WO2020147033A1

WO2020147033A1 - Method, device and computer readable medium for estimating channel state information

Info

Publication number: WO2020147033A1
Application number: PCT/CN2019/071969
Authority: WO
Inventors: Rana Ahmed Salem; Huan Sun; Eugene Visotsky; Frederick Vook
Original assignee: Nokia Shanghai Bell Co., Ltd.; Nokia Solutions And Networks Oy; Nokia Technologies Oy
Priority date: 2019-01-16
Filing date: 2019-01-16
Publication date: 2020-07-23
Also published as: CN113366787A; CN113366787B

Abstract

Embodiments of the disclosure provide a method, device and computer readable medium for estimating control state information. According to embodiments of the present disclosure, the CSI is estimated by SRS sounding on reference antennas instead of CSI feedback. In this way, the overhead has been reduced.

Description

METHOD, DEVICE AND COMPUTER READABLE MEDIUM FOR ESTIMATING CHANNEL STATE INFORMATION

FIELD

Embodiments of the present disclosure generally relate to communication techniques, and more particularly, to methods, devices and computer readable medium for estimating channel state information.

BACKGROUND

In wireless communication systems, channel state information (CSI) describes how signals propagate from the transmitter to the receiver. In particular, downlink (DL) CSI is essential at the base station (for example, gNodeB (gNB) ) in multiple input multiple output (MIMO) systems. The gNB performs DL transmissions and scheduling and the like according to the CSI. In frequency division duplex (FDD) systems, the terminal device needs to feed back the DL CSI back to the base station since the uplink (UL) and DL channels are not on the same frequency. In time division duplex (TDD) systems, the UL-DL reciprocity is exploited.

SUMMARY

Generally, embodiments of the present disclosure relate to a method for estimating channel state information and feeding back the CSI to the base stations and the corresponding communication devices.

In a first aspect, embodiments of the disclosure provide a network device. The network device comprises: at least on processor; and a memory coupled to the at least one processor, the memory storing instructions therein, the instructions, when executed by the at least one processor, causing the network device to: perform a measurement of Sounding Reference Signals (SRS) on at least one reference antenna selected from a plurality of antennas of the terminal device. The network device is further caused to determine, based on the measurement, a channel response between the network device and the least one reference antenna. The network device is also caused to receive, from the terminal device, phase information associated with the plurality of antennas. The network device is further caused to generate an estimation of channel state information (CSI) between the network device and the plurality of antennas, based on the phase information and the channel response.

In a second aspect, embodiments of the disclosure provide a terminal device. The terminal device comprises: at least on processor; and a memory coupled to the at least one processor, the memory storing instructions therein, the instructions, when executed by the at least one processor, causing the network device to: transmit, to a network device, Sounding Reference Signals (SRS) with a plurality of antennas of the terminal device to obtain a channel response between at least one reference antenna and the network device by the network device. The terminal device is also caused to transmit, to the network device, phase information associated with the plurality of antennas. The terminal device is further caused to receive, from the network device, downlink transmission which is based on channel state information (CSI) between the network device and the plurality of antennas. The CSI is estimated based on the channel response and the phase information.

In a third aspect, embodiments of the present disclosure provide a method. The method comprises: performing, at a network device, a measurement of Sounding Reference Signals (SRS) on at least one reference antenna selected from a plurality of antennas of a terminal device. The method also comprises determining, based on the measurement, a channel response between the network device and the least one reference antenna. The method further comprises receiving, from the terminal device, phase information associated with the plurality of antennas. The method also comprises generating an estimation of channel state information (CSI) between the network device and the plurality of antennas, based on the phase information and the channel response.

In a fourth aspect, embodiments of the present disclosure provide a method. The method comprises: transmitting, to a network device, Sounding Reference Signals (SRS) with a plurality of antennas of the terminal device to obtain a channel response between at least one reference antenna and the network device by the network device. The method further comprises transmitting, to the network device, phase information associated with the plurality of antennas. The method also comprises receiving, from the network device the downlink transmission which is based on channel state information (CSI) between the network device and the plurality of antennas. The CSI is estimated based on the channel response and the phase information.

