CN113037347B

CN113037347B - CSI feedback for MIMO wireless communication systems with polarized active antenna arrays

Info

Publication number: CN113037347B
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: 2024-07-26
Anticipated expiration: 2035-11-17
Also published as: CN106797242A; KR102373467B1; CN106797242B; KR20160058716A; CN113037347A

Abstract

The present disclosure relates to pre-5 th generation (5G) or 5G communication systems that will be used to support higher data rates than super 4 th generation (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, for 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, the uplink signal 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 relates to a divisional application of Chinese patent application with the application number 201580053807.4 and the application date 2015, 11, 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 Multiple Input Multiple Output (MIMO) system, commonly referred to as "full dimension" (FD-MIMO).

Background

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

A 5G communication system is considered to be implemented in a higher frequency (millimeter wave) band (e.g., 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 antennas, analog wave velocity formation, massive antenna techniques are discussed in 5G communication systems.

Further, in the 5G communication system, development for system network improvement is underway based on advanced small cells, cloud Radio Access Networks (RANs), super-dense networks, device-to-device (D2D) communication, wireless backhaul, mobile networks, cooperative communication, cooperative multipoint (CoMP), reception-side interference cancellation, and the like.

In 5G systems, hybrid FSK with QAM modulation (FQAM) and Sliding Window Superposition Coding (SWSC) have been developed as Advanced Coding Modulation (ACM), as well as Filter Bank Multicarrier (FBMC), non-orthogonal multiple access (NOMA) and Sparse Code Multiple Access (SCMA) as advanced access technologies.

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 billions and continues to grow rapidly. The demand for wireless data services is rapidly increasing as smartphones and other mobile data devices (such as tablet computers, "notebook" computers, netbooks, e-book readers and machine-type devices) are becoming more popular among consumers and the services are growing. To meet the high growth of mobile data traffic and support new applications and deployments, improvements in radio interface efficiency and coverage are paramount.

Disclosure of Invention

Technical problem

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

Solution to the problem

In accordance with an aspect of 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 channel state information-reference signal (CSI-RS) configured according to the CSI-RS and a downlink signal containing a CSI-RS configuration on a Physical Downlink Shared Channel (PDSCH), and to receive an uplink signal from the UE containing Channel State Information (CSI) derived from the 8-port CSI-RS; 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 includes: a transceiver configured to receive a downlink signal containing a CSI-RS configuration on a PDSCH transmitted by the BS and an 8-port CSI-RS according to the CSI-RS configuration, 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 the 8-port CSI-RS by utilizing channel estimation, the CSI 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 channel state information-reference signal (CSI-RS) configured according to the CSI-RS and a downlink signal containing a CSI-RS configuration on a Physical Downlink Shared Channel (PDSCH), and receiving an uplink signal from the UE containing Channel State Information (CSI) derived from the 8-port CSI-RS; and mapping the CSI to one of predetermined precoding vectors, the precoding vectors including:

In some embodiments, two CSI-RSs on antenna ports 15 and 19 among 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 the dual polarized pair, and wherein the 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 to receive an uplink signal from the UE containing a second CSI comprising a non-negative integer derived from the N ₂ -port CSI-RS, and wherein the controller is further configured to determine the precoding vector as an oversampled DFT vector according to 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 a 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 the 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) includes: transmitting a downlink signal containing a first RS configuration on a downlink channel and a first set of Reference Signals (RSs) according to a first RS configuration 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 the predetermined precoding vectors.

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

The method for operating the UE in communication with the BS includes: receiving a downlink signal transmitted by the 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 the downlink signal; and deriving a PMI based on the first set of RSs by using channel estimation, the PMI being translated into one of the precoding vectors.

The method for the UE to communicate with the BS includes: 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 maps to a 2-dimensional array of N transceiver units, each of which maps to N antenna sub-arrays placed on a 2-dimensional antenna panel.

Before proceeding with the detailed description that follows, it is advantageous to list 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," and 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 are intended to include, be included in, interconnect with, contain, be contained in, be connected to or be connected with, be coupled to or be in communication with, cooperate with, intersect, be juxtaposed with, be proximate to, be joined to or with, have the properties of, be in relation to, etc. The term "controller" refers to any device, system, or portion 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. When used with a list of items, the phrase "at least one" means that different combinations of one or more of the listed items can be used and that only one item in the list may 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, and A and B and C.

