TECHNICAL FIELD

At least some example embodiments relate to configuring full-duplex links, and in particular to configuring full-duplex links between a network entity of a communications network system and a user equipment that has attached to the communications network system.

LIST OF ABBREVIATIONS

3GPP third generation partnership project

5G fifth generation

DL downlink

DMRS demodulation reference signal

FD full-duplex

FDD frequency division duplex

gNB 5G node B

NR new radio

ORS orthogonal reference signal

PRB physical resource block

RF radio frequency

RS reference signal

RSRP reference signal received power (reported in dBm)

RX receiver

SI self interference

SIC self interference cancellation

SRS sounding reference signal

TDD time division duplex

TSN time-sensitive network

TX transmitter

UE user equipment

UL uplink

URLLC ultra reliable low latency communication BACKGROUND

Current 3GPP NR specifications support frequency division duplexing (FDD) and time division duplexing (TDD) modes, as illustrated in Fig. 1.

For FDD, non-overlapping carriers are configured for the downlink (DL) and uplink (UL) transmissions, respectively. Network densification of e.g. 10E2- 10E3 devices/cell in ultra-reliable applications e.g. with error rates less than 10E-5, however, pose stringent requirements which FDD cannot meet.

TDD implies that a cell either have exclusive UL, DL, or no transmission for each time-instant. Hence, no option for simultaneous UL and DL - as is the case for FDD - is supported. This is especially a challenge for URLLC and TSN use cases, where multiple simultaneously active UEs must be served immediately and therefore often require a cell to have simultaneous UL and DL to accommodate the strict latency of e.g. no more than 1ms and ultra reliability requirements for all users.

A solution to meet these stringent requirements is full-duplex (FD) operation which promises doubling the throughput. FD enables a device to receive and transmit simultaneously in the same frequency band, i.e. the device uses dedicated TX and RX chains for transmission and reception in the same PRBs. FD however comes with the limitation of self-interference (SI) and residual SI, in which the TX chain leaks a non-negligible amount of energy onto the RX chain, contaminating the received signal.

SUMMARY

At least some example embodiments aim at providing a bi-directional FD link between a network entity (e.g. a gNB) of a communications network system and a user equipment (UE) that has attached to the communications network system. According to at least some example embodiments, this is achieved through a selection of transmit and receive spatial beams at the gNB side and the UE side.

According to at least some example embodiments, methods and signaling involved in selecting gNB and UE configurations of spatial beams are provided, which enable bi-directional FD for any pair gNB-UE.

According to at least some example embodiments, methods, apparatuses and non-transitory computer-readable storage media are provided as specified in the appended claims.

In the following, example embodiments and example implementations will be described with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 shows a schematic diagram illustrating duplexing options.

Fig. 2 shows a schematic diagram illustrating a bi-directional full-duplex scenario between a UE and a gNB as an example of a network entity.

Figs. 3A, 3B and 3C show flowcharts illustrating processes according to at least some example embodiments.

Fig. 4 shows a schematic block diagram illustrating a configuration of control units in which at least some example embodiments are

implementable.

Figs. 5 and 6 show schematic diagrams illustrating a method for probing FD capability according to a first example embodiment.

Fig. 7 shows time charts illustrating transmission and reception of ORS in a FD setup according to the first example embodiment. Fig. 8 shows a signaling diagram illustrating FD probing and configuration according to the first example embodiment.

Fig. 9 shows flowcharts illustrating processes of FD capability re-evaluation according to a second example embodiment.

Fig. 10 shows a signaling diagram illustrating FD probing in half-duplex type of operation according to a third example embodiment.

Fig. 11 shows a signaling diagram illustrating FD establishment based on channel estimation according to a fourth example embodiment.

DESCRIPTION OF THE EMBODIMENTS

A variation of FD implementation in which both network entity (e.g. gNB) and UE operate in FD mode is called bi-directional FD.

In bi-directional FD, the UE and gNB transmit and receive in the same PRBs, by using dedicated transmit and receive RF chains. While, in theory, this doubles the throughput, in practice, comes at the cost of self-interference (SI), i.e. the transmit chain leaks energy onto the receive chain,

contaminating the reception of the useful incoming signals. The problem - depicted in Error! Reference source not found.- occurs both at the gNB and at the UE and it is handled through various SI cancellation (SIC) techniques, implemented either in analog, digital domains or a hybrid combination of these. SIC alone may not be able to ensure enough cancellation, i.e. residual SIC is non-negligible, in which case FD may not be feasible without additional TX/RX separation.

According to at least some example embodiments, since bi-directional FD generates SI at both gNB and UE sides, before enabling it, the gNB probes and configures itself and the UE to maintain a "good enough" FD

communication link. According to at least some example embodiments, such link is achieved and maintained through the selection of transmit and receive spatial beams at both the gNB and UE side. The selection of the spatial beams serves at least two purposes:

It enhances the isolation between TX and RX chains.

It utilizes the characteristics of the multi-path environment, to find the best combination of radiation patterns at both sides of the

communication link.

At least some example embodiments provide methods and signaling involved in selecting gNB and UE configurations of spatial beams which enable bi-directional FD for any pair gNB-UE.

For example, according to at least some example embodiments, a method and associated signaling for establishing and maintaining a bi-directional FD link are provided, in which the gNB configures TX and RX spatial beams for itself and for the UE to maximize the signal to self-interference ratio in both directions.

Reference is made to Figs. 3A, 3B and 3C which show flowcharts illustrating processes according to at least some example embodiments.

Fig. 3A shows a process 1 which, according to an example implementation, is executed by a network entity of a communications network system based on e.g. 5G NR.