In a fifth aspect, embodiments of the disclosure provide an apparatus for communication. The apparatus comprises means for performing a measurement of Sounding Reference Signals (SRS) on at least one reference antenna selected from a plurality of antennas of a terminal device. The apparatus further comprises means for determining, based on the measurement, a channel response between the network device and the least one reference antenna. The apparatus also comprises means for receiving, from the terminal device, phase information associated with the plurality of antennas. The apparatus further comprises means for generating an estimation of channel state information (CSI) between the network device and the plurality of antennas, based on the phase information and the channel response.

In a sixth aspect, embodiments of the disclosure provide an apparatus for communication. The apparatus comprises means for transmitting, to a network device, Sounding Reference Signals (SRS) with a plurality of antennas of the terminal device to obtain a channel response between at least one reference antenna and the network device by the network device. The apparatus further comprises means for transmitting, to the network device, phase information associated with the plurality of antennas. The apparatus also comprises means for receiving, from the network device, downlink transmission which is based on channel state information (CSI) between the network device and the plurality of antennas. The CSI is estimated based on the channel response and the phase information.

In a seventh aspect, embodiments of the disclosure provide a computer readable medium. The computer readable medium stores instructions thereon, the instructions, when executed by at least one processing unit of a machine, causing the machine to implement the methods according to the third and fourth aspects.

Other features and advantages of the embodiments of the present disclosure will also be apparent from the following description of specific embodiments when read in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of embodiments of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the disclosure are presented in the sense of examples and their advantages are explained in greater detail below, with reference to the accompanying drawings, where

Fig. 1 illustrates a schematic diagram of a communication system according to embodiments of the present disclosure;

Fig. 2 illustrates a schematic diagram of a terminal device with a plurality of antennas according to embodiments of the present disclosure;

Fig. 3 illustrates a flow chart of a method implemented at a communication device according to embodiments of the present disclosure;

Fig. 4 illustrates a flow chart of a method implemented at a communication device according to embodiments of the present disclosure; and

Fig. 5 illustrates a schematic diagram of a device according to embodiments of the present disclosure.

Throughout the figures, same or similar reference numbers indicate same or similar elements.

DETAILED DESCRIPTION OF EMBODIMENTS

The subject matter described herein will now be discussed with reference to several example embodiments. It should be understood these embodiments are discussed only for the purpose of enabling those skilled persons in the art to better understand and thus implement the subject matter described herein, rather than suggesting any limitations on the scope of the subject matter.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a, ” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises, ” “comprising, ” “includes” and/or “including, ” when used herein, specify the presence of stated features, integers, steps, operations, elements and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and/or groups thereof.

It should also be noted that in some alternative implementations, the functions/acts noted may occur out of the order noted in the figures. For example, two functions or acts shown in succession may in fact be executed concurrently or may sometimes be executed in the reverse order, depending upon the functionality/acts involved.

As used herein, the term “communication network” refers to a network following any suitable communication standards, such as Long Term Evolution (LTE) , LTE-Advanced (LTE-A) , Wideband Code Division Multiple Access (WCDMA) , High-Speed Packet Access (HSPA) , and so on. Furthermore, the communications between a terminal device and a network device in the communication network may be performed according to any suitable generation communication protocols, including, but not limited to, the first generation (1G) , the second generation (2G) , 2.5G, 2.75G, the third generation (3G) , the fourth generation (4G) , 4.5G, the future fifth generation (5G) communication protocols, and/or any other protocols either currently known or to be developed in the future.

Embodiments of the present disclosure may be applied in various communication systems. Given the rapid development in communications, there will of course also be future type communication technologies and systems with which the present disclosure may be embodied. It should not be seen as limiting the scope of the present disclosure to only the aforementioned system. For the purpose of illustrations, embodiments of the present disclosure will be described with reference to 5G communication system.

