Bit mapping method for improving overall performance of MIMO and channel coding system

Abstract

The invention provides a bit mapping method for improving the overall performance of an MIMO and channel coding system, and the method comprises the steps: S1, carrying out the channel estimation, and obtaining the channel feedback information, which comprises a rank indication RI, an average CQI, and a bit mapping indication BMI; s2, determining a modulation mode based on the average CQI, determining the number of data streams based on a rank indication (RI), and determining the number of bit streams of bit mapping based on the modulation mode and the number of data streams; s3, determining the priority of bit mapping of the bit streams based on the bit mapping indication BMI and the number of the bit streams of the bit mapping; s4, performing channel coding on the original information bits according to a coding rate specified by the average CQI, and reordering the information bits after channel coding according to importance; and S5, performing bit mapping on the reordered information bits according to the priority of bit mapping of the bit stream. According to the invention, the best resource is allocated to the bit with high importance in the information bits after channel coding, the optimization of system resource allocation is realized, and the transmission performance of the system is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of wireless mobile communication, and in particular, to a bit mapping method. Background Art

[0002] In multiple-input multiple-output (MIMO) technology and massive MIMO technology, with the transmit power and spectrum resources remaining unchanged, by configuring multiple antennas at the transmitting and receiving ends, multiple data streams can be transmitted in parallel between the transmitting and receiving ends, thereby doubling the system transmission rate. Since MIMO technology and massive MIMO technology can effectively achieve higher spectral efficiency and data transmission rate to meet the exponential growth of communication, MIMO technology is still regarded as one of the key technologies for the 6th generation of mobile communication.

[0003] In the process of signal transmission in wireless communication, various interferences and noises will inevitably be encountered, resulting in errors in the transmitted data. Channel coding, that is, error control coding, aims to detect and correct errors at the receiving end by adding redundant information. Channel coding is an important part of wireless communication, and its application can effectively improve the quality of signal transmission. Since channel coding adds redundant bit information on the basis of the original bit information, the importance of each bit information after channel coding is different. Generally, for a systematic code, the importance of the original bit information in the front among the coded bits is higher than that of the redundant information in the back. In addition, the code weights of different bits are also different, and the importance of a bit with a larger code weight is higher than that of a bit with a smaller code weight. During the transmission of coded information, if the transmission quality of the bits with greater importance can be guaranteed first, the transmission performance of the system will be greatly improved.

[0004] MIMO and massive MIMO systems support the simultaneous transmission of multiple data streams through spatial multiplexing. It should be noted that the transmission performances (bit error rates) of different data streams are different. The invention patent with the publication number CN101072062B discloses a method for transmitting signals in a multiple-input multiple-output (MIMO) communication system. In this method, first, an input information data stream is encoded into a codeword using a coding scheme, and then, according to the channel quality information (CQI) of each antenna received from the receiving device, the antennas to be used by the signal transmitting device are determined and MIMO mapping is used. MIMO mapping assigns coded bits with different importance levels to transmitting antennas with different transmission performances and generates mapped symbols. After MIMO mapping, the modulator modulates the mapped symbols into modulated symbols, and finally, the transmitter transmits the modulated symbols through the determined transmitting antennas.

[0005] Although this technology can improve performance by allocating coding bits with high importance to transmit antennas with good transmission performance through MIMO mapping, this operation requires the receiving end to feedback the CQI information of each transmit antenna respectively and perform the mapping operation in the order of their CQI magnitudes. Therefore, the amount of feedback required by this scheme is extremely large, and the feedback channel can hardly bear it.

[0006] In addition, this method does not consider that the transmission performances of the respective bits included in the high-order modulation symbols (such as 16QAM, 64QAM, and 256QAM) are also different (the bit error rates are different), which will cause some bit information transmitted by the antenna with good transmission performance to be worse than some information transmitted by the antenna with poor transmission performance, that is, the transmission quality of the bit streams between data streams is uncertain, thus degrading the overall performance. In order to truly allocate the bits with high importance in the information bits after channel coding to the data streams with good transmission performance, the different transmission performances of the respective bits included in the QAM modulation symbols should be considered.

[0007] In the existing 5G system, such as Figure 2 In the MIMO system under high-order modulation shown, after the original information bits pass through channel coding (such as turbo code / polarization code / LDPC code), they need to be specially designed for bit interleaving and then perform QAM modulation. Bit interleaving can make the bits with high importance in the information bits after channel coding be allocated to positions with good transmission performance for transmission, thus improving the performance of the system. Since both MIMO and massive MIMO can support parallel transmission of multiple data streams, the modulated information symbols need to be serially-parallel converted according to the number of data streams to be transmitted to obtain multiple parallel QAM symbols. These QAM symbols need to be precoded before transmission. The precoding maps multiple QAM symbols to each transmit antenna, and finally the signals are sent out through these antennas.

