CN101183919B - Self-adaptive mixture automatic request retransmission method - Google Patents

Abstract

The invention discloses a combined hybrid automatic repeat request (HARQ) method, belonging to the field of wireless communication technology, aiming to effectively reduce the signal error rate, reduce retransmission number and increase throughout rate. The utility model is characterized that: a data transmission link is established between the sending end and the receiving end, the channel coding and the space-time coding structure are cascade connected; wherein, the number of the transmitting antenna at the sending end M is larger than one, M constellations or M kinds of bit sequence are stored at the sending end and the receiving end; one constellation is mapped or a bit sequence is rearranged and then mapped on a fixed constellation before each retransmission; then space-time coding is done according to a space-time coding structure; finally soft information combination and iterative decoding is done at the receiving end. The utility model has an advantage that the antenna diversity gain and the bit-symbol mapping diversity gain can effectively reduce the retransmission number and optimize system performance.

Description

A combined hybrid automatic request retransmission method

technical field

The invention belongs to wireless communication technology, in particular to a combined hybrid automatic request retransmission method in a multi-antenna system.

Background technique

The wireless communication system expects to obtain higher data transmission rate and higher reliability. However, the multipath fading characteristics of the wireless channel limit the performance of the system. The space-time code is a multi-antenna technology that can effectively resist multi-path fading. It can be roughly divided into two categories: one is space-time codes based on space diversity, commonly used space-time trellis codes (STTC) and space-time block codes (STBC); the other is space-time codes based on space multiplexing , there is layered space-time code (BLAST). Channel coding (such as LDPC, TURBO code) can obtain good error performance through bit interleaving and iterative decoding. Even so, wireless communication systems still need an Automatic Repeat Request (ARQ) protocol to ensure reliable transmission of data packets.

Hybrid Automatic Repeat Request (HARQ) technology makes full use of the useful information in the retransmitted codewords, and combines these useful information in different ways, thereby effectively reducing the number of retransmissions, and the system can obtain better performance than traditional ARQ. performance. On the one hand, HARQ can almost guarantee the error-free transmission of data, on the other hand, HARQ will greatly reduce the capacity of the system. Therefore, it will be very effective and meaningful to consider combining Hybrid Automatic Repeat Request (HARQ) with Multiple Input Multiple Output (MIMO).

In wireless communication, in order to support higher rate transmission, it is necessary to use high spectral efficiency modulation technology. With the in-depth research on high spectral efficiency communication systems, various non-adaptive and adaptive high-order quadrature amplitude modulation (MQAM) techniques are widely valued in wireless communication. However, since MQAM modulation provides different error protection for different bits of modulation symbols, the data output after demapping at the receiving end has unequal reliability, which will reduce the error correction performance of Turbo codes for decoding data with the same reliability. Japan Matsushita Electronics Industry Co., Ltd. filed an international patent application WO 02067491 titled "Hybrid ARQ Method with Different Constellation Rearrangement" on August 29, 2002, and invented a signal constellation for HARQ systems with 16QAM and 64QAM modulation modes. The HARQ scheme of graph rearrangement proposes several different uniform constellation diagrams of bit-to-symbol mapping according to the unequal error protection characteristics of QAM modulation, and uses different constellation diagrams for modulation mapping and demapping in transmission and retransmission, or Corresponding rearrangement and de-rearrangement are performed on the bits, so that the data sent to the input end of the Turbo decoder after retransmission and combination at the receiving end has the same reliability, and the throughput rate of the HARQ system is improved. This method can improve the efficiency of decoding, thereby reducing the error rate. However, this retransmission combination mechanism is based on chase combination, that is, the same symbol is used for each retransmission, and it is useless to make full use of the diversity gain of multiple antennas.

Contents of the invention

The invention provides a combined hybrid automatic request retransmission method, aiming to effectively reduce the error rate of symbols, thereby reducing the number of retransmissions and improving the throughput rate of the system.