The term “network device” used herein includes, but not limited to, a base station (BS) , a gateway, a registration management entity, and other suitable device in a communication system. The term “base station” or “BS” represents a node B (NodeB or NB) , an evolved NodeB (eNodeB or eNB) , a NR NB (also referred to as a gNB) , a Remote Radio Unit (RRU) , a radio header (RH) , a remote radio head (RRH) , a relay, a low power node such as a femto, a pico, and so forth.

The term “terminal device” used herein includes, but not limited to, “user equipment (UE) ” and other suitable end device capable of communicating with the network device. By way of example, the “terminal device” may refer to a terminal, a Mobile Terminal (MT) , a Subscriber Station (SS) , a Portable Subscriber Station, a Mobile Station (MS) , or an Access Terminal (AT) .

The term “circuitry” used herein may refer 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) combinations of hardware circuits and software, such as (as applicable) :

(i) a combination of analog and/or digital hardware circuit (s) with

software/firmware and

(ii) any portions of hardware processor (s) with 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) hardware circuit (s) and or processor (s) , such as a microprocessor (s) or a portion of a microprocessor (s) , that requires software (e.g., firmware) for operation, but the software may not be present when it is not needed for operation. ”

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 also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and/or firmware. The term circuitry also covers, for example and if applicable to the particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in server, a cellular network device, or other computing or network device.

The term “sounding reference signal (SRS) ” used herein refers to a reference signal transmitted by a terminal device in the uplink direction which is used by a network device to figure out the channel quality of uplink path for each subsections of frequency region.

The term “channel state information (CSI) ” used herein refers to known channel properties of a communication link. This information describes how a signal propagates from the transmitter to the receiver and represents the combined effect of, for example, scattering, fading, and power decay with distance.

As mentioned above, in TDD systems, the UL-DL reciprocity is used where the network device utilizes UL SRS to acquire CSI in DL. Due to different terminal device capabilities there are some terminal devices which have less transmitting antenna ports than receiving antenna ports. Therefore, only those antennas with transmitting ports can be sounded using SRS signals in UL, with the result that only partial CSI is available at the network device, that is to say, partial channel reciprocity.

To deal with the problem of partial channel reciprocity, several solutions have been proposed.

Solution 1: No-precoding matrix indicator (PMI) Feedback. In this scheme, the gNB just uses the available SRS measurements to build the DL precoder. However, with partial channel reciprocity, the overall performance of the DL precoder is compromised.

Solution 2: Partial CSI feedback for gNB to acquire full CSI. In this scheme, the DL CSI obtained by gNB is divided into two parts, one is based on SRS measurement, the other is based on CSI feedback from the UE.

Solution 3: CSI feedback with non-precoded/beamformed CSI-RS including CQI, RI and PMI. In this scheme, the gNB acquires long-term/wideband DL CSI from the SRS measurement and forms beamformed CSI-RS based on that precoder.

Solution 4: SRS antenna switching. In this scheme, UE transmits SRS from different antenna sets in different OFDM symbols or different subframes.

In recent the release Rel-15, it has decided to adopt the Scheme 4, that is, SRS antenna switching. However, there are two main drawbacks: (1) hardware related issue, like insertion loss and switch transient; (2) delay introduced by multiple SRS transmission. Channel matrix is estimated based on different SRS transmission, thus making it an ill choice for very fast users because of the channel aging effect.

Variations on scheme 2 are also enabled in recent the release Rel-15. For example, SRS from a UE can be used to determine a long-term beam, and UE-specific CSI-RS can then be precoded with that long-term beam to enable subsequent up-to-date RI/CQI/PMI feedback for the channel formed by the long term beam.

In Scheme 2, a scheme with partial CSI feedback information is proposed where the 2nd part of CSI information is reported by explicitly signaling the reduced channel frequency response (CFR) part H ₂ or by feeding back the covariance matrix information of H ₂.

It is clear that sending back the quantized version of CFR with no special compression would consume a significant amount of UL overhead. Furthermore, in this solution, the correlation between partial information available at the gNB by SRS sounding, i.e. H ₁ and the missing information H ₂ hasn’t been used to reduce the overall required overhead, which means the required UL overhead is the same as that of an FDD system with no channel reciprocity at all.

