CN113037347A

CN113037347A - CSI feedback for MIMO wireless communication systems with polarized active antenna arrays

Info

Publication number: CN113037347A
Application number: CN202110275622.5A
Authority: CN
Inventors: 南映瀚; 李旸; 埃科·昂高萨努斯
Original assignee: Samsung Electronics Co Ltd
Current assignee: Samsung Electronics Co Ltd
Priority date: 2014-11-17
Filing date: 2015-11-17
Publication date: 2021-06-25
Also published as: CN106797242B; CN106797242A; KR102373467B1; KR20160058716A

Abstract

The present disclosure relates to pre-generation 5 (5G) or 5G communication systems that will be used to support higher data rates than super generation 4 (4G) communication systems such as Long Term Evolution (LTE). A base station capable of communicating with a User Equipment (UE) includes: a transceiver configured to transmit, to a UE, a downlink signal containing a first reference signal (RS configuration) on a downlink channel and a first set of RSs according to the first RS configuration, and to receive an uplink signal from the UE containing a Precoding Matrix Indicator (PMI) derived using the first set of RSs; and a controller configured to convert the PMI into one of predetermined precoding vectors.

Description

CSI feedback for MIMO wireless communication systems with polarized active antenna arrays

The application is a divisional application of Chinese patent application with application number of 201580053807.4 and application date of 2015, 11 and 17.

Technical Field

The present disclosure relates generally to codebook designs and structures associated with two-dimensional transmit antenna arrays. Such two-dimensional arrays are associated with a type of MIMO system commonly referred to as "full-dimensional" multiple-input multiple-output (MIMO) (FD-MIMO).

Background

In order to meet the increasing demand for wireless data services since the deployment of 4 th generation (4G) communication systems, efforts have been made to develop improved 5 th generation (5G) or pre-5G (pre-5G) communication systems. Therefore, the 5G or pre-5G communication system is also referred to as a 'super 4G network' or a 'post-LTE system'.

The 5G communication system is considered to be implemented in a higher frequency (millimeter wave) band (for example, 60GHz band) in order to accomplish higher data rates. In order to reduce propagation loss of radio waves and increase transmission distance, beamforming, massive Multiple Input Multiple Output (MIMO), full-dimensional MIMO (FD-MIMO), array antenna, analog wave velocity formation, massive antenna techniques are discussed in the 5G communication system.

Further, in the 5G communication system, development for system network improvement is being performed based on advanced small cells, cloud Radio Access Network (RAN), ultra-dense network, device-to-device (D2D) communication, wireless backhaul, mobile network, cooperative communication, coordinated multipoint (CoMP), reception-side interference cancellation, and the like.

In 5G systems, hybrid FSK and QAM modulation (FQAM) and Sliding Window Superposition Coding (SWSC) have been developed as Advanced Coding Modulation (ACM), and filter bank multi-carrier (FBMC), non-orthogonal multiple access (NOMA), and Sparse Code Multiple Access (SCMA) as advanced access techniques.

Wireless communication has become one of the most successful innovations in modern history. In recent years, the number of subscribers to wireless communication services exceeds an billion and continues to grow rapidly. The demand for wireless data services is rapidly increasing as smart phones and other mobile data devices, such as tablet computers, "notebook" computers, netbooks, e-book readers, and machine type devices, are becoming increasingly popular among consumers and the services are growing. In order to meet the high growth of mobile data traffic and support new applications and deployments, improvements in radio interface efficiency and coverage are of paramount importance.

Disclosure of Invention

Technical problem

An aspect of the present disclosure provides an antenna array with higher performance.

Solution to the problem

In an aspect according to the present disclosure, a base station capable of communicating with a User Equipment (UE) includes: a transceiver configured to transmit, for a UE, an 8-port CSI-RS configured according to a channel State information-reference Signal (CSI-RS) and a downlink signal containing a CSI-RS configuration on a Physical Downlink Shared Channel (PDSCH), and receive an uplink signal containing Channel State Information (CSI) derived from the 8-port CSI-RS from the UE; and a controller configured to map the CSI to one of predetermined precoding vectors, the precoding vectors comprising:

in a second embodiment, a user equipment comprises: a transceiver configured to receive a downlink signal containing a CSI-RS configuration on a PDSCH transmitted by a BS and an 8-port CSI-RS configured according to the CSI-RS, and transmit an uplink signal containing Channel State Information (CSI); a controller configured to decode a CSI-RS configuration from a downlink signal and derive CSI based on an 8-port CSI-RS by utilizing a channel estimate, the CSI being mapped to one of precoding vectors comprising:

in a third embodiment, a method for communicating with a User Equipment (UE), the method comprising: transmitting, for a UE, an 8-port CSI-RS configured according to a channel state information-reference signal (CSI-RS) and a downlink signal containing a CSI-RS configuration on a Physical Downlink Shared Channel (PDSCH), and receiving an uplink signal containing Channel State Information (CSI) derived from the 8-port CSI-RS from the UE; and mapping the CSI to one of predetermined precoding vectors, the precoding vectors comprising:

in some embodiments, two CSI-RSs on

antenna ports

15 and 19, out of the 8-port CSI-RSs, are mapped to a first and second set of the same number of antenna elements, respectively, that apply substantially similar beamforming weight vectors, wherein the antenna elements on the first set are polarized according to a first angle, the antenna elements on the second set are polarized according to a second angle, and the two antenna elements on the first and second sets are located at the same physical location comprising a dual-polarized pair, and wherein a difference between the first and second angles is substantially equal to 90 degrees.

In some embodiments, each of the 8-port CSI-RSs is beamformed by a beamforming weight vector that is estimated by a Sounding Reference Signal (SRS) transmitted by the UE.

In some embodiments, the CSI-RS is beamformed by a beamforming weight vector, and wherein the controller is further configured to derive the beamforming weight vector by processing a precoding vector reported by the UE.

In some embodiments, the transceiver is further configured to transmit a downlink signal containing a second CSI-RS configuration on the PDSCH and an N-port CSI-RS according to the second CSI-RS configuration, N being a positive integer, and receive an uplink signal from the UE containing the second CSI, the second CSI comprising a secondary CSI from N₂A non-negative integer derived in the port CSI-RS, and wherein the controller is further configured to determine the precoding vector as an oversampled DFT vector as a function of the second CSI.

In some embodiments, the transceiver is further configured to transmit a downlink signal containing a second CSI-RS configuration on the PDSCH and an N-port CSI-RS according to the second CSI-RS configuration, and to receive an uplink signal from the UE containing the second CSI comprising two non-negative integers derived from the N-port CSI-RS, and wherein the controller is further configured to determine the precoding vector as a kronecker product of two oversampled DFT vectors corresponding to the second CSI.

In some embodiments, a method for operating a BS in communication with a User Equipment (UE) comprises: transmitting a downlink signal containing a first RS configuration on a downlink channel and a first set of Reference Signal (RS) configurations according to a first RS of a UE; and receiving an uplink signal from the UE, the uplink signal containing a Precoding Matrix Indicator (PMI) derived using the first set of RSs, and converting the PMI into one of predetermined precoding vectors.

A UE capable of communicating with a BS, the UE comprising: a transceiver configured to receive downlink signals transmitted by a BS containing a first RS configuration on a downlink channel and a first set of RSs according to the first RS configuration, and to transmit uplink signals containing a PMI; and a controller configured to decode a first RS configuration from the downlink signal and derive a PMI based on the first set of RSs by utilizing channel estimation, the PMI being converted into one of the precoding vectors.

The method for operating a UE communicating with a BS includes: receiving a downlink signal transmitted by a BS containing a Reference Signal (RS) configuration on a downlink channel and a first set of RSs according to the first RS configuration; transmitting an uplink signal containing a PMI; decoding a first RS configuration from a downlink signal; and deriving a PMI by using channel estimation based on the first set of RSs, the PMI being converted into one of the precoding vectors.

The method for the UE to communicate with the BS comprises the following steps: receiving a first set of Reference Signals (RSs) from a BS; transmitting a first feedback signal to the BS; receiving a second set of RSs from the BS; and transmitting a second feedback signal to the BS, wherein the second set of RSs are beamformed using a predetermined precoder based on the first feedback signal, wherein the first feedback signal includes channel direction information generated based on the first set of RSs, and wherein the second feedback signal includes channel state information generated based on the second set of RSs.

In some embodiments, the N CSI-RS are mapped to a 2-dimensional array of N transceiver elements, which are respectively mapped to N antenna sub-arrays disposed on a 2-dimensional antenna panel.

