KR20160116046A - Codebook construction - Google Patents

Codebook construction Download PDF

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KR20160116046A
KR20160116046A KR1020167026694A KR20167026694A KR20160116046A KR 20160116046 A KR20160116046 A KR 20160116046A KR 1020167026694 A KR1020167026694 A KR 1020167026694A KR 20167026694 A KR20167026694 A KR 20167026694A KR 20160116046 A KR20160116046 A KR 20160116046A
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codebook
layer
matrix
amp
index
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KR1020167026694A
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Korean (ko)
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나라얀 프라사드
구오센 유에
모하마드 코자스터포어
샘파스 란가라잔
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닛본 덴끼 가부시끼가이샤
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Priority to US201361774275P priority Critical
Priority to US61/774,275 priority
Priority to US201361775058P priority
Priority to US61/775,058 priority
Priority to US61/808,934 priority
Priority to US201361808934P priority
Priority to US201361817247P priority
Priority to US201361817150P priority
Priority to US61/817,150 priority
Priority to US61/817,247 priority
Priority to US61/821,989 priority
Priority to US201361821989P priority
Priority to US14/198,653 priority patent/US9020061B2/en
Priority to US14/198,653 priority
Application filed by 닛본 덴끼 가부시끼가이샤 filed Critical 닛본 덴끼 가부시끼가이샤
Priority to PCT/US2014/021535 priority patent/WO2014138525A1/en
Publication of KR20160116046A publication Critical patent/KR20160116046A/en

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    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04BTRANSMISSION
    • H04B7/00Radio transmission systems, i.e. using radiation field
    • H04B7/02Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/0413MIMO systems
    • H04B7/0456Selection of precoding matrices or codebooks, e.g. using matrices antenna weighting
    • H04B7/046Selection of precoding matrices or codebooks, e.g. using matrices antenna weighting taking physical layer constraints into account
    • H04B7/0469Selection of precoding matrices or codebooks, e.g. using matrices antenna weighting taking physical layer constraints into account taking special antenna structures, e.g. cross polarized antennas into account
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04BTRANSMISSION
    • H04B7/00Radio transmission systems, i.e. using radiation field
    • H04B7/02Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/0413MIMO systems
    • H04B7/0456Selection of precoding matrices or codebooks, e.g. using matrices antenna weighting
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04BTRANSMISSION
    • H04B7/00Radio transmission systems, i.e. using radiation field
    • H04B7/02Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/0413MIMO systems
    • H04B7/0456Selection of precoding matrices or codebooks, e.g. using matrices antenna weighting
    • H04B7/0478Special codebook structures directed to feedback optimization
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04BTRANSMISSION
    • H04B7/00Radio transmission systems, i.e. using radiation field
    • H04B7/02Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/0413MIMO systems
    • H04B7/0456Selection of precoding matrices or codebooks, e.g. using matrices antenna weighting
    • H04B7/0486Selection of precoding matrices or codebooks, e.g. using matrices antenna weighting taking channel rank into account
    • HELECTRICITY
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    • H04B7/06Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
    • H04B7/0613Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission
    • H04B7/0615Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal
    • H04B7/0617Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal for beam forming
    • HELECTRICITY
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    • H04B7/06Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
    • H04B7/0613Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission
    • H04B7/0615Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal
    • H04B7/0619Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal using feedback from receiving side
    • H04B7/0621Feedback content
    • H04B7/0626Channel coefficients, e.g. channel state information [CSI]
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    • H04B7/02Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/06Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
    • H04B7/0613Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission
    • H04B7/0615Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal
    • H04B7/0619Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal using feedback from receiving side
    • H04B7/0636Feedback format
    • H04B7/0639Using selective indices, e.g. of a codebook, e.g. pre-distortion matrix index [PMI] or for beam selection
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04BTRANSMISSION
    • H04B7/00Radio transmission systems, i.e. using radiation field
    • H04B7/02Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/06Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
    • H04B7/0613Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission
    • H04B7/0615Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal
    • H04B7/0619Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal using feedback from receiving side
    • H04B7/0636Feedback format
    • H04B7/0641Differential feedback
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04BTRANSMISSION
    • H04B7/00Radio transmission systems, i.e. using radiation field
    • H04B7/02Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/06Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
    • H04B7/0613Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission
    • H04B7/0615Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal
    • H04B7/0619Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal using feedback from receiving side
    • H04B7/0636Feedback format
    • H04B7/0645Variable feedback
    • H04B7/065Variable contents, e.g. long-term or short-short
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00Arrangements for detecting or preventing errors in the information received
    • H04L1/0001Systems modifying transmission characteristics according to link quality, e.g. power backoff
    • H04L1/0023Systems modifying transmission characteristics according to link quality, e.g. power backoff characterised by the signalling
    • H04L1/0026Transmission of channel quality indication
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00Arrangements for detecting or preventing errors in the information received
    • H04L1/0001Systems modifying transmission characteristics according to link quality, e.g. power backoff
    • H04L1/0023Systems modifying transmission characteristics according to link quality, e.g. power backoff characterised by the signalling
    • H04L1/0027Scheduling of signalling, e.g. occurrence thereof
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00Arrangements for detecting or preventing errors in the information received
    • H04L1/02Arrangements for detecting or preventing errors in the information received by diversity reception
    • H04L1/06Arrangements for detecting or preventing errors in the information received by diversity reception using space diversity
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L25/00Baseband systems
    • H04L25/02Details ; Arrangements for supplying electrical power along data transmission lines
    • H04L25/03Shaping networks in transmitter or receiver, e.g. adaptive shaping networks ; Receiver end arrangements for processing baseband signals
    • H04L25/03891Spatial equalizers
    • H04L25/03898Spatial equalizers codebook-based design
    • H04L25/0391Spatial equalizers codebook-based design construction details of matrices
    • HELECTRICITY
    • H04ELECTRIC COMMUNICATION TECHNIQUE
    • H04LTRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00Modulated-carrier systems
    • H04L27/18Phase-modulated carrier systems, i.e. using phase-shift keying includes continuous phase systems
    • H04L27/20Modulator circuits; Transmitter circuits

Abstract

A method implemented in a base station for use in a wireless communication system is disclosed. The method comprises the steps of: providing a 1-layer, 2-layer, 3-layer, and 4-layer codebook for 4TX (4 transmit) antenna transmission, each codebook comprising a plurality of precoding matrices Precoding data to one of the plurality of precoding matrices; and transmitting the precoded data to a user equipment, wherein the one-layer and two-layer codebooks comprise a first codebook and a second codebook, 2 codebook, and each precoding matrix in the first codebook includes a first index and a second index. Other devices, systems, and methods are also disclosed.

Description

Codebook Configuration {CODEBOOK CONSTRUCTION}

This application claims priority to US Provisional Application No. 61 / 774,275 entitled " Observations on Codebook Construction, " filed on Mar. 7, 2013, entitled " Observations on Codebook Construction Provisional Application No. 61 / 775,058, filed April 5, 2013, entitled " Enhancements to a Structured Codebook, " U.S. Provisional Application No. 61 / 808,934, No. 61 / 817,150 entitled " Enhancement to the 4 Transmit Antenna Precoding Codebook, " filed on April 29, 2013, entitled " Enhancement to the 4 Transmit Antenna Precoding Codebook, 61 / 817,247, entitled " Improvements to the 4 Transmit Antenna Precoding Codebook, "filed on May 10, 2013, , The contents of which are incorporated herein by reference in their entirety. .

The present invention relates to precoding matrix design and, more particularly, to precoding matrix design that derives a precoding matrix as a product of two matrices.