Therefore, it is necessary to design a new scheme for acquiring the CSI. According to embodiments of the present disclosure, the CSI is estimated by SRS sounding on reference antennas instead of CSI feedback. In this way, the overhead has been reduced.

Fig. 1 illustrates a schematic diagram of a communication system 100 in which embodiments of the present disclosure can be implemented. The communication system 100, which is a part of a communication network, comprises terminal devices 110-1, 110-2, ..., 110-N (collectively referred to as “terminal device (s) 110” where N is an integer number) , a network device 120. It should be noted that the communication system 100 may also comprise other elements which are omitted for the purpose of clarity. The network device 120 may communicate with the terminal devices 110. It is to be understood that the numbers of terminal devices and network devices shown in Fig. 1 are given for the purpose of illustration without suggesting any limitations.

Communications in the communication system 100 may be implemented according to any proper communication protocol (s) , including, but not limited to, cellular communication protocols of the first generation (1G) , the second generation (2G) , the third generation (3G) , the fourth generation (4G) and the fifth generation (5G) and on the like, wireless local network communication protocols such as Institute for Electrical and Electronics Engineers (IEEE) 802.11 and the like, and/or any other protocols currently known or to be developed in the future. Moreover, the communication may utilize any proper wireless communication technology, including but not limited to: Code Divided Multiple Address (CDMA) , Frequency Divided Multiple Address (FDMA) , Time Divided Multiple Address (TDMA) , Frequency Divided Duplexer (FDD) , Time Divided Duplexer (TDD) , Multiple-Input Multiple-Output (MIMO) , Orthogonal Frequency Divided Multiple Access (OFDMA) and/or any other technologies currently known or to be developed in the future.

Fig. 2 illustrates a schematic diagram of a terminal device with a plurality of antennas. As shown in Fig. 2, the terminal device 110-1 may have the antennas 210-1, 210-2, ..., 210-M (collectively referred to as “antenna (s) 210” where M is an integer number) . In some embodiments, the antennas 210 may be cross-polarization antennas. For example, if the terminal device 110-1 has four cross-polarization antennas, there may be eight ports of the antennas. It should be noted that the antennas shown in Fig. 2 are only examples not limitations. The terminal device 1101-1 may have any other suitable configurations of antennas.

Fig. 3 illustrates a flow chart of a method 300 in accordance with embodiments of the present disclosure. The method 300 may be implemented at any suitable network devices. Only for the purpose of illustrations, the method 300 is described to be implemented at the network device 120.

At block 310, the network device 120 performs a measurement of SRS on at least one reference antenna (for example, the antenna 210-1) selected from the plurality of antennas 210 of the terminal device 110-1. Ifthere is one reference antenna 210-1, the network device 120 may perform the measurement of SRS on the antenna 210-1 at both polarizations. Alternatively, there may be more than reference antennas, for example, the antennas 210-1 and 210-2. The network device 120 may perform the measurement of SRS on the antennas 210-1 and 210-2 with different polarization, respectively.

In some embodiments, the terminal device 110-1 may transmit the index of the at least one reference antenna. For example, the terminal device 110-1 may detect the antenna with the strongest overall coefficients for each polarization and send the index to the network device 120.

In other embodiments, the network device 120 may determine the at least one reference antenna. For example, the network device 120 may obtain the configuration of the plurality of antennas 210. The network device 120 may also obtain historical DL CSI information. The network device 120 may determine the at least one reference antenna based on the configuration and the DL CSI information. The configuration may be obtained from the terminal device 110-1. Alternatively, the configuration may be stored in a storage device accessible by the network device 120. The network device 120 may transmit the index of the determined at least one reference antenna to the terminal device 110-1. The index may be transmitted via any suitable DL signaling.

In some embodiments, the at least one reference antenna may be fixed for every antenna configuration. If the network device 120 obtains the configuration of antennas of the terminal device 110-1, the network device 120 may determine the fixed reference antenna for the terminal device 110-1. In this way, hardware complications are reduced since no antenna switching is needed. Only for the purpose of illustrations, the reference antenna used herein refers to the antenna 210-1.