Before proceeding with the detailed description below, it may be advantageous to set forth definitions of certain words and phrases used in this patent document. The term "couple" and its derivatives refer to any direct or indirect communication between two or more elements, whether or not those elements are in physical contact with one another. The terms "transmit," "receive," and "communicate," as well as derivatives thereof, encompass both direct and indirect communication. The terms "include" and "comprise," as well as derivatives thereof, mean inclusion without limitation. The term "or" is open-ended, meaning and/or. The phrase "associated with … …" and derivatives thereof is intended to mean including, included within, interconnected with, containing, contained within, connected to, or connected to, coupled to or coupled with, communicable with, cooperative with, intersecting, juxtaposed, proximate to, joined to or joined with, having the nature of, having a relationship to, etc. The term "controller" refers to any device, system, or part thereof that controls at least one operation. Such controllers may be implemented in hardware or a combination of hardware and software and/or firmware. The functionality associated with any particular controller may be distributed or centralized, whether locally or remotely. The phrase "at least one of," when used in conjunction with a list of items, means that a different combination of one or more of the listed items can be used and only one item in the list can be required. For example, "at least one of A, B and C" includes any one of the following combinations: A. b, C, A and B, A and C, B and C as well as A and B and C.

Further, the various functions described below may be implemented or supported by one or more computer programs, each of which is formed from computer-readable program code and embodied in a computer-readable medium. The terms "application" and "program" refer to one or more computer programs, software components, sets of instructions, procedures, functions, objects, classes, instances, related data, or a portion thereof adapted for implementation in suitable computer readable program code. The phrase "computer readable program code" includes any type of computer code, including source code, target code, and executable code. The phrase "computer readable medium" includes any type of medium capable of being accessed by a computer, such as Read Only Memory (ROM), Random Access Memory (RAM), a hard disk drive, a Compact Disc (CD), a Digital Versatile Disc (DVD), or any other type of memory. "non-transitory" computer-readable media exclude wired, wireless, optical, or other communication links that transport transitory electrical or other signals. Non-transitory computer readable media include media that can permanently store data and media that can store and later rewrite data, such as rewritable optical disks or erasable storage devices.

Definitions for certain other words and phrases are provided throughout this patent document. Those of ordinary skill in the art should understand that in many, if not most instances, such definitions apply to prior, as well as future uses of such defined words and phrases.

The invention has the advantages of

The performance of the communication system can be improved.

Drawings

For a more complete understanding of the present invention and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, wherein like reference numbers represent like parts:

fig. 1 illustrates an example wireless network in accordance with this disclosure;

fig. 2A and 2B illustrate example wireless transmit and receive paths according to the present disclosure;

fig. 3A illustrates an example user device in accordance with this disclosure;

fig. 3B illustrates an example enhanced nodeb (enb) according to the present disclosure;

fig. 4A and 4B illustrate an example 2D antenna array including 16 dual polarized antenna elements according to the present disclosure;

fig. 5 illustrates another numbering of TX antenna elements according to the present disclosure;

fig. 6 illustrates a polarized CSI-RS transmission according to the present disclosure;

fig. 7A and 7B illustrate a sequentially polarized CSI-RS transmission 700 according to the present disclosure;

fig. 8 illustrates flexible polarized CSI-RS transmission according to the present disclosure;

fig. 9A and 9B illustrate eNB transmissions and corresponding UE feedback for two types of CSI-RS according to the present disclosure;

FIG. 10 illustrates an example CSI-RS port virtualization implementation in accordance with the present disclosure;

11A and 11B illustrate DFT beam index grids in accordance with the present disclosure;

fig. 12 illustrates a flow diagram relating to UE and eNB operations related to short-term CSI feedback in accordance with the present disclosure; and

fig. 13 illustrates a short-term CSI estimation time window according to the present disclosure.

Detailed Description

Fig. 1 through 13, discussed below, and the various embodiments used to describe the principles of the present disclosure in this patent document are by way of illustration only and should not be construed in any way to limit the scope of the disclosure. Those skilled in the art will understand that the principles of the present disclosure may be implemented in any suitably arranged wireless communication system.

The following documents and standard descriptions are hereby incorporated into this disclosure as if fully set forth herein: (1) 3 rd generation partnership project (3GPP) TS36.211, "E-UTRA, Physical channel and modulation", Release-12; (2)3GPP TS 36.212, "E-UTRA, Multiplexing and channel coding", Release-12; and (3)3GPP TS36.213, "E-UTRA, Physical layer procedures", Release-12.

Fig. 1 illustrates an example wireless network 100 in accordance with this disclosure. The embodiment of the wireless network 100 shown in fig. 1 is for illustration only. Other embodiments of wireless network 100 may be used without departing from the scope of this disclosure.

The wireless network 100 includes an enodeb (eNB)101, an eNB 102, and an eNB 103. The eNB 101 communicates with the eNB 102 and the eNB 103. The eNB 101 also communicates with at least one Internet Protocol (IP) network 130, such as the internet, a proprietary IP network, or other data network.

Other well-known terms may be used instead of "eNodeB" or "eNB," such as "base station" or "access point," depending on the network type. For convenience, the terms "eNodeB" and "eNB" are used in this patent document to refer to network infrastructure components that provide wireless access to remote terminals. In addition, other well-known terms may be used instead of "user equipment" or "UE," such as "mobile station," "subscriber station," "remote terminal," "wireless terminal," or "user equipment," depending on the network type. For convenience, the terms "user equipment" and "UE" are used in this patent document to refer to a remote wireless device that wirelessly accesses an eNB, whether the UE is a mobile device (such as a mobile phone or smartphone) or generally considered a stationary device (such as a desktop computer or vending machine).

eNB 102 provides wireless broadband access to network 130 for a first plurality of User Equipments (UEs) within coverage area 120 of eNB 102. The first plurality of UEs includes: UE 111, which may be located in a small enterprise (SB); UE 112, which may be located in company (E); UE 113, which may be located in a WiFi Hotspot (HS); UE 114, which may be located in a first residence (R); UE 115, which may be located in a second residence (R); and a UE 116, which may be a mobile device (M), such as a cell phone, wireless laptop, wireless PDA, etc. eNB 103 provides wireless broadband access to network 130 for a second plurality of UEs within coverage area 125 of eNB 103. The second plurality of UEs includes UE 115 and UE 116. In some embodiments, one or more of the enbs 101-103 may communicate with each other and with UEs 111-116 using 5G, Long Term Evolution (LTE), LTE-A, WiMAX, or other advanced wireless communication technologies.

The dashed lines illustrate the approximate extent of

coverage areas

120 and 125, which are shown as approximately circular for purposes of illustration and explanation only. It should be clearly understood that the coverage areas associated with the enbs (such as coverage areas 120 and 125) may have other shapes, including irregular shapes, depending on the configuration of the eNB and variations in the radio environment associated with natural and man-made obstructions.

As described in more detail below, one or more of BS 101, BS 102, and BS 103 include a 2D antenna array as described in embodiments of the present disclosure. In some embodiments, one or more of BS 101, BS 102, and BS 103 support codebook design and structure for systems with 2D antenna arrays.

Although fig. 1 illustrates one example of a wireless network 100, various changes may be made to fig. 1. For example, wireless network 100 may include any number of enbs and any number of UEs in any suitable arrangement. In addition, the eNB 101 may communicate directly with any number of UEs and provide those UEs wireless broadband access to the network 130. Similarly, each eNB 102 to 103 may communicate directly with network 130 and provide direct wireless broadband access to network 130 for UEs. Further, the

enbs

101, 102 and/or 13 may provide access to other or additional external networks, such as a voice over internet protocol network or other types of data networks.

Fig. 2A and 2B illustrate example wireless transmit and receive paths according to this disclosure. In the following description, the transmit path 200 may be described as being implemented in an eNB (such as eNB 102), while the receive path 250 may be described as being implemented in a UE (such as UE 116). However, it should be understood that the receive path 250 may be implemented in the eNB and the transmit path 200 may be implemented in the UE. In some embodiments, receive path 250 is configured to support codebook design and structure for systems with 2D antenna arrays as described in embodiments of the present disclosure.

The transmit path 200 includes a channel coding and modulation block 205, a serial-to-parallel (S-to-P) block 210, an Inverse Fast Fourier Transform (IFFT) block 215 with a number of samples N, a parallel-to-serial (P-to-S) block 220, an add cyclic prefix block 225, and an up-converter (UC) 230. Receive path 250 includes a down-converter (DC)255, a remove cyclic prefix block 260, a serial-to-parallel (S-to-P) block 265, a Fast Fourier Transform (FFT) block 270 with a number of samples N, a parallel-to-serial (P-to-S) block 275, and a channel decode and demodulation block 280.

In transmit path 200, a channel coding and modulation block 205 receives a set of information bits, applies a coding, such as Low Density Parity Check (LDPC) coding, and modulates (such as by Quadrature Phase Shift Keying (QPSK) or Quadrature Amplitude Modulation (QAM)) the input bits to generate a sequence of frequency domain modulation symbols. The serial-to-parallel block 210 converts (e.g., demultiplexes) the serial modulation symbols into parallel data to generate N parallel symbol streams, where N is the number of samples of the IFFT/FFT used in the eNB 102 and UE 116. IFFT block 215, having a number of samples N, performs an IFFT operation on the N parallel symbol streams to generate a time domain output signal. Parallel-to-serial block 220 converts (such as demultiplexes) the parallel time-domain output signals from IFFT block 215 with a number of samples N to generate a serial time-domain signal. Add cyclic prefix block 225 inserts a cyclic prefix to the time domain signal. Upconverter 230 modulates (such as upconverts) the output of add cyclic prefix block 225 to an RF frequency for transmission over a wireless channel. The signal may also be filtered at baseband before conversion to RF frequency.