Wireless communication systems require even higher spectral efficiencies to accommodate higher throughput requirements within limited frequency bands. Multiple antenna or multiple-input and multiple-output (MIMO) systems and closed loop transmission techniques, especially beamforming and precoding, have been extensively considered to improve spectral efficiency. In MIMO precoding schemes, the data to be transmitted is divided into one or more streams, which are mapped to one or more transport layers, and the data in the transport layers are pre-coded or pre-coded Lt; / RTI > The number of transport layers is referred to as the transmission rank. This transmission rank can be optimally selected for a given channel implementation, for example, by taking into account the transmission power and overall channel statistics.

In codebook-based precoding strategies, a predetermined codebook is made available to the transmitter, i. E. The base station (BS), and all receivers, i. E., Mobile stations (MS) or user equipment (UE). Then, the receiver selects, from the codebook, a precoder that maximizes its performance (e.g., data rate) and feeds back the precoder index. In addition, the selection of the precoder rank may be included in the precoder selection algorithm. The feedback rate may vary from short-term feedback once every consecutive time interval to long-term feedback once every several consecutive time intervals.

In many systems, the optimal precoders from the codebook for two adjacent transmission blocks are close to the appropriate distance measurement in all possible sets of precoders. Here, the neighboring blocks can be used for a set of tones in, for example, orthogonal frequency-division multiplexing (OFDM) systems, since in real systems the channel does not change abruptly from one transmission block to the adjacent block. Time or frequency. Thus, the precoder used in these blocks may be the same if the channel is fairly stable and the codebook resolution is not too high. By increasing the codebook resolution or by providing a more dynamic channel, the precoders of adjacent blocks are no longer identical, but can be close together. The proximity between two precocoders can be measured based on the appropriate distance metric in the space of all these precoders. Some examples of differential, dual and multi-resolution codebooks are described in references [5] and [6].

In order to obtain an effective codebook for both a uniform linear array (ULA) and a cross-pole configuration, it is advantageous to use four transmit antennas TX) MIMO downlink channel and provides a detailed description of a suitable codebook structure for both uniform linear array (ULA) and cross-pole antenna configurations. Some documents have proposed codebook designs for specific antenna configurations [7]. The basic properties of the spatial correlation matrices used by the present invention are not used in the prior art. In the present specification, the codebook structure is derived using basic properties of spatial correlation matrices under ULA and cross-pole antenna configurations. Each precoded codeword is derived as a product of two matrices, which makes the matrices efficient and also achieves a lower feedback overhead for a given performance level and better performance for a given feedback overhead.

References

[1] Ericsson, ST-Ericsson, "Design and Evaluation of 4 TX Precoder Codebooks for CSI Feedback," 3GPP TSG RAN WG1 R1-104847 62, Madrid, August 2010.

[2] A. Forenza, D. Love and R. Heath, "Simplified Spatial Correlation Models for Clustered MIMO Channels with Different Array Configurations," IEEE Trans. Veh . Tech. , July 2007.

[3] S. Loyka, "Channel capacity of MIMO architecture using the exponential correlation model," IEEE Commun . Letters , 2001.

[4] D. Love, R. Heath and T. Strohmer, "Grassmannian beamforming for multiple-input multiple-output wireless systems," IEEE Trans. Inf . Theory , Oct. 2003.

[5] MA Khojastepour et al ., "STATIC AND DIFFERENTIAL PRECODING CODEBOOK FOR MIMO SYSTEMS," US Patent Application Publication US 2008/0232501 A1.

[6] MA Khojastepour et al ., "MULTI-RESOLUTION PRECODING CODEBOOK," US Patent Application Publication US 2009/0274225 A1.

[7] 3GPP TS 36.213 V10.8.0 (2012-12), 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA); Physical layer procedures (Release 10), http://www.3gpp.org/ .

[8] NEC Group, "DL MU-MIMO Enhancement Schemes," 3GPP TSG RAN WG1 R1- 130364.

[9] NEC Group, MU-MIMO: "CQI Computation and PMI Selection," 3GPP TSG RAN WG1 R1-103832.

[10] NEC Group, "DL MU-MIMO enhancement via Residual Error Norm feedback," 3GPP TSG RAN WG1 R1-113874 .

It is an object of the present invention to provide a codebook with efficient precoding codewords that requires a lower feedback overhead for a given performance level and that also achieves better performance for a given feedback overhead.

One aspect of the invention includes a method implemented in a base station for use in a wireless communication system. The method comprises the steps of: 1-layer, 2-layer, 3-layer, and 4-layer codebooks for transmitting 4TX (4 transmit) antennas, wherein each codebook comprises a plurality of precoding matrices Precoding data to one of the plurality of precoding matrices; and transmitting the precoded data to a user equipment, wherein each of the one-layer and two-layer codebooks comprises 1 codebook and a second codebook, and each precoding matrix in the first codebook includes a first index and a second index.

Another aspect of the invention includes a method implemented in a user equipment for use in a wireless communication system. The method includes receiving precoded data from a base station, wherein each of the 1-layer, 2-layer, 3-layer, and 4-layer codebooks for transmitting 4TX (4 transmit) Coding matrices and each of the one-layer and two-layer codebooks includes a first codebook and a second codebook, wherein each precoding matrix in the first codebook includes a first index and a second index do.

Another aspect of the present invention includes a base station used in a wireless communication system. The base station includes a transmitter for transmitting precoded data to the user equipment, and each of the 1-layer, 2-layer, 3-layer, and 4-layer codebooks for transmitting 4TX (4 transmit) Wherein each of the one-layer and two-layer codebooks includes a first codebook and a second codebook, and each precoding matrix in the first codebook includes a first index and a second index, .

Another aspect of the invention includes user equipment used in a wireless communication system. Wherein the user equipment comprises a receiver for receiving precoded data from a base station and wherein each of the 1-layer, 2-layer, 3-layer, and 4-layer codebooks for transmitting 4TX (4 transmit) Wherein each of the first-layer and the second-layer codebooks includes a first codebook and a second codebook, and each precoding matrix in the first codebook includes a first index and a second codebook, 2 index.

Another aspect of the present invention includes a wireless communication system, wherein the wireless communication system is configured as a one-tier, two-tier, three-tier, and four-tier codebook for transmitting 4TX (4 transmit) A base station having the codebooks comprising a plurality of precoding matrices and precoding data to one of the plurality of precoding matrices and user equipment for receiving the precoded data from the base station, Layer and the 2-layer codebooks each include a first codebook and a second codebook, and each precoding matrix in the first codebook includes a first index and a second index.

Yet another aspect of the invention includes a method implemented in a wireless communication system. The method includes precoding data; And transmitting the precoded data from a base station to a user equipment, wherein each of the 1-layer, 2-layer, 3-layer, and 4-layer codebooks for transmitting 4TX (4 transmit) And wherein each of the one-layer and two-layer codebooks includes a first codebook and a second codebook, and each precoding matrix in the first codebook includes a first index and a second index .

The first index may be for a plurality of subbands, and the second index may be for each subbands.

The second codebook may include a legacy codebook or a house-holder codebook.

Each of the 3-layer and 4-layer codebooks may include a legacy codebook or a house-holder codebook.

Each precoding matrix W in the first codebook satisfies W = W (1) W (2) , and the first matrix W (1)

Figure pat00001
And the second matrix W (2) may be selected from the outer codebook.

Another aspect of the invention includes a method implemented in a base station for use in a wireless communication system. The method comprising: providing a codebook comprising a plurality of precoding matrices; precoding data to one of the plurality of precoding matrices; and transmitting the precoded data to a user equipment , And each precoding matrix W satisfies W = W (1) W (2) , and the first matrix W (1)

Figure pat00002
And the second matrix W (2) is selected from the second codebook.

