KR100968118B1 - Device and method for transmitting channel sounding signal in wireless communication system - Google Patents

Abstract

The present invention relates to an apparatus and method for transmitting a channel sounding signal in a multi-antenna system. A channel sounding signal transmission method in a terminal of a multi-antenna system according to the present invention includes estimating a channel for each of a plurality of receiving antennas, and using each channel information obtained through the estimation. Calculating a received signal power for a receive antenna, selecting a receive antenna having the largest received signal power, and transmitting a channel sounding signal to a base station through the selected receive antenna. It features.

Channel Sounding, Antenna Selection, Beamforming, Line Coding, Scheduling

Description

Channel sounding signal transmission apparatus and method in a wireless communication system {APPARATUS AND METHOD FOR TRANSMITTING CHANNEL SOUNDING SIGNAL IN WIRELESS COMMUNICATION SYSTEM}

The present invention relates to an apparatus and method for transmitting a channel sounding signal in a wireless communication system, and more particularly, to an apparatus and method for transmitting a channel sounding signal in a time division duplex based multiple antenna system. will be.

Due to the rapid growth of the wireless mobile communication market, various multimedia services are required in a wireless environment. Accordingly, in order to provide the multimedia service, a research on a multi-antenna system (for example, MIMO (Multiple Input Multiple Output)) capable of efficiently using a limited frequency is being conducted as the capacity of transmission data and the speed of data transmission are increased. .

The MIMO technology of the multi-antenna system may be classified into an open loop method and a closed loop method according to whether channel information is recognized by a transmitter. First, the open loop method indicates a method of transmitting data in a state where a transmitter does not know information about a channel. For example, space-time coding, vertical-bell lab spaced space time (V-BLAST), and the like exist in the open loop scheme. Next, the closed loop scheme indicates a scheme in which a transmitter acquires information about a channel and transmits data using the acquired channel information. For example, there are singular value decomposition (SVD), spatial division multiple access (SDMA) in the closed loop scheme.

When the closed loop scheme is used in the multi-antenna system, a method of obtaining channel information of a transmitting end depends on a duplexing scheme of the multi-antenna system. For example, when a frequency division duplex (FDD) method is used in the multi-antenna system, the receiving end measures a channel through a signal received from the transmitting end and feeds it back to the transmitting end. In this way, the transmitting end can obtain channel information. On the other hand, when the time division duplex (TDD) method is used in the multi-antenna system, each receiving end transmits a channel sounding signal that can distinguish each other, and transmits the same. The end measures the uplink channel using this and uses this as information on the downlink channel. This is due to the nature of channel reciprocity that the channels of uplink and downlink are identical.

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Meanwhile, in the multi-antenna system, the base station and the terminal have a plurality of antennas. As such, when the terminal includes a plurality of antennas, the terminal may obtain diversity gain by receiving signals through the plurality of antennas. In addition, in the case of the base station, a plurality of antennas may be provided to transmit a plurality of streams to one terminal, thereby increasing a transmission rate of the corresponding terminal. However, in the case of the terminal, it is common to use only one transmission antenna because transmission should be performed at a much lower power than the transmission power of the base station due to the limitation of battery life. That is, all of the plurality of antennas are used for reception, but only one antenna is used for transmission. Accordingly, when the multi-antenna system uses a closed loop scheme, the terminal transmits a channel sounding signal to the base station using only one transmit antenna, thereby transmitting the information on the entire downlink channel with the terminal. There is a problem that can not be obtained, which may cause the data reception rate of the terminal is lowered.

Accordingly, an object of the present invention is to provide an apparatus and method for transmitting a channel sounding signal in a multi-antenna system.

Another object of the present invention is to provide an apparatus and method for selecting an antenna for transmitting a channel sounding signal by using power of a signal received through each antenna in a terminal of a multi-antenna system.

Another object of the present invention is to provide an apparatus and method for performing scheduling using channel sounding signals provided from terminals in a base station of a multi-antenna system.