In step S310, a probing operation of transmitting and receiving

beamformed reference signals between the network entity and a user equipment that has attached to the communications network system is performed. In step S320, a configuration of a bi-directional full-duplex link between the network entity and the user equipment is decided based on the outcome of the probing operation of S310.

Fig. 3B illustrates details of the probing operation performed in S310.

In S312, a first evaluation is computed from a first signal of the

beamformed reference signals, wherein the first signal is received by the network entity and has been transmitted by the user equipment to the network entity, and a second evaluation is computed from a second signal of the beamformed reference signals, wherein the second signal is received by the network entity and has been transmitted by the network entity to the user equipment.

In step S314, reports about a third evaluation from the second signal received by the user equipment and a fourth evaluation from the first signal received by the user equipment are received from the user equipment.

It is noted that the order of steps S312 and S314 is not limited to that shown in Fig. 3B and may be reversed. According to an example

embodiment, steps S312 and S314 are performed in parallel.

According to an example embodiment, in steps S312 and S314, FD transmission of spatially beamformed orthogonal reference signals (ORSs) is performed between the gNB and UE, and spatially beamformed reception of the ORSs is performed at both gNB and UE. The power of useful ORSs (first and third evaluations) and the power of self-interference ORSs

(second and fourth evaluations) experienced at either ends of the

communication link between the gNB and the UE are computed.

Computations effected at the UE are reported to the gNB.

In other words, according to the example embodiment, the first evaluation comprises a power of the first signal received by the network entity, the second evaluation comprises a power of the second signal received by the network entity, the third evaluation comprises a power of the second signal received by the user equipment, and the fourth evaluation comprises a power of the first signal received by the user equipment.

Then, in step S320, the configuration of the bi-directional full-duplex link between the network entity and the user equipment is decided based on at least one of the first evaluation of the first signal, the second evaluation of the second signal, the third evaluation of the second signal and the fourth evaluation of the first signal.

According to an example embodiment, in step S320, as the configuration of the bi-directional full-duplex link, a set is selected, which comprises:

(i) an analog transmitting scheme capability of the plurality of analog transmitting scheme capabilities of the network entity,

(ii) an analog receiving scheme capability of the plurality of analog receiving scheme capabilities of the network entity,

(iii) an analog transmitting scheme capability of the plurality of analog transmitting scheme capabilities of the user equipment, and

(iv) an analog receiving scheme capability of the plurality of analog receiving scheme capabilities of the user equipment.

Then, the network entity signals the selected transmitting scheme capability of the user equipment and the selected receiving scheme capability of the user equipment to be used in the bi-directional full-duplex link to the user equipment.

Fig. 3C illustrates a process 2 of a probing operation which, according to an example implementation, is executed by the UE.

In step S330, the third evaluation is computed from the second signal of the beamformed reference signals, wherein the second signal is received by the user equipment and has been transmitted by the network entity to the user equipment, and the fourth evaluation is computed from the first signal of the beamformed reference signals, wherein the first signal is received by the user equipment and has been transmitted by the user equipment to the network entity.

In step S332, reports about the third evaluation and the fourth evaluation are transmitted to the network entity.

According to an example embodiment, the UE receives an instruction from the network entity to use the first signal in the probing operation.

According to an example embodiment, the network entity comprises at least one of a plurality of analog transmitting scheme capabilities and a plurality of analog receiving scheme capabilities.

According to an alternative example embodiment or in addition to the example embodiment, the user equipment comprises at least one of a plurality of analog transmitting scheme capabilities and a plurality of analog receiving scheme capabilities.

According to an example implementation, the plurality of analog

transmitting scheme capabilities comprises a plurality of analog precoders, and the plurality of analog receiving scheme capabilities comprises a plurality of analog combiners.

According to an example embodiment, the first and second signals for the probing operation are decided by the network entity based on at least one of the plurality of analog transmitting scheme capabilities of the network entity, the plurality of analog receiving scheme capabilities of the network entity, the plurality of analog transmitting scheme capabilities of the user equipment and the plurality of analog receiving scheme capabilities of the user equipment. According to an example embodiment, at least one of the plurality of analog transmitting scheme capabilities of the user equipment and the plurality of analog receiving scheme capabilities of the user equipment is received from the user equipment.

Now, before exploring further details of various embodiments and implementations, reference is made to Fig. 4 for illustrating a simplified block diagram of various electronic devices that are suitable for use in practicing the example embodiments and implementations.

Fig. 4 shows a control unit 410 comprising processing resources (e.g.

processing circuitry) 411, memory resources (e.g. memory circuitry) 412 and interfaces (e.g. interface circuitry) 413 coupled via a connection 414. According to an example implementation, the memory resources 412 store a program which is assumed to include program instructions that, when executed by the processing resources 411, enable the control unit 410 to operate in accordance with example embodiments of a network entity.

According to an example implementation, the interface 413 comprises a suitable radio frequency (RF) transceiver (not shown) coupled to antennas (not shown) for bidirectional wireless communications over wireless links 430 with a control unit 420.

The control unit 420 comprising processing resources (e.g. processing circuitry) 421, memory resources (e.g. memory circuitry) 422 and interfaces (e.g. interface circuitry) 423 coupled via a connection 424.

According to an example implementation, the memory resources 422 store a program which is assumed to include program instructions that, when executed by the processing resources 421, enable the control unit 420 to operate in accordance with example embodiments of a user equipment.

According to an example implementation, the interface 423 comprises a suitable radio frequency (RF) transceiver (not shown) coupled to antennas (not shown) for bidirectional wireless communications over the wireless links 430 with the control unit 410.