Another aspect of the invention includes a method implemented in a user equipment for use in a wireless communication system. The method includes receiving precoded data from a base station into one of a plurality of precoding matrices, wherein the codebook comprises the plurality of precoding matrices and each precoding matrix W further comprises: W = W (1 ) W (2) , and the first matrix W (1) satisfies the first codebook

Figure pat00003
And the second matrix W (2) is selected from the second codebook.

Another aspect of the present invention includes a base station used in a wireless communication system. The base station to the user equipment, comprising: a transmitter for transmitting the pre-coded data into one of a plurality of precoding matrices, the codebook comprises the plurality of precoding matrices, and each precoding matrix W is W = W ( 1) W (2) , and the first matrix W (1)

Figure pat00004
And the second matrix W (2) is selected from the second codebook.

Another aspect of the invention includes user equipment used in a wireless communication system. The user equipment includes a receiver for receiving data to be pre-coding one of a plurality of precoding matrix from the base station, and the codebook comprises the plurality of precoding matrices, and each precoding matrix W is W = W ( 1) W (2) , and the first matrix W (1)

Figure pat00005
And the second matrix W (2) is selected from the second codebook.

Another aspect of the present invention is directed to a wireless communication system including a base station having a codebook including a plurality of precoding matrices and precoding data to one of the plurality of precoding matrices, Wherein each precoding matrix W satisfies W = W (1) W (2) , and wherein the first matrix W (1)

Figure pat00006
And the second matrix W (2) is selected from the second codebook.

Yet another aspect of the invention includes a method implemented in a wireless communication system. The method includes precoding data to one of a plurality of precoding matrices, and transmitting the precoded data from a base station to a user equipment, wherein the codebook comprises the plurality of precoding matrices, Also, each precoding matrix W satisfies W = W (1) W (2) , and the first matrix W (1)

Figure pat00007
And the second matrix W (2) is selected from the second codebook.

FIG. 1 illustrates an exemplary embodiment of a receiver having N T transmit-antennas at the transmitter and N R / RTI > is a diagram of a downlink multiuser MIMO system with receive antennas.
Figure 2 shows the

Figure pat00008
Lt; / RTI > is a diagram of a 3-bit codebook of gain vectors that refer to a codebook.
3 is a diagram of common-phase terms in the 8-PSK alphabet for rank-1.
4A is a diagram of common-phase terms in the 16-PSK alphabet for rank-2.
4B is a diagram of other common-phase terms in the 16-PSK alphabet for rank-2.
5 is a diagram of common-phase terms in the 8-PSK alphabet for rank-2.
6A is a diagram of common-phase terms in the 8-PSK alphabet for rank-1.
6B is a diagram of other common-phase terms in the 8-PSK alphabet for rank-1.
7 is a diagram of common-phase terms in the 24-PSK alphabet for rank-2.
8A is a diagram of common-phase terms in the 24-PSK alphabet for rank-2.
8B is a diagram of common-phase terms in the 12-PSK alphabet for rank-2.
9 is a diagram of common-phase terms in the 16-PSK alphabet for rank-2.
10 is a diagram for common-phase terms in the 16-PSK alphabet for rank-2.

1 shows a downlink multi-user MIMO system with N T transmit-antennas at the BS and with N R receive antennas at the UE. A multi-antenna communication system 100 with a multi-level precoding codebook is schematically illustrated in FIG. Transmitter 110 transmits to r receive antennas 121.1-121.r coupled to receiver 120 through fading channels 130 through r from t transmit antennas 111.1-111.t . The channel estimator 125 provides an estimate of the channel 130 to the receiver 120. The channel estimate is also quantized and provided to the transmitter 110 via a quantization rate control feedback channel 135.

In systems using beamforming such as MIMO systems, a beamforming matrix (also referred to as a precoding matrix, precoder, code word, or precoded codeword) generated corresponding to received channel conditions is first transmitted to a receiver (E.g., via feedback) after being computed and quantized in the source transmitter. A conventional approach to reducing the overhead associated with this feedback is to provide matrix codebook (s) in each of the transmitter and the receiver, where each codebook (s) can be used according to channel conditions recognized at the receiver A plurality of potential beamforming matrices or a set of beamforming matrices. If the receiver has identified the proper matrix codebook (s), the receiver will feed back one or more indexes (instead of the actual matrix entries) indicating the appropriate codeword in the codebook (s) stored in the transmitter.

I. Example 1

1 Uniform Linear Array

Unless otherwise stated below, it is assumed that co-polarized antennas are closely spaced.

The inventors have made the following observations on the construction of a uniform linear array (ULA) transmission antenna. Consider a system with N common-polarized transmit antennas, where C is set to indicate a transmit spatial correlation matrix. J is a matrix with zeros everywhere except for cross diagonal elements, i. E.

Figure pat00009
, Where < RTI ID = 0.0 >

Figure pat00010

In the following equations, the vector becomes a Hermitian

Figure pat00011

here,

Figure pat00012
The
Figure pat00013
Lt; / RTI > The present inventors propose a set of properties as follows. The first observation relates to the spatial correlation matrix of the ULA transmit antenna configuration, which is effective with wide versatility (see [2]).

observe One procession C Hermitage Teplitz  Matrix, C ≪ / RTI > satisfies <

Figure pat00014

here,

Figure pat00015
Represents the pair of C.

Lemma 1, any Hermitian eigenspace of Te pleated matrix (eigenspace) can be fully described by the LE is committed vector. In other words,

Figure pat00016
And the eigen vector x of the Hermitian trellis matrix A satisfy the following equations
Figure pat00017
Y. & Lt ; / RTI >

Figure pat00018

Lemma 2

Figure pat00019
Is an eigenvalue of the Hermitian Teplitz matrix A with an algebraic multiplicity value . Then, x
Figure pat00020
If the eigenvector satisfies < RTI ID = 0.0 &
Figure pat00021
The following is obtained.

Figure pat00022

here

Figure pat00023
to be.

The simplification model for the correlation matrix is the exponential correlation model [3], which is further explained in the appendix and is given as follows.

Figure pat00024

here,

Figure pat00025
to be.

2.1 4  TX ULA

In this section, consider the case of N = 4 common-polarized transmit antennas. First, if there is no loss of generality, the following structure can be applied to each eigenvector x of the spatial correlation matrix C :

Figure pat00026

here,

Figure pat00027
Considering that the matrix C must be an Hermitian trellis matrix, we can deduce that if we call the lemmas 1 and 2,

Figure pat00028

Then, any two eigen-vectors of the form (8) given by the following are considered.

Figure pat00029

here,

Figure pat00030
And a sufficient condition to enhance the orthogonality between these two eigenvectors is to ensure the following equation.

Figure pat00031

This can be simplified to the next.

Figure pat00032

(11) is not required, but the scalar of all possible values

Figure pat00033
Lt; / RTI >

2 polarized waves  Setting (Polarized Setup)

The transmitter is assumed to have 2N cross-polarized antennas, each of which includes a pair of N common-polarized antennas. The correlation matrix for each of these two common-polarization sets is then denoted by C , which is Hermitian and Toeplitz. The entire 2N x 2N correlation matrix

Figure pat00034
Can be expressed as:

Figure pat00035

here,

Figure pat00036
Represents a kronecker product,
Figure pat00037
to be.
Figure pat00038
≪ / RTI >
Figure pat00039
Can be represented as having the following form.

Figure pat00040

here,

Figure pat00041
The matrix
Figure pat00042
And x is an eigenvector of C. Also,
Figure pat00043
The two eigenvectors of
Figure pat00044
And
Figure pat00045
, Where
Figure pat00046
Represents a transpose operation, and if there is no loss of optimality
Figure pat00047
Can be ignored. The two eigenvalues are
Figure pat00048
to be. Also,
Figure pat00049
Is a model of the correlation matrix of two transmitted ULA.