Furthermore, the various functions described below may be implemented or supported by one or more computer programs that are each formed from computer readable program code and that are 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 a suitable computer readable program code. The phrase "computer readable program code" includes any type of computer code, including source code, object 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 transmit transitory electrical signals 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 beneficial effects of the invention are that

Communication system performance may 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, in which like reference numerals represent like parts:

Fig. 1 illustrates an example wireless network according to this disclosure;

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

Fig. 3A illustrates an example user device according to this disclosure;

fig. 3B illustrates an example enhanced NodeB (eNB) according to this disclosure;

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

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

fig. 6 illustrates 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 polarization 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 this disclosure;

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

fig. 12 illustrates a flow chart relating to UE and eNB operation in connection with 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

Figures 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 (3 GPP) TS 36.211, "E-UTRA, PHYSICAL CHANNEL AND modulation," Release-12; (2) 3GPP TS 36.212, "E-UTRA Multiplexing AND CHANNEL coding," Release-12; and (3) 3GPP TS 36.213, "E-UTRA, PHYSICAL LAYER procedures," Release-12.

Fig. 1 illustrates an example wireless network 100 according to 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 is also in communication 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 in place 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 the network infrastructure components that provide wireless access to remote terminals. In addition, other well-known terms may be used in place of "user equipment" or "UE" such as "mobile station", "subscriber station", "remote terminal", "wireless terminal" or "user equipment", depending on the type of network. For convenience, the terms "user equipment" and "UE" are used in this patent document to refer to a remote wireless device of a radio access eNB, whether the UE is a mobile device (such as a mobile phone or a smart phone) or is generally considered a stationary device (such as a desktop computer or a vending machine).

The eNB 102 provides wireless broadband access to the network 130 for a first plurality of User Equipment (UEs) within a coverage area 120 of the eNB 102. The first plurality of UEs includes: UE 111, which may be located in a Small Business (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 home (R); UE 115, which may be located in a second home (R); and UE 116, which may be a mobile device (M), such as a cell phone, wireless notebook, wireless PDA, etc. The eNB 103 provides wireless broadband access to the network 130 for a second plurality of UEs within the coverage area 125 of the eNB 103. The second plurality of UEs includes UE 115 and UE 116. In some embodiments, one or more of enbs 101 to 103 may communicate with each other and UEs 111 to 116 using 5G, long Term Evolution (LTE), LTE-A, wiMAX, or other advanced wireless communication technology.

The dashed lines illustrate the general extent of coverage areas 120 and 125, which are shown as approximately circular for illustration and explanation purposes only. It should be clearly understood that coverage areas associated with 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 BS101, BS102, and BS103 include a 2D antenna array as described in embodiments of the present disclosure. In some embodiments, one or more of BS101, BS102, and BS103 support codebook designs and structures 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 with wireless broadband access to the network 130. Similarly, each eNB 102-103 may communicate directly with network 130 and provide UEs with direct wireless broadband access to network 130. Furthermore, enbs 101, 102 and/or 13 may provide access to other or additional external networks, such as a network telephony 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, transmit path 200 may be described as being implemented in an eNB (such as eNB 102), while 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 an eNB and the transmit path 200 may be implemented in a UE. In some embodiments, receive path 250 is configured to support codebook designs and structures 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 sample number N, a parallel-to-serial (P-to-S) block 220, an add cyclic prefix block 225, and an up-converter (UC) 230. The 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 sample-N Fast Fourier Transform (FFT) block 270, a parallel-to-serial (P-to-S) block 275, and a channel decoding and demodulation block 280.

In transmit path 200, a channel coding and modulation block 205 receives a set of information bits, applies coding, such as Low Density Parity Check (LDPC) coding, and modulates input bits, such as by Quadrature Phase Shift Keying (QPSK) or Quadrature Amplitude Modulation (QAM), 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. The IFFT block 215, which has a number of samples N, performs an IFFT operation on the N parallel symbol streams to generate a time domain output signal. The parallel-to-serial block 220 converts (such as demultiplexes) the parallel time-domain output signal from the sample-N IFFT block 215 to generate a serial time-domain signal. The add cyclic prefix block 225 inserts a cyclic prefix into the time domain signal. Up-converter 230 modulates (such as up-converts) the output of add cyclic prefix block 225 to an RF frequency for transmission via a wireless channel. The signal may also be filtered at baseband before being converted to RF frequency.

The transmitted RF signal from the eNB 102 arrives at the UE 116 after passing through the wireless channel, and the reverse operation at the eNB 102 is performed at the UE 116. The down-converter 255 down-converts the received signal to a baseband frequency and the 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 into a parallel time-domain signal. The FFT block 270, which has a 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 into a sequence of modulated data symbols. The channel decoding and demodulation block 280 demodulates and decodes the modulation symbols to recover the original input data stream.

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

Each of the components in fig. 2A and 2B may be implemented using hardware alone or using a combination of hardware and software/firmware. As a specific 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, the FFT block 270 and the IFFT block 215 may be implemented as a configurable software algorithm, wherein the value of the number of samples N may be modified according to the implementation.

