideband reference.

[00291] As another optimization in this structure the Subband CQI IE can be made optional in which case the CQI for this subband is assumed to be the same as that of the last preceding subband for which a CQI is indicated. The CQI for the first sub band is always indicated. This optimization helps to avoid redundancies that can arise for instance in conveying best-M feedback as described before.

[00292] We note that here maximum number of subbands can be 28 (assuming 110 DL RBs and subband size of 4 under aperiodic mode 2-0 or 2-2).

[00293] Option C : Subband Index + Subband Size

Table E6

Ignored if the Subband

Index corresponds to the highest frequency

subband.

[00294] Notes for Option C :

[00295] - Description: The Subband Size IE is used by sending eNB to explicitly indicate the subband partitioning (rather than receiving eNB deriving the subband partitioning based on information about the UE's CSI reporting configuration). The PRB number of the first PRB in the subband is calculated as (Subband Index x Subband Size).

[00296] - Allows sending "raw" CQI over X2, in a format similar to what is received from the UE (i.e. Subband Index)

[00297] - Allows sending both Periodic and Aperiodic reports in the same X2 message; in case of overlapping Aperiodic and Periodic CSI reports, the sending eNB can process (e.g. merge) according to implementation-specific algorithms

[00298] If overlapping Aperiodic and Periodic CSI reports are received, then sending eNB can (as implementation option) "split" the Periodic subband into two Aperiodic subbands over X2. Assumption is that, according to subband definitions in TS 36.213, a Periodic subband is always composed of two Aperiodic subbands.

[00299] Example: is 50, and eNB receives two CSI reports over Uu during a given interval:

Aperiodic Mode 2-* for subband index 1 (subband size 3) and Periodic Mode 2-* for subband index 0

(subband size 6). Then, eNB has several options for sending the information over X2:

[00300] a) Send both reports over X2 and let receiving eNB decide how to handle

[00301] b) Select one of the two reports to send over X2 (e.g. the latest report)

[00302] c) Merge the Aperiodic and Periodic reports into two Aperiodic reports over X2

(subband index 0 and 1)

[00303] The observation made in option- A regarding the need to send separate wideband components in case both aperiodic and periodic reports are sent on the same X2 message also holds in this case.

[00304] Thus, we need to modify option-C as the following: Table E7

CSI Report per UE 1 ..

<maxUEReport>

>UE ID M BIT STRING ID of the UE served

(SIZE(16)) by the cell in eNB ₂ .

>CSI Report per CSI 1 ..

Process <maxCSIProces

s>

» Refence type per CSI 0..1

process

»>Reference Type M ENUMERATE

D (periodic,

aperiodic, ...)

»>RI M INTEGER (1..8, Defined in TS

■ ^■■ ) 36.213 [1 1].

»>Wideband CQI M 9.2.bb

»Subband CQI List 0 ..

<maxSubband>

»>Subband CQI M 9.2.CC

»>Subband Index 0 INTEGER Included in case of

(0..27, ...) UE selected

subband CQI reporting.

»>Subband Size M ENUMERATE Corresponds to a

D (2, 3, 4, 6, 8, value of subband ■ ^■■ ) size k defined in TS

36.213 [1 1] for the system bandwidth. Ignored if the Subband Index corresponds to the highest frequency subband. [00305] Other equivalent variations of the optimized structure are possible with the common theme being that a separate wideband component (comprising RI and wideband CQI(s)) is conveyed as a reference for the aperiodic and the periodic subband reports, respectively, and where the structure should allow the receiving eNB to unambiguously associate the periodic and aperiodic subband components with their respective wideband counterparts. Notice that under the optimized structure if only one of the aperiodic or periodic subband information is reported in the X2 message, it will include only the corresponding wideband information. Further, in case the structure includes merged CSI (where the merging or processing is done by the sender) then only one wideband component will be included and in this case all the subband CQIs will be conveyed as absolute CQIs (using 4 bits or 16

possibilities).

[00306] In this option the sending eNB must ensure that it uses the right number of subbands in its message when conveying the aperiodic CSI information. As described for option- A, doing so is important since it will enable receiving eNB to determine what the differential CQI conveyed for that subband means. This is because in aperiodic mode 3-0 (or 3-1) and aperiodic mode 2-0 (or 2-2) the same differential value can be mapped to different offsets, respectively. Thus, the only way the receiving eNBl can deduce the right offset value to use is to utilize the fact that for the given system bandwidth (or given total number of PRBs available at sending eNB2 (which is known or conveyed separately to eNBl)) the number of sub bands for which CQIs are reported is distinct under those two aperiodic modes, respectively.

