Patent ID: 12250039

DESCRIPTION OF SOME EXEMPLARY EMBODIMENTS

Some embodiments, see, for example,FIG.1A,2,3, relate to an apparatus100(FIG.1A) for a communication system1000(FIG.2), the apparatus100comprising at least one processor102(FIG.1A), and at least one memory104storing instructions106that, when executed by the at least one processor102, cause the apparatus100to: determine300(FIG.3) a first measurement RS-M-1of first reference signals associated with a first analog beam1(seeFIG.5) used to receive the first reference signals, determine302(FIG.3) a second measurement RS-M-2of second reference signals associated with a second analog beam2(FIG.5) used to receive the second reference signals, determine304(FIG.3) first information I-1characterizing a digital beamformer DBF based on the first measurement RS-M-1and the second measurement RS-M-2. In some embodiments, the first information I-1may, e.g., be used for performing aspects of digital beamforming, see, for example, the optional block306.

In some embodiments,FIG.2, the communication system1000may be a wireless communication system.

In some embodiments, the wireless communication system1000may adhere to and/or may be based on some accepted (and/or planned) standard, such as, e.g. 3G, 4G, 5G, 6G, or some other wireless communication standard.

In some embodiments,FIG.2, the apparatus100may be an apparatus for a network device10, e.g., a base station, e.g., a gNB.

In some embodiments, the apparatus100or its functionality, respectively, may be provided within the network device10. In some other embodiments, the apparatus100or its functionality may be provided outside of the network device10. Both exemplary variants are symbolized by dashed rectangles100inFIG.2.

In some embodiments,FIG.2, the apparatus100may be an apparatus for a terminal device10, e.g., a user equipment (UE).

In some embodiments, the apparatus100or its functionality, respectively, may be provided within the terminal device20. In some other embodiments, the apparatus100or its functionality may be provided outside of the terminal device20. However, for the sake of clarity, and without loss of generality, the following exemplary disclosure focuses on exemplary embodiments wherein the apparatus100or its functionality, respectively, is provided for and/or within a network device10, such as a gNB.

In some embodiments,FIG.2, the apparatus100may be configured to perform hybrid beamforming, see the exemplary block HBF ofFIG.2, the hybrid beamforming HBF comprising aspects of digital beamforming, see the exemplary block DBF, and of analog beamforming, see the exemplary block ABF.

In some embodiments, the first analog beam1(FIG.5) used to receive the first reference signals RS-1may e.g. be attained by means of analog beamforming ABF. Similarly, the second analog beam2used to receive the second reference signals RS-2may e.g. also be attained by means of the analog beamforming ABF.

In some embodiments,FIG.2, the first and second reference signals RS-1, RS-2may e.g. be sounding reference signals, e.g. according to some accepted standard, e.g. Sounding Reference Signals (SRS) according to a 5G or 6G standard.

In some embodiments,FIG.3, the first measurement RS-M-1and the second measurement RS-M-2are consecutive measurements. In other words, in some embodiments, no further measurements associated with reference signals, e.g., SRS, are performed between the first measurement RS-M-1and the second measurement RS-M-2.

FIG.5illustrates an exemplary scenario, wherein element E1symbolizes a gNB (see, for example, also block10ofFIG.2), wherein element E2symbolizes a UE (see, for example, also block20ofFIG.2). The arrows a1, a2, a3, a4symbolize respective reference signals, e.g. SRS, transmitted, for example periodically, by the UE E2to the gNB E1. SRS according to arrow a1are for example received by the gNB E1using the first analog beam1, wherein SRS according to arrow a2are for example received by the gNB E1using the second analog beam2. Optionally, further SRS a3, a4may be received by the gNB E1using further analog beams3,4.

As an example, the SRS transmission a1ofFIG.5may e.g. correspond with the first reference signals RS-1ofFIG.2, and the SRS transmission a2ofFIG.5may e.g. correspond with the second reference signals RS-2ofFIG.2.

In some embodiments,FIG.5, a time duration TD between the first measurement and the second measurement may be an SRS period, e.g. according to some accepted standard.

