KR101413937B1 - Method and appratus selecting transmit antenna and estimating uplink multiple-input multiple-output channels in time-division multiplexing wireless communication systems - Google Patents

Abstract

In a wireless communication system using a multiple-input multiple-output (MIMO) scheme, a mobile station transmits a downlink signal based on a reference signal (RS) transmitted from each transmission antenna included in a base station. Selects a first transmit antenna that provides the largest uplink channel gain among a plurality of transmit antennas as a transmit antenna to transmit uplink traffic based on the estimated downlink channel information, Determines uplink channel information for at least one remaining transmission antenna except for the first transmission antenna among the plurality of transmission antennas and transmits the uplink channel information and the uplink traffic through the first transmission antenna , The uplink channel information is transmitted using one of a first transmission scheme and a second transmission scheme, Represents a scheme of transmitting the uplink channel information in consideration of a first time interval in which a sounding RS is transmitted and a second time interval in which the uplink channel information is transmitted using the sounding RS, And the second transmission scheme is a scheme of predistorting the sounding RS and transmitting the uplink channel information.

Speed packet communication, mobile communication system, time division multiplexing system, MIMO system, MIMO, channel estimation, transmission antenna selection, sounding RS

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an apparatus and method for transmitting / receiving data for transmission antenna selection and multiple input / output channel estimation for uplink data transmission in a time division multiplexing wireless communication system including multiple input / OUTPUT CHANNELS IN TIME-DIVISION MULTIPLEXING WIRELESS COMMUNICATION SYSTEMS}

The present invention relates to a method and apparatus for selecting a transmit antenna for uplink data transmission in a time division multiplexing wireless communication system using a transmit / receive multiple antenna and for estimating an uplink multiple-input multiple-output (MIMO) channel through a selected transmit antenna. And an apparatus and method for transmitting and receiving data.

In order to provide high-speed and high-quality data services in wireless communication, a multiple-input multiple-output (MIMO) system using multiple antennas at a transmitter and a receiver has been proposed. The spatial multiplexing (SM) technique, which is one of the MIMO techniques, forms a plurality of spatial sub-channels simultaneously in one receiving period with one transmitter, and independently generates data It is possible to increase the data transmission capacity of each link. Also, space division multiple access (SDMA) techniques can increase the transmission capacity of a system by sending data streams to multiple receivers simultaneously. The spatial multiplexing and spatial division multiple access require spatial processing in the transmitter and the receiver. To do so, the transmitter and the receiver must have MIMO channel state information (CSI) between the transmitter and the receiver .

A time division multiplexing (TDM) system is a system in which a downlink from a transmitter of a base transceiver station (BTS) to a receiver of an access terminal (AT) and an uplink from a transmitter of an AT to a receiver of a BTS share the same frequency band Therefore, the downlink channel can be estimated from the uplink channel estimation using the reciprocity between the uplink and downlink channels. Therefore, if calibration is performed to compensate for the difference between the transmission RF chains and the reception RF chains in the transmitter and the receiver, it can be assumed that the channel responses of the downlink and the uplink are mutually related to each other . That is, when represent the uplink channel response calculated in the TDD MIMO system using n _T of transmit / receive antennas in n _T of transmit / receive antennas and the AT from the BTS to the H _U n _T xn _R matrix, the calculation The matrix H _D representing the downlink channel response is expressed by Equation (1) below.

In Equation (1), A ^T represents a transpose matrix of A and h _{u and m} are channel vectors received from the m th transmit antenna of the AT to n _T receive antennas of the BTS. In order to operate MIMO techniques such as spatial multiplexing and space division multiple access in the downlink, the transmitter of the BTS must know the downlink channel matrix H _D of n _T xn _R size. Therefore, in the TDD system in which the uplink and downlink channels are mutually correlated, the uplink channel matrix H _U is estimated in the BTS using a sounding RS (reference signal) transmitted from the AT transmitter, And estimate the downlink channel matrix H _D.

AT is a portable communication device and should maximize battery performance. Therefore, the AT can not use many RF transmission chains consuming a lot of power. As a result, the AT processes the signals received from the n _R transmit / receive antennas through n _R receive RF chains at the time of reception, and processes the signals processed through a single transmit RF chain at the n _R transmit / receive One antenna is selected and transmitted among the antennas. When the AT uses the single transmit chain, a sounding RS processed through a single transmit chain of the AT is transmitted through only one of the n _R transmit antennas. In this case, it is impossible to estimate the uplink channel matrix H _U of n _T xn _R , which is the channel matrix of the AT and the BTS, and only the n _T x 1 channel vector of the selected single transmit antenna and the receive antenna of the BTS Can be estimated. That is, only one column vector of n _R column vectors constituting the uplink channel matrix H _U can be estimated. Therefore, an effective sounding RS transmission technique for reverse link MIMO channel estimation is required under the constraint that the AT only uses a single transmission chain.

Also, since the AT uses a single transmit chain, when the AT transmits data in the uplink, data processed through a single transmit chain of the AT is transmitted through the d * th antenna selected among n _R transmit antennas. Here, d * can be selected by a certain rule in the range from 1 to n _R. Since the propagation environments from the AT transmit antennas to the BTS receive antennas in the uplink MIMO channel are very different, the channel gain from each transmit antenna to the BTS receive antennas is very different. Accordingly, there is a need for a technique for selecting and transmitting a transmit antenna that provides the highest UL channel gain instantaneously among n _R transmit antennas.

