CARRIER AGGREGATION

TECHNICAL FIELD;

The exemplary and non-limiting embodiments of this invention relate generally to wireless communication systems, methods, devices and computer programs and, more specifically, relate to carrier state information signaling between a mobile device and a network access node in a system that uses carrier aggregation.

BACKGROUND:

This section is intended to provide a background or context to the invention that is recited in the claims. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived, implemented or described. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and claims in this application and is not admitted to be prior art by inclusion in this section.

The following abbreviations that may be found in the specification and/or the drawing figures are defined as follows:

3 GPP third generation partnership project

ACK acknowledge

BS base station

CC component carrier

CQI channel quality indicator

CSI channel state information, including CQI/PMI RI

DL downlink (eNB towards UE)

eNB E-UTRAN Node B (evolved Node B)

EPC evolved packet core

E-UTRAN evolved UTRAN (LTE) IMT-A international mobile telecommunications association

ITU-R international telecommunication union-radiocommunication sector

LTE long term evolution of UTRAN (E-UTRAN)

LTE-A LTE advanced

MAC medium access control (layer 2, L2)

MIMO multiple input multiple output

MM/MME mobility management/mobility management entity

NAK negative acknowledge

NodeB base station

OFDMA orthogonal frequency division multiple access

O&M operations and maintenance

PDCP packet data convergence protocol

PDSCH physical downlink shared channel

PHY physical (layer 1, LI)

PMI precoding matrix indicator

PRB physical resource block

PUCCH physical uplink control channel

PUSCH physical uplink shared channel

Rel release

RI rank indicator

RLC radio link control

RRC radio resource control

RRM radio resource management

SGW serving gateway

SC-FDMA single carrier, frequency division multiple access

TDD time division duplex

UCI uplink control information

UE user equipment, such as a mobile station, mobile node or mobile terminal

UL uplink (UE towards eNB)

UPE user plane entity

UTRAN universal terrestrial radio access network One modern communication system is known as evolved UTRAN (E-UTRAN, also referred to as UTRAN-LTE or as E-UTRA).In this system the DL access technique is OFDMA, and the UL access technique is SC-FDMA.

One specification of interest is 3 GPP TS 36.300, V8.11.0 (2009-12), 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Access Network (EUTRAN); Overall description; Stage 2 (Release 8), incorporated by reference herein in its entirety. This system may be referred to for convenience as LTE Rel-8. In general, the set of specifications given generally as 3GPP TS 36.xyz (e.g., 36.21 1 , 36.31 1, 36.312, etc.) may be seen as describing the Release 8 LTE system. More recently, Release 9 versions of at least some of these specifications have been published including 3 GPP TS 36.300, V9.3.0 (2010-03). Additionally a Release 10 (Rel-10) version of 3 GPP TS 36.300, VI 0.1.0 (2010-10) has been published.

Figure 1A reproduces Figure 4.1 of 3GPP TS 36.300 V8.1 1.0, and shows the overall architecture of the EUTRAN system (Rel-8). The E-UTRAN system includes eNBs, providing the E-UTRAN user plane (PDCP/RLC/MAC PHY) and control plane (RRC) protocol terminations towards the UEs. The eNBs are interconnected with each other by means of an X2 interface, The eNBs are also connected by means of an SI interface to an EPC, more specifically to a MME by means of a SI MME interface and to a S-GW by means of a SI interface (MME/S-GW 4). The SI interface supports a many-to-many relationship between MMEs / S-GWs / UPEs and eNBs.

The eNB hosts the following functions:

functions for RRM: RRC, Radio Admission Control, Connection Mobility Control,

Dynamic allocation of resources to UEs in both UL and DL (scheduling);

IP header compression and encryption of the user data stream;

selection of a MME at UE attachment;

routing of User Plane data towards the EPC (MME/S-GW);

scheduling and transmission of paging messages (originated from the MME); scheduling and transmission of broadcast information (originated from the MME or O&M); and

measurement and measurement reporting configurations for mobility and scheduling.