3 codebooks  Configuration

We now proceed to assign codebooks using the observations generated in section 1 and section 2. In particular, it allows to specify a subset of codebooks that are well suited to other configurations as well as to closely spaced 4TX ULA and cross-pole antenna configurations. First, consider a rank-1 codebook that includes a set of 4x1 vectors. If there is no loss of generality,

Figure pat00050
Is considered first, where
Figure pat00051
to be. Thereby defining three component codebooks configured to form a rank-1 codebook. The first component codebook is referred to as a gain vector codebook
Figure pat00052
Lt; RTI ID = 0.0 >
Figure pat00053
This is the derived codebook. The other two component codebooks are phase terms
Figure pat00054
Lt; RTI ID = 0.0 > codebooks, < / RTI &
Figure pat00055
And
Figure pat00056
Respectively. Gain vector codebook
Figure pat00057
. To cover the closely spaced 4TX ULA, sufficient vectors are needed in the rank-1 codebook with the (8) -shaped structure.
Figure pat00058
2 as a gain vector, and in Figure 2 provides a 3-bit codebook for gain vectors, where a settable scalar
Figure pat00059
, ≪ / RTI >
Figure pat00060
to be. Note that the gain vectors corresponding to indices 0, 1, and 2 are suitable for the ULA case spaced at 4 TX spacing by following the constraints in (8). The gain vector corresponding to index 0 is suitable for a 4 TX cross-pole case and the gain vectors corresponding to indices 3, 4 are referred to herein as a power imbalance case (see Appendix 8) . Index 7 represents re-use of the existing default codebook, and indices 5, 6 are included to provide more choices.

Next, to quantize the phases, two phase codebooks,

Figure pat00061
And
Figure pat00062
.
Figure pat00063
(8), so that the vector x can be expanded as follows.

Figure pat00064

Codebook

Figure pat00065
Using
Figure pat00066
And also selects a codebook
Figure pat00067
Using
Figure pat00068
. A simple scheme for constructing these two codebooks is through uniform quantization of [0, 2 [pi]) using a predetermined number of bits for each codebook. By choosing a gain vector corresponding to index 0 in the gain vector codebook of FIG. 2 with the choice of adopting these phases, it can be seen that the result vector follows the general eigenvector structure of the 4TX cross-poll correlation matrix. Similarly, when adopting a gain vector corresponding to any of indices 0, 1, 2 in the gain vector codebook, it can be seen that the result vector follows the general eigenvector structure of the 4TX ULA correlation matrix.

Now consider a rank-2 codebook consisting of a set of semi-unitary 4x2 matrices. From the observations made in section 1, we can define a subset of matrices with the following structure.

Figure pat00069

This structure does not satisfy the 4TX ULA (see Section 1) and also does not satisfy the structure of the first two major eigenvectors of the 4TX ULA configuration with the exponential correlation model (discussed in Section 6)

Figure pat00070
Figure pat00071
, It is noted that this structure may be suitable for a 4TX cross-pole configuration (discussed in Section 2). It is also possible to include matrices having the following structure,

Figure pat00072

This does not satisfy 4TX ULA.

4 products  Configuration of a codebook

In the following, two codebook configurations are discussed, in which each code word is derived as a matrix product, based on the principles outlined in section 1 and section 2. In each case, we use the codebook designed in [1] as a base, and extend it by following the principles outlined in section 1 and section 2.

Figure pat00073
, ≪ / RTI >
Figure pat00074
. This codebook is referred to as a first embodiment, and its inner (wideband) codebook is defined as follows.

Figure pat00075

here,

Figure pat00076
Represents a Hadamard product, and

Figure pat00077

here,

Figure pat00078
The rank-1 outer codebook is defined as follows.

Figure pat00079

Here, e i represents a 4 × 1 column selection vector. The outer rank-2 codebook is defined as follows.

Figure pat00080

Scalar a q , b q Lt; RTI ID = 0.0 > scalable < / RTI &

Figure pat00081
, ≪ / RTI >
Figure pat00082
,
Figure pat00083
.

In each feedback interval for selecting rank-2 code words, one for each subband, an inner (broadband) codebook

Figure pat00084
One common matrix, i. E.
Figure pat00085
. Then, on each subband n, an outer (subband) rank-2 codebook
Figure pat00086
≪ / RTI >
Figure pat00087
Is selected, and the final precoder selection for that subband is
Figure pat00088
. for your convenience,
Figure pat00089
(Final) codebook corresponding to rank-2, which corresponds to the
Figure pat00090
Lt; RTI ID = 0.0 > precoder < / RTI > Other ranks and internal precoder
Figure pat00091
Similar procedures and notations are adopted for other choices on the.

Figure pat00092
Lt; RTI ID = 0.0 > scalar < / RTI &
Figure pat00093
, ≪ / RTI >
Figure pat00094
In order to ensure that there is no problem. Under this choice, the triple set
Figure pat00095
Will be described below. From the discussion in Appendix 7 using the exponential correlation model, the (non-quantized)
Figure pat00096
Is assumed to be uniformly distributed at [0, 1) so that it is a desirable choice
Figure pat00097
. Therefore,
Figure pat00098
Is through uniform quantization of [0, 1) using a predetermined number of bits. For example,
Figure pat00099
.

Figure pat00100
, One possibility is to consider them as variables < RTI ID = 0.0 >
Figure pat00101
. Accordingly, the correlation magnitude parameter
Figure pat00102
A finite set of values for < RTI ID = 0.0 >
Figure pat00103
Can be obtained. For example, the correlation size parameter
Figure pat00104
Set for
Figure pat00105
. Then, by applying the equations in Appendix 7,
Figure pat00106
end
Figure pat00107
As shown in Fig. Then, triple set
Figure pat00108
(Cartesian product)
Figure pat00109
, Which is used herein to denote a Cartesian product
Figure pat00110
Were used. For example, the specific instances provided above
Figure pat00111
And
Figure pat00112
Lt; RTI ID = 0.0 >
Figure pat00113
Lt; RTI ID = 0.0 > 16, < / RTI > Another example is
Figure pat00114
Figure pat00115
And three values for the correlation magnitude parameter
Figure pat00116
A set that uses only
Figure pat00117
To obtain a cartesian product having a size of 15 by using < RTI ID = 0.0 > Another example is that the Cartesian product has size 16,
Figure pat00118
And two values for the correlation size parameter
Figure pat00119
A set that uses only
Figure pat00120
.

Now, let us consider another alternate codebook, hereinafter referred to as a second embodiment, whose codewords are also derived in product form. Now, the inner broadband codebook is defined as follows.

Figure pat00121

here,

Figure pat00122

or,

Figure pat00123

The rank-1 outer codebook is defined as follows.

Figure pat00124

The rank-2 outer codebook is defined as follows.

Figure pat00125

In either case, rank-3 and rank-4 codebooks are fixed to legacy (house holder) rank-3 and rank-4 codebooks. In addition, the entire legacy codebook can be included as a subset.

Note that the first embodiment has desirable characteristics that are overlooked in the second embodiment. This characteristic is expressed by the following equation

Figure pat00126
In this case,
Figure pat00127
In each selection of the codebook, the codebook corresponding to the rank
Figure pat00128
And that the expected value of the standard square of each row for the selected precoder matrix (i.e., the sum of the magnitude squared of the elements of the row) is the same. This characteristic is beneficial in operating the power amplifiers (i.e., controlling the backoff of the power amplifiers) and utilizing available transmit power.