According to an exemplary embodiment of the present invention, a channel sounding signal transmission method in a terminal of a multi-antenna system includes: estimating a channel for each of a plurality of receiving antennas; Calculating received signal power for each receive antenna using channel information obtained through the estimation, selecting a receive antenna having the largest received signal power, and transmitting the selected receive antenna to the base station through the selected receive antenna. And transmitting a channel sounding signal.

According to an embodiment of the present invention, an apparatus for transmitting channel sounding signals in a terminal of a multi-antenna system includes a channel estimator for estimating a channel for each of a plurality of receiving antennas; A reception signal power calculation unit for calculating reception signal power for each reception antenna using the channel information obtained through the estimation, an antenna selection unit for selecting a reception antenna having the largest reception signal power, and And a transceiving converter for transmitting a channel sounding signal to the base station through the selected receiving antenna.

According to an embodiment of the present invention for achieving the objects of the present invention, the data transmission method of the base station in a multi-antenna system, each terminal through a receiving antenna having the largest received signal power of the plurality of terminal receiving antennas from the terminals; Receiving a channel sounding signal transmitted by the method, estimating a channel between a reception antenna of the corresponding terminal and antennas of the base station using the received channel sounding signal for each terminal, and obtaining the estimation And calculating a beamforming weight for each terminal by using the received channel information for each terminal.
According to an embodiment of the present invention for achieving the objects of the present invention, the data transmission apparatus of the base station in the multi-antenna system, each terminal through the receiving antenna having the largest received signal power of the plurality of terminal receiving antennas from the terminals; A transceiving converter for receiving a channel sounding signal transmitted by a channel estimator, a channel estimator for estimating a channel between a reception antenna of a corresponding terminal and antennas of a base station using the received channel sounding signal for each terminal, and the estimation And a beamforming control unit configured to calculate beamforming weights for the respective terminals by using channel information for each terminal obtained through the terminal.

The present invention compares the power of a signal received through each antenna in a TDD-type multi-antenna system and transmits a channel sounding signal through the antenna having the largest reception power, thereby reducing the complexity of the antenna through the antenna selection method. There is an advantage to improve signal reception performance.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In describing the present invention, when it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

Hereinafter, a description will be given of a technique for transmitting a channel sounding signal in a multi-antenna system.

In the following description, a multi-antenna system includes a base station having M _t antennas and a terminal having M _r antennas. The terminal receives a signal using the M _r of the antenna, and transmits the signal using a smaller number of antennas than the N M _r. In the following description, it is assumed that the terminal has two antennas and transmits a signal using one antenna. However, the terminal has a plurality of antennas and uses a number of antennas smaller than the number of antennas as a transmitting antenna. In all cases, the same applies.

In addition, in the following description, the multi-antenna system is assumed to use a beamforming technique, but may be equally applicable to a system using another precoding technique. Moreover, it is not limited to the closed loop scheme. In addition, in the following description, a multi-antenna system of a TDD scheme is described as an example, but is not limited thereto, and also includes orthogonal frequency division multiplexing (OFDM) and orthogonal frequency division multiple access (OFDMA) systems. Applicable

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1 shows a configuration of a multi-antenna system using beamforming according to the present invention.

As shown in FIG. 1, the multi-antenna system includes a base station having a plurality of antennas and a terminal. Here, the terminal includes a transceiving converter 101, a channel estimator 103, a received signal power calculator 105 and an antenna selector 107, the base station is a transceiving converter 111, a channel estimator ( 113, the beam forming control unit 115, the scheduler 117, the encoder 119, the modulator 121, and the beam former 123.

First, referring to the configuration of the terminal, the transceiving converter 101 receives a signal from the base station through the plurality of antennas during the downlink period, according to the TDD scheme, and of the plurality of antennas during the uplink period Signals are transmitted to the base station through some fixed antennas. In addition, the transceiving converter 101 transmits a channel sounding signal to the base station by using the antenna selected by the antenna selecting unit 107 during the uplink period through the sounding channel previously assigned by the base station. .