Of particular interest herein are the further releases of 3GPP LTE (e.g., LTE Rel-10) targeted towards future IMT-A systems, referred to herein for convenience simply as LTE- Advanced (LTE-A). Reference in this regard may be made to 3 GPP TR 36.913 V9.0.0 (2009-12) Technical Report 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Requirements for further advancements for Evolved Universal Terrestrial Radio Access (E-UTRA) (LTE- Ad anced) (Release 9). Reference can also be made to 3 GPP TR 36.912 V9.3.0 (2010-06) Technical Report 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Feasibility study for Further Advancements for E-UTRA (LTE- Advanced) (Release 9).

A goal of LTE-A is to provide significantly enhanced services by means of higher data rates and lower latency with reduced cost. LTE-A is directed toward extending and optimizing the 3GPP LTE Rel-8 radio access technologies to provide higher data rates at lower cost. LTE-A will be a more optimized radio system fulfilling the ITU-R requirements for IMT-Advanced while keeping the backward compatibility with LTE Rel-8.

As is specified in 3GPP TR 36.913, LTE-A should operate in spectrum allocations of different sizes, including wider spectrum allocations than those of LTE Rel-8 (e.g., up to 00MHz) to achieve the peak data rate of lOOMbit s for high mobility and 1 Gbit/s for low mobility. It has been agreed that carrier aggregation is to be considered for LTE-A in order to support bandwidths larger than 20 MHz. Carrier aggregation, where two or more component carriers (CCs) are aggregated, is considered for LTE-A in order to support transmission bandwidths larger than 20MHz. The carrier aggregation could be contiguous or non-contiguous. This technique, as a bandwidth extension, can provide significant gains in terms of peak data rate and cell throughput as compared to non-aggregated operation as in LTE Rel-8. A terminal may simultaneously receive one or multiple component carriers depending on its capabilities. A LTE-A terminal with reception capability beyond 20 MHz can simultaneously receive transmissions on multiple component carriers. A LTE Rel-8 terminal can receive transmissions on a single component carrier only, provided that the structure of the component carrier follows the Rel-8 specifications. Moreover, it is required that LTE-A should be backwards compatible with Rel-8 LTE in the sense that a Rel-8 LTE terminal should be operable in the LTE-A system, and that a LTE-A terminal should be operable in a Rel-8 LTE system.

Figure IB shows an example of the carrier aggregation, where M Rel-8 component carriers are combined together to form AT" Rel-8 BW (e.g. 5 * 20MHz = 100MHz given M = 5). Rel-8 terminals receive/transmit on one component carrier, whereas LTE-A terminals may receive/transmit on multiple component carriers simultaneously to achieve higher (wider) band widths.

In carrier aggregation multiple DL carriers can be configured to one UE for PDSCH transmission. In order to support this type of operation corresponding control signaling needs to be specified.

The currently defined feedback mechanisms can be found in 3GPP TS 36.213 V9.3.0 (2010-09) Technical Specification 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA); Physical layer procedures (Release 9), in Section 7.2 "UE procedure for reporting channel quality indication (CQI), precoding matrix indicator (PMI) and rank indication (RI)", incorporated by reference herein. Note that this Rel-9 specification is not directed to the use of carrier aggregation. As is stated in Section 7.2 the time and frequency resources that can be used by the UE to report CQI, PMI, and RI are controlled by the eNB. For spatial multiplexing the UE determines a RI corresponding to the number of useful transmission layers. A UE in transmission mode 8 is configured with PMI/RI reporting if the parameter pmi-RI-Report is configured by higher layer signalling; otherwise, it is configured without PMI/RI reporting. The CQI, PMI, and RI reporting is periodic or aperiodic. The UE transmits periodic CQ1/PMI, or RI reporting on the PUCCH in subframes with no PUSCH allocation. The UE transmits periodic CQI/PMI or RI reporting on the PUSCH in subframes with PUSCH allocation, where the UE uses the same PUCCH-based periodic CQI/PMI or RI reporting format on the PUSCH. The UE transmits aperiodic CQI/PMI, and RI reporting on the PUSCH if certain conditions are met. For aperiodic CQI reporting, RI reporting is transmitted only if a configured CQI/PMI RI feedback type supports RI reporting. Sub-section 7.2.1 , "Aperiodic CQI/PMI/RI Reporting using PUSCH" and Sub-section 7.2.2., "Periodic CQI/PMI/RI Reporting using PUCCH" describe various transmission modes and corresponding reporting modes.

