TW200835212A - Method and apparatus for hybrid automatic repeat request in multiple antenna system - Google Patents

Abstract

The present invention proposes a method of hybrid automatic repeat request for a multiple antenna system and an apparatus thereof, where the method and the apparatus thereof only retransmit two symbols that constitute an Alamouti code word together with a 5 part of initial transmitted symbols when performing symbol retransmission, and thus retransmission power consumption is reduced and receiving complexity is decreased due to the retransmitted symbols decreasing.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio communication technology and, in particular, to a hybrid automatic repeat request method and apparatus for use in a multi-antenna system. [Prior Art] Compared to a single input single output (SISO) antenna wireless communication system, a multiple input multiple f output (ΜΙΜΟ) wireless communication system can provide higher channel capacity. Recently, spatial multiplexing transmission schemes for chirp systems with four transmit antennas have been proposed in a variety of wireless communication standards. This scheme simultaneously transmits four independent data streams by four transmit antennas, providing a higher data transfer rate in a full-rank (Full_Rank) channel (ie, a rank of the channel matrix of 4 in the system). However, this scheme is more sensitive to the environment of the rank of the channel. In a spatial multiplexing system, to maintain an acceptable performance, the number of data streams transmitted simultaneously should not exceed the rank of the channel matrix. When the ^ ΜΙΜΟ channel matrix rank is reduced, that is, when the channel has a rank deficiency (Rank_Deficient), a large number of transmission errors occur. In order to solve this problem, a current scheme introduces an automatic repeat request (ARQ) in the MIM0 system. Table 1 below is an example of one such ΜΙΜΟ-ARQ scheme for a four-transmit antenna system. 0 118607.doc 200835212

Txl Tx2 Τχ3 Τχ4 Initial transmission Eve 2 Retransmission: Time slot 1 *^2 0 0 Retransmission: Time slot 2 0 0 夕3 Table 1

As shown in Table 1, the ΜΙΜΟ-ARQ scheme retransmits the initially transmitted data packet (including four symbols) by multiple time slots according to the status of the rank of the ΜΙΜΟ channel, and recovers these symbols based on the corresponding transmission time slot. Instead of using the data from the initial transmission. The ΜΙΜΟ-ARQ scheme can obtain a lower packet error rate (PER) after several times of transmission, but since each retransmission requires more than one time slot, the retransmission delay is longer. Ο To this end, another scheme proposes to introduce Hybrid Automatic Repeat Request (HARQ) into the system. Compared with ARQ, HARQ can re-use the data from the initial transmission instead of giving up, so it is more efficient. For a system with two transmit antennas, a Space-Time Block Code (STBC) HARQ scheme (hereinafter referred to as STBC-HARQ) retransmits the initial transmission symbols according to the Alamouti rule, corresponding to the transmission of the transmit antenna. The symbols are shown in Table 2 below.

Txl Tx2 Initial Transmission Retransmission * One *^2 ♦ S1 Table 2 118607.doc 200835212 This STBC-HARQ scheme with Alamouti rules has better performance than the STBC-HARQ scheme with non-Alamouti rules. Based on a similar principle, for a system with four transmit antennas, a scheme called Double Space-Time Transmit Diversity (Double-STTD) HARQ can be used. The scheme retransmits the initial transmission symbols according to the Double-STTD rule, and the symbols transmitted by the corresponding transmitting antennas are shown in Table 3 below.

