KR101221023B1 - Method for generating differential codebook using temporally correlated in multiple input multiple output antenna transmission channels, and thereof recording medium - Google Patents

Method for generating differential codebook using temporally correlated in multiple input multiple output antenna transmission channels, and thereof recording medium Download PDF

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KR101221023B1
KR101221023B1 KR1020110087974A KR20110087974A KR101221023B1 KR 101221023 B1 KR101221023 B1 KR 101221023B1 KR 1020110087974 A KR1020110087974 A KR 1020110087974A KR 20110087974 A KR20110087974 A KR 20110087974A KR 101221023 B1 KR101221023 B1 KR 101221023B1
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codebook
differential codebook
differential
codeword
nebula
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KR1020110087974A
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Korean (ko)
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김영주
이신
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충북대학교 산학협력단
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/0413—MIMO systems
    • H04B7/0456—Selection of precoding matrices or codebooks, e.g. using matrices antenna weighting
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
    • H04B7/0613—Diversity 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
    • H04B7/0615—Diversity 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
    • H04B7/0619—Diversity 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
    • H04B7/0636—Feedback format
    • H04B7/0639—Using selective indices, e.g. of a codebook, e.g. pre-distortion matrix index [PMI] or for beam selection

Abstract

The present invention relates to a new differential codebook that can be used when applying a precoding technique in a mobile communication system using a multiplex transmission antenna. The present invention supports a line encoding scheme, and a plurality of transmit antennas. A differential codebook generation method in a multiple transmit / receive antenna system in which a transmitter having a receiver and a receiver having a plurality of receive antennas communicate based on a predetermined differential codebook, the method comprising: a long term evolution (LTE) system in the multiple transmit / receive antenna system Marking as a nebula conforming to a defining standard, searching for a codeword centering on a codeword of which all factors are 1 among the codewords represented by the nebula, and as much as a predetermined codebook size based on the searched codeword Selecting a codeword and using the selected codewords Eojin includes generating a difference code book. According to the present invention, instead of quantizing the entire area of the channel in the time-correlated fading channel using the differential codebook, some areas can be quantized, thereby increasing the system capacity as a whole.

Description

Method for generating differential codebook using temporally correlated in multiple input multiple output antenna transmission channels, and about recording medium}

The present invention relates to a new differential codebook that can be used when the precoding scheme is applied in a mobile communication system using multiple transmit antennas. More specifically, the present invention relates to a channel space in a multiple transmit / receive channel having a time correlation. A spherical cap codebook which quantizes only a spherical cap having a certain radius without quantizing the whole. In particular, unlike the complicated design and application of the spherical cap codebook, 8-PSK constellation, which is a feature of codebook generation of long term evolution (LTE) or LTE-Advanced (LTE-A) system, is used and nested. A method for generating a new differential codebook for improving the performance of a codebook while maintaining properties and the like, a method for operating a mobile communication system supporting the same, and a transmitting and receiving device for supporting the same.

Recently, the multiplexed transmit / receive wireless antenna channel is not modeled as a block fading channel—a model that assumes that fading channel coefficients are constant and independent of fading channel coefficients of other block intervals in one block section of transmission data. A differential codebook using time correlation has been proposed and shows very good channel capacity performance compared to the codebook assuming a block fading channel. In this case, the temporal correlation of the channel state information must be considered, but it is assumed that the channel state information has a constant channel coefficient in the transport block section.

Existing researches using temporal correlation include the method of compressing feedback bits or variable feedback bit methods, channel subspace tracking methods, perturbation, and projection-based adaptation methods. Proposed.

Recent studies related to differential codebooks include the method of finding quasi-diagonal matrices for the Doppler frequency using a computer, the perturbation of differential rotation matrices, and the optimal differential codebooks by Procrustes orthogonalization or Gram-Schmidt orthogonalization. The method has been proposed.

These recent studies can further improve the channel capacity by quantizing only the spherical cap, which is a part, without quantizing the entire space of the channel coefficients. However, there is a problem that the codebook has to be searched for many hours depending on the degree of time correlation (Doppler frequency) of the channel.