However, in the case of Rel-10 (and beyond Rel-10) carrier aggregation multiple DL carriers can be configured to a single UE for PDSCH transmissions. For efficient radio resource management (e.g., packet scheduling and link adaptation) and MIMO operation (e.g., precoding/beamforming and rank selection) it is desirable that CQI/PMI/RI can be provided for every DL carrier with a proper reporting period. In other words it would be desirable to avoid a situation where the eNB has no CSI available for any of the DL carriers for an extended period of time.

SUMMARY

The foregoing and other problems are overcome, and other advantages are realized, by the use of the exemplary embodiments of this invention,

In a first aspect thereof the exemplary embodiments of this invention provide a method that comprises, during operation of a user equipment when reporting channel state information for individual ones of a plurality of component carriers, detecting that a channel state information report for a first component carrier is blocked for transmission during an uplink subframe allocated for sending the channel state information report; and sending the channel state information report for the first component carrier in another subframe that is allocated for sending a channel state information report for a second component carrier, where the channel state information report for the first component carrier is sent along with the channel state information report for the second component carrier.

In another aspect thereof the exemplary embodiments of this invention provide an apparatus that comprises at least one data processor and a memory including computer program code. Where the memory and computer program code are configured to, with the at least one data processor, cause the apparatus to, when reporting channel state information for individual ones of a plurality of component carriers, detect that a channel state information report for a first component carrier is blocked for transmission during an uplink subframe allocated for sending the channel state information report; and send the channel state information report for the first component carrier in another subframe that is allocated for sending a channel state information report for a second component carrier, where the channel state information report for the first component carrier is sent along with the channel state information report for the second component carrier.

In another aspect thereof the exemplary embodiments of this invention provide an apparatus that comprises means, responsive to operation of a user equipment when periodically reporting channel state information for individual ones of a plurality of component carriers on a physical uplink shared channel, for detecting that a channel state information report for a first component carrier is blocked for transmission during an uplink subframe allocated for sending the channel state information report. The apparatus further comprises means for sending the channel state information report for the first component carrier in another subframe that is allocated for sending a channel state information report for a second component carrier, where the channel state information report for the first component carrier is sent along with the channel state information report for the second component carrier, and where a periodic channel state information report is scheduled to be sent on a physical uplink shared channel where there is a physical uplink shared channel allocation.

In another aspect thereof the exemplary embodiments of this invention provide a method that comprises, when receiving channel state information for individual ones of a plurality of component carriers, detecting that a channel state information report for a first component carrier was not received during an uplink subframe allocated for sending the channel state information report; and receiving the channel state information report for the first component carrier in another subframe that is allocated for receiving a channel state information report for a second component carrier, where the channel state information report for the first component carrier is received along with the channel state information report for the second component carrier.

In yet another aspect thereof the exemplary embodiments of this invention provide an apparatus that comprises at least one data processor and a memory including computer program code. Where the memory and computer program code are configured to, with the at least one data processor, cause the apparatus to, when receiving channel state information for individual ones of a plurality of component carriers, detect that a channel state information report for a first component carrier was not received during an uplink subframe allocated for sending the channel state information report; and to receive the channel state information report for the first component carrier in another subframe that is allocated for receiving a channel state information report for a second component carrier, where the channel state information report for the first component carrier is received along with the channel state information report for the second component carrier.

In a still further aspect thereof the exemplary embodiments of this invention provide an apparatus that comprises means, responsive to receiving channel state information for individual ones of a plurality of component carriers, for detecting that a channel state information report for a first component carrier was not received during an uplink subframe allocated for sending the channel state information report. The apparatus further comprises means for receiving the channel state information report for the first component carrier in another subframe that is allocated for receiving a channel state information report for a second component carrier, where the channel state information report for the first component carrier is received along with the channel state information report for the second component carrier, where the channel state information report for a particular component carrier is scheduled to be received periodically on a physical uplink shared channel. BRIEF DESCRIPTION OF THE DRAWINGS In the attached Drawing Figures:

Figure 1A reproduces Figure 4.1 of 3GPP TS 36.300, and shows the overall architecture of the EUTRAN system.