A combined hybrid automatic request retransmission method of the present invention establishes a data transmission link between the sending end and the receiving end, the number M of transmitting antennas at the sending end is greater than 1, and the sending end and the receiving end store M constellation diagrams or M bit arrangements order, perform the following steps:

(1) The sender prepares new data, performs error detection coding, channel coding, and bit interleaving on the data in sequence, stores them in the sending buffer, and initializes the number of NACKs to 0;

(2) If the sender receives the ACK, release the current data from the buffer area, and go to step (1); otherwise, go to step (3);

(3) The sending end sets the transmission sequence number N=NACK number+1;

(4) For the Nth transmission at the sending end, if the transmission sequence number N is greater than the number of transmitting antennas M, go to step (5); otherwise, select the Nth constellation from the constellation stored at the sending end, and store it in the sending buffer The bit sequence is mapped, or the Nth bit sequence is selected from the bit sequence stored at the sending end, and the bit sequence stored in the sending buffer is rearranged before performing fixed constellation map mapping; The Nth column of the orthogonal space-time code array encodes, sends data packets, and turns to step (6);

(5) The sending end performs a modulo operation on N to M, updates the N value, and turns to step (4);

(6) The receiving end receives the data and performs MIMO detection;

(7) The receiving end selects the Nth constellation diagram that is consistent with the sending end for demapping, or restores the bit sequence and then performs fixed constellation diagram mapping to obtain the current bit soft information, that is, the log likelihood ratio, and store it in In the receiving buffer area, and merged with all previously stored bit soft information;

(8) The receiving end performs iterative decoding using all the combined bit soft information;

(9) The receiving end performs error checking on the decoded information, if correct, proceed to step (10), otherwise turn to step (11);

(10) The receiving end feeds back ACK to the sending end, and turns to step (2);

(11) The receiving end feeds back NACK to the sending end, and then go to step (2).

The combined HARQ method is characterized in that the M constellation diagrams are uniform constellation diagrams of Gray-coded high-order quadrature amplitude modulation and the rearranged M- 1 constellation diagram, the selection rule of the M-1 constellation diagrams is: in all the constellation diagrams after the rearrangement of the uniform constellation diagrams based on Gray coded high-order quadrature amplitude modulation, select M-1 constellation diagrams, which can Make the soft information combination value difference between each bit mapped to the M constellation diagrams the smallest, that is, the reliability difference is the smallest; the M kinds of bit arrangement order, in order to fully arrange the original bit arrangement order, select M The order of bit arrangement makes the difference of soft information combination value between each bit the smallest, that is, the difference of reliability is the smallest.

The hybrid automatic request for retransmission method of a kind of combination is characterized in that, the fixed constellation diagram described in the step (4) and the step (7) is the uniform constellation diagram of the high-order quadrature amplitude modulation of Gray coding .

The present invention uses the space-time code structure based on diversity gain as internal coding, combines constellation rearrangement and channel coding, and at the same time performs symbol rearrangement on the antenna and rearrangement between bits for the transmission data, so that two aspects can be obtained Gain, using the combined soft information value for iterative decoding can effectively reduce the number of retransmissions and optimize system performance.

Description of drawings

Fig. 1 is a block flow diagram of the present invention;

Figure 2(A)-Figure 2(D) are four types of constellation diagrams of 16QAM modulation;

Fig. 2 (A) is constellation diagram 1;

Fig. 2 (B) is constellation diagram 2;

Fig. 2 (C) is constellation diagram 3;

Figure 2(D) is the constellation diagram 4.

Detailed ways

The example adopted by the present invention is: a MIMO system with 4 transmitting antennas and 4 receiving antennas, the channel coding adopts Turbo code, the modulation mode adopts 16QAM, and the space-time code adopts the commonly used ABBA type quasi-orthogonal code structure.