The transmission RF signal from the eNB 102 reaches the UE 116 after passing through the wireless channel, and the reverse operation at the eNB 102 is performed at the UE 116. Downconverter 255 downconverts the received signal to baseband frequency and remove cyclic prefix block 260 removes the cyclic prefix to generate a serial time-domain baseband signal. Serial-to-parallel block 265 converts the time-domain baseband signal to parallel time-domain signals. The FFT block 270 with the number of samples N performs an FFT algorithm to generate N parallel frequency domain signals. Parallel-to-serial block 275 converts the parallel frequency domain signals to a sequence of modulated data symbols. Channel decode and demodulation block 280 demodulates and decodes the modulated symbols to recover the original input data stream.

each of the enbs 101 to 103 may implement a transmit path 200 similar to transmission to UEs 111 to 116 in the downlink and may implement a receive path 250 similar to reception from UEs 111 to 116 in the uplink. Similarly, each of the UEs 111 to 116 may implement a transmit path 200 for transmission in the uplink to the enbs 101 to 103 and may implement a receive path 250 for reception in the downlink from the enbs 101 to 103.

Each of the components in fig. 2A and 2B may be implemented using hardware alone or a combination of hardware and software/firmware. As a particular example, at least some of the components in fig. 2A and 2B may be implemented in software, while other components may be implemented by configurable hardware or a mixture of software and configurable hardware. For example, FFT block 270 and IFFT block 215 may be implemented as configurable software algorithms, where the value of the number of samples N may vary depending on the implementation.

Furthermore, although described as using an FFT and IFFT, this is for illustration only and should not be construed as limiting the scope of the disclosure. Other types of transforms may be used, such as Discrete Fourier Transform (DFT) and Inverse Discrete Fourier Transform (IDFT) functions. It should be appreciated that the value of the variable N may be any integer for the DFT and IDFT functions (such as 1, 2, 3, 4, etc.), while the value of the variable N may be a power of two for the DFT and IDFT functions (such as 1, 2, 4, 8, 16, etc.).

Although fig. 2A and 2B show examples of wireless transmission and reception paths, various changes may be made to fig. 2A and 2B. For example, various components in fig. 2A and 2B may be combined, further subdivided, or omitted, and additional components may be added according to particular needs. In addition, fig. 2A and 2B are intended to illustrate examples of the types of transmit and receive paths that may be used in a wireless network. Any other suitable architecture may be used to support wireless communications in a wireless network.

Fig. 3A illustrates an example UE 116 according to the present disclosure. The embodiment of UE 116 shown in fig. 3A is for illustration only, and UEs 111-115 of fig. 1 may have the same or similar configurations. However, UEs have a wide variety of configurations, and fig. 3A does not limit the scope of the disclosure to any particular implementation of a UE.

The UE 116 includes an antenna 305, a Radio Frequency (RF) transceiver 310, Transmit (TX) processing circuitry 315, a microphone 320, and Receive (RX) processing circuitry 325. The UE 116 also includes a speaker 330, a main processor 340, an input/output (I/O) Interface (IF)345, a keypad 350, a display 355, and a memory 360. Memory 360 includes a basic Operating System (OS) program 361 and one or more applications 362.

The RF transceiver 310 receives an input RF signal from the antenna 305 that is transmitted by an eNB of the network 100. The RF transceiver 310 down-converts an input RF signal to generate an Intermediate Frequency (IF) or baseband signal. The IF or baseband signal is sent to RX processing circuitry 325 to generate a processed baseband signal by filtering, decoding, and/or digitizing the baseband or IF signal. RX processing circuitry 325 transmits the processed baseband signal to speaker 330 (such as for voice data) or to main processor 340 for further processing (such as for web browsing data).

TX processing circuitry 315 receives analog or digital voice data from microphone 320 or other outgoing baseband data (such as network data, e-mail, or interactive video game data) from main processor 340. TX processing circuitry 315 encodes, multiplexes, and/or digitizes the output baseband data to generate a processed baseband or IF signal. RF transceiver 310 receives the output processed baseband or IF signal from TX processing circuitry 315 and upconverts the baseband or IF signal to an RF signal, which is transmitted via antenna 305.

Main processor 340 may include one or more processors or other processing devices and executes basic OS programs 361 stored in memory 360 in order to control overall operation of UE 116. For example, main processor 340 may control the reception of forward channel signals and the transmission of reverse channel signals by RF transceiver 310, RX processing circuitry 325, and TX processing circuitry 315 in accordance with well-known principles. In some embodiments, main processor 340 includes at least one microprocessor or microcontroller.

Main processor 340 may also be capable of executing other processes and programs resident in memory 310, such as operations for channel quality measurement and reporting for systems having 2D antenna arrays as described in embodiments of the present disclosure. Main processor 340 may move data to and from memory 360 as needed for the execution process. In some embodiments, main processor 340 is configured to execute applications 362 based on OS program 361 or in response to signals received from an eNB or operator. Main processor 340 is also coupled to I/O interface 345, which provides UE 116 with the ability to connect to other devices, such as laptops and handhelds. I/O interface 345 is the communication path between these accessories and main processor 340.

Main processor 340 is also coupled to keypad 350 and display unit 355. An operator of the UE 116 may input data to the UE 116 using the keypad 350. Display 355 may be a liquid crystal display or other display capable of presenting text and/or at least limited graphics, such as from a web page.

Memory 360 is coupled to main processor 340. A portion of memory 360 may include Random Access Memory (RAM) and another portion of memory 360 may include flash memory or other Read Only Memory (ROM).

Although fig. 3A shows one example of the UE 116, various changes may be made to fig. 3A. For example, various components in fig. 3A may be combined, further subdivided, or omitted, and additional components may be added according to particular needs. As a particular example, main processor 340 may be divided into multiple processors, such as one or more Central Processing Units (CPUs) and one or more Graphics Processing Units (GPUs). Additionally, although fig. 3A illustrates the UE 116 configured as a mobile phone or smartphone, the UE may be configured to operate as other types of mobile or fixed devices.

Fig. 3B illustrates an example eNB 102 in accordance with this disclosure. The embodiment of eNB 102 shown in fig. 3B is for illustration only, and the other enbs of fig. 1 may have the same or similar configurations. However, enbs have a wide variety of configurations, and fig. 3B does not limit the scope of the disclosure to any particular implementation of an eNB. It should be noted that eNB 101 and eNB 103 may include the same or similar structure as eNB 102.

As shown in fig. 3B, the eNB 102 includes multiple antennas 370a through 370n, multiple RF transceivers 372a through 372n, Transmit (TX) processing circuitry 374, and Receive (RX) processing circuitry 376. In certain embodiments, one or more of the plurality of antennas 370a through 370n comprises a 2D antenna array. The eNB 102 also includes a controller/processor 378, memory 380, and a backhaul or network interface 382.

RF transceivers 372a through 372n receive incoming RF signals from antennas 370a through 370n, such as signals transmitted by a UE or other eNB. RF transceivers 372a through 372n down-convert the input RF signals to generate IF or baseband signals. The IF or baseband signal is sent to RX processing circuitry 376 to generate a processed baseband signal by filtering, decoding, and/or digitizing the baseband or IF signal. The RX processing circuit 376 transmits the processed baseband signals to the controller/processor 378 for further processing.

TX processing circuitry 374 receives analog or digital data (such as voice data, network data, email, or interactive video game data) from controller/processor 378. TX processing circuitry 374 encodes, multiplexes, and/or digitizes the output baseband data to generate a processed baseband or IF signal. RF transceivers 372a through 372n receive the output processed baseband or IF signals from TX processing circuitry 374 and upconvert the baseband or IF signals to RF signals transmitted via antennas 370a through 370 n.

The controller/processor 378 may include one or more processors or other processing devices that control overall operation of the eNB 102. For example, the controller/processor 378 may control the reception of forward channel signals and the transmission of reverse channel signals by the RF transceivers 372a through 372n, the RX processing circuitry 376, and the TX processing circuitry 374 in accordance with well-known principles. The controller/processor 378 may also support additional functions such as higher-level wireless communication functions. For example, controller/processor 378 may perform a Blind Interference Sensing (BIS) process, such as by a BIS algorithm, and decode the received signal minus the interfering signal. In the eNB 102, the controller/processor 378 may support any of a wide variety of other functions. In some embodiments, controller/processor 378 includes at least one microprocessor or microcontroller.

Controller/processor 378 may also be capable of executing programs and other processes resident in memory 380, such as a base OS. The controller/processor 378 can also support channel quality measurement and reporting for systems with 2D antenna arrays as described in embodiments of the present disclosure. In some embodiments, the controller/processor 378 supports communication between entities, such as the network RTC. The controller/processor 378 may move data to and from the memory 380 as needed to perform processes.