[00307] Option C ' : Subband Index + Subband Size

Table E8

»>Subband Index 0 INTEGER Included in case of

(0..27, ...) UE selected subband

CQI reporting.

[00308] Notes for Option C:

[00309] - Description: Like Option C, but the Subband Size is fixed for all subbands. Here maximum number of subbands can be 28 (assuming 110 DL RBs and subband size of 4 under aperiodic mode 2-0 or 2-2).

[00310] eRNTP enhancements.

[00311] We provide an eRNTP version which allows the sender eNB to seamlessly convey either explicitly convey the applied power level (relative to one or more specified thresholds) or to convey whether a resource will be interference protected or not. We note that a resource can be interference protected by multiple methods which include lower power or by using an appropriate beam forming vector etc.

Table E9

IE/Group Name Presence Range IE type and Semantics Criticality Assigned reference description Criticality

RNTP per PRB M BIT Each position in

STRING the bitmap

(6..1 10, ...) represents a n _PRB

value (i.e. first

bit=PRB 0 and so

on), for which the

bit value

represents RNTP

(ripRe), defined in

TS 36.213 [1 1].

Value 0 indicates

"Tx not

exceeding RNTP

threshold".

Value 1 indicates

"no promise on

the Tx power is

given".

This IE is ignored

if the Enhanced

RNTP IE is

present.

RNTP Threshold 0 ENUMERA RNTPthreshold I ^s

TED (-∞, defined in TS

-1 1 , -10, -9, 36.213 [1 1]. This

-8, -7, -6, -5, IE is always

-4, -3, -2, -1 , present if the

0, 1 , 2, 3, Enhanced RNTP

...) IE is not present.

Number Of M ENUMERA P (number of

Cell-specific TED (1 , 2, 4, antenna ports for

Antenna Ports ...) cell-specific

reference signals) defined in TS 36.21 1 [10]

P_B M INTEGER P _B is defined in

(0..3, ...) TS 36.213 [1 1].

PDCCH M INTEGER Measured by

Interference (0..4, ...) Predicted

Impact Number Of

Occupied PDCCH OFDM

Symbols (see TS 36.21 1 [10]).

Value 0 means "no prediction is available".

Enhanced RNTP O BIT Each position in IE STRING the bitmap

(6..4400, represents a ...) PRB in a

subframe. If the RNTP Threshold IE is present then the value "1" indicates 'no promise on the Tx power is given' and value "0" indicates 'Tx not exceeding RNTP threshold. ' If the

RNTP Threshold IE is not present then value "1" indicates 'resource with no utilization constraints' and value "0" indicates 'interference protected resource.' The first bit corresponds to PRB 0 of the first subframe for which the Enhanced RNTP IE is valid, the second bit corresponds to PRB 1 of the first subframe for which the Enhanced RNTP IE is valid, and so on.

The length of the bit string is an integer

(maximum 40) multiple of .

Ν ^ is defined in

TS 36.21 1 [10]. The bit string may span across multiple contiguous subframes. The pattern across contiguous subframes formed by Enhanced RNTP IE is continuously repeated.

Enhanced 0..1

RNTP IE start

time

>Starting SFN M INTEGER SFN of the radio

(0..1023, frame containing

... ) the first subframe when the

Enhanced RNTP

IE is valid. >Starting M INTEGER Subframe number,

Subframe Index (0..9, ...) within the radio

frame indicated by

the Start SFN IE,

of the first

subframe when the

Enhanced RNTP

IE is valid.

[00312] Embodiment F

[00313] Fl. Introduction

[00314] In this document we discuss some issues with subband indexing schemes and then present our preference in a proposal.

[00315] F2. Discussion

[00316] F2.1 Conveying both Periodic and Aperiodic reports

[00317] A desirable feature that should be supported by a CSI signaling scheme is the exchange of both periodic and aperiodic CSI reports in the same X2 message, possibly in a combined (or merged) form. In the absence of this feature, i.e., when the sending eNB is forced to choose either the periodic or the aperiodic CSI report obtained under a CSI process of some user, the sending eNB will have to drop available CSI reports. This would be unfortunate given that precious over-the-air signaling resources have already been spent in acquiring these reports and these reports can together convey more CSI that either individual one.