In some embodiments,FIG.4, the instructions, when executed by the at least one processor, cause the apparatus100to: perform310digital beamforming using the digital beamformer DBF in a first direction DIR-1, perform312analog beamforming ABF in a second direction DIR-2, which is different from the first direction DIR-1.

In some embodiments, digital beamforming DBF is e.g. performed in a horizontal direction, and analog beamforming ABF is e.g. performed in a vertical direction (e.g., associated with an elevation).

In some other embodiments, both digital beamforming and analog beamforming may also be done in the vertical direction.

As an example, in some embodiments,FIG.5, four comparatively narrow analog beams1,2,3,4may be used in the vertical direction, wherein, for example, each of the analog beams1,2,3,4is associated with another elevation angle.

FIG.6exemplarily depicts aspects of signal processing related to measurements associated with received SRS in some embodiments, wherein a configuration as may be used for one column of a hybrid beamformer architecture, see block HBF ofFIG.2, is depicted. Element E10symbolizes inputs before application of analog phase shifters of an analog beamformer (see block ABF ofFIG.2), element E11symbolizes respective channels through the analog beamformer, element E12symbolizes weights of analog phase shifters of the analog beamformer, and element E13symbolizes digital ports, e.g. inputs.

As an example, when reference signals such as SRS are received, they are processed by the exemplary configuration ofFIG.6in a substantially horizontal direction from the right side ofFIG.6to the left side ofFIG.6, e.g. undergoing at least one of: a) analog phase shifting, if any, b) combining, c) amplification, d) analog-to-digital conversion.

FIG.11exemplarily depicts aspects of signal processing related to measurements associated with received SRS in some embodiments. Element E20symbolizes user layers, e.g. associated with user data to be transmitted, element E21symbolizes a digital beamforming, element E22symbolizes digital Transmit/Receive Chain (“TRX”) streams obtained by the digital beamforming E21. Element E23symbolizes analog beamforming, e.g. by applying a chosen phase shifter weight, and element E24symbolizes analog streams as obtained by the analog beamforming E23. Element E25symbolizes a pre-tilt application, e.g., characterizing a phase shifter-to-radiator mapping, and element E26symbolizes radiator streams.

Element E27symbolizes SRS signals, element E28symbolizes a pre-tilt application, e.g., similar to element E25, e.g., characterizing a phase shifter-to-radiator mapping (for a receive direction). Element E29symbolizes analog streams in a receive direction, element E30symbolizes analog beamforming, e.g., by applying a chosen phase shifter weight. Element E31symbolizes digital TRX streams, element E32symbolizes a determination of a respective covariance matrix, e.g., according to the principle of the embodiments, and element E33symbolizes digital weights as e.g. obtained by the determination block E32. In some embodiments,FIG.7, the instructions, when executed by the at least one processor, cause the apparatus100to: determine320a measurement vector MV characterizing the first and second reference signals RS-1, RS-2(FIG.2) based on the first measurement RS-M-1and the second measurement RS-M-2, determine322(FIG.7) a first covariance matrix CV-M-1based on the measurement vector MV, determine324a second covariance matrix CV-M-2, which is associated with at least one of the first analog beam1(FIG.5) and the second analog beam2, based on first covariance matrix CV-M-1, wherein, for example, the second covariance matrix CV-M-2is determined for any analog beam, e.g., including the first analog beam1and the second analog beam2. The optional block326ofFIG.7symbolizes an optional determination of the first information I-1characterizing the digital beamformer DBF based on the second covariance matrix CV-M-2.

In some embodiments,FIG.7, the instructions, when executed by the at least one processor, cause the apparatus100to perform determining320the measurement vector MV in accordance with ZSRS=(wHw)−1wHy, wherein ZSRScharacterizes, e.g., denotes, the measurement vector MV, wherein

y=[yiyk],
wherein yicharacterizes the first measurement RS-M-1(FIG.3) of the first reference signals RS-1(FIG.2) associated with the first analog beam1(FIG.5), wherein ykcharacterizes the second measurement RS-M-2(FIG.3) of the second reference signals RS-2(FIG.2) associated with the second analog beam2(FIG.5), wherein

w=[wiwk],
wherein wicharacterizes a weight matrix (e.g., as usable by block E12ofFIG.6) associated with the first analog beam1, wherein wkcharacterizes a weight matrix associated with the second analog beam, wherein wHis the conjugate transpose of w, wherein ( )−1characterizes a matrix inversion.