In conclusion, in a TDD MIMO system using a single transmit chain in an AT, an AT transmission antenna selection technique for uplink data transmission and a sounding RS transmission technique for effectively combining uplink channel estimation are required.

Therefore, the present invention provides new data transmission / reception apparatuses and methods for improving the transmission rate and error of traffic and sounding RS data transmitted in the reverse link in a TDD MIMO system using a single transmission chain at AT.

Also, in the TDD MIMO system using a single transmit chain in the AT, the AT selects a transmit antenna that maximizes the reverse channel gain instantaneously through the downlink channel estimation, and transmits a single transmit chain of the AT to the selected antenna RF switching. And AT provides an apparatus and method for transmitting uplink traffic and uplink channel status through a selected transmission antenna.

The present invention also provides new methods and apparatus for estimating an uplink MIMO channel by effectively transmitting a reverse link sounding RS through a transmission antenna selected for traffic transmission.

Also, in order to maximize the performance of transmitting the uplink channel state, the present invention provides an uplink channel state of other non-selected transmit antennas through a transmission antenna selected by the AT, And provides a method and apparatus for delivering to a BTS using a sounding RS.

In the present invention, the predistorted sounding RS transmission scheme multiplexes the predistorted sounding RS through the downlink channel estimation of the AT, and estimates the uplink channel information for each reception antenna of the BTS. In this way, the channel-weighted sounding RS scheme simultaneously transmits a weighted sounding RS and a channel weighted sounding RS in one reverse link time slot, and the BTS receives the signaling RS and estimates the uplink channel information. ≪ / RTI >

A method according to an embodiment of the present invention comprises: A method for transmitting uplink channel information in a wireless communication system using a multiple-input multiple-output (MIMO) scheme, the method comprising: receiving a reference signal : Estimating downlink channel information based on the downlink channel information (RS); calculating a downlink channel information based on the estimated downlink channel information by using a first transmit antenna that provides the largest uplink channel gain among the plurality of transmit antennas, Determining uplink channel information for at least one remaining transmission antenna except for the first transmission antenna among the plurality of transmission antennas by using uplink channel information, And transmitting the uplink traffic through the first transmission antenna, wherein the uplink channel information includes Wherein the first transmission scheme uses a first time interval during which a sounding RS is transmitted and the uplink channel information using the sounding RS, the first transmission scheme is transmitted using one of a first transmission scheme and a second transmission scheme, And transmitting the uplink channel information in consideration of a second time interval to transmit the uplink channel information. The second transmission scheme is a method of predistorting the sounding RS and transmitting the uplink channel information .
Another method according to an embodiment of the present invention comprises: A method for receiving uplink channel information in a wireless communication system using a multiple-input multiple-output (MIMO) scheme, the method comprising: transmitting a reference signal to a terminal And receiving uplink traffic and uplink channel information transmitted through a first transmission antenna among a plurality of antennas included in the mobile station, wherein the uplink channel information includes a plurality of transmission antennas, The uplink channel information for at least one remaining transmission antenna except for the first transmission antenna, and the uplink channel information is transmitted from the terminal using one of a first transmission scheme and a second transmission scheme Wherein the first transmission scheme uses a first time interval during which a sounding RS is transmitted and the uplink interval using the sounding RS, The uplink channel information is transmitted in consideration of a second time interval for transmitting link channel information, and the second transmission scheme is a method of predistorting the sounding RS and transmitting the uplink channel information .
An apparatus according to an embodiment of the present invention includes: 2. Description of the Related Art In a wireless communication system using a multiple-input multiple-output (MIMO) scheme, a UE transmits a downlink channel (RS) based on a reference signal (RS) A first downlink channel estimator for estimating uplink channel gain of the uplink traffic channel based on the estimated downlink channel information, a first transmit antenna that provides the largest uplink channel gain among a plurality of transmit antennas, A controller for determining uplink channel information for at least one remaining transmission antenna except for the first transmission antenna among the plurality of transmission antennas, And a transmitter for transmitting traffic through the first transmission antenna, wherein the uplink channel information includes a first transmission Wherein the first transmission scheme is transmitted using a first time interval during which a sounding RS is transmitted and a second time period during which the uplink channel information is transmitted using the sounding RS, And transmitting the uplink channel information by predistorting the sounding RS according to the second transmission scheme. The method of transmitting uplink channel information according to an embodiment of the present invention will now be described with reference to the accompanying drawings.
Another apparatus according to an embodiment of the present invention includes: A base station in a wireless communication system using a multiple-input multiple-output (MIMO) scheme, the base station comprising: a transmitter for transmitting a reference signal to a terminal using each transmission antenna; And a receiver for receiving uplink traffic and uplink channel information transmitted through a first transmission antenna among a plurality of antennas, the uplink channel information including at least one of the plurality of transmission antennas excluding the first transmission antenna And uplink channel information for at least one remaining transmission antenna, wherein the uplink channel information is transmitted from the terminal using one of a first transmission scheme and a second transmission scheme, A second time slot for transmitting the uplink channel information using the sounding RS and a second time slot for transmitting the uplink channel information, And the second transmission scheme is a scheme of predistorting the sounding RS and transmitting the uplink channel information. [0033] FIG.