Controller/processor 378 is also coupled to backhaul or network interface 382. The backhaul or network interface 382 allows the eNB 102 to communicate with other devices or systems over a backhaul connection or over a network. Interface 382 may support communication via any suitable wired or wireless connection. For example, when eNB 102 is implemented as part of a cellular communication system (such as a 5G, LTE or LTE-a enabled system), interface 382 may allow eNB 102 to communicate with other enbs over a wired or wireless backhaul connection. When eNB 102 is implemented as an access point, interface 382 may allow eNB 102 to communicate over a wired or wireless local area network or over a wired or wireless connection to a larger network, such as the internet. Interface 382 includes any suitable structure that supports communication via a wired or wireless connection, such as an ethernet or RF transceiver.

A memory 380 is coupled to the controller/processor 378. A portion of memory 380 may include RAM and another portion of memory 380 may include flash memory or other ROM. In some embodiments, a plurality of instructions (such as a BIS algorithm) are stored in memory. The plurality of instructions are configured to cause the controller/processor 378 to perform a BIS process and decode the received signal after subtracting at least one interfering signal determined by a BIS algorithm.

As described in more detail below, the transmit and receive paths of the eNB 102 (implemented using the RF transceivers 372 a-372 n, the TX processing circuitry 374, and/or the RX processing circuitry 376) support communication with an aggregation of FDD and TDD cells.

Although fig. 3B illustrates one example of an eNB 102, various changes may be made to fig. 3B. For example, eNB 102 may include any number of each of the components shown in fig. 3. As a particular example, the access point may include some interfaces 382 and the controller/processor 378 may support routing functions to route data between different network addresses. As another particular example, although illustrated as including a single instance of TX processing circuitry 374 and a single instance of RX processing circuitry 376, the eNB 102 may include multiple instances of each (such as one per RF transceiver).

Fig. 4A and 4B illustrate an example 2D antenna array consisting of 16 dual polarized antenna elements arranged in a 4 x 4 rectangular format, according to an embodiment of the present disclosure. Fig. 4A shows a 4 x 4 dual-polarized antenna array 400 with an Antenna Port (AP) index of 1, and fig. 4B is the same 4 x 4 dual-polarized antenna array 410 with an antenna port index (AP) index of 2. The embodiments shown in fig. 4A and 4B are for illustration only. Other embodiments may be used without departing from the scope of this disclosure.

In some embodiments, each tagged antenna element is logically mapped to a single antenna port. In general, one antenna port may correspond to a plurality of antenna elements (physical antennas) combined via virtualization. This 4 × 4 dual-polarized array can be regarded as an array of elements of 16 × 2 ═ 32 elements. In addition to azimuth beamforming in the horizontal dimension (consisting of 4 columns of dual-polarized antennas), the vertical dimension (consisting of 4 rows) contributes to elevation beamforming. MIMO precoding in rel.12lte standardization (according to TS36.211 sections 6.3.4.2 and 6.3.4.4 and TS36.213 section 7.2.4) is mainly designed to provide precoding gain for one-dimensional antenna arrays. Although fixed beamforming (i.e., antenna virtualization) can be implemented in the elevation dimension, it does not achieve the potential gain supplied by the spatial and frequency selectivity of the channel.

Fig. 5 illustrates another numbering of TX antenna elements 500 (or TXRUs) according to an embodiment of the disclosure. The embodiment shown in fig. 5 is for illustration only. Other embodiments may be used without departing from the scope of this disclosure.

In certain embodiments, the eNB 103 is equipped with a 2D rectangular antenna array (or TXRU) comprising M rows and N columns of P-2 polarization, where the index of each element (or TXR) is (M, N, P) and M-0, … …, M-1, N-0, … …, N-1, P-0, … …, P-1, as shown in fig. 5, where M-N-4. When the example shown in fig. 5 represents a TXRU array, a TXRU may be associated with multiple antenna elements. In one example (1-dimensional (1D) sub-array partitioning), an antenna array comprising columns with the same polarization as a 2D rectangular array is partitioned into M groups of contiguous elements, and the M groups correspond to M TXRUs with the same polarization as in the columns of the TXRU array in fig. 5.

In legacy LTE, MIMO precoding (for spatial multiplexing) may be implemented with CRS (see TS36.211, section 6.3.4.2) or UE-specific reference signals (UE-RS) (see TS36.211, section 6.3.4.4). In either case, each UE operating in spatial multiplexing mode is configured to report CSI, which may contain a Precoding Matrix Indicator (PMI) (i.e., a precoding codebook index). The PMI report is derived from one of the following standardized codebook sets: two antenna ports: { TS36.211 Table 6.3.4.2.3-1 }; four antenna ports: { TS36.211 Table 6.3.4.2.3-2} or { TS36.213 Table 7.2.4-0A, B, C and D }; and eight antenna ports: { TS36.213 tables 7.2.4-1, 2, 3, 4, 5, 6, 7, and 8 }.

If the eNB 103 follows the PMI recommendation of the UE 115, it is expected that the eNB 103 precodes its transmitted signals according to the recommended precoding vector/matrix (for a given subframe and Physical Resource Block (PRB)). Whether or not the eNB 108 follows the recommendations of the UE 115, the UE 115 is configured to report the PMI according to the precoding codebook described above. Here, PMI (which may consist of a single index or a pair of indices) is associated with a size of N_C×N_LIs associated with a precoding matrix W, where N_CIs the number of antenna ports in a row (the number of columns) and N_LIs the number of transport layers.

Rel.12 ITE 8-Tx double codebook

Tables 1 and 2 are for codebooks for rank-1 and rank-2 (1-layer and 2-layer) CSI reporting for UEs configured with 8Tx antenna port transmissions in order to determine the CW of each codebook, two indices, i.e., i₁And i₂. In these precoder expressions, the following two variables are used:

v_m＝[1 e^j2πm/32 e^j4πm/32 e^j6πm/32]^T

table 1 codebook for 1-layer CSI reporting using antenna ports 15 to 22

If the most recently reported RI is 1, then according to Table 1, by two indices i₁And i₂Deriving m and n, deriving a rank-1 precoder,

table 2 codebook for 2-layer CSI reporting using antenna ports 15 to 22

If the most recently reported RI is 2, then according to table 2, by two indices i₁And i₂Deriving m, m' and n, deriving a rank-2 precoder,

it should be noted that it is possible to note,

is constructed such that it can be used to facilitate two different types of channel conditions for level-2 transmissions.

And i₂A subset of the 0, 1, … …,7 associated codebook comprises m-m' codewords, or the same beam (v)_m) For constructing a rank-2 precoder:

in this case, the two columns in the 2-layer precoder are orthogonal (i.e.,

) This is because for two columns, different flags apply

These rank-2 precoders are likely to be used for those UEs that can receive strong signals along two orthogonal channels generated by two differently polarized antennas.

Rel, 12LTE instead of 4-Tx dual codebook

Based on a similar concept as 8-Tx, an alternative 4-Tx codebook can be written as follows:

table 3 codebook for 1-layer CSI reporting using antenna ports 0 to 3 or 15 to 18

Table 4 codebook for 2-layer CSI reporting using antenna ports 0 to 3 or 15 to 18

Rel.8 LTE 2-Tx codebook

For transmissions on two antenna ports p e {0, 1} and for the purpose of CSI reporting based on two antenna ports p e {0, 1} or p e {15, 16}, the precoding matrix w (i) should be selected from table 5 or a subset thereof. For the closed-loop spatial multiplexing transmission mode, when the number of layers is v-2, codebook index 0 is not used.

Table 5 for transmissions on antenna port {0, 1} and codebooks for CSI reporting based on antenna {0, 1} or {15, 16 }.

For FD-MIMO with 2D antenna arrays (and thus with 2D precoding), the need for a high performance, scalable (with respect to the number and geometry of the transmit antennas) and flexible CSI feedback framework and structure is essential. One approach is for the eNB 103 to send some precoded CSI-RSs. In one such example, each CSI-RS port covers a certain angular range of the service area, rather than the entire service area. The precoder for the CSI-RS may be determined by, for example, estimating an uplink channel using the uplink signal. Benefits of precoded CSI-RS transmission are: (1) allow the eNB to efficiently deliver CSI-RS power to the UE and reduce the CSI-RS transmissions required, and (2) allow the UE to reduce CSI-RS feedback by selecting a subset of CSI-RS ports for feedback.

The eNB according to some embodiments of the present disclosure operates as follows:

eNB determination for N based on uplink Sounding Reference Signal (SRS), history of PUSCH/PUCCH or PMI feedback, or a combination thereof_PPre-encoder (or angular direction) of the individual CSI-RS ports.