In other words, the generation of a differential codebook for a specific Doppler frequency requires a computer-based optimization process called 'exhausted search' for quite some time. In addition, since the 8-PSK constellation for simple precoding and decoding calculation, which is the codebook design principle of the LTE system, cannot be kept as an element of the codebook, the complexity of the transceiver is increased and the peak-to-average power ratio (PAPR) is increased. There is a problem.

The present invention has been made to solve the above problems, assuming that the number of feedback bits of the fixed channel state information, in consideration of the time correlation that must occur in the actual wireless channel, in a mobile communication system using multiple transmit antennas The purpose of this paper is to propose an improved new differential codebook design algorithm, which is simpler than the previously proposed differential codebook method and has almost the same performance, and to provide a new precoding method using the same.

Accordingly, the present invention aims to design a codebook that shows an optimal performance tradeoff when considering factors such as system capacity, link level and system level performance of a limited feedback communication system, transceiver complexity, and transmission PAPR simultaneously. Shall be. Specifically, a technique for maintaining the performance of the existing differential codebook is proposed while following the codebook generation principle of the LTE mobile communication system.

The object of the present invention is not limited to the above-mentioned object, and other objects not mentioned will be clearly understood by those skilled in the art from the following description.

In order to achieve the above object, the present invention supports a line encoding method, and in a multiple transmit / receive antenna system in which a transmitter having a plurality of transmit antennas and a receiver having a plurality of receive antennas communicate based on a predetermined differential codebook. A method of generating a differential codebook, the method comprising: marking a nebula conforming to a standard defined in a long term evolution (LTE) system in the multiple transmit / receive antenna system, centering on a codeword having all factors of 1 among the codewords represented by the nebula; Searching for a codeword, selecting a codeword corresponding to a predetermined codebook size based on the found codeword, and generating a differential codebook consisting of the selected codewords.

The nebula meeting the standard defined in the LTE system is preferably an 8-PSK nebula.

The step of selecting the codeword is, when a precoding vector having all factors 1 is F 1 , selecting F 1 as a central precoding matrix, all precoding matrices and Fs that can be generated by the 8-PSK nebula. The method may include obtaining a chordal distance between 1 and sequentially selecting codewords from the minimum noseband distance to selecting N codewords having a predetermined codebook size.

F diff is the differential codebook, F τ is the codebook when the time index is τ,

Figure 112011068090537-pat00001
Ρ is the signal-to-noise ratio (SNR),
Figure 112011068090537-pat00002
Is an identity matrix of size M s × M s , M s is the number of spatial streams in the transmitting end, and when a <·> operation means a Hadamard product operation, the differential codebook shared in the multiple transmit / receive antenna system is
Figure 112011068090537-pat00003
It can be updated at each time index using the equation of.

F τ is a new generated codebook at time τ to determine the optimal precoding matrix indicator for feedback at time τ, and PMI τ is the optimal line determined from the codebook generated at time τ When defined as a coding matrix indicator,

Figure 112011068090537-pat00004
May satisfy the following equation.

When τ = 0, an arbitrary codebook having the existing QEGT feature is designated as an initial codebook F initial to select an optimal precoding matrix indicator.

Figure 112011068090537-pat00005
The optimal precoding matrix value F τ may be determined using the equation of.

According to the present invention, instead of quantizing the entire area of the channel in the time-correlated fading channel using the differential codebook, some areas can be quantized, thereby increasing the system capacity as a whole.

In particular, the present invention is a differential codebook having 8-PSK nebula, which is a feature of LTE codebook generation, as a factor, has a gain-specific transmission, and has a feature nested in a high-rank codebook. .