The code array structure of the quasi-orthogonal code of the ABBA type is as follows:

$\left(\begin{array}{cccc}{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}& {<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{<span\; class="notranslate">\; *</span>}& {\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}& {<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}^{<span\; class="notranslate">\; *</span>}\\ {\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}& {\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; *</span>}& {\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}& {\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}^{<span\; class="notranslate">\; *</span>}\\ {\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}& {<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}^{<span\; class="notranslate">\; *</span>}& {\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}& {<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}^{<span\; class="notranslate">\; *</span>}\\ {\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}& {\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}^{<span\; class="notranslate">\; *</span>}& {\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}& {\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; *</span>}\end{array}\right)<span\; class="notranslate">\; \&CenterDot;</span>$

The ABBA-type space-time code has an M×p matrix structure, where M is the number of transmitting antennas, and p is the number of symbol time slots. Each column of the matrix corresponds to the symbol vector transmitted on each symbol slot, and each row corresponds to the transmitted symbol on each transmit antenna.

Select the 4 constellation diagrams or 4 kinds of bit arrangement sequences stored at the sending end and the corresponding space-time code columns as shown in Table 1. Figure 2(A) to Figure 2(D) are the 4 constellation diagrams of 16QAM modulation; here The fixed constellation diagram used in the example is shown in Fig. 2(A). In these four constellation diagrams, map every 4 bits c _i1 c _i2 c _i3 c _i4 into a 16QAM complex symbol z={z _I , z _Q }, z _I , z _Q ∈{±Δ ₁ ,± Δ ₂ }, where ${\mathrm{\&Delta;}}_1^2+{\mathrm{\&Delta;}}_2^2=1,$ Δ ₂ =2Δ ₁ . z _I is mapped by the two bits c _i1 c _i3 sent to the I way, and z _Q is mapped by the two bits c _i2 c _i4 sent to the Q way. As shown in Figure 2(A), in bit sequence 1011, bit 11 is mapped to -Δ ₂ , bit 01 is mapped to Δ ₂ , then 1011 is mapped to complex symbol -Δ ₂ +jΔ ₂ , similarly, bit 0001 is mapped to Complex number symbol Δ ₁ +jΔ ₂ . According to the above rules, each constellation maps 16 4-bit bit sequences into 16 complex symbols.

Table 1: Sending end rearrangement mode and space-time coding mode (16QAM)

(c_ij为0或1)为取反运算。第1种比特排列顺序为c_i1c_i2c_i3c_i4；第2种比特排列顺序为 

第3种比特排列顺序为c_i3c_i4c_i1c_i2；第4种比特排列顺序为 

整个系统工作流程如图1所示：This example will be described in detail below by adopting bit rearrangement. It is assumed that the original order of bits is c _i1 c _i2 c _i3 c _i4 ,

(c _ij is 0 or 1) is the negation operation. The first bit arrangement order is c _i1 c _i2 c _i3 c _i4 ; the second bit arrangement order is

The third bit arrangement order is c _i3 c _i4 c _i1 c _i2 ; the fourth bit arrangement order is

The workflow of the whole system is shown in Figure 1:

(1) The sender prepares new data, performs error detection coding, channel coding, and interleaving in sequence, and stores them in the buffer area. Note that the bit sequence stored in the buffer area is C=(c ₁₁ , c ₁₂ , c ₁₃ , c ₁₄ , c ₂₂ , c ₂₃ , c ₂₄ , ...), divide each 4 information bits into a group, and record a binary symbol as c ₁ =c ₁₁ c ₁₂ c ₁₃ c ₁₄ .