[0008] In the existing 5G system, considering that the transmission performances of the respective bits included in the QAM modulation symbols are different (the bit error rates are different), bit interleaving is used to make the bits with high importance in the information bits after channel coding be allocated to positions with good transmission performance for transmission, improving the transmission performance. It should be noted that the transmission performances (error rates) of different data streams in the MIMO and massive MIMO systems are also different. The existing 5G system does not consider this point when allocating resources to the bits with high importance in the information bits after channel coding. This will result in the resources allocated to the bits with high importance in the information bits after channel coding by the original scheme not being the best, and may even be worse than the resources of unimportant bits, thus making the performance of the entire system not reach the optimal. Summary of the Invention

[0009] In view of the technical problem that the existing technology cannot reasonably allocate resources while considering the performance differences of different data streams in MIMO and different bits in high-order modulation, resulting in insufficient system transmission performance, the present invention proposes a bit mapping method for improving the overall performance of MIMO and channel coding systems. Considering different modulation methods, through bit mapping, the performance differences of different data streams in the MIMO system and the different transmission performances of each bit in high-order digital modulation are comprehensively considered, and the best resources are allocated to the bits with greater importance in the information bits after channel coding, realizing the optimization of system resource allocation and improving the system transmission performance.

[0010] To achieve the above object, the technical solution of the present invention is implemented as follows:

[0011] A bit mapping method for improving the overall performance of MIMO and channel coding systems, including the steps of:

[0012] S1: Perform channel estimation and obtain channel feedback information, including rank indicator RI, average CQI, and bit mapping indicator BMI;

[0013] S2: The transmitting end determines the modulation method based on the average CQI, determines the number of data streams based on the rank indicator RI, and determines the number of bit streams for bit mapping based on the modulation method and the number of data streams;

[0014] S3: Determine the priority order of bit mapping of bit streams based on the bit mapping indicator BMI and the number of bit streams for bit mapping;

[0015] S4: The transmitting end performs channel coding on the original information bits according to the coding rate specified by the average CQI, and reorders the information bits after channel coding according to importance;

[0016] S5: The transmitting end performs bit mapping on the reordered information bits according to the priority order of bit mapping of bit streams:

[0017] S6: The transmitting end performs digital modulation on the information bits after bit mapping, and transmits the modulated signal through multiple transmitting antennas after precoding.

[0018] The rank indicator RI is used to indicate the number M of data streams transmitted by MIMO; the average CQI is used to indicate the average signal-to-noise ratio of M data streams, as well as the modulation method and channel coding rate that can be supported under the average signal-to-noise ratio; the bit mapping indicator BMI is used to indicate the information on the transmission performance of each data stream and the bit mapping method required by the bit mapping method for improving the overall performance of MIMO and channel coding systems;

[0019] The number of bit streams is M×S, where S represents a multiple parameter determined by the modulation method.

[0020] The calculation method of the average CQI is as follows: obtain the channel matrix H, the precoding matrix C, and the noise variance σ according to channel estimation 2 , and the number M of data streams;

[0021] Use the channel matrix H and the precoding matrix C to calculate the equivalent channel matrix of M data streams

[0022] According to the equivalent channel matrix and the noise variance σ 2 , calculate the signal-to-noise ratio of each data stream;

[0023] According to the signal-to-noise ratio of each data stream, calculate the average signal-to-noise ratio of M data streams:

[0024]

[0025] where erfcinv(·) is the inverse function of the erfc(·) error function, and SINR i represents the signal-to-noise ratio of the i-th data stream;

[0026] According to the average signal-to-noise ratio SINR_ave, obtain the modulation method and the code rate of the channel coding corresponding to the highest transmission rate that M data streams can support.

[0027] The bit mapping indicator BMI mentioned above includes BMI1 information and BMI2 information; the BMI1 information is used to indicate the sorting of each data stream from high to low according to the transmission performance under the high-order modulation method and the low-order modulation method; the BMI2 information is used to indicate the method of performing bit mapping under the high-order modulation method, and the method of performing bit mapping includes performing bit mapping in the order of the transmission performance of the data streams and performing bit mapping in the order of the transmission performance of each bit stream that requires high-order modulation.

[0028] The indication method of the BMI1 information is as follows:

[0029] Obtain the signal-to-noise ratio of M data streams through channel estimation, and sort the signal-to-noise ratio of M data streams to determine the high and low order of the transmission performance of M data streams;

[0030] If the transmission of an information bit after channel coding requires two data streams, use 1 bit in the feedback value of the BMI1 information to indicate the high and low of the transmission performance of the data streams;

[0031] If the transmission of an information bit after channel coding requires three data streams, use 4 bits in the feedback value of the BMI1 information to indicate the data stream with the best transmission performance and the second-best data stream;

[0032] If the transmission of information bits after channel coding requires four data streams, the feedback value of BMI1 information uses 4 bits to indicate the data stream with the best transmission performance and the second-best data stream.

[0033] The indication method of the BMI2 information is as follows:

[0034] a. Obtain the signal-to-noise ratios of M data streams through channel estimation, and calculate the equivalent signal-to-noise ratios of each bit stream according to the signal-to-noise ratios of the M data streams, where SINR i,j represents the equivalent signal-to-noise ratio of the j-th bit stream of the i-th data stream;

[0035] b. Calculate SINR 1,S 、SINR 2,S 、…SINR M-1,S The average SINR is denoted as SINR_ave1:

[0036]

[0037] c. Calculate SINR 2,1 、SINR 3,1 、…、SINR M,1 The average SINR is denoted as SINR_ave2:

[0038]

[0039] d. If SINR_ave1 > SINR_ave2, then BMI2 = 1, indicating that bit mapping is performed in the order of the transmission performance of each bit stream requiring higher-order modulation; if SINR_ave1 ≤ SINR_ave2, then BMI2 = 0, indicating that bit mapping is performed in the order of the transmission performance of the data streams.