Txl Tx2 Tx3 Tx4 Initial transmission S1 retransmission The transmitters for the above two HARQ schemes can obtain better reception performance in various channel environments by using the packet combination method at the receiver end. . Although the Double-STTD HARQ takes up less retransmission time and has better I, detection performance, it is more efficient than the MIMO-ARQ scheme, but it needs to retransmit four symbols in the same time slot, thus increasing the power of the transmitter. The complexity of the receiver combined with the packet. SUMMARY OF THE INVENTION One object of the present invention is to provide a HARQ method and apparatus for a multi-antenna system that reduces power consumption and reduces reception complexity by reducing retransmission symbols. A hybrid automatic repeat request for a multi-antenna system according to the present invention 118607.doc 200835212 A transmitter method comprising the steps of: a) transmitting a symbol to be transmitted via a corresponding antenna channel; b. obtaining a corresponding feedback Information; and c. If the feedback information indicates that retransmission is required, only two symbols are retransmitted to form an Aiarnouti codeword with the partial symbols in the symbol transmitted in step a. A hybrid automatic repeat request receiver method for a multi-antenna system according to the present invention comprises the steps of: a) receiving a transmission symbol by a corresponding antenna channel; b. issuing a corresponding feedback message according to the received transmission symbol And e. The right feedback information indicates that retransmission is required, and then two retransmitted symbols are received 'where the two retransmitted symbols and some symbols in the transmitted symbol form an Alamouti codeword; d· according to the received transmission Symbols and symbols of retransmissions restore the corresponding data. A transmitter for a multi-antenna system according to the present invention comprises: a spatial multiplexing unit for transmitting symbols to be transmitted via respective antenna channels; a packet retransmission unit for retransmission and the transmission symbol The middle part symbol constitutes two symbols of an Alamouti code word; and a switch unit is configured to control the packet retransmission unit to perform symbol retransmission according to a corresponding feedback information obtained. A receiver for a multi-antenna system according to the present invention comprises: a spatial multiplexing detecting unit for receiving a transmission symbol via a corresponding antenna channel and generating a corresponding feedback according to the received transmission symbol 118607.doc 200835212 And a packet combining unit, configured to receive two retransmitted symbols, and recover corresponding data according to the received transmission symbol and the retransmitted symbol, wherein the two retransmitted symbols and the partial symbols in the transmitted symbol form An Alamouti code, and an antenna selection unit, for transmitting the received retransmission symbol to the packet combining unit when the feedback information indicates that retransmission is required. According to the prior art, the HARq method and the apparatus of the multi-antenna system of the present invention only need to retransmit two symbols, and thus have relatively low reception complexity and low retransmission power consumption. Other objects and effects of the present invention will become more apparent from the detailed description of the appended claims. [Embodiment] The process of symbol transmission by the PSTBC-HARQ method of the present invention is as shown in Fig. i, wherein it is assumed that the transmission symbol vector (i.e., a packet) in a certain time slot is an outer W4f, which is .../= 1,2, ..., 4 denotes a symbol multiplexed by 1 through the ith transmit antenna. Referring to ^, the symbol [s, ^] is transmitted first at the transmitter. When the receiver receives an error, it returns a non-acknowledgement (NACK) requesting the transmitter to retransmit the data, and the transmitter transmits the symbol Uvj. The two symbols of the transmitter transmission and the corresponding kd in the first transmitted symbol form a code word conforming to the Alam〇uU袼, which is the portion indicated by the dotted circle in the figure. The packet transmission format performed by the C-HARQ method of the present invention may also be as shown in Table 4 below:

/, 0 means that no symbols are transmitted on the corresponding time slot and antenna. This rabbit's PSTBC-HARQ method, although available at the receiver end

f匕,和曰曰方法' However, this method is more complicated to implement, so for the packet transmission format of PSTBC-HARQ, the present invention proposes a low-reproduction Tairi Shi's P-based interference cancellation (Interference Cancellation, Ic) packet Combination method. For the sake of generality, the IC-based packet combining method of the present invention will be described in detail by taking the packet transmission format of pSTBC_HARQ shown in Table 4 as an example. For the scheme of Table 4, the signal models in the initial transmission and retransmission slots can be expressed by the following equations: r(1)=H(V)+n(1) (1) r(2) =H(2)s(2 +n(2) (2) where the superscripts i=l and 2 represent the signal models in the initial transmission and retransmission slots, respectively. r(0 , /= 1,2, represents the received signal vector of the Nr dimension, where the element of the matrix represents the signal received by the receiving antenna m in the corresponding transmission time slot. s(1) = [41), 41 ), 4),) ί = [A,6,A,^ and s(2)=[force(7),42)]Γ=b denotes a transmission symbol vector, where the element β of the matrix is represented in the corresponding transmission time slot 118607. Doc -11- 200835212 Signal transmitted by the internal transmit antenna η. The transmission symbols in a transmission slot are modeled as zero-mean and the variance is < identical and identically distributed (i.i.d.) random variables. &heart?),...,like".=1,2, indicating the additional white Gaussian noise vector of the receiver in the corresponding transmission time slot, where all elements are modeled as zero mean and the variance is N Complex Gaussian random variables of Li.d cycle symmetry. The matrix of 1^1) and 11(2), as shown in equations (3) and (4), respectively represent a channel matrix of 1^11^, where the elements of the matrix are represented in the corresponding transmission time slot. The channel gain between the transmitting day f line 11 and the receiving antenna 111. ««...3⁄4.^«...3⁄4. V)/ 垮 垮玛...^ |_| IIΗ(1 Η (2) ^(2) (4) .3⁄4 ^,2 ◎ according to the above equations (1) and (2) In the signal model of the medium and referring to FIG. 2, the packet combining method based on 1C mainly recovers the packet by performing the following steps: First, according to the signal received in the corresponding retransmission slot, by line space multiplexing detection The measurement algorithm detects two symbols of the retransmission (step sl1). As shown in equation (2), the retransmission signal model of PSTBC_HARQ* is a signal model of a two-transmission multi- (NR) reception spatial multiplexing system. In this way, traditional linear spatial multiplexing detection algorithms can be directly used, such as H8607.doc -12 · 200835212 (Zero Forcing, ZF) and Minimum Mean Square Error (MMSE) algorithms. As an example, the two retransmission symbols h and h are detected by the following equations (5) and (6): s(7)=[-i2y f =(h(2(10)Η(7) + today 12)-1 H(2 )//r(2) (5)