In the TDD MIMO system using a single transmit chain in the AT, the AT transmission antenna selection technique for uplink traffic data transmission and the sounding RS for the uplink channel estimation that are effectively combined can be transmitted using the present invention

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description, only parts necessary for understanding the operation according to the present invention will be described, and the description of other parts will be omitted so as not to obscure the gist of the present invention.

The present invention proposes a transmission antenna selection technique for uplink data transmission in a TDD MIMO system and a sounding RS transmission method for uplink channel estimation effectively combined

The structure of a TDD MIMO system proposed by the present invention will be described with reference to FIG.

<Structure of the proposed TDD MIMO system>

FIG. 1 illustrates a TDD MIMO system in which the AT 100 proposed by the present invention uses a single transmission chain. A single transmit chain 124 is switched for each uplink slot by switching to one of the n _R transmit antennas 102 to 106 and then transmitted. In the present invention, an uplink traffic generator 122 for forming data and an RF unit for up-converting and transmitting the uplink traffic signal to an RF band are referred to as a transmission chain 124. The transmission chain is generally referred to as an RF unit excluding a transmission antenna. The traffic generated by the uplink traffic generator 122 is up-converting through the transmission Chain (124), the rising converted traffic is selected among n _R transmit antennas (102 ~ 106) via the RF switch 128 And transmitted through a single antenna. A concrete method of selecting a transmission antenna for uplink traffic transmission will be described in detail as follows.

(1) Uplink transmission antenna selection of AT for uplink traffic transmission

The present invention proposes an uplink transmission antenna selection method of an AT that maximizes the uplink channel gain through downlink channel estimation of an AT when the AT uses a single transmission chain in the uplink of the TDD MIMO system.

를 추정한다.During the t _D downlink time slot, the signals received from the n _R receive antennas 102-106 of FIG. 1 are each treated as a baseband signal by n _R receive chains 108-112. Using the downlink sounding RS transmitted in n _T transmission chains in the BTS, the downlink channel estimator 114 of the AT calculates a downlink channel matrix of n _T xn _R size as shown in Equation (2)

.

은 상기 BTS의 n_T개의 송신 안테나로부터 AT의 m번째 수신 안테나로의 채널 벡터를 나타낸다. here,

Represents the channel vector from the n _T transmit antennas of the BTS to the mth receive antenna of the AT.

를 이용하여, 송신 안테나 선택기(116)에서는 t_U번째 상향 링크 시간 슬롯에서의 트래픽 전송을 위해, 총 n_R개의 송신 안테나들 중에서 최대 이득을 제공하는

번째 송신 안테나를 다음 <수학식 3>에 따라 선택하여 RF 스위치(128)에게 전달한다.The downlink channel estimator 114 estimates the downlink channel matrix

, The transmit antenna selector 116 provides the maximum gain among the total n _R transmit antennas for traffic transmission in the t _{U <} th > uplink time slot

Th transmission antenna according to the following Equation (3) and transmits it to the RF switch 128.

를 구성하는 n_R개의 행벡터(row vector)

중에서 최대 채널 이득을 갖는 안테나를 선택하 는 동작을 나타낸 것이다. 상기 <수학식 1>과 같이 TDD 시스템의 상향 링크와 하향 링크 채널간의 상호 연관성에 의해, 하향 링크 타임 슬롯과 상향 링크 타임 슬롯간의 시간 차이, 즉 t_U - t_D가 채널의 상관 시간(coherence time) 이내 라면,

가 성립하기 때문에, 상기 추정된 하향 링크 채널 행렬을 이용하여 선택된 AT에서의 d(t_U) 번째 송신 안테나는 n_R개의 송신 안테나들 중에서 상향 링크 채널 이득을 최대화 한다. 본 발명에서 제시한 상기 방법과 같이 순시적으로 채널 이득을 최대로 하는 송신 안테나를 선택하는 방식은 고정된 하나의 송신 안테나를 사용하는 경우보다 공간 다이버시티 효과가 n_R배 증가하여 다이버시티 이득이 증가하고, 평균 신호 대 잡음비 (signal to noise ratio, SNR)가 약 0.75n_R배 정도 개선되는 효과가 있다. 즉 본 발명의 송신 안테나 선택 방법은 다이버시티 이득과 평균 SNR 이득을 제공함으로써 역방향 링크 트래픽 데이터 전송률과 에러율을 상당히 향상 시킬 수 있다.Equation (3) can be expressed as Equation (3)

N _R row vectors constituting the < _{RTI ID} = 0.0 &_gt;

And selecting the antenna having the maximum channel gain among the antennas. The time difference between the downlink time slot and the uplink time slot, that is, t _U - t _D is the coherence time of the channel due to the correlation between the uplink and the downlink channel of the TDD system as in Equation (1) ),

, The d (t _U ) th transmit antenna at the selected AT using the estimated downlink channel matrix maximizes the uplink channel gain among n _R transmit antennas. The method of selecting the transmit antenna that maximizes the channel gain instantaneously as in the above-described method of the present invention increases the spatial diversity effect by n _R times as compared with the case of using one fixed transmit antenna, And the signal to noise ratio (SNR) is improved by about 0.75 n _R times. That is, the transmit antenna selection method of the present invention can significantly improve the reverse link traffic data rate and the error rate by providing the diversity gain and the average SNR gain.