[0040] The low-order modulation method is QPSK modulation. For QPSK modulation, the number of bit streams is equal to the number of data streams; the high-order modulation method is QAM modulation. For QAM modulation, the number of bit streams is a multiple of the number of data streams;

[0041] For QPSK modulation, the method for determining the priority order of bit mapping of bit streams based on BMI in step S3 is as follows:

[0042] If the number of data streams M ≤ 3, the BMI1 information indicates the priority order of bit mapping of all data streams from high to low in terms of transmission performance;

[0043] If the number of data streams M > 3, the BMI1 information indicates the two data streams with the best transmission performance and the priority order of bit mapping of these two data streams; the remaining data streams obtain the priority order of bit mapping according to the original data stream numbers during channel estimation.

[0044] For QAM modulation, the method for determining the priority order of bit mapping of the bit stream based on BMI described in step S3 is as follows:

[0045] S3.1. Determine the priority order of bit mapping of each data stream according to the BMI1 information;

[0046] S3.2. Determine the way of bit mapping according to BMI2:

[0047] If the BMI2 fed back by the channel is 0, perform bit mapping in the order of the transmission performance of the data streams: the priority order of all bit streams of the data stream with good transmission performance is higher than that of all bit streams of the data stream with low priority;

[0048] If the fed-back BMI2 = 1, perform bit mapping in the order of the transmission performance of each bit stream of QAM modulation: allocate the 1st to S bit streams in turn according to the priority order of the data streams.

[0049] The method for reordering the information bits after channel coding according to importance is as follows:

[0050] If the system uses non-systematic codes for channel coding, sort according to the code weight of the coded bits; if systematic codes are used for channel coding, the sorting method is:

[0051] According to the priority rule, place the original information bits after channel coding at the front of the sequence, and based on the code weight metric criterion, perform a descending order arrangement on the original information bits after channel coding;

[0052] According to the priority rule, arrange the redundant bits after channel coding in sequence after the original information bits, and based on the code weight metric criterion, perform a descending order arrangement on the redundant bits.

[0053] The method for performing bit mapping on the reordered information bits according to the priority order of bit mapping of the bit stream is as follows: for QPSK modulation, the reordered information bits b 0 、b 1 、……b K-1 are allocated to the corresponding data streams for transmission in turn according to the priority order of bit mapping under QPSK modulation;

[0054] For QAM modulation, the reordered information bits b 0 、b 1 、……b K-1 are allocated to the corresponding bit streams for transmission in turn according to the priority order of bit mapping under QAM modulation.

[0055] Advantages of the present invention:

[0056] Different from the prior art which only considers the transmission performance differences of different data streams in MIMO systems or only considers the transmission performance differences of each bit in high-order digital modulation, the present invention comprehensively considers the transmission performance differences of different data streams in MIMO and massive MIMO systems and the transmission performance differences of each bit in high-order digital modulation. The proposed method performs bit mapping according to the feedback information. If the modulation method is QPSK, the bit mapping assigns the bits with greater importance in the information bits after channel coding to the data streams with better transmission performance for transmission. If the modulation method is QAM, since the transmission performance of each bit included in the QAM modulation symbol is different (the bit error rate is different), at this time, the bit mapping generates multiple bit streams for each data stream, and the bit mapping assigns the bits with greater importance in the information bits after channel coding to the bit stream with the best transmission performance for transmission, realizing the optimization of system resource allocation and improving the system transmission performance.

[0057] The present invention does not require the feedback of the channel quality information (CQI) of each data stream, but only feedbacks an average CQI of these data streams, and at the same time, uses a very small amount of information to feedback the sorting of the transmission quality of these data streams from high to low. For high-order QAM modulation, instead of feedbacking the pros and cons of the transmission performance of specific bit streams, only an additional 1 bit is used to feedback the bit stream allocation method of the bit mapping operation, thus greatly reducing the feedback amount. Brief Description of the Drawings

[0058] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0059] Figure 1 It is a flowchart of a bit mapping method for improving the overall performance of MIMO and channel coding systems according to the present invention.

[0060] Figure 2 It is a block diagram of a MIMO system under 5G high-order modulation.

[0061] Figure 3 It is a block diagram of the system of Embodiment 1 of the present invention in the FDD mode.

[0062] Figure 4 It is a flowchart of bit mapping in the FDD mode of Embodiment 1 of the present invention.

[0063] Figure 5 It is a block diagram of the system of Embodiment 2 of the present invention in the TDD mode.

[0064] Figure 6 This is the bit mapping flowchart of Embodiment 2 of the present invention in the TDD mode.