The example embodiments may be implemented by computer software stored in the memory resources 412, 422 and executable by the processing resources 411, 421, or by hardware, or by a combination of software and/or firmware and hardware in any or all of the devices shown.

The various example embodiments of the user equipment can include, but are not limited to, mobile stations, 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.

Further, as used in this application, the term "circuitry" refers to one or more or all of the following :

(a) hardware-only circuit implementations (such as implementations in only analog and/or digital circuitry) and

(b) to combinations of circuits and software (and/or firmware), such as (as applicable): (i) to a combination of processor(s) or (ii) to portions of processor(s)/software (including digital signal processor(s)), software, and memory(ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions) and

(c) to circuits, such as a microprocessor(s) or a portion of a

microprocessor(s), that require software or firmware for operation, even if the software or firmware is not physically present. This definition of "circuitry" applies to all uses of this term in this

application, including in any claims. As a further example, as used in this application, the term "circuitry" would also cover an implementation of merely a processor (or multiple processors) or portion of a processor and its (or their) accompanying software and/or firmware. The term "circuitry" would also cover, for example and if applicable to the particular claim element, a baseband integrated circuit or applications processor integrated circuit for a mobile phone or a similar integrated circuit in server, a cellular network device, or other network device.

As mentioned above, at least some example embodiments provide for a method and associated signaling to probe, configure and maintain a bi directional FD link between a gNB and a UE based on bi-directional spatial beam selection. According to an example embodiment, the method is gNB- driven and relies on the:

- FD transmission of spatially beamformed orthogonal reference signals (ORSs) between the gNB and UE.

- Spatially beamformed reception of the ORSs at both gNB and UE.

- Computation and reporting of the power of the useful ORSs and the self interference ORSs experienced at either ends of the communication link.

According to an example implementation, the following steps are

performed :

- The UE reports to the gNB its analog precoder and combiners codebooks, e.g. UE reports its transmit and receive spatial beam indices.

- The gNB selects and informs the UE which ORS sequence to use for the signaling associated with the FD-probing procedure.

- The UE and gNB perform FD beamed ORS transmission.

- The UE and gNB listen with all their available analog combiners for incoming signals and compute beamed RSRPs of the useful and leaked signals respectively.

- The UE reports to the gNB its own beamed RSRP lists. - The gNB uses the reported lists and its own generated RSRP lists to decide:

- If the link can be operated in bi-directional FD.

- The gNB and UE analog precoders and combiners which provide the best link quality, e.g. which minimize the leakage while not severely degrading the RSRP of the useful signal.

- The gNB signals to the UE whether the UE can operate in FD, and if so, the selected analog precoder, combiner pair.

First Example Embodiment

In the following a first example embodiment will be described by referring to Figs. 5 to 9.

In the first example embodiment, the beamformed reference signals described with respect to Figs. 3A-C, which are used in the probing operation, are spatially beamformed reference signals, and the first signal of the spatially beamformed reference signals comprises a reference signal sequence and the second signal of the spatially beamformed reference signals comprises another reference signal sequence which is orthogonal to the reference signal sequence.

The method depicted in Fig. 8 is triggered by the gNB after UE attach.

According to an example implementation of the first example embodiment, the gNB requests the UE to signal its analog precoder and combiner capabilities (not shown in Fig. 8).

In step S801, the UE reports back with the answer to this request, e.g. it signals to the gNB that it can form AUE different spatial precoders PUE 521 and BUE combiners CUE 522.

The gNB can form A ₉ NB different spatial precoders P ₉ NB 511 and B ₉ NB spatial combiners C ₉ NB 512. The gNB generates two orthogonal sequences "O", one for its own

transmission and one for the UE transmission. Without loss of generality, these sequences are referred to as:

DMRS = OgnB and SRS = OUE.

These sequences will be sent spatially beamformed, simultaneously by the gNB and the UE as shown by steps S803 and S804 in Fig. 8 and in Figs. 5 to 7, and can be released after the probing operation has ended.

In step S802, the gNB signals to the UE to use the SRS= OUE to send beamed SRS.

The gNB and UE send DMRS and SRS respectively, with each of their analog precoders PUE 521 and P ₉ NB 511; simultaneously, they listen for incoming signals using each of their combiners CUE 522 and C ₉ NB 512 as depicted in Fig. 5. Their transmission and reception are detailed in steps S803, S804, S805 and S806 in Fig. 8 and in Fig. 7. It is to be noted that the gNB sending DMRS and the UE sending SRS merely is an example and is not limiting.

The gNB may transmit DMRS, CSI-RS or SSB, and the UE may also transmit DMRS or SRS.

As shown in Fig. 7, the first signal transmitted by UE TX (e.g. UE TX chain shown in Fig. 5) comprises sequentially transmitted first symbols SRSi- SRSA _UE each corresponding to at least one of the plurality of analog transmitting scheme capabilities (e.g. analog spatial precoders PUE 521) of the UE. Each of the first symbols SRSI-SRSA _UE is repeatedly transmitted based on the plurality of analog receiving scheme capabilities (e.g. analog spatial combiners C ₉ NB 512) of the gNB. For example, each of the first symbols is repeated B ₉ NB times, B ₉ NB corresponding to the number of analog receiving scheme capabilities of the gNB. The UE TX duration then is B ₉ NB X AUE symbols. Similarly, the second signal transmitted by gNB TX (e.g. gNB TX chain shown in Fig. 5) with a time-advance d comprises sequentially transmitted second symbols DMRSi-DMRS _AgNB each corresponding to at least one of the plurality of analog transmitting scheme capabilities (e.g. analog spatial precoders P ₉ NB 511) of the gNB. Each of the second symbols DMRSi- DM RSA _9NB is repeatedly transmitted based on the plurality of analog receiving scheme capabilities (e.g. analog spatial combiners CUE 522) of the UE. For example, each of the second symbols is repeated BUE times, BUE corresponding to the number of analog receiving scheme capabilities of the UE. The gNB TX duration then is BUE X A ₉ NB symbols.