[00318] Then, a problem that needs to be overcome in order to send both aperiodic and periodic subband reports together in the same X2 message, is described next. In particular, the associated reference wideband reports that are used to compute the constituent subband parts of the aperiodic and periodic CSI reports, respectively, can be different. Indeed, the wideband rank indicators (RIs) that are determined by the UE under the configured aperiodic mode and the configured periodic mode can be different. Similarly, the wideband CQIs determined by the UE under the configured periodic mode and the configured aperiodic mode are also more likely to be different. Furthermore, each subband CQI determined by the UE under the configured mode can be reported by it as a differential value with respect to a corresponding reference CQI. For example, suppose aperiodic feedback mode 2-2 and periodic feedback mode 2-1 are configured. Then, under the aperiodic mode 2-2 the UE will report (over PUSCH) one wideband CQI (per codeword) as well as one subband CQI (per codeword) for the selected best-M feedback as a differential value (using 2 bits) with respect to the wideband CQI corresponding to that codeword. On the other hand, under the periodic 2-1 mode the UE will report (over PUCCH) one wideband CQI (per codeword), with the wideband CQI of the second codeword being reported as a differential value with respect to the wideband CQI of the first one. In addition the UE will report one subband CQI for the first codeword and the second codeword subband CQI as a differential value with respect to the subband CQI of the first one.

[00319] Therefore it becomes clear that we have to alternatives to overcome this issue:

[00320] Alternative- 1 : Provision to include

[00321] two separate sets of RIs and wideband CQIs in the X2 message whenever that message contains both aperiodic and periodic subband reports. This will allow simple forwarding of both aperiodic and periodic reports in the same X2 message. In this context, we note that a structure which does not provide for including two separate sets of wideband components, forces the sending eNB to merge the wideband components and use a common reference for both aperiodic and periodic subband information. This defeats the purpose of conveying separate aperiodic and periodic subband reports in the same X2 message. Another issue in including the report type IE (specifying periodic or aperiodic report) within the list of subbands, is that ambiguity can be introduced when certain aperiodic and periodic reports are combined.

[00322] Alternative-2: Always merge separate sets of wideband components into one wideband component that will also be used as a common reference. In this case it is logical to merge the respective subband information as well, and upon doing so there is no need to indicate the type of the subband CSI report. However, this view prevents simple forwarding of both aperiodic and periodic reports in the same X2 message.

[00323] In order to obtain the merits of both the aforementioned alternatives, we propose a simple structure. This structure is presented in three versions, with the second and third ones being more bit-efficient version of the first.

[00324] The benefits of this proposal are as follows:

[00325] It allows for simple forwarding of both aperiodic and periodic reports in the same X2 message. In fact it allows for forwarding of multiple aggregated aperiodic or periodic CSI reports (from a UE under a CSI process) or their combinations in the same X2 message. [00326] The parameter Ν°β together with the conveyed subband size IE defines the subband partition, which corresponds to one of those defined in TS36.213.

[00327] It also allows for merging an aperiodic and a periodic report (or merging combinations of multiple periodic and/or multiple aperiodic CSI reports) without introducing any new subband definitions. This is because for a given total number of RBs (or PRBs), the subband size in aperiodic mode 2-* is exactly half of that of the aperiodic mode 3-* as well as periodic mode 2-*. Thus, in order to combine such reports we can use the subbands defined by the smaller subband size and convey (possibly processed) CQIs for them.

[00328] Other implementation based processing of the short-term CSI is also supported.

[00329] The first version is relatively straightforward. Two of its features are however worth pointing out:

[00330] For each CSI process we can convey up-to maxReferenceType reports. The Reference

Type IE can be ENUMERATED for instance as periodic or aperiodic. Alternatively, the Reference Type IE can simply be dropped.

[00331] The subband CQIs are conveyed sequentially in the increasing order of subband indices.

Then, in case the subband CQI IE for a subband is not conveyed, the receiving eNB must use the CQI conveyed for the last preceding subband. The CQI for the first subband must always be included. This feature can significantly save overhead by avoiding redundancy. Note that when a UE is configured in the aperiodic mode 2-*, it selects and reports indices for M out of N subbands. However, only one CQI (per codeword) is reported by it for all the M selected subbands. Therefore, it is beneficial that redundancy is avoided in reporting such CQIs.