At block 320, the network device 120 may determine a channel response between the network device 120 and the reference antenna 210-1. For example, the channel response may be represented by the following matrices:

where

refers to the N _s × B channel matrix between polarization 0 of antenna#m ₀ and

refers to o the N _s × B channel matrix between polarization 1 of antenna#m ₁; N is the number of receive antenna ports, B is the number of transmit antenna ports (beams) ; and N _s is the channel support length.

At block 330, the network device 120 receives phase information associated with the plurality antennas from the terminal device 110-1. The phase information may be related to all antennas excluding the reference antenna. The terminal device 110-1 may transmit UL CSI feedback comprising the phase

For example, the phase information may be represented by the following matrix.

where n may be any suitable integer from 0 to M-1. Ifp equals 0, n does not equals m ₀ and ifp equals 1, n does not equals m ₁.

At block 340, the network device 110-1 generates an estimation of CSI between the network device 110-1 and the plurality of antennas 210 based on the phase information and the channel response.

In some embodiments, the network device 110-1 may estimate amplitude information of the plurality of antennas 210 based on the channel response. For example, the terminal device 110-1 may perform the SRS measurement at two polarizations and obtain the channel response on both polarizations (for example, matrices 1 and 2) . The terminal device 120 may determine the amplitude of the antennas at polarization 0 to be the same as the amplitude of the reference antenna 210-1 at polarization 0 and determine the amplitude of the antennas at polarization 1 to be the same as the amplitude of the reference antenna 210-1 at polarization 1.

The network device may determine the CSI based on the channel response and the estimated amplitude information. In this situation, the overall UL overhead is (N _s. B. (N-2) ) × N _phase, where N _phase is the number of bits used to quantize phase component. In this way, the overall overheads have been reduced.

Alternatively, the network device 120 may receive amplitude information from the terminal device 110-1. For example, the terminal device 110-1 may form the amplitude differential matrix by dot division. The amplitude differential matrix may be presented as below:

The terminal device 110-1 may quantize the amplitude information in

is quantized and feed it back to the network device 120. The network device 120 may obtain the amplitude information based on

and the amplitude information of the reference antenna 210-1. The overall UL overhead is (N _s. B. (N-2)) ×(N _phase + N _ampD) , where N _phase is the number of bits used to quantize phase component and N _ampD is the is the number of bits used to quantize amplitude part of the differential matrix. In this way, UL overhead is reduced with improved accuracy.

In some embodiments, the network device 120 may perform DL transmission based on the estimated CSI. Alternatively or in addition, the network device 120 may schedule resources for the terminal device 110-1 based on the estimated CSI.

In some embodiments, an apparatus for performing the method 300 (for example, the network device 120) may comprise respective means for performing the corresponding steps in the method 300. These means may be implemented in any suitable manners. For example, it can be implemented by circuitry or software modules.

In some embodiments, the apparatus comprise: means for performing a measurement of Sounding Reference Signals (SRS) on at least one reference antenna selected from a plurality of antennas of a terminal device; means for determining, based on the measurement, a channel response between the network device and the least one reference antenna; means for receiving, from the terminal device, phase information associated with the plurality of antennas; and means for generating an estimation of channel state information (CSI) between the network device and the plurality of antennas, based on the phase information and the channel response.

In some embodiments, the at least one reference antenna comprises a first cross-polarization antenna, and the means for performing the measurement of SRS comprises means for performing the measurement of SRS on the first cross-polarization antenna at two polarizations.

In some embodiments, the at least one reference antenna comprises a first cross-polarization antenna and a second cross-polarization antenna, and the means for performing the measurement of SRS comprises: means for performing the measurement of SRS on the first cross-polarization antenna at a first polarization; and means for performing the measurement of SRS on the second cross-polarization antenna at a second polarization.

In some embodiments, the means for generating the estimation of the CSI comprises: means for generating a further estimation of amplitude information associated with the plurality of antennas, based on the channel response; and means for generating the estimation of the CSI based on the estimated amplitude information and the phase information.