CSI-RS virtualization example:

2.1 mixing N_PThe ports are divided into two groups, the CSI-RS of the antenna ports belonging to the first group being transmitted from a first group of antennas having a first polarization p ═ 0, and the CSI-RS of the antenna ports belonging to the second group being transmitted from a second group of antennas having a first polarization p ═ 1 of a second polarization. In one example, when N_PAt 7, ports 0, … …, N_PThe CSI-RS on/2-1 is polarized at +45 ° on the first set of antennas to transmit (m, n,p＝0) M-0, … …, M-1, N-0, … …, N-1, and port N_P/2、……、N_PCSI-RS on-1 is transmitted on the second set of antennas with-45 ° polarization (m, n,p＝1)，m＝0、……、M-1，n＝0、……、N-1}。

2.2N_Peach antenna port is divided into N _P2 pairs of antenna ports. The two antenna ports of each pair are mapped to the same set of antenna element positions with the same precoding or beamforming (i.e. both are mapped to the same set of { (m, n) } and the same precoding is applied on the set of antennas with the same polarization), but they are on antennas with different polarizations, i.e. the first port is mapped to p-0 and the second port is mapped to p-1.

2.2.1 in one example, a first CSI-RS in a first pair of CSI-RS ports transmits { (m, n,p＝0) M-0, … …, M-1, N-0, … …, N-1}, wherein the first antenna virtualizes the precoder w⁽¹⁾Applied to the set of antennas; and a second CSI-RS in the pair of CSI-RS ports transmits the { (m, n,p＝1) M-0, … …, M-1, N-0, … …, N-1}, wherein the same antenna virtualizes precoder w⁽¹⁾Applied over the set of antennas. When M-8 and N-2, for example, a virtualized mapping (denoted as s) on MN element with a first polarization for a first CSI-RS_a＝0) And a mapping (denoted as s) for a second CSI-RS_a＝1) Will be:

wherein x_(m，n，p)Is a signal mapped on an element (m, n, p), and

3.N_Pcan be decomposed into N_P＝N_H·N_VIn which N is_HIs the number of antenna ports in a row; and N is_VIs the number of antenna ports in a column of the 2D rectangular antenna array. In one example, N _V4 and N_HWhere the x-pol dimension is calculated towards the rows rather than towards the columns.

The UE 115 according to some embodiments of the present disclosure operates as follows:

UE 115 reception of N_PCSI-RS configuration of each antenna port and corresponding CSI-RS.

UE 115 selection of N_PQ (N) in each antenna port_P) The CSI-RS ports are selected, for example, based on the received power on the ports. If Q is equal to N_PThen the UE 115 selects all configured number of CSI-RS ports to proceedAnd (4) CSI derivation.

2.1 in one approach, the UE 115 is configured to select Q ═ Q/2 pairs of CSI-RS ports, where the same precoding w is applied to each, but with different polarizations, or in other words with Q beams. Thus, each beam corresponds to a pair of CSI-RS ports.

2.1.1 in one example, the CSI-RS ports are numbered such that the pair of CSI-RS ports is CSI-RS port a and CSI-RS port a + a.

2.1.2 in another example, the CSI-RS ports are numbered such that the pair of CSI-RS ports is CSI-RS port 2a and CSI-RS port 2a + 1.

2.1.3 in another example, two CSI processes are configured for the UE 115, with a first CSI process for those CSI-RS ports associated with a first polarization (i.e., p ═ 0) and a second CSI process for those CSI-RS ports associated with a second polarization (i.e., p ═ 1).

In these examples, the UE 115 should select two CSI-RS ports as a pair and not allow selection of only one CSI-RS port of a pair.

3. After selecting q pairs of CSI-RS ports (or q beams), the UE 115 is configured to derive a common phase factor for each pair of ports.

3.1 in one approach, the UE 115 derives q co-phasing factors for the two ports of each pair.

3.2 in another approach, the UE 115 derives one common phase factor between the two ports of all pairs.

4. Conditioned on the Q selected ports and the Q co-phasing factors, the UE 115 derives the CQI, PMI, and/or RI.

4.1 in one example, when selecting Q2 (Q1) ports, the UE 115 performs a hypothesis test as to whether class 1 or class 2 supports higher transmission rates. For the rank-1 assumption, the UE 115 assumes that the received signals from the two ports carry one information stream and are combined at the receiver; for the rank-2 assumption, the UE 115 assumes that the received signals from the two ports carry two information streams and applies a MIMO receiver.

4.1.1CSI-RS antenna Port aThe signal being represented as y_a. Then, in case of the rank-1 assumption, the UE assumes that the received signal is according to the following equation:

where x is the signal on the DMRS port,

will correspond to the precoder indicated by the feedback PMI. In the case of the level-2 assumption, the UE assumes:

wherein x₁、x₂Are signals on two DMRS ports (ports 7 and 8).

Here, the number of the first and second electrodes,

is the co-phasing factor that will include the feedback PMI. In one example, for ranking

From

And for level 2

From

To select.

4.2 in another example, when selecting Q2 (Q1) ports, the UE reports PMI/CQI/RI using the Rel-82-Tx codebook (table 5).

4.3 in another example, 8 CSI-RS ports are configured for the UE 115. The UE 115 receives 8-port precoded CSI from the eNB 103-a set of RSs, wherein the 8-port CSI-RSs are divided into two groups, one group having a first polarization (p ═ 0) and the other group having a second polarization (p ═ 1). The UE 115 is also configured to have four precoding vectors u to be applied to each group of four CSI-RS ports₀、u₁、u₂、u₃Each of which has a size of 4 x 1. Four vectors u₀、 u₁、u₂、u₃May be configured by the eNB 103 or may be hard coded. Assume that the received signal on the 8-port CSI-RS is composed of [ y ]₀、y₁、y₂、y₃、y₄、y₅、y₆、y₇]Is represented by (a) in which y₀、y₁、 y₂、y₃Having p ═ 0 and y₄、y₅、y₆、y₇Has p ═ 1. Furthermore, CSI-RS port a is paired with CSI-RS port a +4, a being 0, 1, 2, 3, where the paired ports are precoded using the same precoder on the same set of (m, n) but on different p. When applying the legacy LTE expedition port coding scheme for CSI-RS, a is 15, 16, 17, 18. Subsequently, to derive the rank-1 CQI/PMI, the UE assumes the following signal model, where it is assumed that the rank-1 precoder W has been applied:

wherein [ a ]₀、a₁、a₂、a₃、a₄、a₅、a₆、a₇]Is a vector of unit canonical complex numbers in exp (-j θ) form. When the UE 115 selects q of the four precoding vectors, the UE 115 should feed back 2q non-zero complex numbers, where the first complex number (e.g., ai with the smallest index) is hard coded to 1. In this case, the PMI includes

To a

And [ alpha ]₀，α₁，α₂，α₃，α₄，α₅，α₆，α₇]The information of (1).

4.3.1. In one example of the use of a magnetic resonance imaging system,

and hard coded. In case Q precoding vectors (beams) are selected, Q-2Q CSI-RS reports are selected.

Here, precoder W may be represented by W ═ W₁W₂Is shown in which

Opening device

And it can be seen that W₂Two items of information are included: (1) column (or pair or beam) selection [ c ]₀、c₁、c₂、c₃]And a phase coefficient for the selected column.

4.3.2. For example, if [ c ]₀、c₁、c₂、c₃]＝[1 1 0 0]Then the phase coefficients for the selected column need to be quantized and fed back along with the column selection information: a is₀、a₁、a₄、a₅Wherein a is₀1. In this case, PMI corresponds to [ c ]₀、c₁、c₂、c₃]＝[1 1 0 0]And [ alpha ]₀＝1，α₁，α₄，α₅]。

4.3.3. In another example, W₁I and only one column (beam) is selected. Since there are 4 cases in selecting one column out of 4 columns, 2 bits are required to encode this information, as shown in table 6 below. For example, if [ c ] is selected₀、c₁、c₂、c₃]＝[1 1 0 0]Then there is only one phase coefficient a₁Is required to be reacted with₀＝1，a₄]Quantization is performed. Item a₄Can be quantified as exp (j theta)_m) Wherein

And some example values of M are: m is 2, 4, 8, 16. The combined information of column (beam) selection and co-phase may be fed back in common.

TABLE 6

When [ c ]₀、c₁、c₂、c₃]＝[1 1 0 0]And alpha₄Is quantified into

Where M is 4, a simple combination of sections 4.3.1 and 4.3.3 gives

The UE 115 is configured to include the index of the selected CSI-RS port pair (or beam index) and the PMI/CQI/RI. In the special case where the UE selects only one index, the UE 115 reports the 2-Tx PMI/CQI/RI and the selected beam index.

Example (b): (details of CSI reporting with Beam selection)

In one embodiment, the UE 115 is configured with a CSI-RS source comprising Q-8 CSI-RS ports, and the UE 115 is further configured to select a pair of CSI-RS ports and report a CSI-RS port pair index (or beam index BI) and corresponding CQI/PMI/RI on the selected CSI-RS ports.