[00332] The Subband Index IE is optional. In case this IE is not included then the subband CQI information for each one of the total number of subbands is conveyed. Recall that the parameter together with the conveyed subband size IE defines the subband partition, thereby conveying the total number of subbands N.

[00333] We now consider a more bit efficient second version in which the sub band selection is conveyed by means of a combinatorial index.

[00334] Here, under each Reference Type IE, the parameter together with the conveyed subband size IE defines the subband partition, thereby conveying the total number of subbands N. Also the number of subbands for which subband CQI is conveyed, M, is determined by the size of the Subband CQI List IE. [00335] The combinatorial index, r, is defined based on TS36.213 (section 7.2.1) as follows:

[00336] The positions of the M selected subbands is conveyed using a combinatorial index r defined as =∑( ^N - ^S )

S \ M - i / where N denotes the total number of subbands and the set ^ ' ⁱ⁼⁰ _w> ^ ^≤si≤N ' ^si < ^si + ⁱ ) contains the M

X x≥y

0 x < y

sorted subband indices and is the extended binomial coefficient, resulting in unique r e 0,· · ·,

label

[00337] To illustrate, consider first the case when = 110 and the Reference Type IE is set to be aperiodic. Then, we have two possibilities for subband selection. The first one is when the configured mode is 2-* in which case the subband size is 4 so that N=28 and here M=6. On the other hand, for aperiodic mode 3-* the subband size is 8 so that N=14 and here M=14. Similar argument applies to all other modes as well. It is also apparent that there is significant flexibility in aggregating several different reports under a Reference Type, as long as the subband partition is a valid one, i.e., corresponds to a one defined in TS36.213. Since the maximum value of N=28 (when = 110 and subband size is 4) we represent the combinatorial index using a bit string of length 26. This allows us to convey any possible selection choice of subbands from the maximum of 28 subbands.

[00338] Next, we consider the third version in which the sub band selection is again conveyed by means of a combinatorial index. This version can be somewhat more restrictive compared to the second version but can also be more bit efficient. Here, the number of selected subbands and their size, in addition to their positions or indices, are also indicated by the combinatorial index.

[00339] Consider first the case when the Report Type IE is set to be aperiodic. Then, we have two possibilities for subband selection. The first one is when the configured mode is 2-* in which case the combinatorial index, r, is defined based on TS36.213 (section 7.2.1) as follows:

[00340] The positions of the MUE selected subbands is conveyed using a combinatorial index r defined as

^M lN - s _:

r■ ∑ =o \ M - i where N denotes the number of subbands and the set ^{S ' ' ⁱ⁼⁰ _? ( ^{1≤ ≤} ^ ^{> s} i < ^+ ⁱ ) contains the M sorted

subband indices and is the extended binomial coefficient, resulting in unique label

[00341] One additional possibility must be included to cover the case when the configured mode is 3-* in which case CQIs for all subbands have to be conveyed. We can choose r=-l for this purpose. Then, notice that the combinatorial index, r, along with the parameter, together convey the total number of subbands, N, and the number of selected subbands, M, as well as the size of each subband and their positions or indices.

[00342] Consider next the case when the Report Type IE is set to be periodic. We consider the mode 2-* that is the only mode under which the subband information is reported. Here the user reports CSI for one selected subband from each one of the J bandwidth parts (or portions) sequentially over successive reporting instances. Therefore, depending on the periodicities configured for the X2 CSI exchange and the over-the-air reports, the sending eNB can have subband reports for up-to J subbands. Notice that since the user must report the information for each subband sequentially, no bandwidth part indicator is defined in TS 36.213. We adopt the same approach and enforce that the subband CSI for all available bandwidth parts must be reported in the same X2 message. This nested structure will make the X2 message self-contained and avoid the need for a separate bandwidth part indicator.

[00343] Accordingly, letting Nl , N2,. NJ, denote the number of subbands in each of the J bandwidth parts, the combinatorial index must cover for Nl possibilities for the subband selection from the first bandwidth part, N1 *N2 possibilities for the subband selections together from the first and second bandwidth parts, and so on till Nl *N2* . ..NJ possibilities for the subband selections together from all the J bandwidth parts.

[00344] F3. Conclusion

[00345] We discussed the necessary X2 message to support CSI exchange for inter-eNB CoMP and presented our views on subband indexing along with corresponding proposals.

[00346] 9.1.2.14 RESOURCE STATUS UPDATE

[00347] This message is sent by eNB ₂ to neighbouring eNBi to report the results of the requested measurements. [00348] Direction: eNB ₂ → eNB i .