Sn=Q(snX η = 1,2 (6) where Im represents a unitary matrix, and 0(·) represents a demodulation operation corresponding to the modulation scheme. Next, in step S11, the detected two are used. The retransmission symbol is used for interference cancellation, that is, the influence of the two symbols detected in step S10 is eliminated from the received signal of the initial transmission slot by the following equation (7): Surge u): r(1)-slightly ') (7) ϋ where H^} represents the resulting matrix (Resulting Matrix) formed by taking the 〆 to / column of the matrix 舻. S(10)=[4^ is the decision symbol vector, the element of the matrix comes from step H) and the output of equation (6).仏) indicates the received signal vector 0 in the initial transmission time slot after interference cancellation for &&& then, in step 12, the remaining signal in the received signal except for & The symbol is detected. False μ ^ version sighs the detection of s in step 1〇 is correct, ie ή = Α and = s right 2 2 about the remaining two symbols 5 and the signal model of the interference cancellation of the heart can be 3: X directly "lower equation (8) got r

Su)=H^:4}s(3,4)+n (1) 118607.doc (8) • 13 · 200835212 where s(3,4) -. Equation (8) is also equivalent to a signal model of a two-shot multi-element (Han) receiving spatial multiplexing system. Therefore, the traditional linear spatial multiplexing detection algorithm can be directly used. Taking the MMSE algorithm as an example, the symbols 7 and the two retransmissions are obtained by the following equations (9) and (1):

;(3,4)=[安3Λ]Γ =(H >{3:4} Γττ(1) η:,{3:4} ί) ι •>{3:4} r(l) l /C(l,2) (9) KQ{sn\ ^ = 3,4 Left (10) f ί Subsequently, in step 13, the detected residual symbols are used for interference cancellation, that is, by the following equation ( 11) Eliminating the influence of the two remaining symbols detected in step S12 from the received signal of the initial transmission slot. 01) Asthma 3,4〆)-Heart (10) where s(3,4)=g^]r is the decision symbol vector, and the matrix element is derived from the output of Equation (6). r>c)(34) indicates the received signal vector in the initial transmission slot after interference cancellation for 4 and \. Finally, in step 14, the two retransmitted symbols are again detected to eventually recover all transmitted symbols. Suppose that the detection of the seven and the correctness in step 丨3 is correct, that is, &= seven and Mao=~, and the signal model of the two retransmission symbols & 2's interference cancellation can be directly from the following equation (ί 2) get: ^ τ (12) where S(l,2) . According to equations (12) and (7), after a simple conversion, the equivalent model of the symbol ^ and the heart can be established by the following equation (13): 118607.doc -14- (13) 200835212 Which is included in the initial plug And the equivalent receiving vector of the influence of seven. Round and retransmission time slot Η (1,2) 屺) ι,ζ h(1) nNRa - 纪2)* r\2 gas 1 -Hr a (14) The equation (14) is the corresponding equivalent of the corresponding system Noise vector/car In addition, the wide signal model can be used with the =, and the detection of & can use the following two methods: Ο The first method of debt measurement is the general detection method. Since the equation ((7) is equivalent to a two-transmission multi- (Nr) receiving spatial multiplexing system in the matrix expression form, it can be directly used to compare with traditional linear space-resolved guessing calculations such as ZF or MMSE. The general detection method of the algorithm. Take the singularity method as an example. ' & & & is obtained by the following equations (15) and (10): Qingyi 12 (10) The first detection method is Linear Alam〇uti decoding method. When the Mjm〇 channel changes slowly enough, the initial transmission and retransmission channel gains can be approximately considered to be the same, ie 118607.doc -15- (17) 200835212 m = mn:=zl,2 ""4 The equivalent channel matrix in the model shown in equation (13), - "1" and the two-emission (NR) receiving Alamouti STBC system have the same form. Therefore ^ according to the following equations (18) and (19) Using linear Aiam〇uti solver, it can achieve better detection performance with very low complexity.

