Space-time shift modulation method and system based on MIMO communication

Abstract

The invention discloses a space-time shift modulation method and a space-time shift modulation system based on MIMO (Multiple Input Multiple Output) communication, and the method simultaneously utilizes a space dimension and a time dimension, thereby realizing flexible balance between diversity gain and multiplexing gain while providing a high transmission rate. Compared with a traditional spatial modulation method, the method has the advantages that the performance is improved, and meanwhile, low-complexity signal detection is kept; according to the invention, key problems caused by estimation errors of channel state information (CSI) and system overhead in an actual communication scene are effectively solved, and powerful support is provided for implementation of actual communication.

Description

Technical Field

[0001] The present invention belongs to the field of multiple-input multiple-output MIMO wireless communications, and in particular relates to a novel space-time shift modulation scheme based on MIMO communications. Background Art

[0002] Multiple-input multiple-output (MIMO) technology has made important contributions in the field of wireless communications. MIMO significantly improves the capacity and reliability of wireless communication systems by using multiple antennas to send and receive signals simultaneously, especially in complex interference and multipath propagation environments, which can effectively improve the quality of signal transmission. The core functions of MIMO include spatial diversity gain and spatial multiplexing gain. Spatial diversity gain uses the independence between multiple transmission channels to resist signal fading and interference, thereby improving the robustness and reliability of the communication system; spatial multiplexing gain transmits multiple data streams in parallel through multiple antennas, achieving higher transmission rates within the same frequency band, meeting the high-speed requirements of modern wireless communications.

[0003] In the MIMO system, the vertical Bell Labs layered space-time architecture V-BLAST is a classic spatial multiplexing solution. V-BLAST enables parallel transmission by allowing each antenna to independently transmit its own coded symbol stream, significantly improving data throughput. At the receiving end, the data streams transmitted by multiple antennas are gradually decoded and separated through spatial region decision feedback equalization technology. V-BLAST can make full use of the independence between multiple antennas to achieve efficient data transmission, and has been widely used in wireless communication systems that require high data rates.

[0004] However, V-BLAST focuses on spatial multiplexing gain, emphasizing increasing the number of antennas to improve the transmission rate of the system. Under certain adverse channel conditions, the advantage of multiplexing gain may be limited, especially when there is strong fading or interference in the channel. For this reason, orthogonal space-time block codes (OSTBCs) came into being, focusing on diversity gain, thereby improving the reliability of the system under adverse channel conditions.

[0005] OSTBCs use orthogonal coding technology to map multiple data streams to multiple antennas, effectively resist signal fading and interference, and enhance the reliability of communication. Unlike the spatial multiplexing gain of V-BLAST, OSTBCs provide anti-interference capabilities by utilizing the orthogonality of time and space, and are suitable for situations with poor channel conditions. OSTBCs also have some limitations. The performance of OSTBCs may degrade in channels with high spatial correlation because orthogonal coding assumes that the channels between antennas are independent, but this assumption may not hold true in environments with strong spatial correlation. In addition, the performance of OSTBCs will also be affected when the channel estimation error is large. To overcome these limitations, the researchers proposed a bit error rate BER approximation method based on Rayleigh fading channels, which can more accurately evaluate the performance of OSTBCs in actual communications, especially when the channel correlation is high or the channel estimation is imperfect. In order to better cope with the challenges of small-scale antenna configurations, Alamouti's STBC was proposed as a special OSTBC scheme for 2×1 antenna configurations and played an important role in low-complexity antenna systems.

[0006] Compared with the diversity gain of OSTBCs and the multiplexing gain of V-BLAST, the linear distributed coding LDCs scheme can flexibly balance between diversity and multiplexing gain. LDCs combines the spatial multiplexing gain of V-BLAST and the spatial diversity gain of OSTBCs, and realizes flexible adjustment of performance through linear coding technology. LDCs can not only improve the data transmission rate when the channel conditions are good, but also ensure high reliability when the channel quality is poor, and has strong adaptability. Some studies have proposed an LDCs scheme that combines the two gains by combining V-BLAST and Alamouti STBC. While ensuring the diversity gain, it can also improve the transmission rate through spatial multiplexing, thereby providing flexible performance optimization. However, because of the introduction of inter-carrier interference at the transmitter, the complexity of the maximum likelihood method used in its signal detection is greatly increased. Summary of the invention

[0007] The purpose of the present invention is to address the coding modulation problem in a multiple-input multiple-output system and to propose a space-time shift modulation method and system based on MIMO communication. The method utilizes both the spatial dimension and the temporal dimension, thereby achieving a flexible balance between diversity gain and multiplexing gain while providing a high transmission rate.