(2) If the sender receives the ACK, release the current data from the buffer area, and go to step (1); otherwise, go to step (3);

(3) The sending end sets the transmission sequence number N=NACK number+1;

(4) For the Nth transmission at the sending end, if the transmission sequence number N is greater than 4, go to step (5); if N=1, select the first bit arrangement method, that is, according to the original bit arrangement order c ₁ =c ₁₁ c ₁₂ c ₁₃ c ₁₄ After the fixed constellation map is mapped, encode according to the first column of the space-time code array; if N=2, rearrange the bit sequence as $c_1^{\&prime;}=c_{13}{c}_{14}\stackrel{\&OverBar;}{c_{11}{c}_{12}},$ After performing fixed constellation map mapping, encode according to the second column of the space-time code array; if N=3, rearrange the bit sequence as c ₁ ″=c ₁₃ c ₁₄ c ₁₁ c ₁₂ , after performing fixed constellation map mapping, Encode according to the third column of the space-time code matrix; if N=4, rearrange the bit sequence as $c_1^{\&prime;\&prime;\&prime;}=c_{11}{c}_{12}\stackrel{\&OverBar;}{c_{13}{c}_{14}},$ After performing the fixed constellation map mapping, encode according to the fourth column of the space-time code array, send data, and turn to step (6);

(5) The sending end performs a modulo operation on N to 4, updates the N value, and turns to step (4);

(6) The receiving end receives the data and performs MIMO detection. The detection method is as follows:

Remember the first transmission code vector ${\stackrel{\&Right\; Arrow;}{x}}_1={(x_1,x_2,x_3,x_4)}^T,$ The channel coefficient matrix is denoted as H=(h ₁ , h ₂ , h ₃ , h ₄ ), where h _i is a column vector of dimension n _R (the number of receiving antennas), the noise is denoted as v, and the receiving vector is ${\stackrel{\&Right\; Arrow;}{r}}_1=h{\stackrel{\&Right\; Arrow;}{x}}_1+v_1,$ Detection is performed using methods such as ordered serial interference cancellation (OSIC). Remember the second transmission code vector ${\stackrel{\&Right\; Arrow;}{x}}_2={(-x_2^{*},x_1^{*},-x_4^{*},x_3^{*})}^T,$ The receiving vector is denoted as ${\stackrel{\&Right\; Arrow;}{r}}_2=h{\stackrel{\&Right\; Arrow;}{x}}_2+{\mathrm{<figure-callout\; id="2"\; label="v"\; filenames="S200710168493XE00031.png"\; state="\{\{state\}\}">v</figure-callout>}}_2\&Center\; Dot;$

${{\stackrel{\&Right\; Arrow;}{r}}_2}^{*}=(-{\mathrm{<figure-callout\; id="2"\; label="h"\; filenames="S200710168493XE00031.png"\; state="\{\{state\}\}">h</figure-callout>}}_2^{*}{h}_1^{*}-h_4^{*}{h}_3^{*})\left(\begin{array}{c}{x}_1\\ x_2\\ x_3\\ x_4\end{array}\right)+v^{\&prime;}$ (1)

remember ${\stackrel{\&Right\; Arrow;}{r}}^{\&prime;}={{\stackrel{\&Right\; Arrow;}{r}}_2}^{*},$ $h^{\&prime;}=(-{\mathrm{<figure-callout\; id="2"\; label="h"\; filenames="S200710168493XE00031.png"\; state="\{\{state\}\}">h</figure-callout>}}_2^{*}{h}_1^{*}-h_4^{*}{h}_3^{*}),$

Then formula (1) is transformed into

${\stackrel{\&Right\; Arrow;}{r}}^{\&prime;}=h^{\&prime;}\stackrel{\&Right\; Arrow;}{x}+v^{\&prime;},$ (2)

So far, methods such as OSIC can be used to detect (2) formula.

The detection methods for the third and fourth transmissions can be deduced in the same way.

The number of transmissions N>4, the received vector of this time and the received vector of the N=N mod 4th transmission are chased and merged, and then detected by OSIC and other methods.