In some embodiments,FIG.7, the instructions, when executed by the at least one processor, cause the apparatus100to perform determining322(FIG.7) the first covariance matrix CV-M-1based on the measurement vector MV in accordance with: Rzz=ZSRSZSRSH, wherein Rzzcharacterizes the first covariance matrix CV-M-1. In some embodiments,FIG.7, the instructions, when executed by the at least one processor, cause the apparatus100to perform determining324the second covariance matrix CV-M-2based on first covariance matrix CV-M-1in accordance with:

Ryi⁢yi=wi⁢Rz⁢z⁢wiH,
wherein Ryiyicharacterizes the second covariance matrix CV-M-2. In some embodiments, the second covariance matrix CV-M-2may be determined for any analog beam, e.g., including the first analog beam1and the second analog beam2.

In the following, further exemplary aspects and exemplary embodiments are disclosed, which, in some embodiments, may be combined with each other and/or with at least one of the aforementioned aspects.

In some embodiments, two consecutive sets of SRS measurements, e.g., reference signals RS-1, RS-2(FIG.2), observed through different analog beams1,2(FIG.5) are used to determine the first information I-1and/or a corresponding digital beamformer as described below.

In some embodiments, let yibe an SRS measurement vector after the analog beam i is applied, wherein yiis of size NT×1 where NTis a number of digital transmit/receive chains (“TRXs”) as e.g. used for receiving the SRS.

In some embodiments, let ZSRSbe an SRS measurement vector (e.g., at least similar to measurement vector MV ofFIG.7), before an analog phase (e.g., phase shift) is applied, wherein ZSRSis of size NTNP×1 where NPis a number of phase shifters as e.g. used for receiving the SRS.

In some embodiments, let wibe a weight matrix corresponding to the analog beam i, wherein wiis of size NT×NTNP.

In some embodiments, a relation between yiand ZSRSis given by yi=wiZSRS.

In some embodiments, a first aspect (“Step 1”) may comprise one or more of the following aspects: Determine ZSRSfrom yireceived SRS measurements. In some examples, one measurement of yimay not be sufficient to determine ZSRSbecause it forms an under-determined system to solve for ZSRS. However, in some embodiments, by taking two measurements yiand yk(i≠k) (e.g., two different measurements), e.g. corresponding to two different analog beams i and k (for example analog beam1and analog beam2ofFIG.5), a well determined system may be obtained, where yi=wiZSRSand yk=wkZSRS. In some embodiments, solving for ZSRSusing yiand ykin accordance with
ZSRS=(wHw)−1wHy,
where

w=[wiwk]
and

y=[yiyk]
can be performed. Note that this is one exemplary method of obtaining ZSRSfrom yiand ykaccording to some embodiments. In some embodiments, the exemplarily depicted principle and the subsequent approach according to exemplary embodiments works for, e.g. any, other method of equation solving also.

Note that in some embodiments, e.g., when w is full rank, a pseudo-inverse (wHw)−1wHreduces to w−1.

In some embodiments, a second aspect (“Step 2”) may comprise one or more of the following aspects: In some embodiments, ZSRSmay be used to determine, e.g. compute, a covariance matrix Rzzcorresponding to ZSRSas Rzz=ZSRSZSRS.

In some embodiments, a third aspect (“Step 3”) may comprise one or more of the following aspects: In some embodiments, the covariance matrix Ryiyicorresponding to yiof any analog beam i may be determined as

Ryi⁢yi=yi⁢yiH=wi⁢ZS⁢R⁢S⁢ZS⁢R⁢SH⁢wiH(e.g.,substituting⁢for⁢yi)=wi⁢Rz⁢z⁢wiH.

In some embodiments, e.g., subsequently, Ryiyimay be used, e.g., to determine a digital beam (e.g., DIG-B, seeFIG.8), which, in some embodiments, may be used, e.g., for exchange of signals, e.g., PDSCH transmission and/or PUSCH reception.