[0008] The technical solution of the present invention is: The present invention provides a space-time shift modulation method based on MIMO communication, comprising the following steps: Step 1: Divide the source bit information into two groups through a serial / parallel converter. The length of the first group of bits is log2M, where M is the modulation order, and the length of the second group of bits is log2R, where R is the number of dispersion matrices. Step 2: Modulate and map the first bit group to obtain modulation code elements , and at the same time, construct a set of scattered matrices according to the second group of bits, a total of R, denoted as D1, D2, ..., DR, where m represents the number of combinations mapped to the corresponding modulation mode; Step 3: According to the modulation code and the selected scattered matrix Dr (1≤r≤R) to calculate the space-time matrix S, which is extended in both space and time dimensions, r represents the index of the selected matrix; Step 4: Generate channel matrix using Rayleigh fading channel model , and superimposed with Gaussian white noise Interfere with the signal and obtain the received signal model: ;in, is the index of the transmitted signal, To transmit a signal; Step 5: Use the maximum likelihood detection algorithm to recover the received signal, vectorize the received signal and build an equivalent model; minimize the difference between the received signal and the expected signal to obtain the optimal combination.

[0009] Furthermore, in step 1, the step of dividing the source bit information into two groups through a serial / parallel converter includes: Using log2M bits as a first group for performing modulation mapping in step 2, the modulation includes M-PSK modulation or M-QAM modulation; The log2R bits are used as the second group for selecting the index of the scattered matrix in step 2.

[0010] Further, in step 2; The step of modulating and mapping the first bit group is to map the first bit group into complex-valued modulation symbols according to the constellation diagram. ; The step of constructing a scattered matrix set according to the second group of bits is as follows: , Construct R scattered matrices; among them: , Nt is the number of transmitting antennas, T is the number of transmitting time slots, is represented as the conjugate transposed matrix of Dr, and tr( ) is the trace of the matrix.

[0011] Further, in step 3, the modulation code element and the selected scatter matrix DR calculates the space-time matrix S The steps include: Modulation code and the scattered matrix D r multiplied to obtain the space-time matrix S ; , ; Nt is the number of transmitting antennas, T is the number of transmission time slots.

[0012] Furthermore, the step 5 comprises: For receiving signal Vectorize and get an equivalent model ; ; in, , ; , ; , , ; represents the Kronecker product; Represents vectorization; for Horizontal vectorization of is the identity matrix With channel matrix The Kronecker product, The scattered matrix D The set of r, is the vectorized Gaussian white noise; The transmitted signal predicted by the receiving end; By minimizing the received signal With expected signal The difference between combination; .

[0013] Furthermore, in order to improve the adaptability of the system in the actual channel environment, a joint channel estimation method based on training signals is proposed to solve the coherent communication scenario, including: Calculate the channel estimation matrix by the least squares method ; ; in: t represents the training data number, and represents the training signal matrix; Represents the training signal matrix The conjugate transposed matrix of .

[0014] The estimated channel matrix Substituting the actual channel matrix in step 4 , used for signal detection in step 5.

[0015] Furthermore, the training signal matrix and The method of obtaining is: Assumed Configuration training blocks to generate the transmit signal matrix and the received signal matrix , , t The receiving end vectorizes these matrices horizontally to obtain and ; Nt is the number of transmitting antennas, Nr is the number of receiving antennas, T is the number of transmission time slots.

[0016] Furthermore, in order to overcome the problems of difficult channel estimation and excessive system overhead, a pulse space-time modulation based on Cayley transform is proposed to solve the incoherent communication scenario, including: In step 2, the modulation is performed by M-PAM modulation to obtain a signal , generates the Hermitian matrix ; Generate a unitary matrix using Cayley transform , and obtain the space-time matrix , is the index of the transmitted signal, is the identity matrix, Reason The matrix obtained by differentially encoding the space-time matrix composed of and the unitary matrix; for The resulting unitary matrix; After linear processing through Cayley transform, the resulting matrix Instead of the transmit signal in step 4 , the maximum likelihood detection algorithm ML is used in step 5 to perform signal detection.