Furthermore, although described as using an FFT and an IFFT, this is for illustration only and should not be construed as limiting the scope of the present 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 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 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, the 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 this 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 configuration. However, the UE has a wide variety of configurations, and fig. 3A does not limit the scope of the present disclosure to any particular embodiment of the UE.

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.UE 116 also includes speaker 330, main processor 340, input/output (I/O) Interface (IF) 345, keypad 350, display 355, and memory 360. Memory 360 includes basic Operating System (OS) program 361 and one or more applications 362.

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

The main processor 340 may include one or more processors or other processing devices and execute basic OS programs 361 stored in the memory 360 to control the overall operation of the 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 circuit 325, and TX processing circuit 315 in accordance with well-known principles. In some embodiments, the main processor 340 includes at least one microprocessor or microcontroller.

The main processor 340 is also capable of executing other processes and programs resident in the memory 360, such as operations for channel quality measurements and reporting for systems having 2D antenna arrays as described in embodiments of the present disclosure. The main processor 340 may move data to and from the memory 360 as needed to perform the process. In some embodiments, the main processor 340 is configured to execute the application 362 based on the OS program 361 or in response to a signal received from an eNB or operator. The main processor 340 is also coupled to an I/O interface 345 that provides the UE 116 with the ability to connect to other devices, such as laptop computers and handheld computers. I/O interface 345 is the communication path between these accessories and host processor 340.

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

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 UE 116, various changes may be made to fig. 3A. For example, the 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, the 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). In addition, although fig. 3A shows the UE 116 configured as a mobile phone or smart phone, the UE may be configured to operate as other types of mobile or stationary devices.

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

As shown in fig. 3B, 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, a memory 380, and a backhaul or network interface 382.

The RF transceivers 372a through 372n receive input RF signals from antennas 370a through 370n, such as signals transmitted by a UE or other eNB. The RF transceivers 372 a-372 n down-convert the input RF signals to generate IF or baseband signals. The IF or baseband signal is sent to RX processing circuit 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 signal to a 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. The RF transceivers 372 a-372 n receive the output processed baseband or IF signals from the TX processing circuitry 374 and up-convert the baseband or IF signals to RF signals that are transmitted via the antennas 370 a-370 n.

The controller/processor 378 may include one or more processors or other processing means that control the overall operation of the eNB 102. For example, controller/processor 378 may control the reception of forward channel signals and the transmission of reverse channel signals by RF transceivers 372a through 372n, RX processing circuit 376, and TX processing circuit 374 in accordance with well-known principles. The controller/processor 378 may also support additional functions, such as more advanced wireless communication functions. For example, the 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 is also capable of executing programs and other processes residing in memory 380, such as a basic OS. Controller/processor 378 is also capable of supporting channel quality measurements and reporting for systems having 2D antenna arrays as described in embodiments of the present disclosure. In some embodiments, the controller/processor 378 supports communication between entities, such as a network RTC. The controller/processor 378 may move data to and from the memory 380 as needed to perform the process.

The controller/processor 378 is also coupled to a backhaul or network interface 382. The backhaul or network interface 382 allows the eNB 102 to communicate with other devices or systems through a backhaul connection or through a network. The interface 382 may support communication over 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 the eNB 102 is implemented as an access point, the interface 382 may allow the 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 over 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 BIS algorithm) are stored in a 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 the BIS algorithm.

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

Although fig. 3B shows one example of 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 shown as including a single instance of TX processing circuitry 374 and a single instance of RX processing circuitry 376, eNB 102 may include multiple instances of each (such as one for each RF transceiver).

Fig. 4A and 4B illustrate an example 2D antenna array, according to an embodiment of the present disclosure, composed of 16 dual polarized antenna elements arranged in a 4 x 4 rectangular format. 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 x 4 dual polarized array can be seen as an array of elements of 16 x 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 high degree 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 a high dimension, it does not achieve the potential gains offered by the spatial and frequency selectivity of the channel.

Fig. 5 illustrates another numbering of TX antenna elements 500 (or TXRU) according to an embodiment of the present 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 some embodiments, the eNB 103 is equipped with a 2D rectangular antenna array (or TXRU) comprising M rows and N columns of p=2 polarizations, 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 TXRU an array, 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 sets of contiguous elements, and the M sets correspond to M TXRU with the same polarization as in the columns of the TXRU array in fig. 5.

In conventional LTE, MIMO precoding (for spatial multiplexing) may be implemented by 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 the 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 }; eight antenna ports: { TS36.213 Table 7.2.4-1, 2, 3, 4, 5, 6, 7, and 8}.