[0065] Figure 7 This is the performance comparison diagram of bit mapping in the QPSK modulation mode. Detailed implementation manners

[0066] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0067] Embodiment 1

[0068] A bit mapping method for improving the overall performance of a MIMO and channel coding system, as Figure 1 shown. This embodiment proposes a bit mapping method for improving the overall performance of a MIMO and channel coding system in the Frequency Division Duplexing (FDD) mode, as Figure 4 shown, including the steps:

[0069] S1: Perform channel estimation and obtain channel feedback information, including Rank Indicator (RI), Precoding Matrix Indicator (PMI), average CQI (Channel Quality Indicator), and Bit Mapping Indicator (BMI).

[0070] The system block diagram is as Figure 3 shown. In the FDD mode, since the transmitting end cannot directly obtain the channel feedback information, in order to support the bit mapping for optimizing the overall performance of the MIMO and channel coding system, the receiving end needs to feedback relevant information. The receiving end of the system first performs channel estimation to obtain the channel information from each transmitting antenna to the receiving antenna of the MIMO. Then, based on this channel information, the information related to MIMO transmission is calculated and these related information are fed back to the transmitting end as feedback information. The content of the feedback information is shown in Table 1:

[0071] Table 1. Content of feedback information at the receiving end in the FDD mode

[0072] For CQI information, although the CQIs of different data streams in the MIMO system are different, in the present invention, instead of separately feeding back the CQIs for each data stream, only one average CQI is fed back for multiple data streams to reduce the feedback amount.

[0073] The calculation method of the average CQI is as follows:

[0074] 1. Obtain the channel matrix H, the precoding matrix C, the noise variance σ 2 , and the number M of data streams;

[0075] 2. Use H and C to calculate the equivalent channel matrix of the M data streams

[0076] 3. According to the equivalent channel matrix and the noise variance σ 2 , calculate the signal-to-noise ratio of each data stream; the specific calculation method is as follows:

[0077]

[0078] where Ι is the identity matrix, W represents the weight matrix, w i is an element in the weight matrix W, is an element in the equivalent channel matrix, and SINR i represents the signal-to-noise ratio of the i-th data stream.

[0079] 4. According to the signal-to-noise ratios SINR 1 , SINR 2 , … SINR M of these M data streams, calculate the average signal-to-noise ratio of these M data streams:

[0080]

[0081] where erfcinv(·) is the inverse function of the erfc(·) error function;

[0082] 5. According to the average signal-to-noise ratio SINR_ave, based on Table 2, obtain the modulation mode and the code rate of the channel coding corresponding to the highest transmission rate that these M data streams can support, and feed it back to the transmitter as the average CQI.

[0083] Table 2 Modulation Modes and Coding Rates Supported by Different Average Signal-to-Noise Ratios

[0084]

[0085] In the feedback content of Table 1, the bit mapping indication BMI is proposed by the present invention for the bit mapping to support improving the overall performance of the MIMO and channel coding systems in the FDD mode.

[0086] The described bit mapping indicator BMI includes two parts: The first part is defined as BMI1 information, which is used to indicate the ranking of the transmission performance of each data stream from high to low in high-order modulation mode and low-order modulation mode. In this embodiment, the low-order modulation mode is QPSK modulation and the high-order modulation mode is QAM modulation. Since the average CQI cannot indicate the quality of each data stream's transmission, the present invention uses BMI1 information for indication.

[0087] Since in the current system, a codeword is transmitted by at most 4 data streams at present, the specific indication method of BMI is as follows:

[0088] 1. Obtain the signal-to-noise ratio of M data streams through channel estimation, and sort the signal-to-noise ratios of the M data streams to determine the high-low order of the transmission performance of the M data streams; the larger the signal-to-noise ratio of a data stream, the higher its transmission quality and the better its data stream transmission performance;

[0089] 2. If the transmission of an information bit after channel coding only requires two data streams, use 1 bit of the feedback value of BMI1 information to indicate the high-low of the data stream transmission performance;

[0090] 3. If the transmission of an information bit after channel coding requires three data streams, use 4 bits of the feedback value of BMI1 information to indicate the data stream with the best transmission performance and the second-best data stream; since 2 bits are required to indicate each data stream, 4 bits are needed to indicate the BMI1 information.

[0091] 4. If the transmission of an information bit after channel coding requires four data streams, although theoretically it is necessary to indicate the data streams with the best, second-best, and third-best transmission performances, in order to reduce the feedback overhead, the present invention still only uses 4 bits of the feedback value of BMI1 information to indicate the data stream with the best transmission performance and the second-best data stream. Since 2 bits are required to indicate each data stream, 4 bits are also needed to indicate the BMI1 information.

[0092] The specific feedback content of BMI1 under different numbers of data streams is shown in Table 3:

[0093] Table 3. BMI1 indication content under different numbers of data streams

[0094]

[0095]

[0096] Among them, each data stream has an original data stream serial number during channel estimation, such as the 1st and 2nd in Table 3.

[0097] The present invention defines the second part as BMI2 information, which is used to indicate the way of bit mapping under high-order modulation. The specific indication content of BMI2 information is shown in Table 5.