(7) The receiving end recovers the order of the bits and then uses the fixed constellation diagram map to obtain the current bit soft information, that is, the logarithmic likelihood ratio, and stores it in the receiving buffer area, and merges it with all previously stored bit soft information;

(8) The receiving end uses the combined bit soft information to perform iterative decoding, and the iterative decoding method is described as follows:

The bit soft information obtained by combining all retransmissions is denoted as L(d), and the bit soft information output to the buffer after bit interleaving is denoted as L _a (d), then the buffer area outputs L _e (d)=L(d)- L _a (d), convert the output soft information through parallel to serial conversion, and after deinterleaving, get L _a (c), output L _a (c) to the channel decoder, and get new bit soft information L(c) , after L _e (c) = L (c) - L _a (c) is interleaved, serial-to-parallel conversion is performed to obtain L _a (d), which is input into the buffer area for the next iteration. When the number of iterations is reached, the channel decoder outputs hard decision information L(b).

(9) The receiving end performs error checking on the decoded output information, if correct, proceed to step (10), otherwise turn to step (11);

(10) The receiving end feeds back ACK to the sending end, and turns to step (2);

(11) The receiving end feeds back NACK to the sending end, and then go to step (2).

Claims (3)

1. A combined hybrid automatic request retransmission method. A data transmission link is established between the sending end and the receiving end. The number of transmitting antennas M at the sending end is greater than 1. The sending end and the receiving end store M constellation diagrams or M kinds of bit arrangements. , perform the following steps: (1) The sender prepares new data, performs error detection coding, channel coding, and bit interleaving on the data in sequence, stores them in the sending buffer, and initializes the number of NACKs to 0; (2) If the sender receives the ACK, release the current data from the buffer area, and go to step (1); otherwise, go to step (3); (3) The sending end sets the transmission sequence number N=NACK number+1; (4) For the Nth transmission at the sending end, if the transmission sequence number N is greater than the number of transmitting antennas M, go to step (5); otherwise, select the Nth constellation from the constellations stored at the sending end, and compare the bits stored in the sending buffer sequence, or select the Nth bit sequence from the bit sequence stored at the sending end, rearrange the bit sequence stored in the sending buffer, and then perform fixed constellation map mapping; The Nth column of the space-time code array handed in encodes, sends data packet, turns step (6); (5) The sending end performs a modulo operation on N to M, updates the N value, and turns to step (4); (6) The receiving end receives the data and performs MIMO detection; (7) The receiving end selects the corresponding Nth constellation diagram for demapping, or restores the bit sequence and then performs fixed constellation diagram mapping to obtain the current bit soft information, that is, the logarithmic likelihood ratio, and store it in the receiving buffer area , and merge with all previously stored bit soft information; (8) The receiving end performs iterative decoding using all the combined bit soft information; (9) The receiving end performs error checking on the decoded information, if correct, proceed to step (10), otherwise turn to step (11); (10) The receiving end feeds back ACK to the sending end, and turns to step (2); (11) The receiving end feeds back NACK to the sending end, and then go to step (2). 2. A kind of hybrid automatic retransmission method of combination as claimed in claim 1, it is characterized in that, described M constellation diagrams are the uniform constellation diagrams of high-order quadrature amplitude modulation of Gray coding and carry out on this basis The M-1 constellation diagrams after rearrangement, the selection rule of the M-1 constellation diagrams is: in all the constellation diagrams after the rearrangement of the uniform constellation diagrams based on Gray coded high-order quadrature amplitude modulation, select M- 1 constellation diagram, which can minimize the difference of the soft information combination value between each bit mapped to the M constellation diagrams, that is, the reliability difference is the smallest; the M kinds of bit arrangement order are the original bit arrangement order Full permutation, from which M kinds of bit permutation sequences are selected, so that the difference in the combined value of soft information between each bit is the smallest, that is, the difference in reliability is the smallest. 3. a kind of hybrid automatic retransmission method of combination as claimed in claim 1, is characterized in that, the fixed constellation diagram described in described step (4) and step (7) is the high-order orthogonality of Gray coding Uniform constellation diagram for amplitude modulation.

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