If the eNB 103 follows the PMI recommendation of the UE 115, then the eNB 103 is expected to precode its transmit signal (for a given subframe and Physical Resource Block (PRB)) according to the recommended precoding vector/matrix. Whether or not the eNB 108 follows the recommendation of the UE 115, the UE 115 is configured to report PMI according to the precoding codebook described above. Here, PMI (which may consist of a single index or a pair of indexes) is associated with a precoding matrix W of size N _C×N_L, where N _C is the number of antenna ports (=the number of columns) in a row and N _L is the number of transmission layers.

Rel.12LTE 8-Tx double codebook

Tables 1 and 2 are codebooks for level-1 and level-2 (layer 1 and layer 2) CSI reports for UEs configured with 8Tx antenna port transmission in order to determine the CW of each codebook, two indexes, i.e., i ₁ and i ₂, must be selected. 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 layer 1 CSI reporting using antenna ports 15 to 22

If ri=1, which was recently reported, m and n are derived from two indices i ₁ and i ₂, according to table 1, yielding a level-1 precoder,

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

If ri=2, which was recently reported, then m, m' and n are derived from the two indices i ₁ and i ₂, according to table 2, yielding a level-2 precoder,It should be noted that the number of the components,Constructed such that it can be used to facilitate two different types of channel conditions for level-2 transmissions.

One subset of the codebook associated with i ₂ = {0, 1, … …, 7} includes codewords of m=m', or the same beam (v _m) is used to construct a rank-2 precoder: in this case, two columns in the 2-layer precoder are orthogonal (i.e., ) This is because for two columns, different flags are applied toThese level-2 precoders are possible for those UEs that may receive strong signals along two orthogonal channels generated by two differently polarized antennas.

Rel.12LTE substituted 4-Tx double codebook

Based on a similar concept as 8-Tx, an alternative 4-Tx codebook may 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.8LTE 2-Tx codebook

For transmission 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 is for the transmissions on antenna port 0,1 and the codebook for CSI reporting based on antenna 0,1 or 15, 16.

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

The enb determines the precoder (or angular direction) for N _P CSI-RS ports based on the history of uplink Sounding Reference Signals (SRS), PUSCH/PUCCH, or PMI feedback, or a combination of the above.

Csi-RS virtualization example:

2.1 dividing N _P ports into two groups, CSI-RS of antenna ports belonging to the first group being transmitted from a first group of antennas with a first polarization p=0 and CSI-RS of antenna ports belonging to the second group being transmitted from a second group of antennas with a first polarization p=1 of the second polarization. In one example, when N _P is 7, CSI-RSs on ports 0, … …, N _P/2-1 are transmitted { (M, N, p=0) on the first set of antennas with +45° polarization, m=0, … …, M-1, n=0, … …, N-1}, while CSI-RSs on port N _P/2、……、N_P -1 are transmitted { (M, N, p=1) on the second set of antennas with-45 ° polarization, m=0, … …, M-1, n=0, … …, N-1}.

2.2N _P antenna ports are divided into N _P/2 pairs of antenna ports. The two antenna ports of each pair map to the same set of antenna element positions with the same precoding or beamforming (i.e., both map to the same set of { (m, n) }, and the same precoding is applied on the antenna set with the same polarization), but they are on antennas with different polarizations, i.e., the first port maps to p=0 and the second port maps to p=1.

2.2.1 In one example, a first CSI-RS of a first pair of CSI-RS ports transmits { (M, N, p=0), m=0, … …, M-1, n=0, … …, N-1}, at +45° polarization on a first set of antennas (or TXRU) on which a first antenna virtualization precoder w ⁽¹⁾ is applied; and a second CSI-RS of the pair of CSI-RS ports transmits { (M, N, p=1), m=0, … …, M-1, n=0, … …, N-1}, on a second set of antennas (or TXRU) with a-45 ° polarization, wherein the same antenna virtualization precoder w ⁽¹⁾ is applied on the set of antennas. When m=8 and n=2, for example, the virtualized mapping on the MN element with the first polarization for the first CSI-RS (denoted s _a＝0) and the mapping for the second CSI-RS (denoted s _a＝1) will be respectively:

where x _(m,n,p) is the signal mapped on element (m, n, p), and

N _P can be broken down into N _P＝N_H·N_V, where N _H is the number of antenna ports in a row; and N _V is the number of antenna ports in a column of the 2D rectangular antenna array. In one example, N _V = 4 and N _H = 8, where the x-pol dimension is calculated towards the row and not towards the column.

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

Ue 115 receives CSI-RS configuration of N _P antenna ports and corresponding CSI-RS.