Figure IB shows an example of carrier aggregation as proposed for the LTE-A system.

Figure 2 shows a simplified block diagram of various electronic devices that are suitable for use in practicing the exemplary embodiments of this invention.

Figure 3 shows an example of UCI feedback for TDD.

Figure 4 illustrates an example of the content of aperiodic reporting in different subframes in accordance with an aspect of this invention.

Figure 5 illustrates an exemplary content of periodic reporting in different subframes in accordance with an aspect of this invention.

Figure 6 is a logic flow diagram that illustrates the operation of a method and a result of execution of computer program instructions embodied on a tangible, non-transitory computer readable medium in accordance with the exemplary embodiments of this invention.

Figure 7 is a logic flow diagram that illustrates the operation of a method and a result of execution of computer program instructions embodied on a tangible, non-transitory computer readable medium further in accordance with the exemplary embodiments of this invention. DETAILED DESCRIPTION

The current CSI reporting mechanisms are inadequate to ensure that the eNB has up-to-date and timely channel state information, and thus do not solve the problem noted above in the Background discussion.

For the case of periodic CSI on the PUCCH, and considering the limited payload size supported on the PUCCH, periodic CSI report dropping could possibly occur very frequently when the CSI is transmitted on the PUCCH. This is true at least for the reasons that it is difficult to multiplex periodic CSI for multiple DL carriers, and it is also difficult to multiplex periodic CSI with ACK/NAK, as ACK/NAK full bundling will likely not be used in Rel-10. Even if the use of ACK/NAK full bundling is agreed to, it likely will not be used frequently due to the potential for performance degradation.

As is shown in Figure 3, this problem becomes even more severe for the case of TDD, The UL subframe per 5 ms is used to cany ACK/NAK for 4 DL subframes and multiple DL carriers. For a case of heavy DL transmissions it becomes very difficult to feed back the periodic CSI on the PUCCH due to collisions with ACK NAK feedback transmissions (in TDD, ACK/NAK overhead can be as great as 20-bits).

For the case of aperiodic CSI on the PUSCH, while it is possible to trigger aperiodic CSI for all DL carriers, the overhead becomes an issue. For example, with a reporting mode 3-1 and a carrier with a 20 MHz bandwidth, the payload size could be about 60 bits, which translates into about one PRB on the PUSCH to obtain the proper coverage.

Furthermore, in certain scenarios it is unnecessary to provide such a detailed CSI for all DL carriers. In order to obtain some flexibility in this regard the eNB could indicate a subset of DL carriers for aperiodic reports, however this would require additional signaling between the eNB and the UE. For the case of periodic CSI on the PUSCH, according to Rel-8 (and Rel-9), if there is a PUSCH transmission in one subframe the periodic CSI reports should be piggybacked on the PUSCH. In this case CSI reporting for multiple DL carriers can be supported. However, this mechanism provides limited flexibility in that only those DL carriers which have reporting instances configured in that particular subframe can have their respective periodic CSI reported, whereas other DL carriers (those not configured in that particular subframe) cannot.

For periodic CSI on the PUCCH there have been proposals to use DFT-s-OFDM (discrete Fourier transform spread OFDM) as a container to multiplex ACK/NAK and periodic CSI up to the maximum payload size. However, this is unlikely the case due to the significantly increased ACK/NAK overhead that will be present in Rel-10, especially for TDD.

The various proposals do not adequately address the problems that arise with regard to CSI reporting in the case of carrier aggregation and multiple DL component carriers.

Note can be made of 3GPP TSG RAN WGl Meeting #62bis, Rl-105526, Xi'an, PR China, 1 1th - 15th October, 2010, Agenda item: 6.2.3, Source: Nokia Siemens Networks, Nokia, Title: Aperiodic CSI reporting for Carrier Aggregation. Of more general interest is a submission referenced by Rl-105526, namely 3GPP TSG RAN WGl Meeting #56bis, Rl-091353, Seoul, Korea 23 - 27 March, 2009, Agenda item: 15.2, Source: Nokia Siemens Networks, Nokia, Title: On CSI feedback signalling in LTE- Advanced uplink.