Upon receiving the selected antenna index information from the transmit antenna selector 116, the uplink RF switch 128 switches the transmit chain 124 to the transmit antenna selected from the n _R transmit antennas 102 to 106, The data generated by the generator 122 and the uplink channel information generator 120 using the sounding RS are transmitted.

(2) transmission method of sounding RS of AT for uplink MIMO channel estimation

The d (t _U ) th transmit antenna selected by the above-described method of "selecting the uplink transmission antenna of the AT for transmission of the reverse link traffic" includes the n _R transmit antennas of the AT during the t _U th uplink time slot, To provide the maximum channel gain to the BTS. In the present invention, can be transferred, significantly improve the spatial diversity gain and the average SNR gain estimation performance of an uplink sounding RS by using the transmit antenna selection by using the uplink sounding the selected the RS d (t _U) th transmit antenna have. That is, the uplink sounding RS is transmitted through the d (t _U ) th transmission antenna selected for uplink data transmission.

However, in this case, the channel information of only the selected single antenna is transmitted to the BTS, and the BTS does not know the sounding RS value of the remaining channels. In order to solve the above problem, a method of transmitting sounding RSs of all downlink channels through a single antenna selected for the uplink transmission is needed.

That is, in this case, the BTS estimates the sounding RS transmitted from the selected d (t _U ) -th transmission antenna of the AT for each uplink time slot, so that the channel having the size of n _T x1 from the d (t _U ) Only the vector can be estimated. In order to estimate the uplink channel matrix H _U in the BTS, it is necessary to estimate the n _R row vectors of H _U indicating the channel states from each n _R transmit antennas of the AT to the BTS. d (t _U) using a second transmission antenna, and from the non-selected other antenna of the new transmission AT to pass the uplink channel conditions to the BTS in order to BTS.

The present invention proposes a sounding RS transmission scheme for transmitting an uplink channel state from other unselected transmit antennas to a BTS through a transmit antenna to be selected in an AT and transmitted through uplink traffic to a BTS. That is, assuming that an actual antenna index for transmitting traffic in the uplink is d, and an index of a transmitting antenna for transmitting the uplink channel state is c, the c-th transmitting antenna using the d- We propose a sounding RS transmission scheme that transmits the uplink channel state up to the BTS. Since the selected transmission antenna d and the antenna c for transmitting the uplink channel state are different from each other, d? C. In the present invention, the following two embodiments are proposed according to the type and form of the sounding RS to be transmitted.

&Lt; Embodiment 1 >

(A) Predistorted sounding RS transmission method

가 성립하기 때문에, AT는 c번째 송신 안테나로부터 BTS까지의 상향 채널 벡터 h_{U ,c}(r_U) 와 d번째 송신 안테나로부터 BTS까지의 상향 채널 벡터 h_U,d(t_U)를 알 수 있으며, 이 벡터들은 다음 <수학식 4>와 같이 표현된다.During the t _D- th downlink time slot, the downlink channel estimator 114 of the AT of FIG. 1 uses the downlink sounding RS transmitted from each Tx antenna of the BTS to calculate n _T xn _R Size downlink channel matrix H _D (t _D ). Due to the correlation between the uplink and downlink channels of the TDD system,

The AT can know the up channel vector h _{U , c} (r _U ) from the c-th transmit antenna to the BTS and the up channel vector h _{U, d} (t _U ) from the d-th transmit antenna to the BTS , These vectors are expressed as Equation (4).

Here, the time slot index t _D is omitted for convenience of explanation. _{hi, c, k} and _{hu, d, k} (k = 1, L, _nT ) refer to the kth element of _{hU, c} and _{hU, d} vectors _, respectively. Therefore, in order to transmit the uplink channel vector h _{u, c} from the c-th transmission antenna to the BTS to the BTS, a total of n _T complex symbols must be transmitted through the d-th transmission antenna.

Using the channel information estimated by the downlink channel estimator 114, the transmit antenna selector 116 selects a specific antenna index having the best downlink channel state and transmits the selected antenna index to the RF switch 128. The complex weight a _k to be multiplied by the sounding RS transmitted from the d-th transmission antenna in the predistorter 118 of the AT is calculated using Equation (5) using the channel information estimated from the downlink channel estimator 114, .