Ue 115 selects Q (+.n _P) CSI-RS ports out of N _P antenna ports, e.g., based on the received power on these ports. If q=n _P, then UE 115 selects all configured number of CSI-RS ports for 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, Q beams. Thus, each beam corresponds to a pair of CSI-RS ports.

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

2.1.2 In another example, 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 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 in a pair.

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

3.1 In one approach, the UE 115 derives q co-phase factors for both ports of each pair.

3.2 In another approach, the UE 115 derives a common co-phase factor between the two ports of all pairs.

4. On the condition of Q selected ports and Q co-phase factors, UE 115 derives CQI, PMI and/or RI.

4.1 In one example, when q=2 (q=1) ports are selected, UE 115 performs a hypothesis test as to whether level 1 or level 2 supports higher transmission rates. For the level-1 assumption, UE 115 assumes that the received signals from both ports carry one information stream and combine at the receiver; for the level-2 assumption, UE 115 assumes that the received signals from both ports carry two information streams and applies a MIMO receiver.

The signal on 4.1.1CSI-RS antenna port a is denoted y _a. Then, with the level-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:

where x ₁、x₂ is the signal on the two DMRS ports (ports 7 and 8).

Here the number of the elements is the number,Is the co-phase factor that will include the feedback PMI. In one example, for level 1From the slaveAnd is used for class 2 selectionFrom the slaveIs selected from the group consisting of a plurality of combinations of the above.

4.2 In another example, when q=2 (q=1) ports are selected, the UE reports PMI/CQI/RI using Rel-82-Tx codebook (table 5).

4.3 In another example, 8 CSI-RS ports are configured for UE 115. The UE 115 receives a set of 8-port precoded CSI-RSs from the eNB 103, where the 8-port CSI-RSs are split 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 further configured to have a set of four precoding vectors u ₀、u₁、u₂、u₃ to be applied to each set of four CSI-RS ports, each of which is 4 x1 in size. The four vectors u ₀、u₁、u₂、u₃ may be configured by the eNB 103 or may be hard coded. Assume that the received signal on the 8-port CSI-RS is represented by [ y ₀、y₁、y₂、y₃、y₄、y₅、y₆、y₇ ], where y ₀、y₁、y₂、y₃ has p=0 and y ₄、y₅、y₆、y₇ has p=1. Further, CSI-RS port a is paired with CSI-RS port a+4, a=0, 1,2,3, where paired ports are precoded at the same set of (m, n) but using the same precoder at different p. A=15, 16, 17, 18 when applying the legacy LTE probe port coding scheme for CSI-RS. Subsequently, to derive the rank-1 CQI/PMI, the UE assumes the following signal model, in which it is assumed that the rank-1 precoder W has been applied:

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

Related toAnd [ alpha ₀,α₁,α₂,α₃,α₄,α₅,α₆,α₇ ].

4.3.1. In one example of this, in one implementation,

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

Here, the precoder W may be represented by w=w ₁ W₂, whereAnd is combined withAnd it can be seen that W ₂ includes two items of information: (1) Column (or pair or beam) selection c ₀、c₁、c₂、c₃ and the phase coefficients for the selected column.

4.3.2. For example, if [ c ₀、c₁、c₂、c₃ ] = [ 110 0], then the phase coefficients for the selected column need to be quantized and fed back with the column selection information: a ₀、a₁、a₄、a₅, wherein a ₀ =1. In this case, PMI corresponds to [ c ₀、c₁、c₂、c₃ ] = [ 110 0] and [ α ₀＝1,α₁,α₄,α₅ ].

4.3.3. In another example, W ₁ = I and only one column (beam) is selected. Since there are 4 cases in selecting one column from 4 columns, 2 bits are required to encode this information, as shown in table 6 below. For example, if [ c ₀、c₁、c₂、c₃ ] = [ 110 0] is selected, only one phase coefficient a ₁ needs to be quantized with [ a ₀＝1,a₄ ]. Item a ₄ can be quantized to exp (j theta _m), whereAnd some example values of M are: m=2, 4, 8, 16. The combined information of column (beam) selection and co-phase may be fed back together.

TABLE 6

Column (beam) selection and co-phased field state	Selected columns (beams)	Co-phase (where M=4)
			0-3	1	m＝s
4-7	2	m＝s-4
			8-11	3	m＝s-8
12-15	4	m＝s-12

When [ c ₀、c₁、c₂、c₃ ] = [ 110 0] and α ₄ is quantized toWhere m=4, a simple combination of sections 4.3.1 and 4.3.3 gives

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

Examples: (CSI reporting details 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 a corresponding CQI/PMI/RI for the selected CSI-RS port.