4.1 More  Large codebook Embedding

Note that the channel matrix implementation is determined by a spatial correlation matrix and short-term (so-called fast) fading. In some scenarios, there may be significant deviations in the observed channel matrix due to fast-fading, such as when the common-polarized antennas are widely spaced. Thus, the preferred codebook needs to accommodate significant deviations in the observed channel matrix due to this fast-fading, and therefore needs to include codewords designed using other criteria such as the minimum chordal distance . A useful way of solving these cases is to embed a codebook obtained using the principles described above as a subset within a larger codebook.

5 Conclusion

The anomaly codebook structure has been described in detail and two embodiments according to the matrix product form have been presented. This structure is derived by the basic properties of the spatial correlation matrix and makes it possible to realize the codebook optimization.

6 Appendix : 4 TX with exponential correlation model ULA

Next, consider a case where the correlation matrix is further specialized as follows.

Figure pat00129

here,

Figure pat00130
ego,
Figure pat00131
And
Figure pat00132
. Note that the matrix C is Hermite Teflitz, and may be fully characterized by a single complex scalar. Thus, its eigenvectors can be expected to have more structure than being processed by the eigenvectors of a normal Hermite teplitz matrix. In the following, this additional structure will be utilized. The matrix J for this case can be written as:

Figure pat00133

first,

Figure pat00134
Is considered. In this case, the eigen-vectors for any matrix of the form in (24) will have the following properties. Considering any matrix C of the form in (24)

Figure pat00135

Let (25) be set to indicate its intrinsic decomposition, where

Figure pat00136
Represents a conjugate transpose operation,
Figure pat00137
In this case,
Figure pat00138
And they represent eigenvalues that are four real values. Then, the following equation is obtained,

Figure pat00139

here,

Figure pat00140
Represents a Hadamard product,
Figure pat00141
Quot;
Figure pat00142
, A diagonal matrix of the following form is obtained.

Figure pat00143

The matrix S is a positive real number scalar

Figure pat00144
end
Figure pat00145
And
Figure pat00146
, The following structure is obtained.

Figure pat00147

The matrix H is a 4 × 4 real value Hadamard matrix, ie, the columns of H are mutually orthogonal, and all of its elements belong to the set {± 1}. Then, since each column of E must satisfy the conditions in (5)

Figure pat00148
Each row of the table must satisfy the following conditions.

Figure pat00149

Also, since E must be a unitary matrix, H must also satisfy the following additional conditions.

Figure pat00150

An important example is H :

Figure pat00151

Using the H given above

Figure pat00152
, The following scalar < RTI ID = 0.0 >
Figure pat00153
Can be derived. first,
Figure pat00154
. (26), the following equation is calculated after some processing.

Figure pat00155

here,

Figure pat00156
ego,
Figure pat00157
to be. In special cases,
Figure pat00158
, The correlation matrix C reduces the identity matrix,
Figure pat00159
(The application of each standard constraint). Also,
Figure pat00160
Quot;
Figure pat00161
With a relationship of
Figure pat00162
, Where < RTI ID = 0.0 >
Figure pat00163
to be.

Meanwhile,

Figure pat00164
, Then matrix C is a rank-1 matrix given by

Figure pat00165

Then, the eigenvector of C corresponding to one non-zero eigenvalue can be represented as having the following form.

Figure pat00166

here,

Figure pat00167
And accordingly,
Figure pat00168
.
Figure pat00169
May be arbitrary, since the corresponding eigenvalue is zero (application of standard constraints).

7 Appendix : Acceptance of power imbalance

A more general model for the spatial dependence of the cross-pole antenna configuration is as follows. Consider a transmitter with 2N cross-polarized antennas each including a pair of N common-polarized antennas. Then, the correlation matrix for each of these two common-polarization sets is denoted by Hermit and the triplet C. The entire 2N x 2N correlation matrix

Figure pat00170
Can be expressed as:

Figure pat00171

here,

Figure pat00172
ego,
Figure pat00173
And
Figure pat00174
Lt; / RTI >
Figure pat00175
≪ / RTI >
Figure pat00176
Can have the following form.

Figure pat00177

here,

Figure pat00178
The matrix
Figure pat00179
And x is an eigenvector of C. procession
Figure pat00180
Quot; may represent any 2 x 2 positive semi-definite matrix up to a scaling factor. Thus, a 2x2 unitary matrix formed by two eigenvectors may be any 2x2 unitary matrix. And, in order to design codebooks suitable for such scenarios, considering the first embodiment presented in section 4,
Figure pat00181
To be expanded as follows.

Now, the rank-1 outer codebook is defined as follows.

Figure pat00182

Figure pat00183

here,

Figure pat00184
The
Figure pat00185
Are pre-determined scalars. Now, the outer rank-2 codebook is defined as follows.

Figure pat00186

Likewise, in the case of the second embodiment, the rank-1 outer codebook is defined as follows.

Figure pat00187

In addition, the rank-2 outer codebook is defined as follows.

Figure pat00188

It is noted that the above-defined codebooks are also suitable when the transmitter has geographically separated 4 common-polarized antennas comprising a pair of 2 common-polarized antennas at each location. And, the two common-correlation matrix about each set of polarization is given by the Hermitian and Te of the pleated C. The entire 4x4 correlation matrix

Figure pat00189
Can be expressed as:

Figure pat00190

here,

Figure pat00191
Represents a Kronecker product,
Figure pat00192
Is a normalized gain term that reflects different average propagation gain from the two positions.

II. Example 2

Product-oriented codebook configuration

Now, based on the principles derived above, let us discuss the structured codebook configuration where each codeword is derived as a matrix product.

Figure pat00193
about,
Figure pat00194
. The inner (broadband) codebook is defined as follows. First, the positive integers K, J, and L are defined by the following equations.

Figure pat00195

Here, K is referred to as a step , J is referred to as a width, and L is referred to as an extent . These parameters are generally

Figure pat00196
And
Figure pat00197
. Now let the internal (wideband) codebook be described in detail as follows.

Figure pat00198

here,

Figure pat00199
Represents a Hadamard product,
Figure pat00200
Lt;
Figure pat00201
Its main diagonal is the vector
Figure pat00202
, Where < RTI ID = 0.0 >
Figure pat00203
And is as follows,

Figure pat00204

here,

Figure pat00205
to be.

given

Figure pat00206
about,
Figure pat00207
, Then for continuous k selection
Figure pat00208
Can be introduced. Especially,
Figure pat00209
By ensuring that,
Figure pat00210
Some rows of
Figure pat00211
As shown in Fig. This is a useful feature of the inner broadband codebook because the correlation in time or frequency changes gradually. However,
Figure pat00212
In case of m, it does not need to be maintained. In this case, in order to introduce overlap between different inner codebooks,
Figure pat00213
Lt; RTI ID = 0.0 >
Figure pat00214
sign
Figure pat00215
By appropriately selecting (
Figure pat00216
If you select
Figure pat00217
Quot; is also fixed)
Figure pat00218
And
Figure pat00219
Lt; RTI ID = 0.0 > overlap. ≪ / RTI >

Rank-1 outer codebooks are defined as follows.

Figure pat00220

Here, for given r, s

Figure pat00221
May be any of the four display vectors,
Figure pat00222
Denotes a J × 1 column selection vector that selects the i-th column of the J × J identity matrix. To limit the size, it is noted that only certain combinations of (r, s) referred to herein as feasible combinations may be allowed, where r = s may be a feasible combination . For any subband, the rank-1 final code word may be < RTI ID =
Figure pat00223
from
Figure pat00224
And
Figure pat00225
Lt; RTI ID = 0.0 >
Figure pat00226
By selecting
Figure pat00227
To obtain the final codeword for that subband. Note that the selection of the inner codeword may be common across all subbands.