는 sounding RS에 곱해져, 상향 링크 타임 슬롯 내의 n_T개의 시간 구간

에 나누어져서 TDM( Time Division Multiplexing ) 방식으로 전송되거나, 직교하는 n_T개의 코드가 곱해져서 CDM(Code Division Multiplexing ) 방식으로, 또는 서로 다른 n_T개의 주파수 대역에 나뉘어져서 FDM(Frequency Division Multiplexing) 방식으로 전송될 수 있다. 후술될 본 발명의 실시 예는 n_T개의 복소 심볼 a_k가 TDM 방식으로 전송되는 경우를 설명할 것이다. 그러나 제안된 기술은 CDM과 FDM 방식으로 전송되는 시스템에도 적용 가능하다. 상기 수식에 의해 전치 왜곡기(118)에서 구한 복소 가중치 a_k값은 Sounding RS를 이용한 상향 링크 채널 정보 발생기(120)로 입력된다. Sounding RS를 이용한 상향 링크 채널 정보 발생기(120)는 상기 입력 받은 복소 가중치 값을 사용하여 상기 d번째 송신 안테나에서 전송되는 sounding RS에 곱하여 상향 링크 채널 정보를 발생하고, 이 값을 송신 chain(124)로 전달한다. 송신 chain(124)는 상향링크 트래픽 발생기(122)와 상기 상향링크 채널 정보 값을 조합하여 상승 변환한다. RF스위치(128)는 n_R개의 송신 안테나(102~106)들 중에 송신안테나 선택기(116)에 의해 선택된 단일 송신 안테나로 스위칭 하고, 상기 송신 chain(124)에서 출력된 신호를 송신한다. 상향 링크 타임 슬롯 내의 k 번째 시간 구간 T_P,k에서 전송되는 복소 심 볼은 sounding RS에 복소 가중치 a_k가 곱해진 심볼로, AT의 d번째 송신 안테나를 통해 전송되어 다음 <수학식 6>과 같이 신호 벡터 Y_k가 BTS에 수신된다.That is, the complex weight a _k is obtained by dividing the kth element of hi _{, c by} the kth element of _{hi, d} . The obtained n _T complex weights

Is multiplied by the sounding RS, and n _T time intervals in the uplink time slot

(TDM) scheme or orthogonal n _T codes are multiplied and divided into CDM (Code Division Multiplexing) or different n _T frequency bands, and a FDM (Frequency Division Multiplexing) scheme Lt; / RTI &gt; An embodiment of the present invention to be described below will explain a case where n _T complex symbols a _k are transmitted in a TDM scheme. However, the proposed technique is also applicable to CDM and FDM transmission systems. The complex weight a _k obtained from the predistorter 118 is input to the uplink channel information generator 120 using the sounding RS. The uplink channel information generator 120 using the sounding RS multiplies the sounding RS transmitted from the d &lt; th &gt; transmit antenna using the received complex weight value to generate uplink channel information, . The transmission chain 124 combines the uplink traffic generator 122 and the uplink channel information value and performs up conversion. The RF switch 128 switches among the n _R transmit antennas 102-106 to the single transmit antenna selected by the transmit antenna selector 116 and transmits the signal output from the transmit chain 124. [ The complex symbol transmitted in the k-th time interval T _{P, k} in the uplink time slot is a symbol obtained by multiplying the sounding RS by the complex weight a _{k, and} is transmitted through the d-th transmission antenna of the AT, As such, the signal vector Y _k is received at the BTS.

동안, 해당 수신 안테나에서 수신된 심볼을 복구함으로써 h_{U ,c}를 추정할 수 있다. 도 2는 상기 제 1 실시 예에 의해 AT(202)에서 전송되는 UL(uplink) 타임 슬롯(time slot)과 BTS(200)에서 수신되는 신호를 도시한 것이다. 각 안테나(1,2, …, n_T)의 sounding RS값에 상기 <수학식 5>에 의해 구해진 복소 가중치

가 곱해진 형태의 전치 왜곡된 sounding RS(204)가 역방향 링크 타임 슬롯에서 T_{p ,1} T_p,2, …, T_p,nT의 n_T시간 구간으로 나누어져서 TDM 방식으로 전송된다. 상기 BTS(200)의 각 안테나(1,2, …n_T)에서는 상기 <수학식 6>과 같이 신호성분이 수신되고, 이를 통해 h_U,c의 원소들을 추정할 수 있다.The complex weight a _k passes through the uplink channel and is multiplied with the respective elements of the h _{U, d} vector. Specifically, the signal, i.e., the received signal vector Y _K received at the k-th antenna of the BTS k th element is the uplink channel vector a k-th element of h _{U, c} to the BTS from the C-th transmit antenna h _{U, c, k} Is received. Thus, BTS is able to recover the symbols received in the first receive antenna in T _{P, 1-hour} interval of the reverse link time slots to estimate h _{U, c, 1,} and in the k-th receive antenna at T _{P, k} time intervals _{Hi, c, k} can be estimated by recovering the received symbol. Thus, n _T time intervals of the reverse link timeslot

, We can estimate _{hi , c} by recovering the received symbol at the corresponding receive antenna. 2 shows an UL (uplink) time slot transmitted from the AT 202 and a signal received from the BTS 200 according to the first embodiment. The sounding RS values of the respective antennas 1, 2, ..., n _T are multiplied by the complex weights

The pre-distorted sounding RS 204 in the form of a multiplication is multiplied by T _{p , 1} T _{p, 2} , ... in the reverse link timeslot. , T _p, and n _{T , and} is transmitted in a TDM manner. In each antenna 1, 2, ..., n _T of the BTS 200, a signal component is received as shown in Equation (6), and the elements of h _{u, c} can be estimated therefrom.

&Lt; Embodiment 2 >

(B) Channel weighted sounding RS transmission method

가 곱해진 sounding RS를 d번째 송신 안테나를 통해 TDM, CDM, 또는 FDM 방식으로 전송한다.The second embodiment according to the weighted channel sounding RS transmission method, the AT is one of a reverse link time slot in the unmultiplied weight sounding RS and _{U h, c} n _T more complex element in the present invention

And transmits the multiplied sounding RS through the d &lt; th &gt; transmission antenna by TDM, CDM, or FDM.