1 is an exemplary view showing a closed loop multiple antenna system using a differential codebook supporting multiple users according to an embodiment of the present invention.
FIG. 2 is an explanatory diagram illustrating a pre-coding matrix indicator using a general differential codebook in consideration of feedback timing in a time correlation channel according to an embodiment of the present invention.
3 is a flowchart illustrating a method of generating a differential codebook according to an embodiment of the present invention.
FIG. 4 is a diagram illustrating an example of a proposed codebook having a number of transmit antennas 4, a number of spatial streams within a transmitter, from 1 to 4, and a codebook size of 16 according to an embodiment of the present invention.
FIG. 5 is an exemplary diagram illustrating that a differential codebook is updated with a change in time in a multi-antenna system of a pre-coding method according to an embodiment of the present invention.
FIG. 6 is an explanatory diagram showing channel capacity when a differential codebook is used for a precoding process according to an embodiment of the present invention.
7 is an exemplary operation diagram of a differential precoding technique according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same reference numerals are used for the same reference numerals even though they are shown in different drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear. In addition, throughout the specification, when a part is said to "include" a certain component, it means that it may further include other components, without excluding the other components unless otherwise stated. .

In the following description, specific details of the improved differential codebook generation technique in the multiple antenna system using the codebook of the present invention are shown to provide a more general understanding of the present invention, without these specific details and also by the modifications thereof. It will be apparent to one of ordinary skill in the art that this may be readily implemented.

In the following description, a general process of mapping differential codebook indices in consideration of feedback timing in a time correlation channel in a transmitter according to feedback information in a multi-antenna system supporting a line encoding scheme will be described below. will be. In addition, we will look at the general differential codebook generation method proposed previously for mapping. In addition, the process of generating a new differential codebook proposed in the present invention, which divides the phase of the codeword constituting the index in the codebook into a specific region of the entire region in the fading channel using the channel correlation coefficient, and a method of applying the same to the precoding system Let's take a look at.

First, a general process of mapping a differential codebook index in a transmitter according to feedback information in a multi-antenna system supporting a precoding scheme will be described.

1 is an exemplary view showing a closed loop multiple antenna system using a differential codebook supporting multiple users according to an embodiment of the present invention.

In FIG. 1, one transmitter 110 and one receiver 120 are configured. In the downlink of a mobile communication system using multiple transmit antennas, it may be assumed that the transmitter 110 is a base station, and the receiver 120 may be assumed to be a mobile terminal. Multiple receiving devices may also be connected to one base station. In the uplink of a mobile communication system using multiple transmit antennas, it may be assumed that the transmitter 110 is a mobile terminal, and one receiver 120 may be a base station. The following description is regarded to apply equally to two or more receivers.

The receiver 120 estimates channel state information corresponding to each data stream to perform precoding matrix quantization and codebook update. The quantized feedback information is transmitted to the transmitter 110. At this time, the feedback information is time, including pre-encoding matrix indicator (precoding matrix indicator, PMI) to make good to set the pre-encoding matrix F τ at τ, the channel quality indicating the quality information of the channel indicator (channel quality indicator , CQI), and a rank indicator (RI) indicating whether a spatial multiplexing scheme is applicable using a channel matrix, and if possible, how many ranks a signal stream can be sent. .

The transmitter 110 receives feedback information from all receivers 120. The transmitter 110 selects at least one user (ie, receiver) based on the feedback information. The number of users selected here may be determined by the operation mode. The operation mode consists of a single-user mode and a multi-user mode. One user is selected in single user mode, and multiple users are selected in multi-user mode. The operation mode is determined based on the feedback information.

The transmitter 110 determines a modulation & coding selection level (MCS level) based on the feedback information CQI. When determining the MCS level, a signal detection technique, an operation mode, and the like of a receiver may be considered. The feedback information RI may further consider the number of data streams supporting the selected user and the like.

The transmitter 110 designates an encoding and modulation scheme based on the determined MCS level, and transmits a data stream corresponding to at least one user selected using the designated encoding and modulation scheme.

To this end, the receiver 120 includes a decoding and channel estimation unit 122 having at least one receiving antenna, a precoding matrix quantization 124, and a codebook update 126. The transmitter 110 is composed of a channel code and modulator 112, a precoder 114, a precoder matrix update 116, and a codebook update 118.

Referring to the receiver 120, a signal received from at least one receiving antenna is input to the decoding and channel estimator 122.