Next, in order to extend the selectivity in each subband,

Figure pat00228
To an external codebook. That is,
Figure pat00229
With the outer subband rank-1 codebook of the following equation (2-5)
Figure pat00230
And may define an internal wideband codebook.

Figure pat00231

In all of the above cases, the outer codebook may be determined according to the selection of the inner code word . That is, each of (r, s, q2) in (r, s) or (2-5) in (2-4) may itself be a function of selection of the inner codeword. In other words, the two different inner codewords may have different feasible combinations for selecting codewords from the outer codebook. In each case, a set of feasible combinations for selection of each internal codeword is predetermined and known to all users and base stations.

Now, consider the rank-2 case. The first possibility is to keep the inner codebook defined in (2-2) with the next outer subband rank-2 codebook invariant to the choice of inner code word.

Figure pat00232

To limit the size, only certain combinations of (r, s) may be allowed. Since the set of allowed combinations is common across all choices of the inner codeword, for each allowed (r, s)

Figure pat00233
Lt; / RTI > must be mutually orthogonal for each selection of the inner codeword. r = s is the internal codeword
Figure pat00234
Is an option that ensures orthogonality for each selection of < RTI ID = 0.0 >

In order to extend the last rank-2 code words that can be set not to have excessive overhead, the allowable combinations may be determined according to the selection of the inner code word. Especially,

Figure pat00235
Having the form (2-7) below
Figure pat00236
(Identified by indices q1, q2, k) containing the codewords represented by < RTI ID = 0.0 >
Figure pat00237
Lt; RTI ID = 0.0 > sub-band codebook determined < / RTI >

Figure pat00238

Phase

Figure pat00239
With the permissible combinations (r, s), the resulting final codeword
Figure pat00240
Lt; RTI ID = 0.0 > orthogonal < / RTI > Due to the structure of the inner codebook,
Figure pat00241
Is sufficient to be a function of the < RTI ID = 0.0 >
Figure pat00242
It should be noted that To enable more choices in the outer codebook, as done in the rank-1 case,
Figure pat00243
To an external codebook. That is, for possible combinations (r, s, q2)
Figure pat00244
Having an outer subband rank-2 codebook having codewords of the form
Figure pat00245
And may define an internal wideband codebook.

Figure pat00246

To further extend the set of rank-2 code words, it is possible to ensure orthogonality between the columns of the final codeword resulting in other schemes. The inner codebook is assumed to be defined as in (2-2)

Figure pat00247
And,
Figure pat00248
Omit for cases where the given steps change to external codebooks since they can be applied after simple changes). Then, the rank-2 outer codebook is determined according to the selection of the inner code word, and assumes that it contains code words having the form in (2-7). In addition,
Figure pat00249
For the selection of <
Figure pat00250
Lt;
Figure pat00251
end
Figure pat00252
Satisfying
Figure pat00253
(2-8) below, which are pseudo-inverse of the codeword of the codeword.

Figure pat00254

Figure pat00255
Is an arbitrary unit-norm vector x ,
Figure pat00256
Part-space
Figure pat00257
Lt; / RTI > is a predefined operator that satisfies the fact that it is a unit norm vector in < / RTI > Preferably, such an operator, if the vector x has a constant magnitude property such that all of its elements have a constant magnitude,
Figure pat00258
Can also have characteristics that have such characteristics. One example of such an operator,
Figure pat00259
And for any unit nominal vector x whose first element is a real number value and exactly less than one,
Figure pat00260
Lt; th > column of the 4x4 unitary matrix obtained through the < RTI ID = 0.0 >
Figure pat00261
to be. Here, in the configurations of the present invention,
Figure pat00262
≪ / RTI > satisfies the two conditions required to define the house-holder transformation. Further, when the vector x has a constant size characteristic,
Figure pat00263
And so on.

Another example of such an operator is

Figure pat00264
, Where P is a permutation matrix, and D (x) is its diagonal entries
Figure pat00265
Lt; RTI ID = 0.0 > x < / RTI > If x has a constant size property, the non-zero entries may constitute a diagonal matrix D (x) with a unit size, and
Figure pat00266
And vector
Figure pat00267
Lt; RTI ID = 0.0 > a < / RTI > constant size characteristic.

(2-2) can define a different set of internal codewords (i.e., an internal codebook) for both of them, although both rank-1 and rank-2 and other ranks are assumed to have a general structure . Thus, rank specific internal codebooks can be defined. Recall that the function of the inner codeword may already exist for each subband outer codebook. It should also be noted that, in the above-described codebooks, de-duplication may be performed if necessary. In particular, for any rank r, if there are any two inner code words that produce rank-r code words per equivalent sub-band of the last set, then the inner codebook of that rank-r contains these two inner codes Only one of the words should be retained. Here, one of the two final codewords is the same as the other codeword until the right multiplication by a column permutation and / or a diagonal matrix, and all of its non-zero entries Note that, in the case of a unit size, the two last codewords are the same.

It should be noted that having a rank-2 inner codebook that is larger than the rank-1 codebook may be useful for MU-MIMO. A larger inner codebook may allow for better quantization resolution without excessively increasing the feedback because only one inner codeword needs to be reported for all subbands to be. A better resolution for upper rank-2 may be useful in MU-MIMO as well as in SU-MIMO because a user under MU-MIMO transmission will typically be served using a lower rank than it is reported Because. In this case, better resolution will ensure that the column subsets extracted from the user's reported precoders are also efficient, i.e., have sufficient precision, thus enabling MU-MIMO gains.

III. Example 3

In a Rel-11 LTE cellular network, it is possible for the network to set up a plurality of CSI processes for the same user on a semi-static basis. Each Rel-12 and beyond user needs to support both the legacy 4 TX codebook and the enhanced 4 TX codebook. As described above, these two codebooks can be observed as two subsets (components) of a larger codebook. In addition, a separate codebook subset constraint may be applied for each CSI process. A useful corollary from these two observations can be set for each CSI process (for the user of interest) in a quasi-static manner, i.e. for each CSI process for a given user , Which may establish a component (i. E., Legacy or enhanced) codebook available to the user. In addition, other codebook subset constraints may be applied per CSI process foundation, taking into account the selection of component codebooks for these processes. In order to reduce the signaling overhead, it is proposed to apply only the latter codebook subset constraint for each CSI-process. As a result, even if the CSI process (or, equivalently, the mode defined for that CSI process) requires that the user report subband-by-sub precoding matrices (i.e., PMIs) All such reported matrices will necessarily comply with the (common) subset constraints set for that process.

Product-oriented codebook configuration

First, let us present a general codebook configuration in which each codeword is derived as a matrix product. For convenience, the normalization factor of 1/2 should be ignored.

Figure pat00268
about
Figure pat00269
Let the inner (broadband) codebook be defined as follows.

Figure pat00270

here,

Figure pat00271
Are real-valued scalars, and

Figure pat00272
ego,

here,

Figure pat00273
to be. Certain internal codewords
Figure pat00274
It is noted that two (angle) of separation between the phase terms in two adjacent beam vector in the is / N, thus both the N and J to determine the phase term angular span (angular span) in each of the inner code word . Intuitively, a larger angular span will make it possible to create a suitable codebook for even smaller correlated fading scenarios. Meanwhile,
Figure pat00275
silver
Figure pat00276
, The two inner codewords < RTI ID = 0.0 >
Figure pat00277
And
Figure pat00278
At any two beam vectors that are related to the phase vector, contributes to controlling the separation between the phase terms. Intuitively, small separations may be useful when utilizing correlations in time and frequency.