[0098] Table 5. Indication content of BMI2 under QAM modulation

[0099]

[0100] The specific indication method of BMI2 information is as follows:

[0101] a. Obtain the signal-to-noise ratio of M data streams through channel estimation, and calculate the equivalent signal-to-noise ratio of each bit stream according to the signal-to-noise ratio of M data streams, SINR i,j represents the equivalent signal-to-noise ratio of the jth bit stream of the ith data stream;

[0102] b. Calculate SINR 1,S 、SINR 2,S 、…SINR M-1,S The average SINR of is denoted as SINR_ave1:

[0103]

[0104] c. Calculate SINR 2,1 、SINR 3,1 、…、SINR M,1 The average SINR of is denoted as SINR_ave2:

[0105]

[0106] d. If SINR_ave1 > SINR_ave2, then BMI2 = 1, indicating that bit mapping is performed in the order of the transmission performance of each bit stream that requires high-order modulation; if SINR_ave1 ≤ SINR_ave2, then BMI2 = 0, indicating that bit mapping is performed in the order of the transmission performance of the data streams.

[0107] S2: The sending end determines the modulation method based on the average CQI, determines the number of data streams based on the rank indication RI, and determines the number of bit streams for bit mapping based on the modulation method and the number of data streams. The number of bit streams included in each data stream for various modulation methods is shown in Table 4.

[0108] If the CQI indicates the selection of QPSK modulation, at this time, the performance of each bit of each data stream is the same, so only BMI1 needs to be fed back to complete the bit mapping operation.

[0109] If the CQI indicates the selection of QAM modulation, at this time, since the bit error rates of different bits included in the QAM modulation symbols are different, the transmission performance of each bit of each data stream is different. Therefore, in order to achieve optimal resource allocation, the present invention combines bits with the same performance in each data stream to form bit streams, so that the information to be transmitted in each data stream is divided into multiple bit streams.

[0110] It should be noted that for different QAM modulations, the number S of bit streams into which each data stream is divided is different. It is a multiple of the number of data streams transmitted. The number S of bit streams included in each data stream for different modulation modes is shown in Table 4:

[0111] Table 4. Number of bit streams included in each data stream for various modulation methods

[0112] Modulation method Number of bitstreams QPSK S＝1 16QAM S＝2 64QAM S＝3 256QAM S＝4 1024QAM S＝5

[0113] It can be seen that when QAM modulation is selected, the total number of bit streams is M×S.

[0114] S3: The transmitting end determines the priority order of bit mapping for bit streams based on the bit mapping indication BMI and the number of bit streams of bit mapping.

[0115] For QAM modulation, after the present invention divides the information to be transmitted in each data stream into multiple bit streams, it also assigns the priority order of bit mapping to the bit streams in each data stream. The bit stream with the best performance is arranged as serial number 1, the second-best bit stream is arranged as serial number 2, and so on. For the transmitting end, under the determined modulation mode, the priority order of bit mapping assigned to the bit streams in each data stream is fixed, that is, the transmission performance of each bit stream in each data stream is known, but the transmission performance of each bit stream between data streams is unknown.

[0116] To support bit mapping operations, in the present invention, all bit streams are numbered as a whole, and (i, j) is used to represent the jth bit stream of the ith data stream. SINR i,j represents the transmission quality of the jth bit stream of the ith data stream.

[0117] The transmission quality SINR of different bit streams in the same data stream i,1 > SINR i,2 >…> SINR i,SAs the modulation order increases, the number of bitstreams with different transmission performances becomes larger and larger. If the advantages and disadvantages of the transmission performances among so many bitstreams are indicated, it will result in a huge feedback overhead. To reduce the feedback overhead, for high-order modulation methods (QAM modulation in this embodiment), in addition to feeding back the BMI1 information indicating the order of the transmission performances of each data stream from high to low, only one additional bit is used to indicate the way of bit mapping under QAM modulation. That is, for QAM modulation, the present invention does not feed back the specific advantages and disadvantages of the transmission performances of each bitstream, but feeds back two parts of content, namely the BMI1 information and the BMI2 information described in step S1, to determine the priority order of bit mapping.

[0118] Specifically, for QPSK modulation, the number of bitstreams is equal to the number of data streams. According to the fed-back BMI1 information, the priority order of bit mapping of the data stream is determined, and the data stream with better transmission performance is preferentially allocated information bits:

[0119] If the number of data streams M ≤ 3, the BMI1 information indicates the priority order of bit mapping of all data streams from high to low in terms of transmission performance: i 1 i 2 ……i M 。This priority order of bit mapping of these M data streams is i 1 i 2 ……i M 。

[0120] If the number of data streams M > 3, the BMI1 information indicates the two data streams with the best transmission performance and the priority order of bit mapping of these two data streams: i 1 i 2 When bit mapping, the channel-coded information bits are preferentially allocated to these two data streams. The remaining data streams obtain the priority order of bit mapping according to the original data stream numbers during channel estimation. For example, if M = 4 and the BMI1 indicates that the numbers of the two data streams with the best transmission performance are 2 and 3, then the priority order of bit mapping of the 4 data streams is 2, 3, 1, 4.