In some embodiments, the means for generating the estimation of the CSI comprises: means for receiving, from the terminal device, differential amplitude information associated with the plurality of antennas; and means for generating the estimation of the CSI based on the differential amplitude information and the phase information.

In some embodiments, the apparatus further comprises: means for receiving, from the terminal device, an index of the at least one reference antenna.

In some embodiments, the apparatus further comprises: means for obtaining a configuration of the plurality of the antennas of the terminal device; and means for determining, based on the configuration, the at least one antenna.

Fig. 4 illustrates a flow chart of a method 400 in accordance with embodiments of the present disclosure. The method 400 may be implemented at any suitable network devices. Only for the purpose of illustrations, the method 400 is described to be implemented at the terminal device 110-1.

In some embodiments, the terminal device 110-1 may transmit the index of the at least one reference antenna. For example, the terminal device 110-1 may detect the antenna with coefficients for each antenna and select the reference antenna with the strongest overall coefficients on each polarization. The terminal device 110-1 may send the index to the network device 120.

At block 410, the terminal device 110-1 transmits SRS with the plurality of antennas 210 to the network device 120. For example, the terminal device may transmit the SRS every two subframes at the most and every 32 frame (320 subframe) at the least. SRS is transmitted at the last symbol of UL slot with full system band area and it is transmitted by a certain interval.

The terminal device 110-1 may transmit the SRS according to the configuration set by the signaling message (for example, Radio Resource Control (RRC) Connection Setup, RRC Connection Reconfiguration) .

At block 420, the terminal device transmits phase information associated with the plurality of antennas 210 to the network device 120. The terminal device 110-1 may transmit UL CSI feedback comprising the phase

The phase information may be related to all antennas excluding the reference antenna.

At bock 430, the terminal device 110-1 receives downlink transmission which is based on channel state information (CSI) between the network device and the plurality of antennas. In some embodiments, the terminal device 110-1 may receives DL CSI channel frequency response (CFR)

where N is the number of receive antenna ports, B is the number of transmit antenna ports (beams) and N _a is the number of active subcarriers. Through a compressive sensing scheme (CS) , the terminal device 110-1 may find out channel support (location of significant taps) vector

of the time domain channel counterpart of

where N _s is the channel support length.

In some embodiments, every short term feedback, the time domain channel matrix

is quantized and fed back to the network device 120, while every long term feedback the channel support vector

is sent back to the network device 120 via a UL signalling.

In some embodiments, an apparatus for performing the method 400 (for example, the terminal device 110-1) may comprise respective means for performing the corresponding steps in the method 400. These means may be implemented in any suitable manners. For example, it can be implemented by circuitry or software modules.

In some embodiments, the apparatus comprises: means for transmitting, to a network device, Sounding Reference Signals (SRS) with a plurality of antennas of the terminal device to obtain a channel response between at least one reference antenna and the network device by the network device; means for transmitting, to the network device, phase information associated with the plurality of antennas; and means for receiving, from the network device, downlink transmission which is based on channel state information (CSI) between the network device and the plurality of antennas, the CSI being estimated based on the channel response and the phase information.

In some embodiments, the apparatus further comprises: means for transmitting, to the network device, amplitude information associated with the plurality of antennas.

In some embodiments, the apparatus further comprises: means for selecting, based on amplitude information associated with the plurality of antennas, the at least one reference antenna from the plurality of antennas; and means for transmitting, to the network device, an index of the at least one reference antenna.

Fig. 5 is a simplified block diagram of a device 500 that is suitable for implementing embodiments of the present disclosure. The device 500 may be implemented at the network device 120. The device 500 may also be implemented at the terminal device 110-1. As shown, the device 500 includes one or more processors 510, one or more memories 520 coupled to the processor (s) 510, one or more transmitters and/or receivers (TX/RX) 540 coupled to the processor 510.

The processor 510 may be of any type suitable to the local technical network, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on multicore processor architecture, as non-limiting examples. The device 500 may have multiple processors, such as an application specific integrated circuit chip that is slaved in time to a clock which synchronizes the main processor.

The memory 520 may be of any type suitable to the local technical network and may be implemented using any suitable data storage technology, such as a non-transitory computer readable storage medium, semiconductor based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory, as non-limiting examples.