Using gNB RX (e.g. gNB RX chain shown in Fig. 5), at a T-th symbol, the gNB receives with combiner C ₉ NB (C ₉ NB ^(t) ) 512 a sum of signals: the UE SRS beamed with analog precoder 521 indexed iu _E ^(T) and the own leaked DMRS beamed with analog precoder indexed Ϊ ₉ NB ^(t) : y ^(T) = CgNB (CgNB^) (OUE ( PUE ( lUE^) * h) + OgNB ( PgNB ( igNB^) * flSI-gNB) )

In steps S807 and S808, the gNB computes (e.g. using block 513 shown in Fig. 5) the RSRP of the (useful) beamed UE signal and the RSRP of the (leaked) beamed own signal, by cross-correlating the received signal with each of the two orthogonal sequences (in other words, the gNB computes first and second evaluations). In this way, the gNB obtains two beamed RSRP values:

RSRP ^{(use SRS)} ( iuE ^(T) , CgNB ^(T) ) and RSRP ^{(leak DMRS)} ( i _gNB ^(T) , C ₉ NB ^(t) )

Similarly, using UE RX (e.g. UE RX chain shown in Fig. 5), the UE receives with combiner CUE (CUE ^(t) ) 522 a sum of signals: the gNB beamed DMRS and the own leaked beamed SRS with analog precoder indexed IUE ^(t) : y ^(T) = CUE(CUE ^(T) ) (OgNB ( PgNB ( lgNB ^(T) ) * h) + 0 _UE (PuE ( lUE ^(T+8) ) * hsi-U _E ) ) In steps S809 and S810, the UE computes (e.g. using block 523 shown in Fig. 5) and reports to the gNB a list of RSRPs (in other words, the UE transmits reports on third and fourth evaluations) in S811 : RSRp(use-DMRS) (j _gNB cr ⁾ _{f CU} E ^(T) ) and RSRP ^{(leak SRS)} ( iuE ^(T+8) , CUE ^(T) )

Where the analog precoder and combiner indexes are known at the gNB:

According to an example implementation, the first to fourth evalualtions are calculated for all possible combinations of PUE, C ₉ NB, P ₉ NB and CUE. In other words, the number of the first and second symbols corresponds to the number of analog spatial precoders of the UE multiplied by the number of analog spatial precoders of the gNB, and a number of repetitions of the first and second symbols corresponds to a number of analog spatial combiners of the network entity multiplied by a number of analog spatial combiners of the UE, so that all possible combinations of PUE, C ₉ NB, P ₉ NB and CUE. For example, gNB indexes of P and C are kept fixed while UE cycles through its indexes of P and C. Then gNB indexes of P and C are changed and the UE cycles through its indexes of P and C again.

Using the beamed RSRP lists obtained from the UE, in step S812, the gNB computes a list of signal-to-leakage ratio (SLR) corresponding to each analog precoder, combiner tuples. The SLR subscripted "dmrs" give the FD- DL quality while those subscripted "srs" represent the FD-UL quality.

SLRdmrs(

SLRsrs( iu The gNB chooses the optimum set (I ₉ NB, IUE, CUE, C ₉ NB) with respect to a preferred metric which may be gNB implementation dependent. For example, the gNB can choose the set that maximizes the sum of the SLRs, conditioned that each of the SLRs is above a predetermined threshold. For example, this predetermined threshold ensures that either gNB or the UE can operate in FD, i.e. that SI is low enough to allow for FD operation.

According to an example implementation, if the predetermined thresholds are not met, then the gNB decides to roll-back to e.g. half-duplex operation.

In step S813, the gNB signals the FD decision including the selected analog spatial precoder of the user equipment "precode_UE" e.g. indicated by index " IUE" and the selected analog spatial combiner of the user equipment

"comb_UE" e.g. indicated by index "CUE" to the UE.

In step S814, the UE implements a duplex mode for an actual operation based on the content of the message received in S813.

Second Example Embodiment

In the following, a second example embodiment will be described with reference to Fig. 9. The second example embodiment refers to an event triggered FD capability re-evaluation.

Once the initial FD capability has been probed as describe above, the gNB has information about the amount of SI leakage at the UE. Therefore, according to an implementation example of the second example

embodiment, the quantity RSRP ^{(leak SRS)} (iu _E , CUE) is not measured again, the UE applying and/or reporting only a power offset.

The UE measures and reports back the useful DMRS RSRP (sixth

evaluation), i.e. RSRP ^{(use DMRS)} , which ultimately depends on propagation channel conditions. Similarly, the gNB re-measures the useful SRS RSRP (fifth evaluation), i.e. RSRP ^{(use SRS)} . The procedure follows the same steps S801 to S814 explained above, except that the quantities " Ϊ ₉ NB ^(t) " , "0 ₉ NB ( ^T) ) * hsi-gNB) " , " RSRP( ^leak - ^DMRS ) ( i _gN B ^(T) , CgNB ^(T) ) " , " ϊuE ^(T) " , " 0 _UE (PuE hsi-uE)" and " RSRP ^{(leak SRS)} (i _UE ^(T+8) , CUE ^(t) )" in steps S807 to S810 may not be recomputed, unless the gNB specifically requests it, or the UE announces it. This can happen if the configuration of the FD link changes when either the gNB or the UE have modified their analog

precoders/combiners capabilities, e.g. switched to different antenna groups for TX/RX.