[00349] 9.2.aa UE-C SI Report (Version- 1)

[00350] This IE provides UE-CSI information for a set of UEs served by eNB ₂ .

Table Fl

IE/Group Name Presence Range IE type and Semantics reference description

CSI Report per UE 1 ..

<maxUEReport>

>UE ID M BIT STRING ID of the UE

(SIZE(16)) served by the cell in eNB ₂ .

>CSI Report per CSI 1 ..

Process <maxCSIProces

s>

» UE-CSI process M FFS FFS CSI process Configuration index configuration information.

» Reference type per CSI 1..

process

<maxReference T

ypes>

»>Reference Type M ENUMERATE

D

»>RI M INTEGER (1..8, Defined in TS

...) 36.213 [1 1].

»>Wideband CQI M 9.2.bb

»> Subband Size M ENUMERATE Corresponds to a

D (2, 3, 4, 6, 8, value of subband ...) size k defined in

TS 36.213 [1 1] for the system bandwidth. Ignored if the

Subband Index corresponds to the highest frequency subband.

»>Subband CQI List 1 ..

<maxSubband>

»»Subband CQI 0 9.2.CC If this IE is not present, the CQI is identical to the one provided for the last preceding subband. This IE is always present for the first subband in the list.

»»Subband Index 0 INTEGER

(0..27, ...)

[00351] Alternatively, the value of maxReferenceTypes can be 3 or 4.

[00352] UE-CSI Report (Version-2) Table F2

IE/Group Name Presence Range IE type and Semantics reference description

CSI Report per UE 1 ..

<maxUEReport>

>UE ID M BIT STRING ID of the UE

(SIZE(16)) served by the cell in eNB ₂ .

>CSI Report per CSI 1 ..

Process <maxCSIProces

s>

» UE-CSI process M FFS FFS CSI process Configuration index configuration information.

» Reference type per CSI 1..

process

<maxReference T

ypes>

»>Reference Type M ENUMERATE

D

»>RI M INTEGER (1..8, Defined in TS

...) 36.213 [1 1].

»>Wideband CQI M 9.2.bb

»> Subband Size M ENUMERATE Corresponds to a

D (2, 3, 4, 6, 8, value of subband size k defined in

^■■■ )

TS 36.213 [1 1] for the system bandwidth. Ignored if the

Subband Index corresponds to the highest frequency subband.

»> combinatorial index M BITSTRING As defined in

(SIZE(26)) TS36.213

(section 7.2.1 ).

The indices of the subbands in the list are indicated by this combinatorial index. Subband CQIs are sorted in the order of increasing frequency (increasing subband indices).

»>Subband CQI List 1 ..

<maxSubband>

»»Subband CQI 0 9.2.CC If this IE is not present, the CQI is identical to the one provided for the last preceding subband. This IE is always present for the first subband in the list. Range bound Explanation maxUEReport Maximum number of UE measurement reports. Value is 128. maxCSIProcess Maximum number of CSI processes. The value is 4. maxReferenceTypes Maximum types of of CSI reports. The value is 2. maxSubband Maximum number of subbands. The value is 28

[00353] Version-3:

Table F3

IE/Group Name Presence Range IE type and Semantics reference description

CSI Report per UE 1 ..

<maxUEReport>

>UE ID M BIT STRING ID of the UE

(SIZE(16)) served by the cell in eNB ₂ .

>CSI Report per CSI 1 ..

Process <maxCSIProces

s>

» UE-CSI process M FFS FFS CSI process Configuration index configuration information.

» Reference type per CSI 1..

process

<maxReference T

ypes>

»>Reference Type M ENUMERATE

D

»>RI M INTEGER (1..8, Defined in TS

...) 36.213 [1 1].

»>Wideband CQI M 9.2.bb

»> combinatorial index M As defined in

TS36.213 (section 7.2.1 ).

The number of subbands in the list, their indices, as well their size, are indicated by this combinatorial index. Subband CQIs are sorted in the order of increasing frequency (increasing subband indices).

»>Subband CQI List 1 ..

<maxSubband>

»»Subband CQI 0 9.2.CC If this IE is not present, the CQI is identical to the one provided for the last preceding subband. This IE is always present for the first subband in the list.