In Rl-105526 the following four proposals are made:

Proposal 1 : The CC-specific bandwidth dependent subband sizes and the basic compression mechanisms defined for LTE Rel-8 should remain supported in LTE Rel-10 with carrier aggregation. Proposal 2: It should be possible for the eNodeB to request a detailed, Rel-8 like CSI report for one CC at the time. Additionally, including wideband CSI for other CCs into the same report should be considered,

Proposal 3: It should be further discussed how to indicate the CC for which the detailed CSI report is derived.

Proposal 4: When Aperiodic CSI reports are sent, consider transmitting the report always for all the configured CCs regardless of the activation/deactivation state. For the CCs the UE assumes to be deactivated the report may contain an explicit indication of the deactivation instead of the CSI measurement.

The exemplary embodiments of this invention provide enhancements for carrier aggregation to the CSI reporting mechanisms defined in Rel-8 (and Rel-9), in that a UE can report CSI for more than one DL carrier in one subframe assuming that the CSI is piggybacked on the PUSCH. More specifically, the exemplary embodiments of this invention enable the use of the configuration for periodic reporting to determine the content of an aperiodic report for multiple DL carriers. The exemplary embodiments also enable the multiplexing of dropped periodic CSI reports of multiple DL carriers into one subframe on a PUSCH without aperiodic CSI reporting.

Before describing in detail the exemplary embodiments of this invention, reference is made to Figure 2 for illustrating a simplified block diagram of various electronic devices and apparatus that are suitable for use in practicing the exemplary embodiments of this invention. In Figure 2 a wireless network 1 is adapted for communication over a wireless link 11 with an apparatus, such as a mobile communication device which may be referred to as a UE 10, via a network access node, such as a Node B (base station), and more specifically an eNB 12. The network 1 may include a network control element (NCE) 14 that may include the MME/SGW functionality shown in Figure 1A, and which provides connectivity with a further network, such as a telephone network and/or a data communications network (e.g., the internet). The UE 10 includes a controller, such as at least one computer or a data processor (DP) 10A, at least one non-transitory computer-readable memory medium embodied as a memory (MEM) 10B that stores a program of computer instructions (PROG) IOC, and at least one suitable radio frequency (RF) transceiver 10D for bidirectional wireless communications with the eNB 12 via one or more antennas. The eNB 12 also includes a controller, such as at least one computer or a data processor (DP) 12 A, at least one computer-readable memory medium embodied as a memory (MEM) 12B that stores a program of computer instructions (PROG) 12C, and at least one suitable RF transceiver 12D for communication with the UE 10 via one or more antennas (typically several when multiple input / multiple output (MIMO) operation is in use). The eNB 12 is coupled via a data / control path 13 to the NCE 14. The path 13 may be implemented as the S I interface shown in Figure 1A. The eNB 12 may also be coupled to another eNB via data / control path 15, which may be implemented as the X2 interface shown in Figure 1 A.

For the purposes of describing the exemplary embodiments of this invention the UE 10 can be assumed to also include a physical layer CSI (PL-CSI) reporting function / module 10E configured to compose and send the eNB 12 CSI reports, i.e., to compose an uplink signaling message to report CSI for a plurality n of component carriers, and the eNB 12 includes a complementary physical layer CSI report receiving function / modulel2E configured to receive and interpret the CSI reports sent by the UE 10.

At least one of the PROGs IOC and 12C is assumed to include program instructions that, when executed by the associated DP, enable the device to operate in accordance with the exemplary embodiments of this invention, as will be discussed below in greater detail. That is, the exemplary embodiments of this invention, including the PL-CSI functions / modules 10E and 12E, may be implemented at least in part by computer software executable by the DP 10A of the UE 10 and/or by the DP 12A of the eNB 12, or by hardware, or by a combination of software and hardware (and firmware).

The PL-CSI reporting functions / modules 10E, 12E, in conjunction with the data processors 10A, 12A, memories 10B, 12B, programs 10C, 12C and the transmitter and receivers can be viewed as representing various suitable means for implementing the exemplary embodiments of this invention.

In general, the various embodiments of the UE 10 can include, but are not limited to, cellular telephones, personal digital assistants (PDAs) having wireless communication capabilities, portable computers having wireless communication capabilities, image capture devices such as digital cameras having wireless communication capabilities, gaming devices having wireless communication capabilities, music storage and playback appliances having wireless communication capabilities, Internet appliances permitting wireless Internet access and browsing, as well as portable units or terminals that incorporate combinations of such functions.