When an obstacle suddenly obstructs the communication link, the gNB observes a worsening of the link quality either from :

i. Periodic reception of CQI reports (from the UE regarding the DL quality), ii. Own quality measurements, e.g. SINR,

iii. (A)Periodic reception of other local/UE power measurements of the UE specific reference signals.

Upon processing reports like i.-iii., the gNB raises an FD alarm and needs to re-trigger the FD probing and configuration procedure.

An example implementation of the re-evaluation mechanism is given in Fig. 9. After the initial FD configuration in steps S910, S920 and S930, in step S904, the gNB starts an FD timer and, in S970, processes quality reports, either collected locally in S905, or collected by the UE in S906 and reported periodically by the UE in S907.

Whenever the gNB processes an unsatisfactory report (Yes in S971, Yes in S972), or if the FD timer has expired (Yes in S973), then, in S908, the gNB triggers the FD probing and configuration procedure and resets the FD timer in S974.

For example, the unsatisfactory report comprises a case in which one of the metrics from i.-iii. falls below a predetermined threshold and an alarm is raised. In an example implementation, such predetermined threshold is a relative value allowing a certain degradation of the link quality, e.g. of CQI, SINR, RSRP, RSSI, etc. For example, the predetermined threshold amounts to the link quality of the best combination minus 25%. However, the predetermined threshold is not limited thereto. According to an example implementation, the predetermined threshold is dynamically set based on the level of the channel quality for the current settings of the analog precoders and combiners.

For example, step S910 of Fig. 9 comprises steps S801 to S812 of Fig. 8, step S920 of Fig. 9 comprises step S813 of Fig. 8, and step S930 of Fig. 9 comprises step S814 of Fig. 8.

According to the second example embodiment, when a degradation of the quality is detected (e.g. Yes in S971, Yes in S972) or the timer expires (Yes in S973), the probing operation of steps S801 to S811 is re-performed and the configuration of the bi-directional full-duplex link is re-decided in step S812.

According to an example implementation of the second example

embodiment, the degradation of the quality is detected in case

- the quality reports of the UE transmitted in S907 fall below a first predetermined threshold, and/or

- the measurements of the quality performed by the gNB in S905 fall below a second predetermined threshold, and/or

- a value of the fifth evaluation falls below a third predetermined threshold, and/or

- a value of the sixth evaluation falls below a fourth predetermined threshold.

For example, the first to fourth predetermined thresholds are set as described above with respect to the metrics from i.-iii. According to an example implementation of the second example

embodiment, the value of the fifth evaluation comprises a power of the first reference signal measured by the gNB, and the value of the sixth evaluation comprises a power of the second reference signal measured by the UE.

In a mobile scenario, where the UE moves at a speed v, the channel conditions may considerably change without triggering an FD alarm. In this case, the selection of the analog precoders/combiners need not change, but the gNB and/or UE needs to adapt their digital precoder/combiners to compensate for the channel fluctuations over time. Assuming 50% channel coherence time, different fluctuation periods T _c =0.423/f _c * c/v, c being the speed of light and f _c the carrier frequency, are listed in the table below:

According to an example implementation, channel fluctuations are detected based on at least one of the quality reports, the measurements of the quality, the value of the fifth evaluation and the value of the sixth

evaluation. Based on the detected channel fluctuations, settings of a digital precoder and a digital combiner of the gNB are adapted. Alternatively or in addition, settings of a digital precoder and a digital combiner of the UE are adapted.

According to an example implementation, the gNB adapts the settings of the digital precoder and the digital combiner of the UE and signals these settings to the UE.

Third Example Embodiment

In the following, a third example embodiment will be described with reference to Fig. 10. The third example embodiment refers to sequential power measurements. For example, in the third example embodiment, the beamformed reference signals described with respect to Figs. 3A-C, which are used in the probing operation, are spatially beamformed reference signals, and the second signal described with respect to Figs. 3A-C is transmitted by the gNB to the UE first and then the gNB receives the first signal described with respect to Figs. 3A-C from the UE. According to another example implementation, the gNB receives the first signal from the UE first and then transmits the second signal to the UE.

According to an example implementation, the first and second signals comprise non-orthogonal reference signals, which are transmitted

sequentially. In the third example embodiment, the first and the second signals do not have to be orthogonal to each other but may be orthogonal to other reference signals.

In an example implementation of the third example embodiment, the SRS/DMRS exchange is performed in a sequential manner as illustrated in Fig. 10. For example, the gNB starts its DMRS transmission in S1003 and listens with each of its combiners for its own leakage in S1005. At the same time, the UE is silent and listens with its own combiners for the beamformed DMRS in S1004, S1006. Once the DMRS transmission has ended, the procedure is repeated in the opposite link direction, i.e. the UE starts sending beamed SRS in S1007, while simultaneously listening with each available combiner for the SRS leakage onto its own receive chain in S1010. In turn, the gNB receives the beamed SRS with each of its available analog precoders in S1008, S1009. The procedure doubles the FD-probing time compared with the first example embodiment, since it requires a half duplex message exchange, but comes with the benefit that only one ORS sequence is needed.

According to an example implementation of the third example embodiment, steps S1001, S1002 and S1011, S1012, S1013 and S1014 correspond to steps S801, S802 and S811 to S814 of the first example embodiment. Fourth Example Embodiment

In the following a fourth example embodiment will be described with reference to Fig. 11. The fourth example embodiment refers to sequential channel estimation using wide-beam DMRS and SRS transmission. For example, in the fourth example embodiment, the beamformed reference signals described with respect to Figs. 3A-C, which are used in the probing operation, are wide-beamed reference signals.