The memory 520 stores at least a part of a program 530. The TX/RX 540 is for bidirectional communications. The TX/RX 540 has at least one antenna to facilitate communication, though in practice an Access Node mentioned in this application may have several ones. The communication interface may represent any interface that is necessary for communication with other network elements.

The program 530 is assumed to include program instructions that, when executed by the associated processor 510, enable the device 500 to operate in accordance with the embodiments of the present disclosure, as discussed herein with reference to Figs. 3 and 4. That is, embodiments of the present disclosure can be implemented by computer software executable by the processor 510 of the device 500, or by hardware, or by a combination of software and hardware.

While this specification contains many specific implementation details, these should not be construed as limitations on the scope of any disclosure or of what may be claimed, but rather as descriptions of features that may be specific to particular embodiments of particular disclosures. Certain features that are described in this specification in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable sub-combination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a sub-combination or variation of a sub-combination.

Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Moreover, the separation of various system components in the embodiments described above should not be understood as requiring such separation in all embodiments, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged into multiple software products.

Various modifications, adaptations to the foregoing exemplary embodiments of this disclosure may become apparent to those skilled in the relevant arts in view of the foregoing description, when read in conjunction with the accompanying drawings. Any and all modifications will still fall within the scope of the non-limiting and exemplary embodiments of this disclosure. Furthermore, other embodiments of the disclosures set forth herein will come to mind to one skilled in the art to which these embodiments of the disclosure pertain having the benefit of the teachings presented in the foregoing descriptions and the associated drawings.

Therefore, it is to be understood that the embodiments of the disclosure are not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims. Although specific terms are used herein, they are used in a generic and descriptive sense only and not for purpose of limitation.

Claims

A network device, comprising:

at least one processor; and

a memory coupled to the at least one processor, the memory storing instructions therein, the instructions, when executed by the at least one processor, causing the network device to:

perform a measurement of Sounding Reference Signals (SRS) on at least one reference antenna selected from a plurality of antennas of the terminal device;

determine, based on the measurement, a channel response between the network device and the least one reference antenna;

receive, from the terminal device, phase information associated with the plurality of antennas; and

generate an estimation of channel state information (CSI) between the network device and the plurality of antennas, based on the phase information and the channel response.
The network device of claim 1, wherein the at least one reference antenna comprises a first cross-polarization antenna, wherein the network device is caused to perform the measurement of SRS by:

performing the measurement of SRS on the first cross-polarization antenna at two polarizations.
The network device of claim 1, wherein the at least one reference antenna comprises a first cross-polarization antenna and a second cross-polarization antenna, wherein the network device is caused to perform the measurement of SRS by:

performing the measurement of SRS on the first cross-polarization antenna at a first polarization; and

performing the measurement of SRS on the second cross-polarization antenna at a second polarization.
The network device of claim 1, wherein the network device is caused to generate the estimation of the CSI by:

generating a further estimation of amplitude information associated with the plurality of antennas, based on the channel response; and

generating the estimation of the CSI based on the further estimation of estimated amplitude information and the phase information.
The network device of claim 1, wherein the network device is caused to generate the estimation of the CSI by:

receiving, from the terminal device, differential amplitude information associated with the plurality of antennas; and

generating the estimation of the CSI based on the differential amplitude information and the phase information.
The network device of claim 1, wherein the network device is further caused to:

receive, from the terminal device, an index of the at least one reference antenna.
The network device of claim 1, wherein the network device is further caused to:

obtain a configuration of the plurality of the antennas of the terminal device; and

determine, based on the configuration, the at least one antenna.
A terminal device, comprising:

at least one processor; and

a memory coupled to the at least one processor, the memory storing instructions therein, the instructions, when executed by the at least one processor, causing the terminal device to:

transmit, to a network device, Sounding Reference Signals (SRS) with a plurality of antennas of the terminal device to obtain a channel response between at least one reference antenna and the network device by the network device;

transmit, to the network device, phase information associated with the plurality of antennas; and