The decoding and channel estimator 122 estimates channel characteristics corresponding to each data stream from the received signal by a preset signal detection technique. In this case, the overall characteristic of the channel is CN (0,1) distribution, and fading with time correlation is assumed between time blocks. That is, the fading phenomenon in the radio channel model is assumed to have a time correlation according to the Doppler frequency. In case of spatial multiplexing transmission having a rank of 2 or more, there are a linear detection technique and a nonlinear detection technique as signal detection techniques. Representative examples of the linear detection technique include zero forcing (ZF), minimum mean square error (MMSE), and maximum likelihood (ML) technique. Serial interference cancellation (SIC) technique is a typical example of the nonlinear detection technique.

The channel characteristic matrix of the received signal estimated by the channel estimator 122 is provided to the precoding matrix quantization 124 and quantized. The index of the quantized channel information is fed back as precoding matrix indicator (PMI) information. In the differential codebook scheme, the current precoding matrix updates the differential codebook (126).

The PMI information fed back to the transmitter 110 is an index of a codebook having log 2 N bits when the codebook size is N.

The transmitter 110 selects a precoding matrix 116 using the received PMI, and performs a codebook update 118 using the selected precoding matrix. The selected precoding matrix is multiplied by a matrix with the channel code and modulator 112 output signals and output from the precoder 114.

In the initial operation, since time τ = 0, since there is no previously estimated MIMO channel state information, a precoding matrix is obtained using a conventional codebook having excellent performance. In the case of time τ = 1, a new precoding matrix is obtained by applying the differential codebook proposed in the present invention centering on the precoding matrix obtained using previously estimated MIMO channel information, and the differential codebook is updated. Thereafter, the differential codebook may be used in the same manner, and a codebook refresh period may be set in order to reduce performance due to accumulation of feedback errors.

The codebook at time τ is shown in Equation 1 below. The size of the codebook is N and the codewords that are elements of the codebook are each a matrix of size M t x M s . Where M t is the number of transmit antennas and M s is the number of transmit data streams.

Figure 112011068090537-pat00006

Finding the best codeword at time τ can maximize system capacity, maximize signal-to-noise power ratio (SNR), or minimize received bit error rate (BER). There is a way. Among them, the formula of the method for maximizing the system capacity is shown in Equation 2 below.

Figure 112011068090537-pat00007

Where ρ is the signal-to-noise ratio (SNR),

Figure 112011068090537-pat00008
Is an identity matrix of size M s × M s . And M s is the number of spatial streams in the transmitter.

FIG. 2 is an explanatory diagram illustrating a pre-coding matrix indicator using a general differential codebook in consideration of feedback timing in a time correlation channel according to an embodiment of the present invention.

Referring to FIG. 2, when considering the time correlation of a channel other than block fading, the precoding matrix value F τ at time τ is determined using the previous precoding matrix value F τ-1 and the proposed differential codebook. Determine the optimal precoding matrix value such as>. In this case, the differential codebook is represented by F diff = {F 1 , ..., F N }. The optimal precoding matrix indicator n opt (1 ≦ n opt ≦ N) at time τ is selected using Equation 2.

Figure 112011068090537-pat00009

The optimal precoding matrix indicator selected through the above process is typically fed back in the form of an index of the codebook, that is, stored in the transmitter and the receiver, that is, the information of bits.

The receiving device 120 selects a precoding matrix from the precoding matrix quantization 124 and the codebook update 126 and updates the codebook. The generated feedback information is transmitted to the transmitter 110.

Transmission of the feedback information by the receiver 120 is periodically transmitted. However, if elements for determining the transmission time point are previously promised between the transmitter 110 and the receiver 120, it is also possible to transmit the feedback information aperiodically.

Referring to the transmitter 110, like the receiver 120, the precoding matrix is selected in the precoding matrix selection 116 and the codebook update 118, and the codebook is updated. The selected precoding matrix is precoded at precoder 114.

 The operation mode of the transmitter may operate in a multi-user mode as well as a single user mode.

One of the differential codebooks related to the codebook proposed in the present invention is to generate a quasi-diagonal matrix-based codebook based on Equation 4 below.

Figure 112011068090537-pat00010

Figure 112011068090537-pat00011
Is a random unitary matrix satisfying U H U = I,
Figure 112011068090537-pat00012
It is also a random unitary matrix, and if Δt is small, the quasi-diagonal matrix characteristics are satisfied.