According to an example implementation of the fourth example

embodiment, the UE informs the gNB about its analog precoding/combining capability, e.g. its codebooks, in S1101. In step S1102, the gNB signals to the UE the ORS selection similarly as performed in S802 of the first example embodiment.

In the following reference signals exchange and channel estimation, the UE and gNB exchange wide-beamed SRS and respectively DMRS in consecutive time intervals.

At time index i, in step S1103, the gNB sends wide DMRS using its T ₉ NB transmit antennas.

In step S1105, the gNB receives its own DMRS with each k£ B ₉ NB of its receive beams (e.g. spatial combiners C ₉ NB 512) as:

y _9NB ^(SI) (i) = h ₉ NB ^(SI) ( k) Xdmrs + V,

and estimates the beamed SI channel responses h ₉ NB ^(SI) ( k) . v is the noise contribution of the channel.

In steps S1104, S1106, the UE receives the DMRS with a wide-beam :

yUE( i) ⁼ Hdmrs Xdmrs + 8,

and estimates the response of the channel between itself and the gNB: H _dmrs . e is the noise contribution of the channel. At time index i+1, in step S1107, the UE sends wide SRS using its TUE transmit antennas.

In steps S1108, S1109, the gNB receives the SRS with a wide-beam:

ygNEi(i+l) = Hsrs Xsrs + z,

and estimates the channel response Hsrs. x is the noise contribution of the channel.

In step S1110, the UE receives its own SRS with each of its J£BUE receive beams (e.g. BUE combiners CUE 522):

yu _E ^(SI) (i+l) = hu _E ^(SI) (j) Xsrs + n,

and estimates the beamed SI channels: huE ^(SI) (j). n is the noise contribution of the channel.

In step Sllll, channel reporting from the UE to the gNB is performed. The UE reports the estimated channels H _dmrs and huE ^(SI) (j) to the gNB.

The gNB knows now all the beamed SI and useful channels: h _g NB ^(SI) (k), huE ^(SI) (j), Hdmrs, Hsrs. In step S1112, the gNB can then select the set of analog precoders and combiners (k, p, I, j) at both sides, i.e. gNB and UE, so that e.g. the signal to SI ratios

SLR _gNB (k, p, I) = |CgNB(k) Hsrs PUE(I)| ² / |hgNB^ ^SI ^(k) R _Q NB(R)| ² and

SLRUE , P, I) = ICUE(J) Hdmrs PgNB(p)| ² / |huE ^(SI) (j) PUE(I)| ²

are maximized.

Steps S1113 and S1114 correspond to steps S813 and S814 of the first example embodiment.

According to an example implementation of the fourth example

embodiment, the first evaluation described with respect to Figs.3A-C comprises a channel response computed from the first signal received by the gNB using its plurality of analog receiving scheme capabilities, the second evaluation described with respect to Figs.3A-C comprises channel responses computed from the second signal received by the gNB using each of its plurality of analog receiving scheme capabilities, the third evaluation described with respect to Figs. 3A-C comprises a channel response computed from the second signal received by the UE, and the fourth evaluation described with respect to Figs. 3A-C comprises channel responses computed from the first signal received by the UE.

According to at least some example embodiments, the following advantages are achieved.

The methods and associated signaling described above can be applied to probe FD capability, and as a result, to configure spatial beams for enabling either bidirectional FD or gNB FD and UE half-duplex (HD).

Further, the above-described methods can be applied without any changes to devices operating both below and above 6 GHz.

In addition, by enabling the bidirectional spatial beam selection for establishing the FD link, the above-described methods implicitly realize spatial beams alignment, which ultimately results in steering the beam pair away from a UE served by a neighbor FD cell. This results in minimizing the interference the UEs may potentially cause on each other.

According to an aspect, a network entity of a communications network system and a user equipment that has attached to the communications network system perform a probing operation of transmitting and receiving beamformed reference signals. In the probing operation, evaluations are computed from a first signal of the beamformed reference signals, which is received by the network entity and has been transmitted by the user equipment to the network entity, and from a second signal of the

beamformed reference signals, which is received by the network entity and has been transmitted by the network entity to the user equipment. Based on the evaluations, a decision on a configuration of a bi-directional full- duplex link between the network entity and the user equipment is taken.

According to a further aspect, an apparatus for use by a network entity (e.g. a gNB) of a communications network system is provided. According to an example implementation, the apparatus comprises the control unit 410 shown in Fig. 4. Further, according to an example implementation, the apparatus performs the processes shown in Figs. 3A and 3B.

The apparatus comprises

means for performing a probing operation of transmitting and receiving beamformed reference signals between the network entity and a user equipment that has attached to the communications network system, the probing operation comprising :

computing a first evaluation from a first signal of the beamformed reference signals, wherein the first signal is received by the network entity and has been transmitted by the user equipment to the network entity;

computing a second evaluation from a second signal of the beamformed reference signals, wherein the second signal is received by the network entity and has been transmitted by the network entity to the user equipment; and

receiving, from the user equipment, reports about a third evaluation from the second signal received by the user equipment and a fourth evaluation from the first signal received by the user equipment; and means for deciding on a configuration of a bi-directional full-duplex link between the network entity and the user equipment, based on at least one of the first evaluation of the first signal, the second evaluation of the second signal, the third evaluation of the second signal and the fourth evaluation of the first signal.