receive, from the network device, downlink transmission which is based on channel state information (CSI) between the network device and the plurality of antennas, the CSI being estimated based on the channel response and the phase information.
The terminal device of claim 8, wherein the terminal device is further caused to:

transmit, to the network device, amplitude information associated with the plurality of antennas.
The terminal device of claim 8, wherein the terminal device is further caused to:

select, based on amplitude information associated with the plurality of antennas, the at least one reference antenna from the plurality of antennas; and

transmit, to the network device, an index of the at least one reference antenna.
A method for communication, comprising:

performing, at a network device, a measurement of Sounding Reference Signals (SRS) on at least one reference antenna selected from a plurality of antennas of a terminal device;

determining, based on the measurement, a channel response between the network device and the least one reference antenna;

receiving, from the terminal device, phase information associated with the plurality of antennas; and

generating an estimation of channel state information (CSI) between the network device and the plurality of antennas, based on the phase information and the channel response.
The method of claim 11, wherein the at least one reference antenna comprises a first cross-polarization antenna, and wherein performing the measurement of SRS comprises:

performing the measurement of SRS on the first cross-polarization antenna at two polarizations.
The method of claim 11, wherein the at least one reference antenna comprises a first cross-polarization antenna and a second cross-polarization antenna, and wherein performing the measurement of SRS comprises:

performing the measurement of SRS on the first cross-polarization antenna at a first polarization; and

performing the measurement of SRS on the second cross-polarization antenna at a second polarization.
The method of claim 11, wherein generating the estimation of the CSI comprises:

generating a further estimation of amplitude information associated with the plurality of antennas, based on the channel response; and

generating the estimation of the CSI based on the further estimation of estimated amplitude information and the phase information.
The method of claim 11, wherein generating the estimation of the CSI comprises:

receiving, from the terminal device, differential amplitude information associated with the plurality of antennas; and

generating the estimation of the CSI based on the differential amplitude information and the phase information.
The method of claim 11, further comprising:

receiving, from the terminal device, an index of the at least one reference antenna.
The method of claim 11, further comprising:

obtaining a configuration of the plurality of the antennas of the terminal device; and

determining, based on the configuration, the at least one antenna.
A method for communication, comprising:

at a terminal device,

transmitting, to a network device, Sounding Reference Signals (SRS) with a plurality of antennas of the terminal device to obtain a channel response between at least one reference antenna and the network device by the network device;

transmitting, to the network device, phase information associated with the plurality of antennas; and

receiving, from the network device, downlink transmission which is based on channel state information (CSI) between the network device and the plurality of antennas, the CSI being estimated based on the channel response and the phase information.
The method of claim 18, further comprising:

transmitting, to the network device, amplitude information associated with the plurality of antennas.
The method of claim 18, further comprising:

selecting, based on amplitude information associated with the plurality of antennas, the at least one reference antenna from the plurality of antennas; and

transmitting, to the network device, an index of the at least one reference antenna.
A computer readable medium storing instructions thereon, the instructions, when executed by at least one processing unit of a machine, causing the machine to perform the method according to any one of claims 11-17.
A computer readable medium storing instructions thereon, the instructions, when executed by at least one processing unit of a machine, causing the machine to perform the method according to any one of claims 18-20.
An apparatus comprising:

means for performing a measurement of Sounding Reference Signals (SRS) on at least one reference antenna selected from a plurality of antennas of a terminal device;

means for determining, based on the measurement, a channel response between the network device and the least one reference antenna;

means for receiving, from the terminal device, phase information associated with the plurality of antennas; and

means for generating an estimation of channel state information (CSI) between the network device and the plurality of antennas, based on the phase information and the channel response.
An apparatus comprising:

means for transmitting, to a network device, Sounding Reference Signals (SRS) with a plurality of antennas of the terminal device to obtain a channel response between at least one reference antenna and the network device by the network device;

means for transmitting, to the network device, phase information associated with the plurality of antennas; and

means for receiving, from the network device, downlink transmission which is based on channel state information (CSI) between the network device and the plurality of antennas, the CSI being estimated based on the channel response and the phase information.