Range bound Explanation maxUEReport Maximum number of UE measurement reports. Value

is 128. maxCSIProcess Maximum number of CSI processes. The value is 4. imaxReferenceTypes Maximum types of of CSI reports. The value is 2. maxSubband Maximum number of subbands. The value is 28

[00354] Embodiment G

[00355] Gl. Introduction

[00356] In order to meet the objectives of the Inter eNB CoMP WI it was agreed to extend the RNTP IE to include transmission power level indication per time frequency resources spanning across multiple sub frames.

[00357] In the following, we provide our views on content of this message, as well as proposals.

[00358] G2. Discussion

[00359] G2.1 eRNTP exchange

[00360] One concern that was raised during the discussions in RAN3#87bis was on the semantic description of the enhanced RNTP IE whether it is suitable to use the phrase "TX power not exceeding a threshold". This is because certain implementations can achieve "interference protection" via other means such as beam-forming or beam-steering. We believe that even for such implementations, there is a notion of a threshold on effective radiated power from which the receiving eNB can deduce if a resource would be interference protected or not. We note that effective radiated power is a commonly used metric (terminology) which captures the effect of several relevant parameters such as transmit power, antenna gain, directivity, etc. Consequently, it is suitable to have an explicit threshold associated with the enhanced RNTP which indicates the "action" by the sender. We note that it is possible for sender eNB to send different eRNTP messages to different receiving eNBs to convey the potentially different net impacts of its adopted beam patterns and transmit powers on those receiving eNBs.

[00361] Accordingly, our preference is to retain the baseline agreement from the last meeting with a modification in the semantic description to use the phrase "Effective radiated TX power" instead of "TX power" . This will also accommodate newer implementations that rely on spatial/antenna domain processing to achieve interference mitigation.

[00362] We present two proposals. The first one is a more bit-efficient version of the BL agreement (albeit including the aforementioned modified semantic description). It exploits that fact an RNTP IE indicating transmit power levels for the first subframe (subframe #0) must always conveyed. Then, instead of ignoring this IE in the case when the enhanced RNTP IE is included, we can still use it to convey the per-PRB power level information for the first subframe. Moreover, instead of providing per-PRB power level information for each subsequent subframe in the enhanced RNTP IE, we can optionally adopt a more efficient representation in which such information for a subframe is conveyed only if it differs from that of the preceding one.

[00363]

[00364] The second proposal is based on multiple thresholds, where we note that certain implementation can extract gains from such finer power level indication. The point here is that since the choice Ί Γ already indicates no promise on the effective radiated transmit power level (which covers the case of transmit power being arbitrarily high) we can use three thresholds (instead of two), since there is no need to convey that the power level is greater than HPTH (as this is subsumed by ' 11 ').

[00365] G3. Conclusion [00366] We discussed the necessary X2 message to support eRNTP exchange for inter-eNB

CoMP and presented corresponding proposals.

[00367] Proposal:

[00368] 9.2.19 Relative Narrowband Tx Power (RNTP)

[00369] This IE provides an indication on DL power restriction per PRB in a cell and other information needed by a neighbour eNB for interference aware scheduling.

Table Gl

-1, 0, 1, 2, 3, ...)

Number Of M ENUMERATED (1, P (number of antenna ports Cell-specific 2, 4, ...) for cell-specific reference Antenna Ports signals) defined in TS

36.211 [10]

P_B M INTEGER (0..3, ...) P _B is defined in TS 36.213

[11].

PDCCH M INTEGER (0..4, ...) Measured by Predicted

Interference Number Of Occupied

Impact PDCCH OFDM Symbols

(see TS 36.211 [10]).

Value 0 means "no prediction is available".

Enhanced O BIT STRING Each position in the bitmap

RNTP (6..4290. ... represents a PRB in a subframe, for which value "1" indicates 'no promise on the Effective radiated Tx power is given' and value "0" indicates Effective radiated Tx power not exceeding RNTP threshold. '

The first bit corresponds to PRB 0 of the first subframe for which the IE is valid, the second bit corresponds to PRB 1 of the first subframe for which the IE is valid, and so on.

The length of the bit string is an integer (maximum 39) multiple of ^N ∞> , which is defined in TS 36.211 [10],

The bit string may span across multiple contiguous subframes.

The pattern across contiguous subframes (formed by NTP IE and Enhanced RNTP IE) is continuously repeated

Table G2

power not exceeding RNTP

threshold".