Another existing differential codebook is a rotation generated by the process of the following Equations 5 to 7 limited to the spherical cap, which is a partial region adjacent to any channel region according to time correlation. Matrix technique.

Figure 112011068090537-pat00013

Figure 112011068090537-pat00014
Is a codebook having N candidate rotation matrices, and among the many candidate codebooks, a codebook in which the minimum distance between precoding matrices (codewords) is the largest is used for differential codebook design.

Equation 6 using the time correlation coefficient ε is performed using the selected codebook. ε has a value between 0.991 and 0.999, which results in a different codebook design.

Figure 112011068090537-pat00015

Figure 112011068090537-pat00016
Is an identity matrix of size M T × M T. Using the result of Equation 6, the differential codebook finally fits the time-correlated channel through Procrustes orthogonalization or general Gram-Schmidt orthogonalization of Equation 7
Figure 112011068090537-pat00017
.

Figure 112011068090537-pat00018

In the conventional differential codebook described above, the adjacent channel information H t and H t + Δt in a time-correlated channel do not change significantly, so that the quantized codebook is in a spherical cap, which is not a premise region of the channel. This allows for improved precoding and improves overall system performance.

However, the conventional differential codebook described above generates a lot of random unitary matrices, so the generation time is very long, and the differential codebook design varies according to the time correlation coefficient. Furthermore, in the case of LTE or LTE-A system, the following rules for codebook generation are followed, so the present invention proposes a codebook following these rules.

  -Use 8PSK Nebula as Codebook Argument

  -Constant modulus property for dynamic gain transmission

-Apply nested property in high rank codebook design

Hereinafter, a process of generating a new differential codebook proposed by the present invention will be described. The proposed differential codebook, like the existing differential codebook, uses the property that the precoding matrix changes slowly in the time-correlated fading channel.

Thus differential codebook proposed in the present invention F diff = {F 1, F 2, ..., F n} is designed around a 1 F, wherein F 1 is a factor of 1, all code words (or a pre-encoding matrix )to be.

In order to easily explain the differential codebook design method of the present invention, it is assumed that M t is 4 and M s is 1. First, fix F 1 = [1 1 1 1] T. And the rest (N-1 codewords can be found using the distance used in the codebook design. For example, using the chordal distance defined in the Grassmannian minifold, Equation 8 below is used.

Figure 112011068090537-pat00019

The closest codewords are selected (N-1) by measuring the distance between all possible codewords taking the 8-PSK nebula and F 1 . Where k = 2,3, ..., N.

When the number of streams M s of the transmission data is 2 or more, the precoding matrix F k of the differential codebook has a size of M t x M s , and even in this case, all factors of F 1 have a value of 1. The differential codebook shared by the transmitting and receiving device is updated at each time index and is expressed by Equation 9 below.

Figure 112011068090537-pat00020

In this case, F diff is a differential codebook and F τ is a codebook when the time index is τ. And n opt can be obtained from <Equation 2>, and <·> operation means Hadamard product operation. This operation makes the virtual codebook very large compared to the size N of the actual codebook. For example, if the size of the differential codebook using the 8-PSK nebula proposed in the present invention is N = 16, the virtual codebook size is increased by 32 times to 8 3 = 512.

The optimal differential codebook proposed in the present invention uses Equation 5 or a distance defined in Equation 10 defined in Riemannian manifold, which is a tighter bound than the nose distance of Grassmannian manifold. Design by using.

Figure 112011068090537-pat00021

3 is a flowchart illustrating a method of generating a differential codebook according to an embodiment of the present invention.

Referring to FIG. 3, the codebook proposed by the present invention takes an 8-PSK nebula as a factor, and first, designs a differential codebook having a rank of 1.

First, all codeword factors of the codebook precoding order are expressed as 8-PSK nebulae (S310).

Next, a codeword is searched based on a codeword having all factors of 1 among the codewords represented by the 8-PSK nebula (S320).

Next, as many codewords as the predetermined codebook size are selected (S330).

Then, a differential codebook consisting of the selected codewords is generated (S340).