An alternative mapping method of beam index to a pair of CSI-RS ports is seen as shown in table 7 below, where q=8 is assumed (and for example, Q may be 4 in general):

TABLE 7

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

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

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

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

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

In one alternative, BI is co-coded with PMI/CQI and reported in PMI/CQI region of PUSCH. This alternative supports subband selection for the BI and wideband selection for the BI.

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

Examples: polarized CSI-RS transmission

Fig. 6 illustrates a polarized CSI-RS transmission 600 according to an embodiment of the present 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 precoded by the same weight vector and transmitted via the same set of columns and rows of antennas, with one CSI-RS transmitted via the antennas in the set at +45° polarization and the other CSI-RS transmitted via the antennas in the set at-45 ° as shown in fig. 6.

Examples: sequential polarization CSI-RS transmission

Fig. 7A and 7B illustrate sequential polarized CSI-RS transmissions 700, 710 according to an embodiment of the disclosure. The embodiment shown in fig. 7 is for illustration only. Other embodiments may be used without departing from the scope of this disclosure.

In this embodiment, the CSI-RS may not be transmitted in the pair of polarizations. In one CSI process, CSI-RS may be transmitted from +45°, and in another CSI process, CSI-RS may be transmitted from-45 °. The number of CSI-RS ports transmitted need not be the same during both processes. For cases where there is not much polarization diversity needed, the motivation is to reduce CSI-RS sources and reduce feedback load. The concept of an embodiment is shown in fig. 7A and 7B.

Examples: flexible polarization CSI-RS transmission

Fig. 8 illustrates flexible polarization 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, CSI-RS may not be transmitted in pairs of polarizations, as shown 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 the port number. The motivation is also to reduce CSI-RS sources and reduce feedback load for cases where much polarization diversity is not needed. The eNB 103 may determine CSI-RS to transmit based on the history of uplink measurements or CSI feedback.

Examples: UE partial PMI feedback

The UE 115 is configured to receive 8-port precoded CSI-RS from the eNB 103, wherein the 8-port CSI-RS 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 further configured to have a set of four precoding vectors u ₀、u₁、u₂、u₃ to be applied to each set of four CSI-RS ports, each of which is 4 x 1 in size. The four vectors u ₀、u₁、u₂、u₃ may be configured by the eNB 103 or may be hard coded.

Assume that the received signal on the 8-port CSI-RS is represented by [ y ₀、y₁、y₂、y₃、y₄、y₅、y₆、y₇ ], where y ₀、y₁、y₂、y₃ has p=0 and y ₄、y₅、y₆、y₇ has p=1. Further, CSI-RS port a is paired with CSI-RS port a+4, a=0, 1, 2, 3, where paired ports are precoded at the same set of (m, n) but using the same precoder at different p. When UE 115 derives the rank-1 CQI for u ₀＝[u₀₀、u₀₁、u₀₂、u₀₃]^t on these 8 CSI-RS ports, UE 115 should assume the following signal model for CSI (CQI, PMI, RI) derivation:

Extending this approach, all precoding vectors u ₀、u₁、u₂、u₃ can be considered jointly in a single equation:

Wherein the method comprises the steps of Is a binary vector for the selection of columns of the matrix (i.e., c _i e {0,1}, i=0, 1, 2, 3), andIs the co-phase factor for the four precoding vectors u ₀、u₁、u₂、u₃. When UE 115 selects q precoding vectors of the four precoding vectors, UE 115 should feed back q non-zero co-phase factors.

In this case, the PMI includesAndIs a piece of information of (a). In one example of this, in one implementation,And hard coded. In this case, in case Q precoding vectors are selected, q=2q CSI-RS ports are equally selected.

Examples: CSI-RS for long-term CSI estimation

Fig. 9A and 9B illustrate eNB 103 transmission and corresponding UE 115 feedback for CSI-RS of two types 900, 910 according to some 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-phase, beam-select PMI, RI, and CQI).

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

The eNB 103 may configure a duty cycle of CSI-RS transmission of the first CSI-RS source to be longer than the second CSI-RS source. In accordance with some embodiments of the present 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 channel estimation through the first CSI-RS estimation, the UE 115 estimates and feeds back the long-term CDI. In accordance with some embodiments of the present disclosure, the UE 115 estimates and feeds back co-phase information and beam selection information using channel estimation through the second CSI-RS estimation. In one 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.

According to some embodiments of the present disclosure, a second CSI-RS and related CSI feedback may be constructed/derived, wherein the UE 115 derives short-term CSI from Q (=q/2) antenna ports that 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 _P CSI-RS ports (in one example, N _P = p·m·n; in another example, N _P = m·n according to the symbols in the embodiment associated with fig. 5) are configured for the first CSI-RS source, and N _P CSI-RS ports are mapped one-to-one to N _P TXRU in the antenna array. In this case, the UE 115 estimates Channel Direction Information (CDI) by channel estimation using N _P CSI-RS ports, and feeds back the CDI to the eNB. CDI may be reported on PUCCH or on PUSCH.