[0017] Furthermore, the step of performing signal detection using the maximum likelihood detection algorithm ML includes: Will receive signal Linearization , that is, multiply both sides ;

[0018] in: , , , ; j is an imaginary unit, is an M-PAM modulated signal; They are the equivalent received signal after linear processing, channel matrix, and Gaussian noise respectively; The optimal detection value is determined by minimizing the difference between the received signal and the expected signal after linearization.

[0019] A system adopted by a space-time shift modulation method based on MIMO communication, comprising: The serial-to-parallel conversion unit is used to divide the source bit information into two groups through the serial-to-parallel converter. The length of the first group of bits is log2 M , M is the modulation order, the length of the second group of bits is log2 R , R is the number of scattered matrices; A modulation mapping unit is used to perform modulation mapping on the first bit group to obtain a modulation code element , and construct a scattered matrix set based on the second group of bits, R , recorded as D 1 ,D 2 ,…，D R , m Indicates the number of combinations of corresponding modulation mode mapping; The space-time mapping unit is used to map the modulation code elements according to the and the selected scatter matrix D r, Compute space-time matrix S , which extends both in space and time dimensions, r represents the index of the selected matrix; A receiving signal generating unit is used to generate a channel matrix using a Rayleigh fading channel model , and superimposed with Gaussian white noise Interfere with the signal and obtain the received signal model: ;in, is the index of the transmitted signal, To transmit a signal; The detection optimization unit is used to recover the received signal using the maximum likelihood detection algorithm, vectorize the received signal and build an equivalent model; and obtain the optimal combination.

[0020] Beneficial effects of the present invention: The present invention discloses a space-time coding modulation method and system, which constructs a space-time matrix by acquiring input bit information, a preset constellation diagram and a dispersion matrix, and establishes a receiving signal model in combination with a channel matrix and a noise matrix; adopts a maximum likelihood detection algorithm to restore the transmitted signal, and reduces the detection complexity without the need for channel state information; effectively improves the efficiency of the communication system, especially performs well in scenarios where channel state information is unavailable or difficult to obtain.

[0021] In the present invention, spatial modulation SM is another typical MIMO transmission scheme, which uses the index of the transmitting antenna as an additional information source and combines it with the M-ary modulation constellation, so that data is transmitted not only through the modulation scheme, but also through the activated antenna index. This method effectively reduces the channel interference ICI between different antennas and improves the reliability and transmission efficiency of the system. A special case of SM is spatial shift keying SSK, which completely abandons the traditional amplitude / phase modulation method and transmits information only by selecting different antenna indexes. SSK further simplifies the structure of the system, reduces the computational complexity, and has a strong resistance to channel interference.

[0022] Compared with traditional spatial modulation, the method of the present invention realizes a flexible balance between diversity gain and multiplexing gain, not only improving the performance but also maintaining low-complexity signal detection.

[0023] In addition, based on the improved system, two schemes that can be applied to actual communication scenarios are proposed: one is a joint channel estimation scheme based on training data blocks, and the other is a pulse space-time modulation scheme based on Cayley transform, which are used in coherent communication and incoherent communication scenarios respectively. The present invention effectively solves the key problems caused by the estimation error and system overhead of channel state information (CSI) in actual communication scenarios, and provides strong support for the realization of actual communication.

[0024] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The above and other objects, features and advantages of the present invention will become more apparent through a more detailed description of exemplary embodiments of the present invention in conjunction with the accompanying drawings, wherein like reference numerals generally represent like components throughout the exemplary embodiments of the present invention.

[0026] Figure 1 It is a structural diagram of the space-time shift modulation scheme based on MIMO communication of the present invention.

[0027] Figure 2 It is a bit error rate diagram of the spatial dimension in the implementation of the present invention.

[0028] Figure 3is a bit error rate diagram of the time dimension gain in an embodiment of the present invention.

[0029] Figure 4 3 is a comparison diagram of the bit error rate between spatial modulation and space-time shift modulation in an embodiment of the present invention.

[0030] Figure 5 It is a system schematic diagram of the coherent communication scenario solution of the present invention.

[0031] Figure 6 It is a comparison diagram of the bit error rate of the joint channel estimation of the present invention.

[0032] Figure 7 It is a system schematic diagram of the non-coherent communication scenario solution of the present invention.