[0121] Specifically, for QAM modulation, according to the fed-back BMI1 and BMI2 information, the priority order of bit mapping of the bitstream is determined:

[0122] S3.1. Determine the priority order i of bit mapping of each data stream according to BMI1 1 i 2 ……i M ;

[0123] S3.2. Determine the way of bit mapping according to BMI2. Here, use (i 1, 1) If the j-th bitstream sequence number of the i-th data stream is represented, the implementation method of this operation is as follows:

[0124] If the feedback BMI2 = 0, perform bit mapping in the order of the data stream transmission performance from good to bad. The priority order of all bitstreams of the data stream with good transmission performance is higher than that of all bitstreams of the data stream with low priority. The specific priority order of bitstreams is shown in Table 5;

[0125] Table 5. Priority order of bit mapping of bitstreams when QAM modulation BMI2 = 0

[0126] Bitstream priority sequence number Bitstream sequence number 1 <![CDATA[(i 1 ,1)]]> 2 <![CDATA[(i 1 ,2)]]> …… …… S <![CDATA[(i 1 ,S)]]> S+1 <![CDATA[(i 2 ,1)]]> S+2 <![CDATA[(i 2 ,2)]]> …… …… 2S <![CDATA[(i 2 ,S)]]> …… …… MS <![CDATA[(i M ,S)]]>

[0127] If the feedback BMI2 = 1, perform bit mapping in the order of the transmission performance of each bitstream of QAM modulation. Since the transmission performance of each bitstream between data streams is unknown, in the present invention, the 1st to S-th bitstreams are sequentially allocated according to the priority order of data streams. For example, first allocate the 1st bitstream of each data stream according to the priority order of data streams, then allocate the 2nd bitstream of each data stream until the S-th bitstream of each data stream is allocated. The specific priority order of bitstreams is shown in Table 6.

[0128] Table 6. Priority order of bit mapping of bitstreams when QAM modulation BMI2 = 1

[0129] Bitstream priority sequence number Bitstream sequence number 1 <![CDATA[(i 1 ,1)]]> 2 <![CDATA[(i 2 ,1)]]> 3 <![CDATA[(i 3 ,1)]]> … … M <![CDATA[(i M ,1)]]> M+1 <![CDATA[(i 1 ,2)]]> M+2 <![CDATA[(i 2 ,2)]]> …… …… 2M <![CDATA[(i M ,2)]]> 2M+1 <![CDATA[(i 1 ,3)]]> …… …… (S - 1)M + 1 <![CDATA[(i 1 ,S)]]> (S - 1)M + 2 <![CDATA[(i 2 ,S)]]> …… …… MS <![CDATA[(i M ,S)]]>

[0130] S4: The sending end performs channel coding on the original information bits according to the coding code rate specified by CQI, and reorders the information bits after channel coding according to importance.

[0131] The method of reordering the information bits after channel coding according to importance is as follows:

[0132] In this embodiment, if the system uses a non-systematic code (such as a polar code), we directly sort according to the code weight of the coded bits. If a systematic code (such as an LDPC code) is used for channel coding, the sorting method is as follows;

[0133] 1. According to the priority rule, place the information bits after channel coding at the front of the sequence, and the redundant bits after channel coding are arranged in sequence after the original information bits;

[0134] 2. Based on the code weight metric criterion, perform a descending order arrangement on the original information bits after channel coding;

[0135] 3. According to the code weight metric criterion, perform a descending order arrangement on the redundant bits.

[0136] That is, the sorting of the encoded information bits, the original information bits and the redundant bits are performed separately. The re-ordered information bits after channel coding are represented as: b 0 , b 1 , …… b K-1 .

[0137] S5: The sender performs bit mapping on the re-ordered information bits according to the priority order of bit mapping of the bit stream.

[0138] For QPSK modulation, the re-ordered information bits b 0 , b 1 , …… b K-1 are sequentially allocated to the corresponding data streams for transmission according to the priority order of bit mapping under QPSK modulation. That is, b 0 , b 1 , …… b K / M-1 are allocated to the i 1 th data stream for transmission, b K / M , b K / M+1 , …… b 2K / M-1 are allocated to the i 2 th data stream for transmission, and so on, b K(M-1) / M , b K(M-1) / M+1 , …… b K-1 are allocated to the i M th data stream for transmission.

[0139] For QAM modulation, the re-ordered information bits b 0 , b 1 , …… b K-1 are sequentially allocated to the corresponding bit streams for transmission according to the priority order of bit mapping under QAM modulation.

[0140] Thus, the bits with greater importance in the information bits after channel coding are allocated to the data stream with the highest transmission performance for transmission.

[0141] S6: The sender performs digital modulation on the information bits after bit mapping, and transmits the modulated signal through multiple transmit antennas after precoding.

[0142] Digital modulation:

[0143] After the sender completes bit mapping, it performs digital modulation on the output bit stream of bit mapping. The bit streams output by bit mapping belonging to the same data stream are combined for digital modulation. The specific operations are as follows:

[0144] If the modulation method is QPSK, each data stream has only 1 bit stream. Therefore, only these M bit streams are modulated separately. During QPSK modulation, 2 bits are taken from the bit stream each time to complete the modulation operation.

[0145] If the modulation method is QAM, each data stream has S bit streams, and there are a total of M×S bit streams. When performing QAM modulation, M data streams are modulated separately. During the modulation process of each data stream, 2 bits are taken from each of the S bit streams each time, and a total of 2S bits are taken to complete the modulation operation.

[0146] After digital modulation, M modulated symbols corresponding to the M data streams of MIMO are generated.