In some embodiments, the digital beam thus determined may be used for PDSCH transmission and/or PUSCH reception, e.g. in between reception of subsequent SRS measurements, and can e.g. be updated, e.g. when SRS measurements are received in a next period, e.g., SRS period.

In some embodiments, at least temporarily storing ZSRSmay allow for determination of a digital beamformer independent of a (e.g., currently) best analog beam of a UE20, thus e.g. alleviating a need to store a covariance matrix for each analog beam, as according to some conventional approaches.

In some embodiments, the principle according to the embodiments may be used for a static channel as well as for a time varying channel, over which the reference signals may be received.

In some embodiments, in a case of a static channel, the channel through which the SRS is exchanged (e.g., transmitted, e.g. by the UE20to the gNB10) does not change across two SRS receptions. In this case, in some embodiments, the first information I-1and/or ZSRS, may be determined accurately, consequently Rzzand Ryiyialso.

In some embodiments,FIG.8, the instructions, when executed by the at least one processor, cause the apparatus100to perform at least one of: a) determining330, based on the first information I-1, a digital beam DIG-B for exchanging332, for example transmitting and/or receiving, signals, b) exchanging332, for example transmitting and/or receiving, signals CS using the digital beam DIG-B, c) updating334the digital beam DIG-B, e.g. based on further measurements, e.g. SRS measurements, e.g. after a subsequent SRS period, whereby an updated digital beam DIG-B′ may be obtained. In some embodiments, the updated digital beam DIG-B′ may be used for exchanging signals, e.g., similar to block332ofFIG.8.

In some embodiments, control signals, e.g. control signals according to some accepted standard, may be exchanged using the digital beam (and/or a respective analog beam). In other words, the signals CS that may be exchanged according to block332ofFIG.8may be control signals.

As an example, in some embodiments, at least one of a) signals associated with a Physical Downlink Shared Channel, PDSCH, and/or b) signals associated with a Physical Uplink Shared Channel, PUSCH, e.g., according to some accepted standard, may be transmitted and/or received using the digital beam DIG-B (and/or a respective analog beam1,2,3, or4(FIG.5)).

In some embodiments,FIG.9, the instructions, when executed by the at least one processor, cause the apparatus100to: determine340an estimate EST-MV of a measurement vector MV based on the first measurement RS-M-1and the second measurement RS-M-2, determine342a first covariance matrix CV-M-1-EST-MV for the estimate EST-MV based on the estimate EST-MV, determine344a second covariance matrix CV-M-2-EST-MV related to the estimate, which is associated with one of the first analog beam1and the second analog beam2, based on the first covariance matrix CV-M-1-EST-MV for the estimate. In some embodiments, this process may e.g. be used when exchanging the reference signals RS-1, RS-2through a time-varying channel. The optional block346symbolizes an optional determination of the first information I-1based on the second covariance matrix CV-M-2-EST-MV.

In some embodiments, e.g., in a case of a time varying channel, the channel through which the SRS is transmitted varies, e.g., from one SRS transmission to subsequent SRS transmission. In some embodiments, this means that in two successive or consecutive SRS measurements as considered in some embodiments, the underlying ZSRSis not the same. However, in some embodiments, there may be some degree of correlation between the channels of successive SRS transmissions, i.e., the underlying ZSRSfrom the two respective consecutive measurements may have some degree of correlation between them.

Therefore, in some embodiments, a similar approach as exemplarily explained above with respect to embodiments associated with a static channel can be used.

In some embodiments, let ZSRS,tbe an estimated SRS measurement at time t and ZSRS,t+pbe an estimated SRS measurement at time t+p (e.g., at least similar to estimate EST-MV as obtained by block340ofFIG.9), e.g., before the analog beam is applied.

Note that in some embodiments, ZSRS,tor ZSRS,t+pcannot be directly determined, e.g. observed, because in some embodiments, the associated signals may, e.g. only, be measured/estimated after application of the analog beam weights.

In some embodiments, p may be the SRS transmission period, see, for example, element TD ofFIG.5. In some embodiments, let yi,tbe an SRS measurement after analog beam i is applied at time t and yk,t+pbe an SRS measurement after (another) analog beam k is applied at time t+p.