For example, in the present invention, when a precoding vector having all factors 1 is called F 1 , F 1 is selected as the central precoding matrix. Then, all precoding matrices that can be generated by the 8-PSK nebula and the chordal distance of F 1 are obtained. The codewords are sequentially selected from the smallest nose distance with F 1, and up to N pieces having a predetermined codebook size are selected.

F τ is a new generated codebook at time τ to determine the optimal precoding matrix indicator for feedback at time τ, and PMI τ is the optimal determined from the codebook generated at time τ When defined as a precoding matrix indicator, F τ is given by Equation 11 below.

Figure 112011068090537-pat00022

In the present invention, when τ = 0, since the previous precoding matrix value F τ-1 does not exist, an optimal precoding matrix indicator is selected by designating an arbitrary codebook having an existing QEGT feature as the initial codebook F initial , At this time, the optimal precoding matrix value F τ is determined by Equation 12.

Figure 112011068090537-pat00023

In Equation 12, the initial codebook F initial determination does not limit the specific codebook.

In the present invention, if a differential codebook having a rank of 1 is generated through steps S310 to S340, an optimal differential codebook may be sequentially generated as the rank increases by two or more.

For example, when the rank is 2 or more, a matrix group satisfying Equation 13 below among all possible codebooks may be selected as an optimal codebook n opt .

Figure 112011068090537-pat00024

Alternatively, a random differential codebook using 8-PSK nebulae of steps S310 to S340 in a random rank may be generated, thereby maximizing system performance.

FIG. 4 is a diagram illustrating an example of a proposed codebook having a number of transmit antennas 4, a number of spatial streams within a transmitter, from 1 to 4, and a codebook size of 16 according to an embodiment of the present invention.

FIG. 5 is an exemplary diagram illustrating that a differential codebook is updated with a change in time in a multi-antenna system of a pre-coding method according to an embodiment of the present invention. In the embodiment of FIG. 5, the optimal codebook indexes are selected from τ = 0 to τ = 3.

Referring to FIG. 5, F initial is an initial codebook, F diff is a proposed differential codebook, and Fτ is an optimal precoding matrix indicator for feedback at time τ. The new generated codebook at time τ and PMI τ are defined as the optimal precoding matrix indicator determined from the codebook generated at time τ.

If time τ = 0, the previous precoding matrix value F τ-1 does not exist, so the system designer chooses from a variety of codebooks, including codebooks described in existing LTE, LTE-Advanced, IEEE 802.16, and IEEE 802.16m standardization documents. PMI tau = 0, which is a pre-coding matrix indicator corresponding to the optimal index n opt , is selected in any codebook using Equation 2, and F tau = 0 is determined among the codebooks.

In the case of time τ, F τ is generated by multiplying F τ-1 by F diff proposed in the present invention, and an optimal precoding matrix indicator PMI τ is selected from Equation 2 through Equation 2, F τ is determined.

As shown in FIG. 5, it can be confirmed that a new differential codebook is generated every time interval by applying the proposed differential codebook to the precoding matrix value in the previous time interval. At this time, if the proposed differential codebook is previously stored in the transmitting / receiving terminal and synchronized with each other correctly, there will be no difficulty in simultaneously using the new codebook F τ generated every time interval.

In other words, the differential codebook is generated by quantizing only an area of a channel that is very close to the previous channel state information to have the same size as the existing codebook, that is, subdividing and quantizing only a specific area that is close to the previous precoding matrix value instead of the entire area in the fading channel. In this case, it is possible to determine a more accurate optimal precoding matrix value F τ in a time-correlated fading channel, which can bring a large gain in improving overall system performance.

FIG. 6 is an explanatory diagram showing channel capacity when a differential codebook is used for a precoding process according to an embodiment of the present invention.

In FIG. 6, when the number of transmitting antennas is 4, the receiving antenna is 1 or 4, and the number of transmitting data streams is 1 or 2, the channel capacity of the precoding transmission scheme using the differential codebook of the present invention is shown.

As shown in FIG. 6, the present invention shows superior performance compared to the codebook adopted in the existing LTE standardization document, but slightly deteriorates from the conventional differential codebook. There are features that can be applied.

7 is an exemplary operation diagram of a differential precoding technique according to an embodiment of the present invention. 7 is a diagram illustrating an operation of the differential precoding scheme expressed in Equation (9).