The computer-readable memories 10B and 12B may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor based memory devices, random access memory, read only memory, programmable read only memory, flash memory, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory. The data processors 10A and 12A may be of any type suitable to the local technical environment, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on multi-core processor architectures, as non-limiting examples.

Discussing now in further detail the exemplary embodiments of this invention, in certain cases, in particular for TDD, the eNB 12 has to rely on the PUSCH to obtain CSI feedback due to the significantly increased ACK/NAK overhead on the PUCCH. The exemplary embodiments of this invention address and solve the various problems discussed previously by enhancing CSI reporting on the PUSCH.

In a first exemplary embodiment the configuration used for periodic reporting is used to determine the content of the aperiodic report for multiple DL carriers, In one subframe, if there is a PUSCH transmission with aperiodic reporting, one specific DL carrier will have a detailed CSI (e.g., sub-band CQI or multiple PMI) reported, and all the other DL carriers, which have been configured for periodic reporting, will have wideband CSI reported, according to reporting mode 1-0 (if periodic reporting for this carrier is configured with reporting mode 1-0 or 2-0), or 1-1 (if periodic reporting for this carrier is configured with reporting mode 1-1 or 2-1). This embodiment is shown in the context of a non-limiting example in Figure 4 for subframes n and m, where subframe n contains a detailed aperiodic CSI for carrier 1 , a wideband CSI for carrier 2 and a wideband CSI for carrier 3, and where subframe m contains a detailed aperiodic CSI for carrier 2, a wideband CSI for carrier 1 and a wideband CSI for carrier 3. The content of the wideband report is determined by the configuration of periodic CSI reporting of the corresponding DL carrier.

This embodiment can be extended in cases that if more than one DL carrier would have a detailed aperiodic report then all the other DL carriers will have wideband reports.

In a second exemplary embodiment there is a multiplexing of dropped periodic CSI reports of multiple DL carriers in one subframe on a PUSCH without aperiodic CSI reporting. Reference in this regard can be made to Figure 5. The PUSCH can be a data-only PUSCH, i.e., one without aperiodic CSI reporting.

In one subframe if there is a PUSCH transmission without any aperiodic reporting and at least one DL carrier is configured to report periodic CSI in this subframe, the periodic CSI is transmitted on the PUSCH, Note that a similar concept exists in Rel-8 with single carrier. Further in accordance with the exemplary embodiments of this invention, both the eNB 12 and the UE 10 make a record of some dropped periodic reports for each DL carrier, and the dropped CSI report or reports are subsequently reported on the PUSCH in one subframe, even if some carriers are not configured to report periodic CSI in this particular subframe. The detailed alternatives for determining which dropped CSI reports will be re-sent are discussed below. The non-limiting example of Figure 5 shows three subframes n, m and /. In subframe n the periodic CSI for carrier 1 is reported in a normal fashion. However, in subframe m the periodic CSI for carrier 2 is not reported (is dropped) due to a collision. In accordance with this exemplary embodiment and the non-limiting example shown in Figure 5 the dropped periodic CSI report for carrier 2 is added to or included with or multiplexed with the periodic CSI report for carrier 3 and is reported on the PUSCH in subframe /. As was noted above, the eNB 12 records (stores information, possibly in the memory 12B) that it did not receive in subframe m the periodic CSI report for carrier 2. The eNB 12 can thus expect to receive the missing periodic CSI report for carrier 2 in subframe / (or possibly in some other subframe) in combination with the periodic CSI report for carrier 3, even though the periodic CSI report for carrier 2 is not scheduled to be transmitted in subframe /.

Further in accordance with the exemplary embodiments of this invention there are at least two alternatives to determine which DL carriers will have their respective dropped periodic reports reported in certain subframes.