[0147] Precoding and transmission:

[0148] Based on the PMI, a precoding matrix C with a size of N×M is obtained. Based on the coding matrix C, the M modulated symbols after digital modulation are precoded to generate N transmission signals. The BMI1 information and BMI2 information are added to the signaling information (DCI format) of the control channel. The signaling information of the control channel and the N transmission signals after precoding are transmitted through N antennas at the transmitting end.

[0149] Embodiment 2

[0150] A bit mapping method for improving the overall performance of a MIMO and channel coding system. This embodiment proposes a bit mapping method for improving the overall performance of a MIMO and channel coding system in the Time Division Duplexing (TDD) mode, as Figure 6 shown, including the steps:

[0151] S1: Perform channel estimation and obtain channel feedback information, including RI, PMI, CQI, and Bit Mapping Indicator (BMI).

[0152] In the TDD mode, since the transmitting end can directly obtain channel information through the reverse link, it is not necessary for the receiving end to feedback relevant information. The specific system implementation is as shown in the figure, and the system block diagram is as Figure 5 shown.

[0153] In the TDD mode, the transmitting end first performs channel estimation on the reverse link to obtain the channel information of the reverse link. In the TDD mode, since the uplink and downlink share the same frequency band, the operation of bit mapping can be performed based on the channel information of the reverse link.

[0154] S2: Determine the modulation method based on the CQI, determine the number of data streams based on the RI, and determine the number of bit streams for bit mapping based on the modulation method and the number of data streams.

[0155] S3: Determine the priority order of bit mapping for bit streams based on the BMI.

[0156] S4: Perform channel coding on the original information bits, and reorder the information bits after channel coding according to their importance.

[0157] S5: Perform bit mapping on the reordered information bits according to the priority order of bit mapping of the bit stream.

[0158] Other methods and steps are the same as those in Embodiment 1.

[0159] The bit mapping method proposed by the present invention comprehensively considers the data stream transmission performance of MIMO and large-scale MIMO systems and the different performances of each bit in high-order digital modulation. Bit mapping assigns the bits with greater importance in the information bits after channel coding to the transmission resources with the best transmission performance for transmission, so that the performance of the entire system reaches the optimal.

[0160] Figure 7 The bit error rate performance comparison with and without bit mapping is given under the QPSK modulation mode when the channel coding uses LDPC code. It can be seen that after adopting the bit mapping of the present invention, the bit error rate performance has been greatly improved.

[0161] In addition, the implementation of the present invention can also be extended to the application scenarios of GSM and CDMA technologies using MIMO / large-scale MIMO and channel coding. At this time, the GSM and CDMA systems consider the data stream transmission performance of MIMO and large-scale MIMO systems and the different performances of each bit in high-order digital modulation. Through bit mapping, the bits with greater importance in the information bits after channel coding are assigned to the transmission resources with the best transmission performance for transmission, so that the performance of the entire system reaches the optimal and the performance of the GSM and CDMA systems is improved.

[0162] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A bit mapping method for improving the overall performance of MIMO and channel coding systems, characterized in that: Includes steps: S1: Perform channel estimation and obtain channel feedback information, including rank indicator RI, average CQI and bit mapping indicator BMI; S2: The transmitter determines the modulation mode based on the average CQI, determines the number of data streams based on the rank indication RI, and determines the number of bit streams for bit mapping based on the modulation mode and the number of data streams; S3: Determine the priority of the bitstream bitmap based on the bitmap indication BMI and the number of the bitstreams of the bitmap; S4: The transmitter performs channel coding on the original information bits according to the coding rate specified by the average CQI, and reorders the channel-coded information bits according to their importance; S5: The transmitting end performs bit mapping on the reordered information bits according to the priority order of the bit mapping of the bit stream; S6: The transmitting end digitally modulates the information bits after bit mapping, and transmits the modulated signals through multiple transmitting antennas after precoding.

2. The bit mapping method for improving the overall performance of MIMO and channel coding systems according to claim 1, characterized in that: The rank indication RI is used to indicate the number M of data streams transmitted by MIMO; the average CQI is used to indicate the average signal-to-noise ratio of the M data streams, as well as the modulation mode and channel coding rate that can be supported under the average signal-to-noise ratio; the bit mapping indication BMI is used to indicate the information and bit mapping method of the transmission performance of each data stream required by the bit mapping method for improving the overall performance of the MIMO and channel coding system; The number of bit streams is M×S, where S represents a multiple parameter determined by the modulation method.

3. The bit mapping method for improving the overall performance of MIMO and channel coding systems according to claim 2, characterized in that: The average CQI is calculated by: obtaining the channel matrix H, the precoding matrix C, and the noise variance σ according to the channel estimation. 2 , the number of data streams M; Using the channel matrix H and the precoding matrix C, calculate the equivalent channel matrix of M data streams According to the equivalent channel matrix and the noise variance σ 2 , calculate the signal-to-noise ratio of each data stream; According to the signal-to-noise ratio of each data stream, the average signal-to-noise ratio of M data streams is calculated: Among them, erfcinv(·) is the inverse function of erfc(·) error function, SINR i represents the signal-to-noise ratio of the i-th data stream; According to the average signal-to-noise ratio SINR_ave, the modulation mode and channel coding code rate corresponding to the highest transmission rate supported by the M data streams are obtained.