Value 1 indicates "no promise on the Effective radiated Tx power is given". This IE is ignored when the enhanced RNTP IE is included. NTP M ENUMERAT RNTP _t j _jres j _jo i _d is Threshold ED (-∞, -11, defined in TS

-10, -9, -8, -7, 36.213 -6, -5, -4, -3, Ti ll. This IE is -2, -1, 0, 1, 2, ignored when 3, ...) the enhanced

RNTP IE is included.

Number Of M ENUMERAT P (number of Cell-specific ED (1, 2, 4, antenna ports for Antenna Ports ...) cell-specific reference signals) defined in TS 36.211 [10]

PDCCH M INTEGER Measured by Interference (0..4, .. ·) Predicted

Number Of Impact Occupied

PDCCH OFDM

Symbols (see TS 36.211 [10]).

Value 0 means "no prediction is available".

Enhanced 0 BIT STRING Each position RNTP (12,..8800, in the bitmap represents a PRB in a subframe, for which the value "xx" indicates how the Effective radiated transmission power in a resource block is mapped relative to the three power thresholds:

00 - Effective radiated TX power level not exceedinq the LPTH

01 - Effective radiated TX power level between LPTH and MPTH; 10 - Effective radiated TX power level between MPTH and HPTH;

1 1 - no promise on the Effective radiated TX power is given. The first 2 bits correspond to PRB 0 of the first subframe for which the IE is valid, the following 2 bits correspond to PRB 1 of the first subframe for which the IE is valid, and so on.

The bit string may span across multiple contiguous subframes. The length of the bit string is an integer (maximum 40) multiple of ,

^N ™ which is defined in TS The Enhanced RNTP pattern is continuously repeated

> Enhanced

RNTP

thresholds

»LPTH (Low M ENUMERAT Lower RNTP

Power ED power

Threshold) threshold, usinq the

RNTPthrPihnlrl defined in TS

»MPTH M ENUMERAT Medium RNTP (Medium ED ί power Power threshold, Threshold) usinq the

RNTPthreshnlH defined in TS

»HPTH M ENUMERAT Hiqher RNTP (Hiqh Power ED (-∞, power Threshold) threshold, usinq the

RNTPthrPihnlrl defined in TS

[00370] Alternative structure for subband indexing:

Table G3 IE/Group Name Presence Range IE type and Semantics reference description

CSI Report per UE 1 ..

<maxUEReport>

>UE ID M BIT STRING ID of the UE

(SIZE(16)) served by the cell in eNB ₂ .

>CSI Report per CSI 1 ..

Process <maxCSIProces

s>

» UE-CSI process M FFS FFS CSI process Configuration index configuration information.

» Reference type per CSI 1..

process

<maxReference T

ypes>

»>Reference Type M ENUMERATE

D

»>RI M INTEGER (1..8, Defined in TS

...) 36.213 [1 1].

»>Wideband CQI M 9.2.bb

»>Subband CQI List 0 ..

<maxSubband>

»»Subband CQI 0 9.2.CC If this IE is not present, the CQI is identical to the one provided for the last preceding subband. This IE is always present for the first subband in the list.

»»Subband Start 0 INTEGER Corresponds to

(2..109, ...) the PRB number of the first PRB in a subband defined in TS 36.213 [1 1] for the system bandwidth. If this IE is not present, the subband is contiguous with the previous subband in the list, or starts with PRB 0 if this is the first subband in the list.

»»Subband Size 0 ENUMERATE Corresponds to a

D (2, 3, 4, 6, 8, value of subband ■ ^■■ ) size k defined in

TS 36.213 [1 1] for the system bandwidth.

Ignored for the highest frequency subband. If this IE is not present, the size is identical to the one provided for the last preceding subband. This IE is always present

for the first

subband in the list.

[00371] Embodiment H

[00372] HI. Introduction

[00373] In RAN3#88, after fruitful discussions on the exchange of CSI, a subband indexing scheme has been selected in the baseline CR (change request) [4]. In this document we identify some corrections that can be made and present them in a proposal.

[00374] H2. Discussion

[00375] A desirable feature that should be supported by a CSI signaling scheme is the exchange of both periodic and aperiodic CSI reports in the same X2 message. In the absence of this feature, i.e., when the sending eNB is forced to choose either the periodic or the aperiodic CSI report obtained under a CSI process of some user, the sending eNB will have to drop available CSI reports. This would be unfortunate given that precious over-the-air signaling resources have already been spent in acquiring these reports and that these reports can together convey more CSI that either individual one.