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The channel estimator 103 estimates a channel for each antenna by using the downlink signal provided from the transceiving converter 101. For example, the channel estimator 103 estimates a channel for each antenna by using a pilot signal included in the downlink signal.

The received signal power calculator 105 calculates the received signal power for each antenna using the channel information obtained through the estimation, provided from the channel estimator 103.

The antenna selector 107 compares the received signal power of each antenna provided from the received signal power calculator 105 to select an antenna having the largest power of the received signal. That is, the antenna selector 107 selects the antenna having the best Signal to Noise Ratio (SNR) in order to transmit the uplink signal through the antenna having the best downlink channel state.

Next, referring to the configuration of the base station, the transceiving converter 111 according to the TDD scheme, the signals received from the beamformer 123 during the downlink period to the terminals included in the service area through a plurality of antennas Transmit and receive a signal from the terminals through the plurality of antennas during the uplink period. In particular, the transceiving converter 109 receives a channel sounding signal from the terminals during the uplink period through a sounding channel previously assigned to the terminals. Here, the terminals select an optimal antenna for transmitting the channel sounding signal, and transmit the channel sounding signal to the base station through the selected antenna.

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The channel estimator 113 estimates a channel between the channel sounding signal transmission antennas of the respective terminals and the antennas of the base station using the channel sounding signals of the terminals provided from the transceiving converter 111.

The beamforming control unit 115 calculates a beamforming weight of a corresponding terminal by using channel information for each terminal provided from the channel estimator 113.

The scheduler 117 selects terminals to provide a service in this frame among the terminals included in the service area by using channel information of the terminals provided from the channel estimator 113. For example, when providing a service to k terminals among the N terminals included in the service area, the scheduler 117 selects all possible combinations of terminal sets including k terminals among the N terminals. And select a terminal set to provide a service in this frame among the terminal sets by using the channel information of the terminals provided from the channel estimator 113 to select terminals to provide a service. In this case, the scheduler 117 selects a terminal set using Equation 1 below.

는 선택된 단말 집합을 나타내고, 상기 P는 서비스 영역에 포함되는 전체 N개의 단말들 중 k개의 단말들을 포함하는 모든 가능한 조합의 단말 집합을 나타낸다. 또한, 상기 Hp는 상기 단말 집합에 포함되는 단말들의 채널 정보로 구성되는 행렬을 나타낸다. 상기 tr()은 () 안의 행렬의 모든 대각선 성분들의 합을 구하는 트레이스(trace) 함수를 나타낸다. Where

Denotes the selected terminal set, and P denotes all possible combinations of terminal sets including k terminals among the total N terminals included in the service area. In addition, the Hp represents a matrix composed of channel information of terminals included in the terminal set. Tr () denotes a trace function that calculates the sum of all diagonal components of the matrix in ().

The encoder 119 encodes and outputs a signal to be transmitted to the terminals selected by the scheduler 117 according to a modulation level (eg, modulation and coding scheme level).

The modulator 121 modulates and outputs the encoded signal provided from the encoder 119 according to the modulation level.

The beam former 123 copies the modulated signal provided from the modulator 121 to correspond to a plurality of antennas. Thereafter, the beam former 123 multiplies the plurality of signals by beamforming weights provided from the beamforming controller 115 and outputs the multiplied beamforming to the transceiving converter 111.

2 is a block diagram illustrating a detailed transmission and reception converter of a terminal in a multi-antenna system according to the present invention.