* Then, the rank-1 outer (subband) codebook is defined as

Figure pat00279

Here, e i represents a J × 1 column selection vector (ie, the i-th column of the J × J identity matrix)

Figure pat00280
Is a common-phase term. Thus, the (maximum) size of the rank-1 codebook is JS . A smaller size can be obtained by selecting only a subset of all these possible vectors. The common-phase terms can be obtained by optimizing the appropriate metric, such as the average coded distance, after limiting the positive integers M > 1 to be placed in the design parameter M-PSK alphabet. This optimization can be limited to ensure that the minimum angle separation between the common-phase terms is maintained. For rank-2, the outer (subband) codebook is defined as follows.

Figure pat00281

Note that in the case of different pairs of (m, p) and (m ', p'), they may have different numbers of common-phase terms. These common-phase terms may be optimized by optimizing the appropriate metric, such as the average coded distance, after limiting them to be placed in the M'-PSK alphabet, where the positive integer M ' > 1 is a design parameter and may differ from M ≪ / RTI > This optimization can be limited to ensure that the minimum angle separation between the common-phase terms is maintained.

Next, let us propose two specific embodiments. Both embodiments have a 4 bit wideband codebook. In the case of the first embodiment,

Figure pat00282
Figure pat00283
And
Figure pat00284
So that the inner code word is a 4x4 matrix.
Figure pat00285
. The corresponding sub-band codebook has a 3-bit size for both rank 1 and rank 2. In the rank-1 codebook, the common-phase terms are placed in the 8-PSK alphabet, which is provided in FIG. Note that the notation adopted in the table of FIG. 3 is θ s, i = 2 πt / M (where M = 8 for 8-PSK) if the entry corresponding to ( s, i ) is t . In the case of rank-2 codebook, with the common-phase terms provided in Fig. 4A or 4B
Figure pat00286
. Alternatively, the common-phase terms may be selected as shown in FIG. It should be noted that in FIG. 5 for the beam combination (1, 2), more common-phase selections are used.

In the case of the second embodiment,

Figure pat00287
Figure pat00288
And
Figure pat00289
So that each inner codeword is a 4x8 matrix.
Figure pat00290
. The corresponding sub-band codebook has a 4-bit size for rank 1 and rank 2. In the rank-1 codebook, the common-phase terms are placed in the 8-PSK alphabet, which is provided in Fig. 6a or 6b. In the case of rank-2 codebook, with the common-phase terms provided in Fig. 7
Figure pat00291
. Alternatively, the common-phase terms provided in Figure 8A or 8B may also be selected. Alternatively, the common-phase terms provided in FIG. 9 or 10 may also be selected.

Rank-3 and rank-4 codebooks may be fixed to legacy (house holder) rank-3 and rank-4 codebooks. Note that all codeword matrices in the above-described codebook satisfy the constant size property.

IV. Example 4

Other related problems are that when the user is set to use a legacy 4 TX codebook as one of the CSI processes and when the process (or mode defined for the CSI process equally) provides the user with precoding matrices for each subband And to report it. Here, if the user's preferred rank is 3 or 4, the size of the legacy codebook (4 bits for both rank 3 and rank 4) may be overkill for reporting every subband-by-subband. That is, feedback can be reduced without noticeable impact on performance, since the user is experiencing a good average SINR and will typically be scheduled solely on allocated resources. To achieve feedback reduction, the network defines a sub-sampled version of the legacy codebooks for rank 3 and rank 4 such that if the preferred rank is 3 or 4, the user selects the codewords from these sub-sampled codebooks Can be set to report. Rank-3 codebook is obtained by removing one or more code words from the rank-3 legacy codebook, and the sub-sampled rank-3 codebook is also obtained by removing one or more code words from the rank- A codebook is obtained. These sub-sampled codebooks are defined by the network and are delivered to all users in advance. Another approach to provide more flexibility is to leverage the codebook subset constraints. Here, it is assumed that the size (subband-per-subband) of the rank-3 codebook is limited to M codewords. The network can then determine from the legacy rank-3 codebook a subset (sub-statically and possibly user-specific) that includes less than M codewords and deliver this subset to the user. Then, the user will limit the search (for rank-3 codewords) to this subset on each subband. In order to report the preferred codeword on each subband, the user employs lexicographic ordering (labeling). That is, one new index is assigned to the codewords in the display subset with the smallest index (such as in the original rank-3 legacy codebook) and the second smallest index (such as in the original rank-3 legacy codebook) Two new indexes are assigned to codewords in a display subset with an index. This process continues until all codewords in the subset are assigned new indexes. Clearly, these new indices can range from 1 to M ' , where M'M. It should also be noted that since the subset is common across all subbands, the set of new indices will also be common across all subbands, and hence must be determined by the user. The user then reports a new index for the selected precoder on each subband. Note that the same procedure can be applied to rank-4, where the value of M may be different for rank 4 and rank 3. [

Finally, to improve MU-MIMO performance, additional feedback may be included for the CSI process (or equivalently, the mode defined for that CSI process). The user may also report the MU-CQI (s) with a single-user (SU) CSI (channel state information) report, as described in detail in previous work [8]. This SU-CSI (including broadband or subband-by-PMI, and subband-per-CQI) is calculated using resource elements and pilots for interference measurements that are set for the corresponding CSI process. Several schemes for computing these MU-CQI (s) have been described in detail in previous work [9], one of which sets a set of co-scheduled interferences (for the subband basis if so configured) After the assumption, the PMI (s) determined by the SU-CSI report to calculate the MU-CQI (s) or determined using SU-MIMO rules (hereinafter referred to as base-PMI Quot;). ≪ / RTI > Here, the set of co-scheduled interfering PMIs (i.e., transmission precoders assigned to other users that are co-scheduled to be) that the user assumes for the subband is a function of the base-PMI for which it is determined. Each set of co-scheduled interfering PMIs that the user must assume can be set by the network in a quasi-static (and possibly user-specific) manner. The size of the set of interfering PMIs (for selection for each base-PMI) may be greater than one. In order to reduce the overhead, the final MU-CQI (s) computed for the subband basis may be combined into one (or up to two) wideband MU-CQI (s) Detailed in task [10]), after which it is reported. To further improve performance, a plurality of such sets of interfering PMIs (for each base-PMI) may be set. Thereafter, the user may report one (or at most two) wideband MU-CQI (s) for each set of interfering PMIs, and the differential feedback may be leveraged to reduce the feedback overhead. Alternatively, the above-described process may be repeated for several selections for base-PMs, and the user may select one particular base-PMI (using the appropriate selection rules, such as the rule to maximize the expected MU gain) , And report it with the associated MU-CQI (s).

Return to the next codebook configuration.

Product-oriented codebook configuration

First, let us present a general codebook configuration in which each codeword is derived as a matrix product.

Figure pat00292
For
Figure pat00293
Is set to indicate a 2 × 1 beam vector, and the inner (wideband) codebook is defined as follows.

Figure pat00294

Where {a k } are real scalar values, and

Figure pat00295
Lt;

here,

Figure pat00296
to be. Certain internal codewords
Figure pat00297
(Angular) separation of the phase terms of any two adjacent beam vectors in the beam vector is 2? / N and thus N (referred to as granularity) and J (the number of beam vectors per inner code word) To determine the angular span of the phase term in the inner codeword. Intuitively, (which may be accomplished by having a smaller N (i.e., smaller particle size or larger / N) for a given J, or can be achieved by having a larger J for a given N) A larger angular span can also be made for the codebook to be suitable for smaller correlated fading scenarios as well as to provide robustness against timing alignment errors. However, an increase in the cost of J would increase the size of each of the outer sub-band codebooks, while a smaller N selection could degrade performance in a close-spaced cross-pole configuration, Because it hinders the localization of the beam vectors in the codeword. On the other hand, scalar {d q } (referred to as staggering factors)
Figure pat00298
Lt; RTI ID = 0.0 > 2 < / RTI >
Figure pat00299
And
Figure pat00300
Lt; RTI ID = 0.0 > beam vectors < / RTI > Intuitively, a small separation will be useful in exploiting the correlation in time and frequency.