According to an example implementation, the network entity comprises at least one of a plurality of analog transmitting scheme capabilities and a plurality of analog receiving scheme capabilities; and/or

the user equipment comprises at least one of a plurality of analog transmitting scheme capabilities and a plurality of analog receiving scheme capabilities.

According to an example implementation, the plurality of analog

transmitting scheme capabilities comprises a plurality of analog precoders, and the plurality of analog receiving scheme capabilities comprises a plurality of analog combiners.

According to an example implementation, the probing operation comprises: deciding the first and second signals for the probing operation based on at least one of the plurality of analog transmitting scheme capabilities of the network entity, the plurality of analog receiving scheme capabilities of the network entity, the plurality of analog transmitting scheme capabilities of the user equipment and the plurality of analog receiving scheme capabilities of the user equipment.

According to an example implementation, the apparatus further comprises means for receiving, from the user equipment, at least one of the plurality of analog transmitting scheme capabilities of the user equipment and the plurality of analog receiving scheme capabilities of the user equipment.

According to an example implementation, the probing operation comprises: instructing the user equipment to use the first signal in the probing operation.

According to an example implementation, the probing operation comprises: transmitting the second signal to the user equipment first and then receiving the first signal from the user equipment or vice versa. According to an example implementation, the first signal and the second signal each comprise a reference signal sequence.

According to an example implementation, the probing operation comprises: transmitting the second signal to the user equipment and receiving the first signal from the user equipment in a full-duplex mode.

According to an example implementation, the first signal comprises a reference signal sequence and the second signal comprises another reference signal sequence which is orthogonal to the reference signal sequence.

According to an example implementation, the beamformed reference signals used in the probing operation are spatially beamformed reference signals.

According to an example implementation,

the first signal comprises sequentially transmitted first symbols each corresponding to at least one of the plurality of analog transmitting scheme capabilities of the user equipment, wherein each of the first symbols is repeatedly transmitted based on the plurality of analog receiving scheme capabilities of the network entity, and

the second signal comprises sequentially transmitted second symbols each corresponding to at least one of the plurality of analog transmitting scheme capabilities of the network entity, wherein each of the second symbols is repeatedly transmitted based on the plurality of analog receiving scheme capabilities of the user equipment.

According to an example implementation,

a number of the first symbols corresponds to a number of analog spatial precoders of the user equipment, and a number of repetitions of the first symbols corresponds to a number of analog spatial combiners of the network entity, and a number of the second symbols corresponds to a number of analog spatial precoders of the network entity, and a number of repetitions of the second symbols corresponds to a number of analog spatial combiners of the user equipment.

Alternatively or in addition, a number of the first and second symbols corresponds to a number of analog spatial precoders of the user equipment multiplied by a number of analog spatial precoders of the network entity, and a number of repetitions of the first and second symbols corresponds to a number of analog spatial combiners of the network entity multiplied by a number of analog spatial combiners of the user equipment.

According to an example implementation, the computing in the probing operation comprises

computing the first and second evaluations for combinations of the first symbols and the second symbols.

According to an example implementation, the deciding comprises:

selecting, as the configuration of the bi-directional full-duplex link, a set of an analog spatial precoder of the analog spatial precoders of the user equipment, an analog spatial combiner of the analog spatial combiners of the user equipment, an analog spatial precoder of the analog spatial precoders of the network entity and an analog spatial combiner of the analog spatial combiners of the network entity; and

signaling, to the user equipment, the selected analog spatial precoder of the user equipment and the selected analog spatial combiner of the user equipment to be used in the bi-directional full-duplex link.

According to an example implementation, the first evaluation comprises a power of the first signal received by the network entity, the second evaluation comprises a power of the second signal received by the network entity, the third evaluation comprises a power of the second signal received by the user equipment, and the fourth evaluation comprises a power of the first signal received by the user equipment.

According to an example implementation, the beamformed reference signals used in the probing operation are wide-beamed reference signals.

According to an example implementation, the probing operation comprises: transmitting the second signal using the plurality of analog

transmitting scheme capabilities of the network entity;

receiving the second signal using each of the plurality of analog receiving scheme capabilities of the network entity; and

receiving the first signal using the plurality of analog receiving scheme capabilities of the network entity, wherein the first signal has been transmitted by the user equipment using the plurality of analog transmitting scheme capabilities of the user equipment,

wherein the first evaluation comprises a channel response computed from the first signal received by the network entity using its plurality of analog receiving scheme capabilities, the second evaluation comprises channel responses computed from the second signal received by the network entity using each of its plurality of analog receiving scheme capabilities, the third evaluation comprises a channel response computed from the second signal received by the user equipment, and the fourth evaluation comprises channel responses computed from the first signal received by the user equipment.

According to an example implementation, the deciding comprises:

selecting, as the configuration of the bi-directional full-duplex link, a set of (i) an analog transmitting scheme capability of the plurality of analog transmitting scheme capabilities of the network entity, (ii) an analog receiving scheme capability of the plurality of analog receiving scheme capabilities of the network entity, (iii) an analog transmitting scheme capability of the plurality of analog transmitting scheme capabilities of the user equipment, and (iv) an analog receiving scheme capability of the plurality of analog receiving scheme capabilities of the user equipment; and signaling, to the user equipment, the selected transmitting scheme capability of the user equipment and the selected receiving scheme capability of the user equipment to be used in the bi-directional full-duplex link.