가 곱해진 sounding RS가 TDM 방식으로 전송되는 경우를 설명할 것이다. 따라서, 상향 링크 타임 슬롯은 가중치가 곱해지지 않은 sounding RS가 전송되는 시간 구간 T_NW과 채널 가중치가 곱해진 sounding RS가 전송되는 시간 구간 T_W로 나뉘어 진다. 또한 T_W는 n_T개의 시간 구간

으로 나뉘어져 h_{U ,c}의 n_T개 복소 원소

가 곱해진 sounding RS가 전송된다.Embodiments of the present invention to be described hereinafter is sounding RS and _{U h,} n _{T c} of weight is more complex element unmultiplied

The sounding RS multiplied by the number of times the sounding RS is transmitted in the TDM scheme will be described. Therefore, the uplink time slot is divided into a time interval T _NW through which the sounding RSs whose weights are not multiplied are transmitted, and a time interval T _W through which the sounding RSs multiplied by the channel weights are transmitted. T _W is the number of n _T time intervals

And the n _T complex elements of h _{U , c}

The sounding RS multiplied is transmitted.

The AT transmits a sounding RS with a weight unmultiplied, and the BTS estimates an up channel vector h _{U, d} from the d-th transmit antenna to the BTS using a sounding RS whose weight is not multiplied during the T _NW of the reverse link time slot. do. In the kth time interval T _{W, k} of T _{W in} the uplink time slot _{, the} symbol multiplied by the complex weight h _{u, c, k} is transmitted to the sounding RS and transmitted through the d th transmission antenna of the AT, 7>, the signal vector Y _K is received at the BTS.

The BTS receiver uses the uplink channel vector h _{U, d} estimated by the weighting-unfiltered sounding RS to estimate the received signal vector y _k as a received signal such as maximal ratio combining (MRC) or minimum-mean square error (MMSE) Process. The embodiment of the present invention assumes the case of the MRC received signal processing and if the received signal vector Y _k is subjected to the MRC reception signal processing _, the k th element h _u of the weighted h _{u, c,} as shown in Equation (8) _{, c, k} can be estimated.

Thus, the BTS can recover h _{U, c, 1} by recovering the symbols received at T _{W, 1} of the reverse link timeslot _, and recovering the received symbols at T _{W , k} , Can be estimated. Therefore, h _{U, c} can be estimated by recovering the received symbol during T _W.

FIG. 3 shows UL (uplink) time slots transmitted from the AT 300 and signals received from the BTS 306 according to the second embodiment. During a T _{W, N} interval in a reverse link timeslot, the unweighted sounding RS 302 and T _{W, 1} , T _{W, 2} , ... , T _{W, and n} T _{, the} channel weighted RS 304 is transmitted in a TDM manner. The transmitted signal is transmitted from the BTS 306 to an antenna 1, an antenna 2, ... , Antenna n _T , and the signal is processed by MRC (Maximum Ration Combining) method as indicated by reference numeral 308 to obtain T _{W, 1} , T _{W, 2} , ... , T _{W, and n} T _, the reverse link channel is estimated.

4 and 5 are diagrams showing an operational flow of the transmitting / receiving end.

4 is a flowchart illustrating an operation of a UE for transmitting channel estimation information to a BTS. In step 401, the AT informs the BTS of the number of transmit / receive antennas used by the AT in the initial call set-up process. The sounding RS transmission method of the AT for the proposed uplink MIMO channel estimation transmits the uplink channel information of one AT transmission antenna during one reverse link time slot. Therefore, in order to transmit the uplink channel information of the n _R transmit antennas of the AT, the BTS and the AT must preliminarily promise a rule for determining the index C of the channel state transmit antenna for each reverse link time slot. For example, Let it sequentially changes, such as the index of the C channel status transmission antenna, and 1,2, L, n _R, 1,2, L, from the first reverse link time slot to be c = 1, n _R th C = n _R in the time slot, and c = 1 in the n _R + 1 th time slot.

It is assumed that the downlink timeslot index t _D and the uplink timeslot index t _D sequentially increase from 1 in the example of the proposed invention.

Through step 402, the AT estimates the downlink channel matrix H _D (t _D ) for each downlink time slot using the downlink sounding RS transmitted from each transmission antenna of the BTS. Through the use of the estimated downlink channel matrix H _D (t _D ), through the uplink transmission antenna selection method of AT which maximizes the uplink channel gain proposed by the present invention, in step 403, traffic from t _U transfer selects the transmission antennas d (t _U) of aT.

In step 404, the transmit antenna index c (t _U ) of the AT to which the uplink channel information is to be transmitted is determined through the transmit antenna d (t _U ) selected in step 403. For example, c (t _U ) = rem (t _U , n _R ) is determined when c (t _U ) is sequentially changed as 1,2, L, n _R , 1,2, Here, rem (a, b) is a function that finds the remainder of dividing a by b.

In step 405, the AT uses the d (t _U ) th column vector and the c (t _U ) th column vector of the estimated downlink channel matrix H _D (t _D ) , Calculates the predistortion weight of the sounding RS required for the "transmission scheme" or calculates the channel weight of the sounding RS required for the "channel weighted sounding RS transmission scheme". The calculated weights are multiplied by the sounding RS in step 406 and transmitted according to the respective reverse link timeslot structures described in FIGS. 2 and 3 for each transmission scheme.