An alternative mapping method of beam indices to a pair of CSI-RS ports is seen as shown in table 7 below, where Q is assumed to be 8 (and e.g., general Q may also be 4):

TABLE 7

For PUCCH periodic reporting, several alternative methods on how to multiplex Beam Index (BI), PMI/CQI and RI reporting may be considered.

In an alternative, the BI is reported on the same subframe in which the PMI/CQI is reported. This alternative may provide better output performance when the BI changes rapidly over time.

In another alternative, the BI is reported on the same subframe in which the RI is reported. This alternative may provide more reliable BI transmission without changing the CSI reporting architecture.

In yet another alternative, the BI is reported on a subframe separate from those on which the PMI/CQI and RI are reported. This alternative ensures the most reliable BI reception among all alternatives considered in this disclosure, but it may consume additional resources or may increase the reporting delay of PMI/CQI/RI.

For PUSCH aperiodic reporting, several alternative approaches on how to multiplex Beam Index (BI), PMI/CQI and RI reporting may be considered.

In one alternative, the BI is jointly encoded with PMI/CQI and reported in the PMI/CQI region of the PUSCH. This alternative supports both the sub-band selection of the BI and the wide-band selection of the BI.

In another alternative, the BI is jointly encoded with the RI and mapped on the RI region of the PUSCH. This alternative ensures more reliable transmission of the BI, but it is limited in that the BI selection is wideband.

Example (b):polarization CSI-RSSending

Fig. 6 illustrates a polarized CSI-RS transmission 600 according to an embodiment of the disclosure. The embodiment shown in fig. 6 is for illustration only. Other embodiments may be used without departing from the scope of this disclosure.

In this embodiment, a pair of CSI-RS ports are pre-encoded with the same weight vector and transmitted via the same set of columns and rows of antennas, with one CSI-RS transmitted at +45 ° polarization via the antennas in the set and the other CSI-RS transmitted at-45 ° via the antennas in the set, as shown in fig. 6.

Example (b):sequentially polarized CSI-RSSending

Fig. 7A and 7B illustrate sequential polarized CSI-

RS transmissions

700, 710 according to embodiments of the disclosure. The embodiment shown in fig. 7 is for illustration only. Other embodiments may be utilized without departing from the scope of the present disclosure

In this embodiment, the CSI-RS may not be transmitted in the pair-wise polarization. In one CSI process, the CSI-RS may be transmitted from +45 °, and in another CSI process, the CSI-RS may be transmitted from-45 °. The number of CSI-RS ports transmitted during both procedures need not be the same. The motivation is to reduce the CSI-RS sources and reduce the feedback load for the case of how much polarization diversity is not needed. The concept of an embodiment is illustrated in fig. 7A and 7B.

Example (b):flexible polarization CSI-RSSending

Fig. 8 illustrates flexible polarized CSI-RS transmission according to an embodiment of the present disclosure. The embodiment shown in fig. 8 is for illustration only. Other embodiments may be used without departing from the scope of this disclosure.

In some embodiments, the CSI-RS may not be transmitted in the pair of polarizations, as illustrated in fig. 8. The eNB 103 signals the polarization associated with each of the ports, or the polarization of the ports is implicitly associated with a port number. For the case of not much polarization diversity, the mobile is also to reduce the CSI-RS source and reduce the feedback load. The eNB 103 may determine the CSI-RS to transmit based on the history of uplink measurements or CSI feedback.

Example (b):UE partial PMI feedback

The UE 115 is configured to receive 8-port precoded CSI-RSs from the eNB 103, wherein the 8-port CSI-RSs are divided into two groups, one group having a first polarization (p-0) and the other group having a second polarization (p-1). The UE 115 is also configured with four precoding vectors u to be applied to each group of four CSI-RS ports₀、u₁、u₂、u₃Each of which has a size of 4 x 1. Four vectors u₀、u₁、u₂、u₃May be configured by the eNB 103 or may be hard coded.

Assume that the received signal on the 8-port CSI-RS is composed of [ y ]₀、y₁、y₂、y₃、y₄、y₅、 y₆、y₇]Is represented by (a) in which y₀、y₁、y₂、y₃Having p ═ 0 and y₄、y₅、y₆、y₇Has p ═ 1. Furthermore, CSI-RS port a is paired with CSI-RS port a +4, a being 0, 1, 2, 3, where using the same precoder on the same set of (m, n) but on different p would be pair port precoding. When the UE 115 derives u on these 8 CSI-RS ports₀＝[u₀₀、u₀₁、 u₀₂、u₀₃]^tRank-1 CQI of (1), the UE 115 shall assume the following signal model for CSI (CQI, PMI, RI) derivation:

extending this approach, all precoding vectors u can be considered jointly in a single equation₀、u₁、u₂、u₃：

Wherein

Is a binary vector (i.e., c) for selection of a column of the matrix_iE {0, 1}, i ═ 0, 1, 2, 3), and

is for four precoding vectors u₀、u₁、u₂、u₃Co-phasing factor of (c). When the UE 115 selects q precoding vectors of the four precoding vectors, the UE 115 should feed back q non-zero co-phasing factors.

In this case, the PMI includes a relation

And

the information of (1). In one example of the use of a magnetic resonance imaging system,

and hard coded. In this case, in case Q precoding vectors are selected, Q-2Q CSI-RS ports are equally selected.

Example (b):CSI-RS for long-term CSI estimation

Fig. 9A and 9B illustrate eNB 103 transmission and corresponding UE 115 feedback for two

types

900, 910 of CSI-RS according to certain embodiments of the present disclosure. The embodiment shown in fig. 9 is for illustration only. Other embodiments may be used without departing from the scope of this disclosure.

In these embodiments, the eNB 103 configures two CSI-RS sources for the UE 115: (1) a first CSI-RS source for long-term channel direction estimation; and (2) a second CSI-RS source for short-term CSI estimation (e.g., co-phasing, beam-selection PMI, RI, and CQI)

In another approach, the two CSI-RS sources are configured in a single CSI process.

The eNB 103 may configure the duty cycle of CSI-RS transmission of the first CSI-RS source to be longer than the second CSI-RS source. According to some embodiments of the disclosure, once the eNB obtains the long-term CDI from the UE 115, the eNB 103 performs UE-specific precoding (or beamforming) on the second CSI-RS based on the long-term CDI.

With the channel estimation estimated by the first CSI-RS, the UE 115 estimates and feeds back the long-term CDI. According to some embodiments of the present disclosure, the UE 115 estimates and feeds back the co-phase information and the beam selection information using channel estimation estimated by the second CSI-RS. In an alternative, the UE 115 derives and feeds back the rank information through the second CSI-RS; in another alternative, the UE 115 derives and feeds back the rank information through the first CSI-RS.

In accordance with some embodiments of the present disclosure, a second CSI-RS and related CSI feedback may be constructed/derived, where the UE 115 derives short-term CSI from Q (═ Q/2) antenna ports, which may be decomposed into Q pairs of antenna ports, and each pair includes two antenna ports with the same beamforming vector but with different polarizations.

In one approach for the first CSI-RS source, N is_POne CSI-RS port (N in one example)_PP · M · N; in another example, according to the notation in the embodiment associated with fig. 5, N_PM · N) is configured for a first CSI-RS source, and N is set_POne-to-one mapping of individual CSI-RS ports to N in an antenna array_PAnd TXRU. In this case, the UE 115 uses N_PChannel Direction Information (CDI) is estimated by channel estimation of the CSI-RS ports and fed back to the eNB. CDI may be reported on PUCCH or on PUSCH.

In one example, N_PM · N, and according to the symbols in the embodiment associated with fig. 5, the UE 115 is configured with a first and a second number of antenna ports M and N.

In another example, N_PP · M · N, and according to the notation in the embodiment associated with fig. 5, the UE 115 is configured with a first, second and third number of antenna ports M and N and P.

In another example, N_PP · M · N, and according to the notation in the embodiment associated with fig. 5, the UE 115 is configured with a first and a second number of antenna ports P · M and N.

In one example of the current approach, CDI is two oversampled DFT precoders: one for the azimuth channel direction and the other for the elevation channel direction. In the latter embodiment, the DFT precoder/vector and the oversampled DFT vector are used interchangeably. Further, if M is 4, the DFT vector for the azimuth channel direction has four elements (here, the number of elements in the DFT vector is equal to M):

and

if N is 4, then the DFT vector for the elevation channel direction is(here, the number of elements in the DFT vector is equal to N):

where example values for a are 32, 16, and 8, and example values for B are 16, 8, and 4. The feedback information of the UE 115 may include a · B states; if a-16 and B-8, then the number of states is 128 and it is 7-bit information. The azimuth CDI and the elevation CDI may be encoded separately as shown in table 8 below, or may be encoded together as shown in table 9 below. The information field is encoded and then mapped to a PUSCH (for aperiodic CSI feedback) or PUCCH source (for periodic CSI feedback).