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

In another example, N _P = P M N, and according to the symbols in the embodiment associated with fig. 5, the UE 115 is configured with first, second, and third numbers of antenna ports M and N and P.

In another example, N _P = P M N, and according to the symbols in the embodiment associated with fig. 5, the UE 115 is configured with first and second numbers of antenna ports P M and N.

In one example of the current approach, CDI is two oversampled DFT precoders: one for representing azimuth channel direction and the other for representing elevation channel direction. In the latter embodiment, the DFT precoder/vector and the oversampled DFT vector may be used interchangeably. Further, if m=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=4, then the DFT vector for the high channel direction is (here, the number of elements in the DFT vector is equal to N):

Where example values of a are 32, 16 and 8 and example values of B are 16, 8 and 4. Feedback information for UE 115 may include a·b states; if a=16 and b=8, the number of states is 128 and it is 7-bit information. The azimuth CDI and the elevation CDI may be encoded individually 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 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 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 CDI is shown in table 10 below.

Table 10

In another example of the current method, CDI is implementedOr alternativelyA set of L vectors in form, and the information field for CDI will contain information about L index pairs:

U.S. provisional patent application No. 62/073,782, filed on day 2014, month 10, and 31, which is incorporated herein in its entirety, has presented several methods for encoding CDI information of this type. One example method of quantifying the azimuth CDI is described in table 11 below, where a=32 is assumed:

TABLE 11

Vector set indicator index (5 bits)	Vector combination index (i)	Selected vector set (CDI)
			0,…,15	0,…15	{v_2i,v_2i+1,v_2i+2,v_2i+3}
16,…,23	0,…,7	{v_4i,v_4i+2,v_4i+4,v_4i+6}
			24,…,27	0,…,3	{v_8i,v_8i+4,v_8i+8,v_8i+12}
28 (Option 1)	0	{v₀,v₈,v₁₆,v₂₄}
			29,30,31 (Option 1)	Reservation of
28,29,30,31 (Option 2)	0,…,3	{v_2i+0,v_2i+8,v_2i+16,v_2i+24}

Another example method of quantifying the azimuth CDI is described in table 12 below, where it is assumed that a=32:

table 12

Vector set indicator index (4 bits)	Vector combination index (i)	Selected vector set (CDI)
			0,…,15	0,…15	{v_2i,v_2i+1,v_2i+2,v_2i+3}

It should be noted that the altitude CDI may also be quantized similarly to the azimuth CDI.

Examples: CSI-RS for long-term CSI estimation

According to the symbols associated with the embodiment related to fig. 5, the eNB 103 has a 2D TXRU array of (M, N, P) = (4,4,2). In this case, the total number of TXRU is 32. In this embodiment, the eNB 103 configures the UE 115 with N _P CSI-RS ports, where for CSI-RS of a first type that may be decomposed into (M, N, P _effective) = (4,4,1), N _P = m·n = 16, so that the UE 115 may estimate the long-term CDI.

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

The eNB 103 of (M, N, P) = (4,4,2) may additionally configure and transmit the CSI-RS of the second type. According to some embodiments of the present disclosure, the second type of CSI-RS is precoded by a precoder selected based on CDI feedback of the UE 115, wherein the UE 115 derives 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 _B CSI-RS ports are configured for the first CSI-RS source and N _B CSI-RS ports are beamformed, i.e., precoding weights are applied to each CSI-RS to be mapped onto N _P TXRU in the antenna array. In this case, the CDI estimated by the UE 115 may be a set of CSI-RS ports selected from N _B CSI-RS ports.

The UE 115 may select the L CSI-RS ports with the L strongest received powers among the N _B 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 PUSCH or PUCCH.

Examples: coarse beamforming CSI-RS for long term CSI estimation

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

And

The DFT vectors for the high channel direction are:

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 encapsulated 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 in accordance with 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 an a·b=32 port beamformed CSI-RS as shown. In fig. 11A, a fine mesh and a coarse mesh are shown. The coarse grid comprises 32 elements, each having an index of (a, B), where a = 0, 1, … …, a-1 and B = 0, 1, … …, B-1; similarly, the fine grid includes 128 elements, each having an index of (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 grid correspond to the precoding vectorsThe CSI-RS beams precoded, and similarly, the elements (a ', b') in the fine grid correspond to the precoding vectors passed throughAnd carrying out precoding CSI-RS beams. Subsequently, the eNB 103 receives beam index feedback from the UE 115, where the beam index is estimated in dependence of the 32-port beamformed CSI-RS. In one example, the eNB 103 obtains information from the UE 115 corresponding toFeedback of beam index pair (a, b) = (0, 0). Subsequently, according to some embodiments of the present disclosure, the eNB 103 transmits a plurality of finer beam CSI-RS (where a '> a and B' > B) on the second CSI-RS source for the UE 115, 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 plurality of finer beams corresponds to (a ', B') = (0, 0), (1, 0), (0, 1), (1, 1), where a '=16 and B' =8, corresponding to And