U \12)卿, where /TTSIOW \J π = 1,2 "o-j/ow n(l,2)

△〇,2)= ΣΣι u (18) (19) (20) (21) FIG. 3 shows a structural diagram of a transceiver using an embodiment of the PSTBC-HARQ method of the present invention, for the purpose of simplicity and clarity, other transceivers Modules not directly related to the I invention are not shown in the figure. For the initial transmission transmitter, the information bits of the input signal are processed by Cyclic Redundancy Check (CRC) protection/channel chirping device ιι〇, interleaver 120 and modulation unit 130. The Π 燮 Π Π 唬 唬 唬 唬 唬 唬 唬 唬 唬 唬 唬 唬 唬 唬 唬 唬 唬 唬 唬 唬 唬 唬 唬 唬 唬 唬 唬 140 140 140 140 140 140 140 140 140 140 140 140 140 140 140 140 140 140 140 140 140 140 140 140 The transmission is performed, that is, spatially multiplexed. At the receiver end, it is assumed that the channel state information has been obtained, and the spatially multiplexed signal is separated by the spatial multiplexing detecting unit 220 (using an algorithm such as ZF or MMSE), and then demodulated in turn. The processing of the variable unit 240, the deinterleaver 250, and the CRC verification/channel decoder 260 recovers the transmitted data. Based on the CRC verification results, the corresponding acknowledgment information (ACK/NACK) is sent back to the transmitter to determine if the transmitter is required to retransmit the data. When for some reason, such as a channel missing rank, the rank of the channel is reduced from 4 to 2 or 3, the receiver sends a NACK to the transmitter indicating that the initial transmission has an error. In this case, at the transmitter end, the modulated retransmission signal is sent to the PSTBC packet retransmission unit 160 via the switch 140, spatially multiplexed by the PSTBC packet retransmission unit 160, and then transmitted from the antenna. And at the receiver end, the receiving switch unit 210 sends the received retransmission signal to the PSTBC packet combining unit 230. The PSTBC packet combining unit 230 uses the retransmission signal to perform the 1C-based packet combining method or the general detecting of the present invention. Test method to recover the data of the initial transmission. Compared with the prior art, the complexity of the PSTBC-HARQ method and the apparatus of the multi-antenna system of the present invention is much lower than the complexity of the existing STBC-HARQ scheme, especially when the Alamouti detection method is adopted in step 14, the complexity is reduced. It is obvious. Compared with the non-STBC-HARQ scheme, although the complexity of the present invention is slightly higher, the increase in complexity can bring about a significant performance improvement.

In addition, the existing STBC-HARQ scheme (especially the Double-STTD HARQ 118607.doc 17 200835212 scheme) needs to retransmit 4 symbols, and the present invention only needs to retransmit 2 symbols, thereby reducing the power loss during retransmission. Therefore, the present invention is more attractive for wireless transmission systems having high performance and low complexity requirements. The above embodiments are only described with respect to the present invention for a system having four transmit antennas, but it is apparent that the present invention is equally applicable to a system having more than four transmit antennas.

It should be noted that the above-described embodiments are intended to be illustrative, not limiting, and that the multi-antenna V: PSTBC-HARQ method and apparatus disclosed in the above-described present invention should be understood by those skilled in the art without departing from the scope of the appended claims. Various modifications may be made without departing from the scope of the invention. Accordingly, the scope of the invention should be determined by the scope of the appended claims. In addition, any reference signs in the scope of the claims should not be construed as limiting the scope of the claims. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram showing the basic operation of a partial space block code (PSTBC) HARQ method for transmitting symbols of the present invention. FIG. 2 shows a packet group executed by a receiver of the present invention. Flowchart; 'σ Figure 3 is a block diagram of a transceiver in accordance with one embodiment of the present invention. In the accompanying drawings, the same reference numerals indicate similar or equivalent. [Main component symbol description] 110 CRC/channel encoder 118607.doc • 18- 200835212 120 interleaver 130 modulation unit 140 switch 150 spatial multiplexing unit 160 PSTBC packet retransmission unit 210 receiving switch unit 220 spatial multiplexing detection unit 230 PSTBC packet combining unit (240 demodulation unit 250 deinterleaver 260 CRC/channel decoder 118607.doc -19-