In a first alternative a rules set is considered. For example, one rule can be related to a time window that is defined for each DL carrier, and for each type of report (RI, wideband CQI PMI and subband CQI). All dropped periodic CSI reports for the corresponding carrier are reported during the defined time window in accordance with the second embodiment described above with respect to Figure 5. To avoid redundant reporting the length (duration) of the time window can be defined as being equal to the period of the corresponding report type on the corresponding carrier. For overhead reduction, it is also possible not to re-send subband CQI, but only RI and wideband CQI/PMI, since the RI and wideband CQI/PMI are rather important for radio resource management, and typically have a long reporting period. Note that two or more dropped CSI reports can be sent in the single subframe along with the periodic CSI report that is already allocated for sending in the subframe.

In a second alternative the UE 10 only reports the carrier having the most-recently dropped periodic CSI report, as this carrier will likely experience a longer waiting period until a next reporting instance/opportunity for this carrier. The use of this alternative embodiment thus helps to ensure that the eNB 12 has the most current and up-to-date channel state information for each of the DL carriers, and thus facilitates at least the radio resource allocation and MIMO operations of the eNB 12.

In that for the case of carrier aggregation in TDD it is very likely that the eNB 12 will rely on the PUSCH to obtain CSI feedback, both of the exemplary embodiments discussed above enhance the CSI reporting on the PUSCH with but minor changes to the applicable specification(s).

There are a number of technical effects and technical advantages that can be realized by the use of the exemplary embodiments of this invention. For example, the first exemplary embodiment provides a clear definition of the content of the report when overhead reduction is considered for aperiodic reporting, as the eNB 12 is enabled to dynamically trigger detailed reports for one carrier, and wideband reports for the other carriers are automatically multiplexed into one report. In the second exemplary embodiment the periodic reporting mechanism is maintained in an operational state as much as possible when collisions occur.

Based on the foregoing it should be apparent that the exemplary embodiments of this invention provide a method, apparatus and computer program(s) to provide enhanced signaling to convey information to a network access node, such as an eNB, in a carrier aggregated wireless communication system, where the information is descriptive of channel state information associated with various component carriers.

An aspect of the exemplary embodiments of this invention provides a method that comprises, during operation of a user equipment when reporting periodic channel state information for one or more of a plurality of component carriers, detecting that channel state information reports for some of component carrier were blocked for transmission during an uplink subframe, where those component carriers were configured for sending the periodic channel state information reports. The method further includes sending the channel state information reports, for those component carriers which have blocked channel state information reports in previous subframes, in a current subframe that is allocated for sending a channel state information report for at least one of a plurality of component carriers, and where there is a physical uplink shared channel allocation. The channel state information reports for those component carriers with blocked channel state information reports are sent along with the channel state information report(s) for the component carrier(s) that are configured to send channel state information reports in the current subframe, even when at least some of the component carriers with blocked channel state information reports are not configured for sending channel state information reports in the current subframe.

Figure 6 is a logic flow diagram that illustrates the operation of a method, and a result of execution of computer program instructions, in accordance with the exemplary embodiments of this invention. In Block 6A there is a step performed, during operation of a user equipment when reporting channel state information for individual ones of a plurality of component carriers, of detecting that a channel state information report for a first component carrier is blocked for transmission during an uplink subframe allocated for sending the channel state information report. In Block 6B there is a step of sending the channel state information report for the first component carrier in another subframe that is allocated for sending a channel state information report for a second component carrier, where the channel state information report for the first component carrier is sent along with the channel state information report for the second component carrier.

In the method as depicted in Figure 6, where the channel state information report for a particular component carrier is a periodic channel state information report for the particular component carrier and is scheduled to be sent by the user equipment on a physical uplink shared channel where there is a physical uplink shared channel allocation.

In the method as depicted in Figure 6 and the preceding paragraph, where detecting comprises determining that a collision will occur with other information being reported during the uplink subframe allocated for sending the channel state information report for the first component carrier.

In the method as depicted in Figure 6 and the preceding paragraph, where the channel state information report that is sent along with the channel state information report for the second component carrier is selected in accordance with predefined rules, where a predefined rule is that the channel state information report that is sent along with the channel state information report for the second component carrier is selected as being within a predetermined time window, and where the predetermined time window has a duration associated with a wideband channel quality indicator or a rank indicator on the respective component carrier.

In the method as depicted in Figure 6, where the channel state information report that is sent along with the channel state information report for the second component carrier is selected as being a channel state information report that was most recently detected as being blocked for sending.