As shown in FIG. 2, the transceiving converter of the terminal includes an antenna switching unit 203, a first switching unit 205 and a second switching unit 207, a first antenna 209, and a second antenna 211. It is configured to include). In the following description, it is assumed that the first antenna 209 is an antenna used for both transmitting and receiving data signals, and the second antenna 211 is an antenna used only for receiving data signals. Here, the baseband modem 201 performs an operation including the channel estimator 103, the received signal power calculator 105, and the antenna selector 107 of FIG. 1. That is, the baseband modem 201 selects an optimal antenna for transmitting a channel sounding signal and provides an antenna selection signal to the antenna switching unit 203. In addition, the baseband modem 201 outputs a data signal and a channel sounding signal to be transmitted to the base station during the uplink period to the antenna switching unit 203, and the first switching unit 205 and the first during the downlink period. 2 receives a data signal from the base station via the switching unit (207).

The antenna switching unit 203 outputs a data signal input from the baseband modem 201 to the first switching unit 205 during the uplink period according to the TDD scheme. In addition, the antenna switching unit 203 is a switch unit 205, 207 connected to the antenna in accordance with the antenna selection signal provided from the baseband modem 201, input from the baseband modem 201 Outputs a channel sounding signal. In another embodiment, even when transmitting the data signal, the antenna switching unit 203 is connected to the switching unit (205, 207) connected to the corresponding antenna according to the antenna selection signal provided from the baseband modem 201 The data signal input from the baseband modem 201 may be output.

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The first switching unit 205 outputs a signal from the antenna switching unit 203 to the first antenna 209, and outputs a signal from the first antenna 209 to the baseband modem 201. Output

The second switching unit 207 outputs a signal from the antenna switching unit 203 to the second antenna 211, and outputs a signal from the second antenna 211 to the baseband modem 201. Output

3 illustrates a procedure for performing beamforming according to a channel sounding signal in a base station of a multi-antenna system according to an exemplary embodiment of the present invention.

Referring to FIG. 3, the base station first determines a data transmission method in step 301. For example, the base station determines whether to use a closed loop scheme or an open loop scheme. In this case, the data transmission method may be determined by the terminal and requested by the base station, or may be determined by the base station using information fed back by the terminal.

In step 303, the base station determines whether a closed loop MIMO scheme is selected as the data transmission scheme. If a closed loop MIMO scheme is not selected as the data transmission scheme, the base station transmits data according to the data transmission scheme. In contrast, when the closed loop MIMO scheme is selected as the data transmission scheme, the base station allocates a sounding channel to the terminals included in the service area in step 305.

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In step 307, the base station determines whether a channel sounding signal is received from the terminals through the sounding channel. In this case, the terminals transmit the channel sounding signal using an antenna having the best received signal power among the plurality of antennas included in the terminals.

When the channel sounding signal is received, the base station estimates a channel between the channel sounding signal transmission antenna of the corresponding terminal and the antennas of the base station using the received channel sounding signal for each terminal in step 309. Thereafter, the base station calculates beamforming weights for the respective terminals by using channel information for each terminal obtained through the estimation. Here, the base station calculates the beamforming weight w _i using the following Equation 2 for each terminal.

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로 나누어 주는 것은, 상기 빔 형성 가중치 w_i를 단위-놈(unit-norm)으로 만들어 빔 형성에 의한 파워(power)의 증가를 없애기 위함이다. Here, h _i represents channel information of the i-th antenna of the terminal obtained through the estimation, and * denotes a complex conjugate transpose. Here, as shown in Equation 2 remind

To

In order to divide the beam forming weight w _i into a unit-norm, the increase in power due to beam forming is eliminated.

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In step 313, the base station multiplies the calculated beamforming weight by a transmission data signal and transmits the multiplied beamforming weights to the terminals through a plurality of antennas.

The base station then terminates the algorithm according to the invention.

In the above-described embodiment, in order to use the beamforming technique as the line encoding technique in the multi-antenna system, the beamforming weight is generated using the channel information about the terminal. However, when another line coding scheme is used in the multi-antenna system, the base station may calculate a line coding matrix by using channel information about the terminal and perform line coding on the transmission signal using the same.

In addition, when there are a plurality of terminals included in a service area, the base station estimates a channel by using channel sounding signals transmitted by the terminals, and then uses the channel information obtained through the estimation to schedule the service. Terminals to provide may be selected. Here, the base station performs scheduling using Equation 1.