According to an example implementation, the apparatus further comprises means for applying the selected configuration of the bi-directional full- duplex link between the network entity and the user equipment in an actual operation, the actual operation comprising :

setting a timer;

computing a fifth evaluation from a first reference signal, wherein the first reference signal is received by the network entity using the selected analog receiving scheme capability of the network entity and has been transmitted by the user equipment to the network entity using the selected analog transmitting scheme capability of the user equipment;

receiving, from the user equipment, reports about a sixth evaluation from a second reference signal, wherein the second reference signal is received by the user equipment using the selected analog receiving scheme capability of the user equipment and has been transmitted by the network entity to the user equipment using the selected analog transmitting scheme capability of the network entity;

monitoring quality of the bi-directional full-duplex link based on at least one of the fifth and sixth evaluations;

when a degradation of the quality is detected or the timer expires, re-performing the probing operation and re-deciding on the configuration.

According to an example implementation, the actual operation further comprises:

periodically receiving quality reports on the quality of the bi directional full-duplex link from the user equipment; and/or performing measurements of the quality of the bi-directional full- duplex link; and

detecting the degradation of the quality in case

the quality reports fall below a first predetermined threshold, and/or the measurements of the quality fall below a second predetermined threshold, and/or

a value of the fifth evaluation falls below a third predetermined threshold, and/or

a value of the sixth evaluation falls below a fourth predetermined threshold.

According to an example implementation, the value of the fifth evaluation comprises a power of the first reference signal measured by the network entity, and wherein the value of the sixth evaluation comprises a power of the second reference signal measured by the user equipment.

According to an example implementation, the actual operation further comprises:

detecting channel fluctuations based on at least one of the quality reports, the measurements of the quality, the value of the fifth evaluation and the value of the sixth evaluation; and

adapting, based on the detected channel fluctuations, settings of a digital precoder and a digital combiner of the network entity and/or settings of a digital precoder and a digital combiner of the user equipment; and/or signaling, to the user equipment, the settings of the digital precoder and the digital combiner of the user equipment.

According to a further aspect, an apparatus for use by a user equipment is provided. According to an example implementation, the apparatus comprises the control unit 420 shown in Fig. 4. Further, according to an example implementation, the apparatus performs the process shown in Fig. 3C. The apparatus comprises means for performing a probing operation of transmitting and receiving beamformed reference signals between the user equipment that has attached to a communications network system and a network entity of the communications network system,

the probing operation comprising :

computing a third evaluation from a second signal of the beamformed reference signals, wherein the second signal is received by the user equipment and has been transmitted by the network entity to the user equipment;

computing a fourth evaluation from a first signal of the beamformed reference signals, wherein the first signal is received by the user equipment and has been transmitted by the user equipment to the network entity; and

transmitting, to the network entity, reports about the third evaluation and the fourth evaluation.

According to an example implementation, the beamformed reference signals used in the probing operation are spatially beamformed reference signals.

According to an example implementation,

the first signal comprises sequentially transmitted first symbols each corresponding to at least one of a plurality of analog transmitting scheme capabilities of the user equipment, wherein each of the first symbols is repeatedly transmitted based on a plurality of analog receiving scheme capabilities of the network entity, and

the second signal comprises sequentially transmitted second symbols each corresponding to at least one of the plurality of analog transmitting scheme capabilities of the network entity, wherein each of the second symbols is repeatedly transmitted based on the plurality of analog receiving scheme capabilities of the user equipment.

According to an example implementation, a number of the first symbols corresponds to a number of analog spatial precoders of the user equipment, and a number of repetitions of the first symbols corresponds to a number of analog spatial combiners of the network entity, and

a number of the second symbols corresponds to a number of analog spatial precoders of the network entity, and a number of repetitions of the second symbols corresponds to a number of analog spatial combiners of the user equipment.

Alternatively or in addition, a number of the first and second symbols corresponds to a number of analog spatial precoders of the user equipment multiplied by a number of analog spatial precoders of the network entity, and a number of repetitions of the first and second symbols corresponds to a number of analog spatial combiners of the network entity multiplied by a number of analog spatial combiners of the user equipment.

According to an example implementation, the computing in the probing operation comprises computing the third and fourth evaluations for combinations of the first symbols and the second symbols.

According to an example implementation, the probing operation comprises receiving an instruction from the network entity to use the first signal in the probing operation.

According to an example implementation, the apparatus further comprises means for transmitting, to the network entity, at least one of a plurality of analog transmitting scheme capabilities of the user equipment and a plurality of analog receiving scheme capabilities of the user equipment.

According to an example implementation, the apparatus further comprises means for receiving a message from the network entity, including a selected analog transmitting scheme capability of the plurality of analog transmitting scheme capabilities of the user equipment and a selected analog receiving scheme capability of the plurality of receiving scheme capabilities of the user equipment to be used in a bi-directional full-duplex link between the user equipment and the network entity.

According to an example implementation, the apparatus further comprises means for applying the selected analog transmitting scheme capability and the selected analog receiving scheme capability in the bi-directional full- duplex link between the network entity and the user equipment in an actual operation, the actual operation comprising :

computing a sixth evaluation from a second reference signal, wherein the second reference signal is received by the user equipment using the selected analog receiving scheme capability of the user equipment and has been transmitted by the network entity to the user equipment using the selected analog transmitting scheme capability of the network entity; and

transmitting, to the network entity, reports on the sixth evaluation.

According to an example implementation, the actual operation further comprises:

measuring a quality of the bi-directional full-duplex link;

detecting channel fluctuations based on at least one of the measured quality and a value of the sixth evaluation; and

adapting settings of a digital precoder and a digital combiner of the user equipment based on the detected channel fluctuations.

It is to be understood that the above description is illustrative and is not to be construed as limiting the disclosure. Various modifications and

applications may occur to those skilled in the art without departing from the true spirit and scope as defined by the appended claims.