Also disclosed is a non-transitory computer-readable medium that contains software program instructions, where execution of the software program instructions by at least one data processor results in performance of operations that comprise execution of the method depicted in Figure 6 and described in the preceding several paragraphs.

Figure 7 is a logic flow diagram that illustrates the operation of a method, and a result of execution of computer program instructions, further in accordance with the exemplary embodiments of this invention. In Block 7A there is a step performed, when receiving channel state information for individual ones of a plurality of component carriers, of detecting that a channel state information report for a first component carrier was not received during an uplink subframe allocated for sending the channel state information report. In Block 7B there is a step of receiving the channel state information report for the first component carrier in another subframe that is allocated for receiving a channel state information report for a second component carrier, where the channel state information report for the first component carrier is received along with the channel state information report for the second component carrier.

In the method as depicted in Figure 7,where the channel state information report for a particular component carrier is scheduled to be received periodically on a physical uplink shared channel.

In the method as depicted in Figure 7, where a base station expects to receive the channel state information report for a most-recently blocked channel state information report.

In the method as depicted in Figure 7, where a base station expects to receive the channel state information report for a channel state information report selected as being within a predetermined time window having a duration associated with a wideband channel quality indicator or a rank indicator on the respective component carrier

Also disclosed is a non-transitory computer-readable medium that contains software program instructions, where execution of the software program instructions by at least one data processor results in performance of operations that comprise execution of the method depicted in Figure 7 and described in the preceding several paragraphs.

The various blocks shown in Figures 6 and 7 may be viewed as method steps, and/or as operations that result from operation of computer program code, and/or as a plurality of coupled logic circuit elements constructed to carry out the associated function(s).

In general, the various exemplary embodiments may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. For example, some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device, although the invention is not limited thereto. While various aspects of the exemplary embodiments of this invention may be illustrated and described as block diagrams, flow charts, or using some other pictorial representation, it is well understood that these blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

It should thus be appreciated that at least some aspects of the exemplary embodiments of the inventions may be practiced in various components such as integrated circuit chips and modules, and that the exemplary embodiments of this invention may be realized in an apparatus that is embodied as an integrated circuit. The integrated circuit, or circuits, may comprise circuitry (as well as possibly firmware) for embodying at least one or more of a data processor or data processors, a digital signal processor or processors, baseband circuitry and radio frequency circuitry that are configurable so as to operate in accordance with the exemplary embodiments of this invention- Various modifications and adaptations to the foregoing exemplary embodiments of this invention may become apparent to those skilled in the relevant arts in view of the foregoing description, when read in conjunction with the accompanying drawings. However, any and all modifications will still fall within the scope of the non-limiting and exemplary embodiments of this invention.

For example, while the exemplary embodiments have been described above in the context of the UTRAN LTE-A system, it should be appreciated that the exemplary embodiments of this invention are not limited for use with only this one particular type of wireless communication system, and that they may be used to advantage in other wireless communication systems that use carrier aggregation and / or report channel state information.

It should be noted that the terms "connected," "coupled," or any variant thereof, mean any connection or coupling, either direct or indirect, between two or more elements, and may encompass the presence of one or more intermediate elements between two elements that are "connected" or "coupled" together. The coupling or connection between the elements can be physical, logical, or a combination thereof. As employed herein two elements may be considered to be "connected" or "coupled" together by the use of one or more wires, cables and/or printed electrical connections, as well as by the use of electromagnetic energy, such as electromagnetic energy having wavelengths in the radio frequency region, the microwave region and the optical (both visible and invisible) region, as several non-limiting and non-exhaustive examples.

Further, the various names used for the described parameters (e.g. CQI, PMI, RI, etc.) are not intended to be limiting in any respect, as these parameters may be identified by any suitable names. Further, the various names assigned to different channels (e.g., PUSCH, PUCCH, etc.) are not intended to be limiting in any respect, as these various channels may be identified by any suitable names.

Furthermore, some of the features of the various non-limiting and exemplary embodiments of this invention may be used to advantage without the corresponding use of other features. As such, the foregoing description should be considered as merely illustrative of the principles, teachings and exemplary embodiments of this invention, and not in limitation thereof.