4 illustrates a procedure for transmitting a channel sounding signal in a terminal of a multi-antenna system according to an exemplary embodiment of the present invention.

Referring to FIG. 4, first, the terminal is allocated a sounding channel from the base station in step 401. In step 403, the terminal estimates a channel using a downlink signal received from the base station through the respective antennas. For example, the terminal estimates a channel using a pilot signal included in the downlink signal.

In step 405, the terminal calculates received signal power of each antenna using the channel information obtained through the estimation. In step 407, the terminal receives the largest received signal power among the antennas included in the terminal. In other words, the antenna with the largest received signal-to-noise ratio (SNR) is selected. Here, the terminal selects an antenna by using Equation 3 below.

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을 계산할 수 있으며, 이로써 모든 단말 안테나의 수신 신호 전력을 비교하여 상기 수신 신호 전력이 가장 큰 단말 안테나를 선택할 수 있다. Here, the terminal can obtain information on the 1 × N _t channel row vector h _i corresponding to the i th antenna of the terminal using the downlink M _r × M _t channel matrix H. The beamforming weight w _i of the i-th antenna may be calculated using Equation 2 using the channel information h _i of the antenna. In this case, the terminal receives the received signal power for the i th antenna using the calculated beamforming weight w _i of the i th antenna and the channel matrix H.

It can be calculated, thereby comparing the received signal power of all the terminal antenna it is possible to select the terminal antenna having the largest received signal power.

Thereafter, the terminal transmits a channel sounding signal to the base station through the selected antenna in step 409. In this case, the channel sounding signal is transmitted to the base station through a sounding channel allocated from the base station.

Thereafter, the terminal terminates the algorithm according to the present invention.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications may be made without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined not only by the scope of the following claims, but also by the equivalents of the claims.

1 is a diagram illustrating a configuration of a multiple antenna system using beamforming according to the present invention;

2 is a block diagram illustrating a detailed block configuration of a transceiving converter of a terminal in a multi-antenna system according to the present invention;

3 is a diagram illustrating a procedure for performing beamforming according to a channel sounding signal in a base station of a multi-antenna system according to an embodiment of the present invention; and

4 is a diagram illustrating a procedure for transmitting a channel sounding signal in a multi-antenna system according to an exemplary embodiment of the present invention.

Claims (25)

In the channel sounding signal transmission method in a terminal of a multi-antenna system, Estimating a channel for each of the plurality of receive antennas; Calculating received signal power for each receive antenna using the channel information obtained through the estimation; Selecting a reception antenna having the largest received signal power; Transmitting a channel sounding signal to a base station through the selected receiving antenna; Here, the receiving antenna having the largest received signal power is selected using Equation 4 below.

Here, M _r represents the total number of receiving antennas of the terminal, w _i represents the beamforming weight of the i-th receiving antenna, and H represents a channel matrix. remind

Is the received signal power for the i th receive antenna, calculated using the beamforming weights w _i of the i th receive antenna and the channel matrix H. delete The method of claim 1, And receiving a sounding channel for transmitting the channel sounding signal from the base station. delete The method of claim 1, The beamforming weight is calculated using Equation 5 below.

Hi denotes channel information of the i-th receiving antenna obtained through the estimation, and * denotes complex conjugate transpose. The method of claim 1, The channel is estimated using a pilot signal included in a downlink signal. In a device for transmitting channel sounding signals in a terminal of a multi-antenna system, A channel estimator for estimating a channel for each of the plurality of receive antennas; A reception signal power calculation unit for calculating reception signal power for each reception antenna using the channel information obtained through the estimation; An antenna selection unit for selecting a reception antenna having the largest received signal power; And a transceiving converter for transmitting a channel sounding signal to a base station through the selected receiving antenna. Here, the antenna selector, characterized in that for selecting the receiving antenna using Equation (6).