The extension to the inner codebook described above is to use a set of two (or more) particle sizes, where each particle may have its own set of staggering factors. Typically, this increases the size of the wideband codebook, but it can better meet the different antenna configurations. In the following, I describe a composite inner (broadband) codebook for selection of different particle sizes as follows.

Figure pat00301

here,

Figure pat00302
And
Figure pat00303
Is the set of indices associated with the i-th particle size N i. Note that J remains fixed over the different particle sizes. In certain scenarios (with very low correlation), it may be advantageous to select at least one grain size of the grain sizes that satisfy the mutual orthogonality of one or more of the beam vectors of the plurality with the relevant inner codewords.

Then, the rank-1 outer (subband) codebook is defined as follows.

Figure pat00304

Here, e i is the i-th J × 1 column selection vector (ie, the i-th column of the J × J identity matrix)

Figure pat00305
Is a common-phase term. Thus, the (maximum) size of the rank-1 codebook is JS . A smaller size can be obtained by selecting only a subset of all these possible vectors. The common-phase terms can be obtained by optimizing the appropriate metric, such as the average covariance distance, after limiting it to being placed in the M-PSK alphabet that is a design parameter with a positive integer M > This optimization can be limited to ensure that the minimum angle separation between the common-phase terms is maintained. For rank-2, the outer (subband) codebook is defined as follows.

Figure pat00306

Note that in the case of different pairs of (m, p) and (m ', p'), they may have different numbers of common-phase terms. The common-after the phase terms are, a positive integer M limit them to be placed into '≥ 1 and M is a design parameter and will be different in M' -PSK alphabet, by optimizing an appropriate metric, such as the average distance kodal ≪ / RTI > This optimization can be limited to ensure that the minimum angle separation between the common-phase terms is maintained.

Thus, the present inventors have found that (1) the core structure that each eigenvector of the spatial correlation matrix should have in the ULA transmission antenna configuration, and the core that each eigenvector of the spatial correlation matrix has to have in the cross- (2) the inventors then performed the identified structures in at least one subset of the precoding codebooks to ensure good performance, and (3) And also provides efficient embodiments.

It is to be understood that the above description is intended to be illustrative and explanatory in all respects not restrictive and the scope of the invention as described herein is not to be determined from the foregoing detailed description, Should be determined from the claims of It is to be understood that the embodiments shown and described herein are illustrative only of the principles of the invention, and that those skilled in the art may implement various modifications that do not depart from the scope and spirit of the invention. Those skilled in the art can implement various other feature combinations that do not depart from the scope and spirit of the invention.

Claims (18)

  1. A method implemented in a base station for use in a wireless communication system,
    Layer, 2-layer, 3-layer, and 4-layer codebooks for 4TX (4 transmit) antenna transmission, each codebook comprising a plurality of precoding matrices;
    Precoding data to one of the plurality of precoding matrices; And
    And transmitting the precoded data to a user equipment,
    Wherein each of the one-layer and two-layer codebooks includes a first codebook and a second codebook,
    Wherein each precoding matrix in the first codebook comprises a first index and a second index.
  2. The method according to claim 1,
    Wherein the first index is for a plurality of subbands and the second index is for each subband.
  3. The method according to claim 1,
    Wherein the second codebook comprises a legacy codebook or a householder codebook.
  4. The method according to claim 1,
    Wherein each of the 3-layer and 4-layer codebooks comprises a legacy codebook or a householder codebook.
  5. The method according to claim 1,
    Each precoding matrix W in the first codebook satisfies W = W (1) W (2)
    The first matrix W (1)
    Figure pat00307
    ≪ / RTI >
    And the second matrix W (2) is selected from an outer codebook.
  6. A method implemented in a user equipment used in a wireless communication system,
    Receiving precoded data from a base station,
    Each of the 1-layer, 2-layer, 3-layer, and 4-layer codebooks for 4TX (4 transmit) antenna transmission includes a plurality of precoding matrices,
    Wherein each of the one-layer and two-layer codebooks includes a first codebook and a second codebook,
    Wherein each precoding matrix in the first codebook comprises a first index and a second index.
  7. The method according to claim 6,
    Wherein the first index is for a plurality of subbands and the second index is for each subband.
  8. The method according to claim 6,
    Wherein the second codebook comprises a legacy codebook or a householder codebook.
  9. The method according to claim 6,
    Wherein each of the 3-layer and 4-layer codebooks comprises a legacy codebook or a householder codebook.
  10. The method according to claim 6,
    Each precoding matrix W in the first codebook satisfies W = W (1) W (2)
    The first matrix W (1)
    Figure pat00308
    ≪ / RTI >
    And the second matrix W (2) is selected from an outer codebook.
  11. 1. A base station used in a wireless communication system,
    And a transmitter for transmitting the precoded data to the user equipment,
    Each of the 1-layer, 2-layer, 3-layer, and 4-layer codebooks for 4TX (4 transmit) antenna transmission includes a plurality of precoding matrices,
    Wherein each of the one-layer and two-layer codebooks includes a first codebook and a second codebook,
    Wherein each precoding matrix in the first codebook comprises a first index and a second index.
  12. A user equipment for use in a wireless communication system,
    Comprising: a receiver for receiving precoded data from a base station,
    Each of the 1-layer, 2-layer, 3-layer, and 4-layer codebooks for 4TX (4 transmit) antenna transmission includes a plurality of precoding matrices,
    Wherein each of the first-layer and the second-layer codebooks includes a first codebook and a second codebook,
    Wherein each precoding matrix in the first codebook comprises a first index and a second index.
  13. 1. A wireless communication system,
    Layer, 2-layer, 3-layer, and 4-layer codebooks for transmitting 4TX (4 transmit) antennas, each codebook comprising a plurality of precoding matrices, wherein one of the plurality of precoding matrices A base station for precoding data into one;
    And user equipment for receiving the precoded data from the base station,
    Wherein each of the one-layer and two-layer codebooks includes a first codebook and a second codebook,
    Wherein each precoding matrix in the first codebook comprises a first index and a second index.
  14. A method implemented in a wireless communication system,
    Precoding data; And
    Transmitting the precoded data from a base station to a user equipment,
    Each of the 1-layer, 2-layer, 3-layer, and 4-layer codebooks for 4TX (4 transmit) antenna transmission includes a plurality of precoding matrices,
    Wherein each of the one-layer and two-layer codebooks includes a first codebook and a second codebook,
    Wherein each precoding matrix in the first codebook comprises a first index and a second index.
  15. 15. The method of claim 14,
    Wherein the first index is for a plurality of subbands and the second index is for each subband.
  16. 15. The method of claim 14,
    Wherein the second codebook comprises a legacy codebook or a householder codebook.
  17. 15. The method of claim 14,
    Wherein each of the 3-layer and 4-layer codebooks comprises a legacy codebook or a householder codebook.
  18. 15. The method of claim 14,
    Each precoding matrix W in the first codebook satisfies W = W (1) W (2)
    The first matrix W (1)
    Figure pat00309
    ≪ / RTI >
    And the second matrix W (2) is selected from an outer codebook.
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