 An operation flow chart for channel estimation in the BTS is shown in FIG. In step 501, the BTS acquires information on the number of transmit / receive antennas of the AT fed back from the AT in step 501. In step 502, the BTS computes the number of times the sounding RS transmitted in the corresponding reverse link timeslot is in the reverse direction Link channel information.

로 구성된

를 추정한다. 또한, 이를 transpose하여 505 과정에서는 하향 링크 MIMO processing에서 요구되는 하향 링크 채널 행렬 H_D(n_R)를 구한다. 마지막으로 506 과정을 통해 BTS는 t_U ? n_R 1인 역방향 링크 타임 슬롯에서 추정된 채널 벡터들은 H_U(n_R)의 rem(t_U,n_R) 번째 행 벡터를 업데이트 한다. 본 발명에서는 TDD MIMO 시스템의 상향 링크 채널 이득을 최대로 하는 AT의 송신 안테나 선택 방법을 제안하였다. 제안하는 방식은 AT의 하향 링크 채널 추정을 통해, 순시적으로 채널 이득을 최대로 하는 AT의 송신 안테나를 선택함으로써, 고정된 하나의 송신 안테나를 사용하는 경우보다 공간 다이버시티 order가 n_R배 증가하여 다이버시티 이득이 증가하고, 평균 신호 대 잡음비(signal to noise ratio : SNR)가 약 0.75n_R배 정도 개선된다. 제안하는 송신 안테나를 선택하는 방식은 AT가 하향 링크 채널 추정을 통해 상향 링크 송신 안테나를 독자적으로 결정하기 때문에, BTS와의 추가적인 signaling이 필요 없으며, 다이버시티 이득과 평균 SNR 이득을 제공함으로써 역방향 링크에서 전송되는 트래픽 데이터와 sounding RS의 전송률과 에러율을 상당히 향상 시킬 수 있다.In step 503, the BTS estimates the uplink channel vector of the c ( _tU ) th transmit antenna according to the reverse link timeslot structure described in FIGS. 2 and 3 according to the reverse link sounding RS transmission scheme. In step 504, n _R estimated vectors &lt; _{RTI ID} = 0.0 _&gt; (k) &lt; / _RTI &gt; estimated through a reverse link channel estimation process during n _R consecutive reverse link timeslots

Consisting of

. In step 505, the downlink channel matrix H _D (n _R ) required in the downlink MIMO processing is obtained. Finally, through the process of the BTS 506 t _U? The channel vectors estimated in the reverse link timeslot with n _R 1 update the rem (t _U , n _R ) th row vector of H _U (n _R ). In the present invention, a transmission antenna selection method of AT which maximizes the uplink channel gain of a TDD MIMO system is proposed. The proposed scheme selects the transmit antenna of the AT that maximizes the channel gain instantaneously through the downlink channel estimation of the AT so that the spatial diversity order is n _R times larger than that of the fixed one transmit antenna The diversity gain is increased, and the average signal-to-noise ratio (SNR) is improved by about 0.75 n _R times. Since the AT selects the uplink transmission antenna independently through the downlink channel estimation, the AT does not need to perform additional signaling with the BTS, and the diversity gain and the average SNR gain are provided, The transmission rate and the error rate of the traffic data and the sounding RS can be significantly improved.

In the present invention, two sounding RS transmission schemes for transmitting the uplink channel states of other unselected transmission antennas to the BTS through the transmission antenna selected by the AT and transmitting the uplink traffic are proposed. "Channel weighted sounding RS transmission scheme" transmits a sounding RS multiplied by a channel weight, since a sounding RS having a weight multiplied by a weight is multiplied by n _T channel weights during one reverse link time slot, The time interval becomes smaller than the "predistorted sounding RS transmission method &quot;. The reduction of the time interval for transmitting the sounding RS multiplied by the channel weight causes a decrease in the signal energy for the weighted sounding RS estimation to degrade the channel estimation performance. However, as shown in Equation (8) RS transmission scheme "can compensate for this by further obtaining the MRC gain by the n _T receive antennas of the BTS. The diversity order can be obtained by multiplying the diversity order n _T times by the reception MRC of the BTS, and the average SNR increases n _T times.

On the other hand, the "predistorted sounding RS transmission scheme" does not need to transmit sounding RSs whose weights are not multiplied by predistorting the sounding RSs through downlink channel estimation. Therefore, since the time interval for transmitting the predistorted sounding RS is larger than the "channel weighted sounding RS transmission method ", the signal energy for predistorted sounding RS estimation is increased to improve the estimation performance.

Therefore, when the number n _T of base station receiving antennas is large, a "channel weighted sounding RS transmission method " in which the gain by the MRC receiving signal processing increases is suitable. When the number n _T of base station receiving antennas is small, Quot; predistorted sounding RS transmission scheme "in which the time interval over which the signal is transmitted is relatively large.