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

Examples: CQI estimation time window with respect to two types of CSI-RSs

Fig. 12 illustrates a flow diagram 1200 relating to 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 regarding the following sequence unless explicitly stated: the execution of specific sequences, steps, or portions thereof, performed in succession, not concurrently, or with overlapping fashion, or the steps illustrated may be executed in the absence of intervening or intermediate steps. The process depicted in the illustrated example is implemented 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 a first type of CSI-RS from the eNB 103.

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

In step 3, the eNB 103 may decide to update the precoder for the second type CSI-RS based on the CDI feedback. In such cases, the eNB sends an indication of the beamforming update of the CSI-RS of the second type to the UE 115. The indication may be sent 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 estimate estimated by the CSI-RS of the second type from the memory.

In step 5, after transmitting the indication message, the eNB 103 transmits a second type CSI-RS precoded by a 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 estimate and after receiving the second type of CSI-RS for 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 short-term CSI to the eNB 103.

The UE 103 may store the channel estimate estimated by the CSI-RS of the second type 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 according to 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 the CSI-RS channel estimates, and the UE 115 does not take different CSI-RS channel estimates from two different time windows as input for generating short-term CSI.

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

In one method, the triggering event is an indication message of a beamforming update of the CSI-RS of the second set being received.

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

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

In another method, the triggering event is receipt 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 short-term CSI may be derived from the second type of CSI-RS received in the time window.

In another method, 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, UE 115 is configured to report long-term CSI on a first PUCCH source according to a first periodic CSI feedback configuration and to report short-term CSI on a second PUCCH source according to a second periodic CSI feedback configuration. In a particular subframe in which 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 motivated by the fact that: the long-term information is more important than the short-term information.

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

In some embodiments, UE 115 is configured to have 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 PUCCH sources, reporting frequencies, and reporting time offsets.

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 PUCCH sources, reporting frequencies, and reporting time offsets.

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 cover 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 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

Receiving first CSI feedback including a first PMI from the UE 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 of the 8 CSI-RSs on antenna ports 15 and 19 are mapped to a first and a second set of the same number of antenna elements, respectively, to which substantially similar beamforming weight vectors are applied,

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 the two antenna elements on the first and second groups are located at the same physical location comprising a dual polarized pair, and

Wherein the 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 a beamforming weight vector, 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:

Transmitting a downlink signal containing a second CSI-RS configuration on a physical downlink shared channel PDSCH, and an N-port CSI-RS according to the second CSI-RS configuration, wherein N is a positive integer; and

Receiving an uplink signal from the UE containing the second PMI, the second PMI comprising 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:

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

Receiving an uplink signal containing the second PMI, wherein the second PMI comprises two non-negative integers derived by using the N-port CSI-RS,

Wherein the controller is further configured to determine a precoding vector as a Kronecker product of the two oversampled DFT vectors from 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 units that are mapped to N antenna sub-arrays placed on a two-dimensional antenna panel, respectively.

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 of the 8 CSI-RSs on antenna ports 15 and 19 are mapped to a first and a second set of the same number of antenna elements, respectively, to which substantially similar beamforming weight vectors are applied,

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 a beamforming weight vector, and

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:

Transmitting a downlink signal containing a second CSI-RS configuration on a physical downlink shared channel PDSCH, and an N-port CSI-RS according to the second CSI-RS configuration;

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

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

13. The method of claim 12, further comprising:

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

receiving an uplink signal containing the second PMI, wherein the second PMI comprises two non-negative integers derived by using the N-port CSI-RS; and

And determining a pre-coding 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 units that are mapped to N antenna sub-arrays placed on a two-dimensional antenna panel, respectively.

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) by 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

Causing 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 according to 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 containing 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 a non-negative integer indicative of an oversampled discrete fourier transform, DFT, vector.

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

transmitting an uplink signal containing a second PMI;

Wherein the second PMI comprises two non-negative integers indicative of two oversampled discrete fourier transform DFT vectors and indicates Kronecker products 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 about a trigger for a time window change for channel estimation,

Wherein the controller is further configured to:

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

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

And discarding the channel estimation of the 8-port CSI-RS according to the trigger time.