In some embodiments, e.g., from two successive measurements of yi,tand yk,t+p, determine, e.g., estimate ZSRS,t+p. In some embodiments, let {circumflex over (Z)}SRSbe the estimate of ZSRS,t+p. In some embodiments, determine, e.g., compute {circumflex over (R)}zz={circumflex over (Z)}SRS{circumflex over (Z)}SRSH. In some embodiments, determine, e.g., compute {circumflex over (R)}yiyi=wi{circumflex over (R)}zzwiH, e.g. for at least one, e.g. any, analog beam i.

In some embodiments, it is proposed to determine, e.g., compute a respective covariance matrix of one or more, for example all, analog beams in a current channel.

In some embodiments, e.g., since ZSRS,tand ZSRS,t+pare not same in a time varying channel, the estimate {circumflex over (Z)}SRSmay contain an ingrained information of ZSRS,t(e.g., of the previous channel) with beam i and ZSRS,t+p(e.g., of the present channel) with beam k. Hence, in some embodiments, using {circumflex over (Z)}SRSone can efficiently determine, e.g. compute, yk,t+pand a corresponding covariance matrix {circumflex over (R)}ykyk(e.g., of the present channel). Also, in some embodiments, one can also determine, e.g. compute, yi,tand a corresponding covariance matrix {circumflex over (R)}yiyi(e.g., of the previous channel). However, in some embodiments, in the present channel slot t+p, {circumflex over (R)}yiyi(i≠k) may not be accurate, because {circumflex over (Z)}SRSmay contain information of ZSRS,t+pwith analog beam k, but not with analog beam i.

In view of this, in some embodiments,FIG.10, the instructions, when executed by the at least one processor, cause the apparatus100to perform at least one of: a) determining350an accuracy ACC-EST-MV of the estimate EST-MV of the measurement vector, e.g., based on a normalized mean square error (NMSE), b) determining352an accuracy ACC-2-EST-MV of the second covariance matrix CV-M-2-EST-MV related to the estimate, e.g., based on an NMSE.

Thus, in some embodiments, to measure an accuracy of the estimate {circumflex over (Z)}SRSto ZSRS,t+p, a normalized mean square error (NMSE) may be used, and in some embodiments, to measure an accuracy of {circumflex over (R)}yiyito Ryiyi, an NMSE for Ryiyi(“RNMSE”) may be used, as follows:

NMSE=wk⁢ZˆSRS-wk⁢ZSRS,t+pwkZ⁢SRS,t+p,RNMSE=wk⁢ZˆSRS⁢wkH-yk,t+p⁢yk,t+pHFyk,t+p⁢yk,t+pHF,
where ∥·∥ represents the L2-norm of a vector and ∥·∥Frepresents the Frobenius norm of a matrix.

As an example, in some embodiments, the NMSE may take the norm of the difference in the estimated and actual measurement of yk,t+pand normalizes it with the actual norm of yk,t+p.

As a further example, in some embodiments, similarly, RNMSE may take the Frobenius norm of the difference in the estimated and actual covariance matrix corresponding to yk,t+pand normalizes it with the Frobenius norm of the actual covariance matrix corresponding to yk,t+p.

Some embodiments,FIG.1B, relate to an apparatus100′ for a communication system1000, the apparatus100′ comprising means102′ for determining300(FIG.3) a first measurement of first reference signals associated with a first analog beam used to receive the first reference signals, determining302a second measurement of second reference signals associated with a second analog beam used to receive the second reference signals, determining304first information characterizing a digital beamformer based on the first measurement and the second measurement.

In some embodiments,FIG.1B, the means102′ for determining the first measurement and the second measurement and for determining the first information may, e.g., comprise at least one processor102(FIG.1A), and at least one memory104storing instructions106that, when executed by the at least one processor102, cause the apparatus to perform the aforementioned aspects.

In some embodiments,FIG.1B, the means102′ for determining the first measurement and the second measurement and for determining the first information may, e.g., comprise circuitry configured to perform one or more of the aforementioned aspects.

Some embodiments,FIG.2, relate to a network device10, e.g., base station, e.g., gNB, for a communication system1000comprising at least one apparatus100,100′ according to the embodiments.