1 shows an example of a transmitter structure for switching a single transmission chain of an AT to one antenna selected among transmission antennas in each uplink slot in a TDD MIMO system in which an AT uses a single transmission chain

2 is a diagram showing an example in which the predistorted sounding RS is divided into time segments in a reverse link time slot and transmitted in a TDM manner and received and divided into respective reception antennas of the BTS

3 illustrates an example in which, in a channel-weighted sounding RS transmission scheme, a sounding RS in which a weight is not multiplied within one reverse link time slot and a channel-weighted sounding RS are transmitted in a TDM scheme and an MRC reception signal is processed in the BTS scheme and recovered Drawing

4 is a flowchart illustrating an operation of a terminal for transmitting channel estimation information to a BTS

5 is a flowchart illustrating the operation flow in the BTS for downlink channel estimation

Claims (14)

A method for transmitting uplink channel information in a wireless communication system using a multiple-input multiple-output (MIMO) scheme, Estimating downlink channel information based on a reference signal (RS) transmitted from each transmission antenna included in the base station; Selecting a first transmit antenna that provides the largest uplink channel gain among a plurality of transmit antennas as a transmit antenna to transmit uplink traffic based on the estimated downlink channel information; Determining uplink channel information for at least one remaining transmission antenna except for the first transmission antenna among the plurality of transmission antennas; And transmitting the uplink channel information and the uplink traffic through the first transmission antenna, The uplink channel information is transmitted using one of a first transmission scheme and a second transmission scheme. The first transmission scheme uses a first time interval during which a sounding RS is transmitted and the sounding RS Wherein the uplink channel information is transmitted in consideration of a second time interval in which the uplink channel information is transmitted, and the second transmission scheme is a method of predistorting the sounding RS to transmit the uplink channel information, And transmitting the uplink channel information. The method according to claim 1, The method of predistorting the sounding RS in the second transmission scheme and transmitting the uplink channel information may include transmitting the uplink channel information using the weight determined based on the estimated downlink channel information, And transmitting the uplink channel information. The method according to claim 1, Wherein the first time interval represents a time interval for estimating an uplink channel and the second time interval represents a time interval for detecting the uplink channel information by the base station. How to. delete In a wireless communication system using a multiple-input multiple-output (MIMO) scheme, A downlink channel estimator for estimating downlink channel information based on a reference signal (RS) transmitted from each transmission antenna included in the base station; An antenna selector for selecting a first transmission antenna that provides the largest uplink channel gain among a plurality of transmission antennas as a transmission antenna to transmit uplink traffic based on the estimated downlink channel information; A controller for determining uplink channel information for at least one remaining transmission antenna except for the first transmission antenna among the plurality of transmission antennas; And a transmitter for transmitting the uplink channel information and the uplink traffic through the first transmission antenna, The uplink channel information is transmitted using one of a first transmission scheme and a second transmission scheme. The first transmission scheme uses a first time interval during which a sounding RS is transmitted and the sounding RS Wherein the uplink channel information is transmitted in consideration of a second time interval in which the uplink channel information is transmitted, and the second transmission scheme is a method of predistorting the sounding RS to transmit the uplink channel information, To the terminal. 6. The method of claim 5, The method of predistorting the sounding RS in the second transmission scheme and transmitting the uplink channel information may include transmitting the uplink channel information using the weight determined based on the estimated downlink channel information, To the terminal. 6. The method of claim 5, Wherein the first time interval represents a time interval for estimating an uplink channel and the second time interval represents a time interval for detecting the uplink channel information by the base station. delete A method for receiving uplink channel information in a wireless communication system using a multiple-input multiple-output (MIMO) scheme, Transmitting a reference signal (RS) to a mobile station using each transmit antenna; Receiving uplink traffic and uplink channel information transmitted through a first transmission antenna among a plurality of antennas included in the mobile station, Wherein the uplink channel information includes uplink channel information for at least one remaining transmission antenna except the first transmission antenna among the plurality of transmission antennas, The uplink channel information is transmitted from the UE using one of a first transmission scheme and a second transmission scheme, and the first transmission scheme includes a first time interval during which a sounding RS is transmitted, And transmitting the uplink channel information in consideration of a second time interval in which the uplink channel information is transmitted, wherein the second transmission scheme predistortes the sounding RS to transmit the uplink channel information, And transmitting the uplink channel information. 10. The method of claim 9, The method of predistorting the sounding RS in the second transmission scheme and transmitting the uplink channel information may include receiving the uplink channel information using the weight determined based on the downlink channel information estimated by the terminal, And transmitting the uplink channel information. 10. The method of claim 9, Wherein the first time interval represents a time interval for estimating an uplink channel and the second time interval represents a time interval for detecting the uplink channel information by the base station. How to. 1. A base station in a wireless communication system using a multiple-input multiple-output (MIMO) scheme, A transmitter for transmitting a reference signal (RS) to the terminal using each transmission antenna; And a receiver for receiving uplink traffic and uplink channel information transmitted through a first transmission antenna among a plurality of antennas included in the mobile station, Wherein the uplink channel information includes uplink channel information for at least one remaining transmission antenna except the first transmission antenna among the plurality of transmission antennas, The uplink channel information is transmitted from the UE using one of a first transmission scheme and a second transmission scheme, and the first transmission scheme includes a first time interval during which a sounding RS is transmitted, And transmitting the uplink channel information in consideration of a second time interval in which the uplink channel information is transmitted, wherein the second transmission scheme predistortes the sounding RS to transmit the uplink channel information, Wherein the base station and the base station are connected to the base station. 13. The method of claim 12, The method of predistorting the sounding RS in the second transmission scheme and transmitting the uplink channel information may include receiving the uplink channel information using the weight determined based on the downlink channel information estimated by the terminal, To the base station. 13. The method of claim 12, Wherein the first time interval represents a time interval for estimating an uplink channel and the second time interval represents a time interval for detecting the uplink channel information by the base station.

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