Referring to FIG. 7, it is as if 16 combination locks composed of 8-PSK nebulae move up or down simultaneously for each transmit antenna to find the optimal precoding matrix F τ .

Meanwhile, the method for generating a differential codebook according to the embodiment of the present invention may also be embodied as computer readable codes on a computer readable recording medium. A computer-readable recording medium includes all kinds of recording apparatuses in which data that can be read by a computer system is stored.

For example, the computer-readable recording medium may be a ROM, a RAM, a CD-ROM, a magnetic tape, a hard disk, a floppy disk, a removable storage device, a nonvolatile memory, , Optical data storage devices, and the like, as well as carrier waves (for example, transmission over the Internet).

In addition, the computer readable recording medium may be distributed and executed in a computer system connected to a computer communication network, and may be stored and executed as a code readable in a distributed manner.

While the invention has been described using some preferred embodiments, these embodiments are illustrative and not restrictive. Those skilled in the art will appreciate that various changes and modifications can be made without departing from the spirit of the invention and the scope of the rights set forth in the appended claims.

110 Transmitter 120 Receiver
112 Channel Coder and Modulator 114 Precoder
116 Precoding Matrix Selection 118 Codebook Update
122 Decoding and Channel Estimation 124 Quantization of Precoding Matrix
126 Codebook Update

Claims (7)

A differential codebook generation method in a multiple transmit / receive antenna system supporting a line encoding scheme, wherein a transmitter having a plurality of transmit antennas and a receiver having a plurality of receive antennas communicate based on a predetermined differential codebook.
Marking as a nebula conforming to a standard defined by a long term evolution (LTE) system in the multiple transmit / receive antenna system;
Searching for a codeword centering on a codeword of which all factors are 1 among the codewords represented by the nebula;
Selecting a codeword corresponding to a predetermined codebook size based on the searched codewords; And
Generating a differential codebook consisting of the selected codewords,
The nebula conforming to the standard defined by the LTE system is an 8-PSK nebula,
The step of selecting the codeword,
The method comprising all the factor of 1, when the pre-coding vector as F 1, F 1, select the pre-coding matrix as the center;
Obtaining a chordal distance between all the precoding matrices generated by the 8-PSK nebula and F 1 ; And
And selecting codewords sequentially from the minimum nose length, and selecting up to N pieces having a predetermined codebook size.
delete delete The method of claim 1,
F diff is the differential codebook, F τ is the codebook when the time index is τ,
Figure 112011068090537-pat00025
Ρ is the signal-to-noise ratio (SNR),
Figure 112011068090537-pat00026
Is an identity matrix of size M s × M s , M s is the number of spatial streams in the transmitter, and the <·> operation means a Hadamard product operation.
The differential codebook shared in the multiple transmit / receive antenna system is
Figure 112011068090537-pat00027

The differential codebook generation method, characterized in that for updating at every hour index using the equation.
5. The method of claim 4,
F τ is the new generated codebook at time τ to determine the optimal precoding matrix indicator for feedback at time τ, and PMI τ is the optimal line determined from the codebook generated at time τ When defined as a coding matrix indicator,
Figure 112011068090537-pat00028

Differential codebook generation method characterized in that to satisfy the equation.
The method of claim 5,
When τ = 0, an arbitrary codebook having the existing QEGT feature is designated as an initial codebook F initial to select an optimal precoding matrix indicator.
Figure 112011068090537-pat00029

The method of generating a differential codebook, characterized in that the optimal precoding matrix value F τ is determined using the equation of.
A non-transitory computer-readable recording medium having recorded thereon a program capable of executing the method of claim 1.
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US20100226357A1 (en) 2009-03-03 2010-09-09 Qinghua Li Differential codebook for a wireless network, MIMO beamforming system using same, and method of reducing a quantization error in a MIMO beamforming system for a wireless network using same

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Publication number Priority date Publication date Assignee Title
US20100226357A1 (en) 2009-03-03 2010-09-09 Qinghua Li Differential codebook for a wireless network, MIMO beamforming system using same, and method of reducing a quantization error in a MIMO beamforming system for a wireless network using same

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