[0033] Figure 8 It is a comparison diagram of the bit error rate between the Cayley pulse space-time shift modulation and the coherent space-time shift modulation of the present invention. DETAILED DESCRIPTION

[0034] The preferred embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the preferred embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein.

[0035] Figure 1 It is a structural diagram of the novel space-time shift modulation scheme based on MIMO communication of the present invention.

[0036] like Figure 1 As shown, the system modulation method of the present invention comprises the following steps: Step 1: Group the information: Divide the source bit information into two groups through the serial / parallel converter. The length of one group is log2 M , M is the modulation order, such as BPSK is 2nd order, 1 bit; QPSK is 4th order, 2 bits; 8PSK is 8th order, 3 bits. This group is used as the modulation information of the data. The length of the other group is log2 R , R The number of constructed scattered matrices / vectors. If there are 2 scattered matrices, 1 bit is used, and if there are 4 scattered matrices, 2 bits are used. This group is used as an index to the scattered matrix to select the activated scattered matrix.

[0037] Step 2: Modulation mapping step: convert log2 M The bits are modulated by M-PSK or M-QAM, and the bit information is mapped into complex value information according to the constellation diagram to obtain the code element . Construct a decentralized matrix for activation according to certain rules D ,common R , recorded asD 1 ,D 2 ,…，D R , ,in, Nt is the number of transmitting antennas, T is the number of time slots for transmission. R The bits are mapped to the index of the scattered matrix, and the matrix is ​​selectively activated. The scattered matrix is ​​constructed according to the energy constraint, that is, , , T is the number of time slots.

[0038] Step 3: According to the code in step 2 and the scattered matrix D r(1≤ r ≤ R ) Calculate the space-time matrix S , , The generated space-time matrix S It is mapped to both the spatial dimension and the temporal dimension, i.e. the rows and columns of the matrix. Space-time matrix S The nth row and tth column of represent the signal transmitted by the nth antenna in the tth time slot.

[0039] Step 4: Interfere with the transmitted signal: simulate the situation of poor channel quality. The channel uses a random matrix based on Rayleigh distribution and interferes with the signal with additive Gaussian white noise. The model is ; for Nr × Nt The channel matrix, for Nr × T The additive Gaussian noise matrix of . and Follows a Gaussian distribution with mean zero and variance N 0 and 1.

[0040] Step 5: Enter the signal detection step. The present invention adopts the maximum likelihood detection algorithm (ML). The equivalent model is obtained by vectorizing the signal:

[0041] , , , , Expressed as a Kronecker product.

[0042] Further, . The rth element in this vector and the rest of the elements are zero, indicating that the rth dispersion matrix is ​​activated by the system. The transmitted signal vector Total This system completely eliminates the impact of ICI and uses a low-complexity single-antenna ML detector. By minimizing the difference between the received signal and the expected transmitted signal, the optimal The formula is , in, yes The r-th column vector in the matrix.

[0043] Furthermore, if Figure 2 As shown, the system is marked as ( Nt, Nr, T, D ),express Nt Transmitting antennas, Nr Root receiving antenna, T time slots, D Scattering matrix. Assume that the channel estimate is the true channel value of the perfect estimate, the modulation mode is BPSK, and the system has spatial diversity gain. The 2×4 antenna has a gain of 6-8dB compared to the 2×2 antenna; and when M × N When it is a fixed value, priority is given to increasing the number of receiving antennas. A 2×4 antenna has a 4dB gain compared to a 4×2 antenna.

[0044] like Figure 3 As shown, the use of time slots also has a gain in the time dimension. ，2，T，2 ) in the system, T =3 compared to T =1 has a gain of 6-10dB.

[0045] Furthermore, if Figure 4 As shown, the spatial modulation is compared with the system. The spatial modulation adopts 2×2 antennas and BPSK modulation method. The system of the present invention is (2 ，2，2，2 ), and the modulation mode is BPSK, the space-time shift modulation in this paper is 2-7dB better than the spatial modulation.

[0046] Step 6: Propose a joint channel estimation scheme based on training data: Channel estimation is required in actual coherent communication scenarios. Figure 5 As shown, the solution configures a known training signal at the front end of the data block, processes the received training signal value and the known training signal value, and estimates the channel.