TABLE 8

TABLE 9

In another example where M-4 and N-4, the DFT vector for the azimuth channel direction has four elements (here, the number of elements in the DFT vector is equal to M):

and the DFT vector for the high degree channel direction is (here, the number of elements in the DFT vector is equal to N):

in this case, one possible way of feeding back the CDI is shown in table 10 below.

Watch 10

In another example of the current approach, CDI is employed

Or

A set of L vectors of the form and the information field for the CDI will contain information about the L index pairs:

united states provisional patent application No. 62/073,782, filed on 31/10/2014, incorporated herein in its entirety, has shown several methods for encoding this type of CDI information. One example method of quantifying the orientation CDI is described in table 11 below, where a is assumed to be 32:

TABLE 11

Another example method of quantifying the orientation CDI is described in table 12 below, where assume a-32:

TABLE 12

It should be noted that the height CDI may also be quantified similarly to the orientation CDI.

Example (b): CSI-RS for long-term CSI estimation

According to the symbols associated with the embodiment related to fig. 5, the eNB 103 has a (M, N, P) — (4,2) the 2D TXRU array of (1). In this case, the total number of TXRUs is 32. In this embodiment, the eNB 103 configures the UE 115 to have N_PA number of CSI-RS ports, where a target can be decomposed into (M, N, P)_effective) First type of CSI-RS, N ═ 4, 4, 1_PM · N — 16 so that the UE 115 can estimate the long-term CDI.

In one approach, the 16 CSI-RS antenna ports are mapped one-to-one to 16 TXRUs associated with the same antenna polarization. For example, 16 CSI-RS antenna ports are mapped one-to-one to TXRU (0, 0, 0), (0, 1, 0), (0, 2, 0), (0, 3, 0), (1, 0, 0), (1, 1, 0), (1, 2, 0), (1, 3, 0), (2, 0, 0), (2, 1, 0), (2, 2, 0), (2, 3, 0), (3, 0, 0), (3, 1, 0), (3, 2, 0), (3, 3, 0).

Fig. 10 illustrates an example CSI-RS port virtualization implementation 1000 in accordance with an embodiment of the disclosure: 16 ports for feeding 32 TXRUs. The embodiment shown in fig. 10 is for illustration only. Other embodiments may be used without departing from the scope of this disclosure.

In another approach, the 16 CSI-RS antenna ports are mapped to 32 TXRUs, where each CSI-RS port is associated with a pair of TXRUs (m, n, 0) and (m, n, 1). In one example, the associated weight of each CSI-RS port with a pair of TXRUs (labeled TXRU a and TXRU a') may be [ +1+1]/sqrt (2), as shown in fig. 10. In the figure, the CSI-RS port a is split into two branches and expanded with 1/sqrt (2), respectively, and then fed to TXRUs a and a' associated with antenna sub-arrays (m, n, 0) and (m, n, 1). It should be noted that the particular precoding weights are for illustration only.

The eNB 103 of (M, N, P) ═ 4, 4, 2 may additionally configure and transmit a second type of CSI-RS. According to some embodiments of the present disclosure, the second type of CSI-RS is precoded with a precoder selected based on CDI feedback of the UE 115, where the UE 115 derives the short-term CSI from Q (═ Q/2) antenna ports that can be decomposed into Q pairs of antenna ports, and each pair includes two antenna ports with the same beamforming vector but with different polarizations.

In another method for the first CSI-RS source, N is_BThe CSI-RS ports are configured for a first CSI-RS source, and N is_BBeamforming of individual CSI-RS ports, i.e. applying precoding weights to N to be mapped into an antenna array_PEach CSI-RS on each TXRU. In this case, the CDI estimated by the UE 115 may be from N_BA set of selected ones of the CSI-RS ports.

The UE 115 may be at N_BThe L CSI-RS ports with the L strongest receiving powers are selected from the L CSI-RS ports. Some example values of L are L-1 and L-4.

After selecting L such CSI-RS ports, the UE 115 reports information about the selected L CSI-RS ports to the eNB on the PUSCH or PUCCH.

Example (b): coarse beamforming CSI-RS for long-term CSI estimation

As in some embodiments of the present disclosure, it is assumed that the DFT vector for the azimuth channel direction is:

and

the DFT vector for the elevation channel direction is:

then, the azimuth and elevation DFT beam index space (a, B) is divided into a grid comprising a · B components.

In this embodiment, the eNB 103 configures the first and second CSI-RS sources for the UE. The first CSI-RS and the second CSI-RS are both beamformed, but the first CSI-RS beam is coarsely packed than the second CSI-RS beam; in other words, the first CSI-RS beam is wider than the second CSI-RS beam. In one example, a first CSI-RS beam is constructed with a-8 and B-4 and a second CSI-RS beam is constructed with a '-16 and B' -4.

Fig. 11A and 11B illustrate a DFT beam index grid 1100 according to an embodiment of the disclosure. The embodiment shown in fig. 11A and 11B is for illustration only. Other embodiments may be used without departing from the scope of this disclosure.

For the first CSI-RS source, the eNB may configure a-8 and B-4 and transmit a-B-32 port beamformed CSI-RS, as shown. In fig. 11A, a fine grid and a coarse grid are shown. The coarse grid comprises 32 elements, each indexed (a, B), where a is 0, 1, … …, a-1 and B is 0, 1, … …, B-1; similarly, the fine grid includes 128 elements, each indexed by (a ', B'), where a '-0, 1, … …, a' -1 and B '-0, 1, … …, B' -1, and a '-2A and B' -2B. The elements (a, b) in the coarse mesh correspond to the vector passing through the precoding

The CSI-RS beams precoded, similarly, the elements (a ', b') in the fine grid correspond to the vectors precoded by

And carrying out pre-coding CSI-RS beams. Subsequently, the eNB 103 receives beam index feedback from the UE 115, wherein the beam index is estimated in dependence on the 32-port beamformed CSI-RS. In one example, the eNB 103 obtains a response from the UE 115 corresponding to the UE

The beam index pair (a, b) of (0, 0). Subsequently, for the UE 115, the eNB 103 transmits a plurality of finer beam CSI-RSs (A 'therein) on a second CSI-RS source, in accordance with some embodiments of the present disclosure'>A and B'>B) So that the UE 115 can derive the beam selection and co-phasing information and feed it back to the eNB 103.

In the example of fig. 11B, the multiple finer beams correspond to (a ', B ') (0, 0), (1, 0), (0, 1), (1, 1), where a ' is 16 and B ' is 8, corresponding to (a ', B ') (0, 0), (1, 0), (0, 1), and (B ') is 8

And

in another example, the plurality of finer beams may correspond to 4 finer azimuth beams, i.e., (a ', b) ═ 0, (1, 0), (2, 0), (3, 0), where a' ═ 32, corresponding to the 4 finer azimuth beams

And

example (b):CQI estimation time window relative to two types of CSI-RS

Fig. 12 illustrates a flow diagram 1200 regarding UE 115 and eNB 103 operations related to short-term CSI feedback, in accordance with some embodiments of the present disclosure. Although a signal diagram depicts a series of sequential steps, no inference should be drawn from the following sequence in question unless explicitly stated: the performance of a particular sequence, step, or portion thereof, in succession rather than concurrently or in an overlapping manner, or the performance of exclusively the illustrated steps without the occurrence of intervening or intermediate steps. The processes depicted in the illustrated examples are performed by processing circuitry in, for example, a UE, eNB, or other entity.

In this embodiment, the UE 115 is configured with two types of CSI-RS sources: (1) a first CSI-RS source for long-term channel direction estimation; and (2) a second CSI-RS source for co-phase and beam selection.

In step 1, the UE 115 receives CSI-RS of the first type from the eNB 103.

In step 2, the UE derives and feeds back the CDI using the CSI-RS sent on the first CSI-RS source.

In step 3, the eNB 103 may decide to update the precoder for the CSI-RS of the second type based on the CDI feedback. In such cases, the eNB sends an indication of a beamforming update for the second type of CSI-RS to the UE 115. The indication may be transmitted and configured in a higher layer (MAC or RRC) or dynamically indicated in Downlink Control Information (DCI) on the PHY layer of the PDCCH.

In step 4, after receiving the indication, the UE 115 discards the old channel estimates estimated by the CSI-RS of the second type from memory.

In step 5, after transmitting the indication message, the eNB 103 transmits the CSI-RS of the second type precoded by the new precoder derived by using the feedback CDI to the UE. In some embodiments, step 4 may occur after step 5.

In step 6, after discarding the old channel estimates and after receiving the second type of CSI-RS the first time after receiving the indication message, the UE 115 derives new short-term CSI based on the second type of CSI-RS.

In step 7, the UE feeds back the short-term CSI to the eNB 103.

The UE 103 may store the channel estimates estimated by the second type of CSI-RS for future use. For example, the UE channel estimate may take as input multiple channel estimates from multiple past subframes to make the channel estimate more reliable.

Fig. 13 illustrates a short-term CSI estimation time window 1300 in accordance with some embodiments of the present disclosure. The embodiment shown in fig. 13 is for illustration only. Other embodiments may be used without departing from the scope of this disclosure.