Here, M _r represents the total number of receiving antennas of the terminal, w _i represents the beamforming weight of the i-th receiving antenna, and H represents a channel matrix. remind

Is the received signal power for the i th receive antenna, calculated using the beamforming weights w _i of the i th receive antenna and the channel matrix H. delete The method of claim 7, wherein the transceiving converter, And transmitting the channel sounding signal through a sounding channel previously allocated from the base station. The method of claim 7, wherein the transceiving converter, An antenna switching outputting a data signal input from a baseband modem to a switching unit connected to an antenna for transmitting and receiving data signals, and outputting a channel sounding signal input from the baseband modem to a switching unit connected to the selected receiving antenna Wealth, And a plurality of antenna-specific switching units for outputting a signal from the antenna switching unit to a connected antenna and outputting a signal from the connected antenna to the baseband modem. delete The method of claim 7, wherein The beamforming weight is calculated by using Equation 7 below.

Hi denotes channel information of the i-th receiving antenna obtained through the estimation, and * denotes complex conjugate transpose. The method of claim 7, wherein the channel estimator, And estimating the channel using a pilot signal included in a downlink signal. In the data transmission method of the base station in a multi-antenna system, Receiving, from the terminals, a channel sounding signal transmitted by each terminal through a receiving antenna having the largest received signal power among the plurality of terminal receiving antennas; Estimating a channel between a reception antenna of a corresponding terminal and antennas of a base station using the received channel sounding signal for each terminal; Calculating beamforming weights for the respective terminals by using channel information for each terminal obtained through the estimation; The beamforming weight may be calculated using Equation 8 below.

Where h _i represents channel information of an i-th reception antenna of a corresponding UE, and * denotes complex conjugate transpose. The method of claim 14, And multiplying the calculated beamforming weights by a transmission data signal to transmit to the terminals. delete The method of claim 14, And selecting terminals to provide a service in this frame among the terminals included in the service area by using the channel information for each terminal obtained through the estimation. The method of claim 17, Terminals to provide the service is selected using the following equation (9).

Here, P represents a set of all possible combinations of terminals including a certain number of terminals among all terminals included in the service area. remind

Represents a selected terminal set, and thus selects one terminal set to select terminals to provide the service. The H _p represents a matrix composed of channel information of terminals included in the terminal set. Tr () represents a trace function for calculating the sum of all diagonal components of a matrix in (). The method of claim 14, Allocating a sounding channel for transmitting the channel sounding signal to the terminals. In the data transmission apparatus of the base station in a multi-antenna system, A transceiving converter for receiving a channel sounding signal transmitted by each terminal from the terminals through a receiving antenna having the largest received signal power among the plurality of terminal receiving antennas; A channel estimator for estimating a channel between a reception antenna of a corresponding terminal and antennas of a base station using the received channel sounding signal for each terminal; And a beamforming controller configured to calculate beamforming weights for the respective terminals by using channel information of each terminal obtained through the estimation. Here, the beamforming controller calculates the beamforming weight using Equation 10 below.

Where h _i represents channel information of an i-th reception antenna of a corresponding UE, and * denotes complex conjugate transpose. The method of claim 20, And a beamformer for multiplying the calculated beamforming weights by a transmission data signal and transmitting the same to the terminals through the transceiving converter. delete The method of claim 20, And a scheduler for selecting terminals to provide a service in this frame among the terminals included in the service area by using channel information of each terminal obtained through the estimation. The method of claim 23, wherein the scheduler, The apparatus characterized in that for selecting the terminals to provide the service using the equation (11).

Here, P represents a set of all possible combinations of terminals including a certain number of terminals among all terminals included in the service area. remind

Represents a selected terminal set, and thus selects one terminal set to select terminals to provide the service. The H _p represents a matrix composed of channel information of terminals included in the terminal set. Tr () represents a trace function for calculating the sum of all diagonal components of a matrix in (). The method of claim 20, wherein the transceiving converter, And receiving the channel sounding signal through a sounding channel previously assigned to the terminals.

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