Claims (1)

200835212 X. Patent application scope: A hybrid automatic repeat request method for a passenger machine, and an antenna system transmitter, comprising the following steps: The symbol to be transmitted in winter is transmitted via the corresponding antenna channel; b• obtaining a corresponding feedback information And C. The right feedback information indicates that retransmission is required, then only two numbers are retransmitted, and some symbols in the symbol transmitted by the patchy-four step a constitute an Alamouti code word. The method of claim 1, wherein the multi-antenna system is a four-transmit antenna system, and the transmission in step a transmits four symbols simultaneously in one time slot via four transmit antennas. 3. The method of claim 2, wherein the retransmission in step c transmits two symbols in one time slot by two of the transmit antennas, respectively. 4. The method of claim 1, wherein the feedback information comprises an acknowledgment/non-acknowledgment signal to indicate whether the symbol transmitted in step a is successfully received. 5. A hybrid automatic repeat request method for a multi-antenna system receiver, comprising the steps of: a. receiving a transmission symbol by means of a corresponding antenna channel; b) issuing a corresponding feedback information according to the received transmission symbol; c • The right feedback guest indicates that retransmission is required, and two retransmitted symbols are received, wherein the two retransmitted symbols and the partial symbols in the transmitted symbol form an Alamouti codeword; d· according to the received transmission symbol And retransmit the symbol to restore the corresponding data. 118607.doc 200835212 6. The method of claim 5, wherein the pass symbol comprises, as in the method of claim 6, the two symbols are entered. Wherein the multi-antenna system is four symbols of the four transmission antennas in the time slots of the transmission. The retransmission symbol is a method for transmitting the monthly item 5 in a time slot. The feedback information includes the confirmation/wanhu, and the U 4匕 is used to indicate whether the transmission symbol is successfully received. Acknowledgement 9. The method of claim 5 The following steps: Where the recovery of the corresponding data in step d includes d 1 · detecting the two retransmission symbols; d2·using the detected two retransmission symbols to perform interference cancellation on the transmission symbols; d3· detecting the transmission symbols based on the interference cancellation, and detecting the two Retransmitting the remaining symbols except the two symbols corresponding to the symbol; • performing interference cancellation on the transmitted symbols processed in step d2 by using the detected residual symbols; and d5·using the transmitted symbols and retransmitting symbols to eliminate interference The packet combination 'detects two retransmission symbols again. 10. The method of claim 9, wherein in step d5, the two retransmitted symbols are re-detected using a linear Aiam〇utiw code method. 11. A transmitter for a multi-antenna system, comprising: a spatial multiplexing unit for transmitting symbols to be transmitted via respective antenna channels; a packet retransmission unit for retransmission and transmission of the symbols The partial symbols form two symbols of an Alamouti code word; and 118607.doc 200835212 - a switch single it 'is used to control the packet retransmission unit for symbol retransmission according to the obtained corresponding feedback information. 12. The transmitter of claim 11 includes four transmit antennas, and the spatial multiplexing unit further transmits four symbols simultaneously by four transmit antennas in one time slot. U. The transmitter of claim 12, wherein the packet retransmission unit transmits the two retransmission symbols in one time slot by two of the transmit antennas, respectively. 14. A receiver for a multi-antenna system, comprising: Γ a spatial multiplexing debt measuring unit for receiving transmission symbols via respective antenna channels and generating a corresponding feedback information based on the received transmission symbols; and a packet combining unit For receiving two retransmitted symbols, and recovering corresponding data according to the received transmission symbol and the retransmitted symbol, wherein the two retransmitted symbols and the partial symbols in the transmitted symbol form an AlamoutU| word; A receiving switch unit is configured to send the received retransmission symbol to the packet combining unit when the feedback information indicates that retransmission is required. 15. The receiver of claim 14, wherein the multi-antenna system is a four-transmit antenna system, the initial transmission symbol comprising four symbols transmitted in one time slot. 16. The receiver of claim 15, wherein the retransmission symbol is two symbols transmitted in one time slot. 17. The receiver of claim 14, wherein the feedback information comprises an acknowledgment/non-acknowledgement signal to indicate whether the symbol of the transmission was successfully received. 118607.doc