[00376] Accepting this view an indexing scheme to enable this feature has been selected in [4].

[00377] We identify two corrections and an improvement that can be made to the selected scheme:

[00378] Correction: Changing the subband index range to (0, ...27,..} from {0, ....,13,..}:

[00379] A benefit that can be obtained from the subband indexing scheme of [4] is the simple forwarding of both aperiodic and periodic CSI reports in the same X2 message. Notice that the maxSubband value is 14 and the subband index range is defined to be {0,...,13,..} . This choice allows for simple forwarding with any configured periodic mode and when the configured a-periodic mode is 3-*. This is because in these cases the maximum number of subband reports is 14 and the index range spans {0, ...., 13 } , consistent with the agreed choice.

[00380] However, this choice will not allow the same X2 message to include aperiodic CSI report configured with feedback mode 2-* and periodic CSI report configured under any mode. This is because

N ^DL = 1 1 0

under aperiodic mode 2- * , when the total number of PRBs in the downlink is ∞ , the subband size is k = 4 _an( j _me number of UE selected subbands is M = 6 (Table 7.2.1.5 in TS36.213). Thus, we have N = 28 _su bbands (110 = 4 * 27 + 2) _an( j _me UE is free to select any 6 out of these 28 subbands as its preferred ones. Consequently, the subband index identifying each UE selected subband must belong to the set {0,...,27} ..

[00381] Consequently, one of the two CSI process items should have a subband index range of

{0, ... ,27} . For simplicity we suggest a common subband index range of {0, ... ,27} for both CSI process items. A slightly more efficient alternative could be where one of the two CSI process items (say CSI process item 1) has index range {0,...,27} whereas the other one has index range {0,...,13} .

[00382] 2) Correction: Changing the semantic description to reflect that a different RI and CQI combination can be reported for each one of the two CSI process items under the same CSI process.

[00383] 3) Improvement: Making the subband CQI IE optional with a clarification in the semantic description.

[00384] The subband CQIs are conveyed sequentially in the increasing order of subband indices.

Then, in case the subband CQI IE for a subband is not conveyed, the receiving eNB must use the CQI conveyed for the last preceding subband. The CQI for the first subband must always be included. This approach can significantly save overhead by avoiding redundancy. Note that when a UE is configured in the aperiodic mode 2-*, it selects and reports indices for M out of N subbands. However, only one CQI (per codeword) is reported by it for all the M selected subbands. Therefore, it is beneficial that redundancy is avoided in reporting such CQIs in the X2 message as well.

[00385] H3. Conclusion

[00386] We identified three improvements that can be made in the UE-CSI IE and present them in a proposal.

[00387] 9.2.aa UE-CSI Report

[00388] This IE provides CSI reports of UEs served by the cell for which the information is provided.

Table HI IE/Group Name Presence Range IE type and Semantics reference descriptionSI Report per Cell 1 ..

<maxUEReport

>

>UE ID M BIT STRING ID assigned by

(SIZE(16)) eNB2 for the UE.

>CSI Report per CSI 1 ..

Process <maxCSIProces

s>

»CSI Process M FFS

Configuration Index

»CSI Report per li

CSI Process Item <maxCSIReport

>

»>RI M INTEGER The Rl

(1..8, ...) corresponding to the

CQI being reported for this CSI process Item. Value defined in TS 36.213 [1 1].

»>Wideband CQI M 9.2. bb

»>Subband Size M ENUMERATE Corresponds to a

D (2, 3, 4, 6, 8, value of subband ■ ^■■ ) size /( defined in TS

36.213 [1 1] for the system bandwidth

»>Subband CQI 0 ..

List <maxSubband>

»»Subband 0 9.2.CC If this IE is not CQI present, the CQI is identical to the one provided for the last precedinq subband. This IE is always present for the first

subband in the list.

»»Subband M INTEGER (0..

Index 27, ...)

[00389] The foregoing is to be understood as being in every respect illustrative and exemplary, but not restrictive, and the scope of the invention disclosed herein is not to be determined from the Detailed Description, but rather from the claims as interpreted according to the full breadth permitted by the patent laws. It is to be understood that the embodiments shown and described herein are only illustrative of the principles of the present invention and that those skilled in the art may implement various modifications without departing from the scope and spirit of the invention. Those skilled in the art could implement various other feature combinations without departing from the scope and spirit of the invention.