4. The bit mapping method for improving the overall performance of MIMO and channel coding systems according to any one of claims 1 to 3, characterized in that: The bit mapping indication BMI includes BMI1 information and BMI2 information; BMI1 information is used to indicate the order of each data stream under high-order modulation mode and low-order modulation mode according to transmission performance from high to low; BMI2 information is used to indicate the method of bit mapping under high-order modulation mode, and the method of bit mapping includes bit mapping in the order of data stream transmission performance and bit mapping in the order of transmission performance of each bit stream requiring high-order modulation.

5. The bit mapping method for improving the overall performance of MIMO and channel coding systems according to claim 4, characterized in that: The method for indicating the BMI1 information is as follows: The signal-to-noise ratios of the M data streams are obtained through channel estimation, and the signal-to-noise ratios of the M data streams are sorted to determine the transmission performance order of the M data streams; If the transmission of one channel-coded information bit requires two data streams, the feedback value of the BMI1 information uses one bit to indicate the transmission performance of the data stream; If the transmission of one channel-coded information bit requires three data streams, the feedback value of the BMI1 information uses 4 bits to indicate the data stream with the best transmission performance and the second best data stream; If the transmission of one information bit after channel coding requires four data streams, the feedback value of the BMI1 information uses 4 bits to indicate the data stream with the best transmission performance and the second best data stream.

6. The bit mapping method for improving the overall performance of MIMO and channel coding systems according to claim 4, characterized in that: The method for indicating the BMI2 information is as follows: a. Obtain the signal-to-noise ratio of M data streams through channel estimation, and calculate the equivalent signal-to-noise ratio of each bit stream based on the signal-to-noise ratio of the M data streams, SINR i,j represents the equivalent signal-to-noise ratio of the j-th bit stream of the i-th data stream; b. Calculate SINR 1,S 、SINR 2,S ,…SINR M-1,S The average SINR is denoted as SINR_ave1: c. Calculate SINR 2,1 、SINR 3,1 , …, SINR M,1 The average SINR is denoted as SINR_ave2: d. If SINR_ave1>SINR_ave2, then BMI2=1, indicating that bit mapping is performed in the order of transmission performance of each bit stream requiring high-order modulation; if SINR_ave1≤SINR_ave2, then BMI2=0, indicating that bit mapping is performed in the order of transmission performance of the data stream.

7. The bit mapping method for improving the overall performance of MIMO and channel coding systems according to claim 5 or 6, characterized in that: The low-order modulation mode is QPSK modulation. For QPSK modulation, the number of bit streams is equal to the number of data streams. The high-order modulation mode is QAM modulation. For QAM modulation, the number of bit streams is equal to a multiple of the number of data streams. For QPSK modulation, the method for determining the priority of bit stream bit mapping based on BMI in step S3 is: if the number of data streams M≤3, the BMI1 information indicates the priority of all data stream bit mappings from high to low according to transmission performance; If the number of data streams M>3, the BMI1 information indicates the two data streams with the best transmission performance and the priority of the bit mapping of these two data streams; the remaining data streams obtain the priority of the bit mapping according to the original data stream sequence number during channel estimation.

8. The bit mapping method for improving the overall performance of MIMO and channel coding systems according to claim 6, characterized in that: For QAM modulation, the method for determining the priority of bit mapping of bit streams based on BMI described in step S3 is: S3.1, determining the priority of bit mapping of each data stream according to BMI1 information; S3.

2. Determine the bit mapping method according to BMI2: If BMI2=0 in the channel feedback, bit mapping is performed in the order of data stream transmission performance: the priority of all bit streams of data streams with good transmission performance is higher than the priority of all bit streams of data streams with low priority; If the fed-back BMI2=1, bit mapping is performed in the order of transmission performance of each QAM modulated bit stream: the 1st to S bit streams are allocated in sequence according to the priority of the data streams.

9. The bit mapping method for improving the overall performance of MIMO and channel coding systems according to any one of claims 1 to 3, 5 or 6, characterized in that: The method for reordering the information bits after channel coding according to importance is: If the system uses non-systematic codes for channel coding, the bits are sorted according to the code weight of the coded bits; if the system uses systematic codes for channel coding, the sorting method is: According to the priority rule, the original information bits after channel coding are placed at the front of the sequence, and based on the code weight measurement criterion, the original information bits after channel coding are arranged in descending order; According to the priority rule, the redundant bits after channel coding are arranged in sequence after the original information bits, and according to the code weight measurement criterion, the redundant bits are arranged in descending order.

10. The bit mapping method for improving the overall performance of MIMO and channel coding systems according to claim 9, characterized in that: The method for bit mapping the reordered information bits according to the priority order of bit stream bit mapping is as follows: for QPSK modulation, the reordered channel coded information bits b0, b1, ... b K-1 According to the priority order of bit mapping under QPSK modulation, they are allocated to the corresponding data stream for transmission; For QAM modulation, the reordered channel coded information bits b0, b1, ...b K-1 The bit mapping priorities under QAM modulation are allocated to the corresponding bit streams for transmission.

Images