Some embodiments,FIG.2, relate to a terminal device20, e.g., UE, for a communication system1000comprising at least one apparatus100,100′ according to the embodiments.

Some embodiments,FIG.2, relate to a communication system1000comprising at least one of: a) an apparatus100,100′ according to the embodiments, and/or b) a network device10according to the embodiments, and/or c) a terminal device20according to the embodiments.

Some embodiments,FIG.3, relate to a method for a communication system1000, comprising: determining300a first measurement of first reference signals associated with a first analog beam used to receive the first reference signals, determining302a second measurement of second reference signals associated with a second analog beam used to receive the second reference signals, determining304first information characterizing a digital beamformer based on the first measurement and the second measurement.

In some embodiments, the method may comprise one or more further aspects according to the embodiments.

Further embodiments,FIG.1A, relate to a computer program comprising instructions106which, when the program is executed by a computer, e.g., comprising the processor102, cause the computer to carry out at least some aspects of the method according to the embodiments.

In the following, further exemplary aspects and exemplary embodiments are disclosed, which, in some embodiments, may be combined with each other and/or with at least one of the aforementioned aspects.

In some embodiments, the hybrid beamforming HBF (FIG.2), which uses a combination of digital beamforming DBF and analog beamforming ABF may enable to reduce cost and/or weight of apparatus100and/or a target device10,20for the apparatus. Also, in some embodiments, a complexity and/or power consumption can be reduced by hybrid beamforming HBF, e.g. by reducing a number of RF signal processing chains.

As mentioned above, in some embodiments, a hybrid beamforming architecture may be provided which uses digital beamforming in the horizontal direction and analog beamforming in the vertical direction, e.g., because of a larger spread of UEs or users in the horizontal and relatively lower spread of users in the vertical direction. In some embodiments, a lower spread of users in the vertical direction may imply that a comparatively small number of analog beams in the vertical direction can suffice, e.g., to provide sufficient coverage in the vertical direction.

In some embodiments, a use of hybrid beamforming HBF, e.g., instead of digital beamforming, for SRS reception may result in the SRS measurements being “colored” through the lens of the analog beamformer ABF, because of additional phase shifters that may be comprised in the analog beamformer ABF.

In some embodiments, which may e.g. be used for 5G communication systems1000, four comparatively narrow analog beams1,2,3,4(FIG.5) may be provided, e.g., at elevation angles {−2, −5, −8, −11} degrees.

In some examples, e.g. using conventional approaches, e.g., to determine a digital beamformer for a UE at any time, a channel estimate and the corresponding covariance matrix of at least all four analog beams would have to be determined.

In some examples, there may be a need to compute the channel and the corresponding covariance matrix of up to, e.g., 20 different beams (not shown), e.g. for a case of four analog phase shifter settings and two TRXs per column of a HBF architecture. Thus, there may be a need to compute a digital beamformer for all these analog beams, because in some embodiments, the best analog beam of a UE may keep changing with time based on varying channel conditions. In addition, in HBF, UEs may be scheduled on their second or even third or later best analog beam sometimes, e.g., to reduce the latency of waiting until the best beam of the UE is scheduled.

In some conventional approaches, a digital beamformer is determined by making as many estimations/measurements as there are analog beams, and by using a measurement done on an analog beam to be used for that analog beam alone.

By contrast, the principle according to the embodiments enables to determine the digital beamformer (or the respective first information I-1) such that, e.g., instead of making as many estimations/measurements as there are analog beams and using a measurement done on an analog beam to be used for that analog beam alone, in some embodiments, only two, for example (but not necessarily) consecutive, SRS measurements made on any two different analog beams are used.

In other words, in some embodiments, these two measurements are enough to select a digital beam for any analog beamformer thus e.g. saving on a number of measurements and avoiding latency and staleness of the estimation.

Further, in some embodiments, e.g., instead of storing covariance matrices corresponding to each analog beam, only the covariance matrix of the channel before the phase shifters can be stored and that may, in some embodiments, be subsequently used to determine the covariance matrix at the digital ports, e.g. digital input. In some embodiments, this applies to static channels as well as to time varying channels.