The UE 115 generates short-term CSI feedback within a time window based on CSI-RS channel estimates, and the UE 115 does not take as input for generating short-term CSI different CSI-RS channel estimates from two different time windows.

The UE 115 determines when to switch to a new time window based on a triggering event.

In one approach, the triggering event is the receipt of an indication message of a beamforming update of the CSI-RSs of the second set.

In another approach, the triggering event is an indication message acknowledging receipt of a beamforming update for the second type of CSI-RS, wherein the acknowledgement is sent by the UE 115 to the eNB 103.

In another method, the triggering event is a CSI-RS of the second type received immediately after receiving an indication message of a beamforming update of the CSI-RS of the second type.

In another approach, the triggering event is the reception of a first type of CSI-RS. Within a time window between two consecutive receptions of the first type of CSI-RS, the UE 115 may assume that the short-term CSI may be derived by a CSI-RS of the second type received in the time window.

In another approach, the time window is a single subframe in which the second type of CSI-RS is received.

The method comprises the following steps: collision handling of long-term and short-term CSI feedback

In some embodiments, the UE 115 is configured to report the long-term CSI on the first PUCCH source according to the first periodic CSI feedback configuration and the short-term CSI on the second PUCCH source according to the second periodic CSI feedback configuration. In certain subframes where the UE 115 finds that both CSI reports are scheduled, the UE 115 is configured to terminate short-term CSI feedback and report long-term CSI only on the first PUCCH source. This method is inspired by the fact that: long-term information is more important than short-term information.

The method comprises the following steps: two CSI processes for long-term and short-term CSI feedback

In some embodiments, the UE 115 is configured with two CSI processes: a first CSI process with a first type of CSI-RS for CDI feedback and a second CSI process with a second type of CSI-RS for short-term CSI feedback. The first and second CSI process configurations may also have their own CSI-IM, periodic CSI, and aperiodic CSI configurations. The periodic CSI configuration may include a PUCCH source, a reporting frequency, and a reporting time offset.

The method comprises the following steps: (one CSI process for long-term and short-term CSI feedback)

In some embodiments, the UE 115 is configured to have one CSI process with two types of CSI-RS. The CSI process configuration may also have CSI-IM, periodic CSI, and aperiodic CSI configurations. The periodic CSI configuration may include a PUCCH source, a reporting frequency, and a reporting time offset.

While the present invention has been described with reference to exemplary embodiments, various changes and modifications may be suggested to one skilled in the art. The present invention is intended to embrace such changes and modifications as fall within the scope of the appended claims.

Claims

1. A base station, BS, capable of communicating with a user equipment, UE, the base station comprising:

a controller; and

a transceiver configured to:

transmitting a signal including a channel state information, CSI, processing configuration, wherein the CSI processing configuration includes at least a first CSI-RS resource configuration for identifying CSI reference signal, CSI-RS, resources; and

receiving, from the UE, first CSI feedback including a first PMI at a frequency less than second CSI feedback including a Channel Quality Indicator (CQI) and a second Precoding Matrix Index (PMI),

wherein the first PMI is derived using a first CSI-RS on a first CSI-RS resource, and the CQI and the second PMI are derived using a second CSI-RS on a second CSI-RS resource.

2. The base station of claim 1, wherein two CSI-RSs of the 8 CSI-RSs on antenna ports 15 and 19 are mapped to a first and a second group, respectively, of a same number of antenna elements applying substantially similar beamforming weight vectors,

wherein the antenna elements on the first group are polarized according to a first angle, the antenna elements on the second group are polarized according to a second angle, and both antenna elements on the first group and the second group are located at the same physical location comprising a dual-polarized pair, an

Wherein a difference between the first angle and the second angle is substantially equal to 90 degrees.

3. The base station of claim 1, wherein the first PMI corresponds to a discrete fourier transform, DFT, vector.

4. The base station of claim 1, wherein the first CSI-RS and the second CSI-RS are beamformed with beamforming weight vectors, and

wherein the controller is configured to derive the beamforming weight vector by processing a precoding vector reported by the UE.

5. The base station of claim 4, wherein the transceiver is configured to:

sending a downlink signal containing a second CSI-RS configuration on a Physical Downlink Shared Channel (PDSCH), and an N-port CSI-RS configured according to the second CSI-RS, wherein N is a positive integer; and

receiving an uplink signal from the UE including the second PMI, the second PMI including a non-negative integer derived using the N-port CSI-RS,

wherein the controller is further configured to determine a precoding vector as an oversampled Discrete Fourier Transform (DFT) vector from the second PMI.

6. The base station of claim 5, wherein the transceiver is further configured to:

sending a downlink signal containing the second CSI-RS configuration on the PDSCH, and sending an N-port CSI-RS configured according to the second CSI-RS; and

receiving an uplink signal including the second PMI, the second PMI including two non-negative integers derived using the N-port CSI-RS,

wherein the controller is further configured to determine a precoding vector as a Kronecker product of two oversampled DFT vectors according to the second PMI.

7. The base station of claim 6, wherein the N-port CSI-RS is mapped into a two-dimensional array of N transceiver elements that are respectively mapped to N antenna sub-arrays disposed on a two-dimensional antenna panel.

8. A method of communicating with a user equipment, UE, the method comprising:

transmitting, by a transceiver of a base station, BS, a signal comprising a channel State information, CSI, processing configuration, wherein the CSI processing configuration comprises at least a first CSI-RS resource configuration for identifying CSI reference signal, CSI-RS, resources; and

9. The method of claim 8, wherein two CSI-RSs of the 8 CSI-RSs on antenna ports 15 and 19 are mapped to first and second groups, respectively, of the same number of antenna elements applying substantially similar beamforming weight vectors,

10. The method of claim 8, wherein the first PMI corresponds to a discrete fourier transform, DFT, vector.

11. The method of claim 8, wherein the first CSI-RS and the second CSI-RS are beamformed with beamforming weight vectors, an

Wherein the method further comprises deriving the beamforming weight vector by processing a precoding vector reported by the UE.

12. The method of claim 11, further comprising:

sending a downlink signal containing second CSI-RS configuration on a Physical Downlink Shared Channel (PDSCH), and sending an N-port CSI-RS configured according to the second CSI-RS;

receiving an uplink signal from the UE including the second PMI, the second PMI including a non-negative integer derived using the N-port CSI-RS; and

and determining the precoding vector as an oversampled Discrete Fourier Transform (DFT) vector according to the second PMI.

13. The method of claim 12, further comprising:

sending a downlink signal containing the second CSI-RS configuration on the PDSCH, and sending the N-port CSI-RS configured according to the second CSI-RS;

receiving an uplink signal comprising the second PMI, the second PMI including two non-negative integers derived using the N-port CSI-RS; and

determining a precoding vector as a Kronecker product of two oversampled DFT vectors according to the second PMI.

14. The method of claim 13, wherein the N-port CSI-RS is mapped into a two-dimensional array of N transceiver elements that are respectively mapped to N antenna sub-arrays disposed on a two-dimensional antenna panel.

15. A user equipment, UE, capable of communicating with a base station, the UE comprising:

a transceiver configured to receive a signal comprising a channel state information, CSI, processing configuration, wherein the CSI processing configuration comprises at least a first CSI-RS resource configuration for identifying CSI reference signal, CSI-RS, resources; and

a controller configured to:

deriving a first precoding matrix index, PMI, using a first CSI-RS on a first CSI-RS resource;

deriving a channel quality indicator, CQI, and a second PMI using a second CSI-RS on a second CSI-RS resource; and

cause the transceiver to transmit a first CSI feedback including the first PMI at a frequency less than a second CSI feedback including the CQI and the second PMI.

16. The UE of claim 15, wherein the transceiver is further configured to:

receiving an N-port CSI-RS of a second CSI-RS and a downlink signal containing the second CSI-RS configuration on a Physical Downlink Shared Channel (PDSCH);

transmitting an uplink signal including a second PMI;

wherein the controller is further configured to derive the second PMI by utilizing channel estimation using the received N-port CSI-RS; and

wherein the second PMI comprises one non-negative integer indicating an oversampled Discrete Fourier Transform (DFT) vector.

17. The UE of claim 15, wherein the transceiver is further configured to:

transmitting an uplink signal including a second PMI;

wherein the second PMI comprises two non-negative integers indicating two oversampled discrete Fourier transform, DFT, vectors and indicates a Kronecker product of the two oversampled DFT vectors.

18. The UE of claim 15, wherein the first PMI corresponds to a discrete fourier transform, DFT, vector.

19. The UE of claim 15, wherein the transceiver is further configured to receive a downlink signal containing information related to a trigger for a change in a time window for channel estimation,

wherein the controller is further configured to:

determining a trigger time for starting new channel estimation according to the downlink signal;

derive the second PMI using an 8-port CSI-RS transmitted within a time window; and

discarding channel estimates for the 8-port CSI-RS according to the trigger time.