[0047] After completing steps 1 to 3, assume the configuration before the data block training blocks to generate the transmit signal matrix and received signal matrix The receiving end vectorizes these matrices horizontally to obtain and Then, the least squares channel estimation (LSCE) method is used to calculate the channel estimation matrix, which is: , to ensure is a full rank matrix, the minimum number of training blocks should be .

[0048] Furthermore, the system is marked as ( Nt, Nr, T, D ),express Nt Transmitting antennas, Nr Root receiving antenna, T time slots, D A distributed matrix, the modulation method is BPSK. Figure 6 As shown, the system is (4,2,2,4), The minimum value of should be 2, that is, there are at least 2 training blocks at the front of the data block. Then perform the signal interference method in step 4 and the signal detection method in step 5, and replace the channel matrix with the channel matrix obtained by channel estimation. , and the maximum likelihood detection algorithm is performed. In the figure, when the number of training blocks is 30, the channel estimation value is close to the true channel value of perfect estimation.

[0049] Step 7: Propose a pulse space-time shift modulation scheme based on Cayley transform: Figure 7 As shown, in the case of incoherent communication, the signal can be demodulated without CSI. Repeat step 1. Due to the special properties of Cayley transform, the pulse amplitude modulation problem is focused on. Therefore, the M-PSK or M-QAM modulation in step 2 is replaced with M-PAM modulation, set to 2PAM, and the generation method of the dispersion matrix is ​​changed to generate the Hermitian matrix. The space-time matrix is ​​calculated in step 3. , , using Cayley transformation to obtain the unitary matrix X And encode it to get , use it as the transmitted space-time matrix, and complete step 4 to add interference.

[0050] Furthermore, the signal detection of pulse space-time shift modulation based on Cayley transform is performed. This scheme has 2 T time slots, assuming that the channel does not change during the transmission process, the received signal is

[0051] From this formula, it can be seen that it does not contain channel information, so this solution can avoid the problem caused by channel estimation error. Before performing maximum likelihood, this model needs to be linearized, so we can get

[0052] in, , , Among them . It can be obtained that this formula is similar to the formula in step 5. Repeat the vectorization process in step 5 and perform the maximum likelihood estimation algorithm to obtain the detected signal. Figure 8 As shown, assuming that the coherent communication is the true channel value of the perfect estimation, the pulse space-time shift modulation scheme based on Cayley transform will enhance the interference of the noise variance, and the noise variance is

[0053] As a result, the performance is reduced by about 2-4dB compared to the coherent communication method (BPSK modulation).

[0054] In this embodiment, the system simulation uses Matlab software, and the parameter setting does not affect the generality. In this embodiment, BPSK or 2-PAM modulation is used, and the channel value matrix obeys Rayleigh distribution. Figure 2 , Figure 3 and Figure 8 In the example, the channel estimation values ​​used for equalization are all perfect estimation values. The signal-to-noise ratio range is set to 0-30dB, and a total of 300,000 symbols are transmitted for bit error rate statistics.

[0055] This embodiment uses the bit error rate BER as the evaluation index. Figure 1 , Figure 2 and Figure 3 , this system obtains gain in the time dimension while retaining the gain in the spatial dimension. The 2×4 antenna has a gain of 6-8dB compared to the 2×2 antenna; and when M × N When is a fixed value, the number of receiving antennas is increased first. The 2×4 antenna has a 4dB gain compared to the 4×2 antenna. In the (3,2,T,2) system, T =3 compared to T =1 has a gain of 6-10dB. Combined Figure 4 The performance of the (2,2,2,2) system of the present invention is 2-7dB better than the spatial modulation (Spatial Modulation) of the same scale and the same modulation method (2×2 antennas, BPSK modulation method).

[0056] Combination Figure 6 , the more training data blocks there are, the higher the accuracy of channel estimation will be. In solving the problem of coherent communication scenarios, a feasible communication solution is given. Figure 7 and Figure 8Although the performance of Cayley pulse space-time shift modulation is reduced by 2-4dB, it saves the transmission overhead of the system (by Figure 6 It can be seen that 30 blocks of training data are required to obtain accurate channel estimation values).

[0057] Experimental results show that compared with traditional spatial modulation, the present invention achieves a flexible balance between diversity gain and multiplexing gain, not only improving performance, but also maintaining low-complexity signal detection. In addition, the two schemes designed by the present invention are suitable for coherent and incoherent communication scenarios, effectively solving the key problems caused by channel state information (CSI) estimation errors and system overhead in actual communication scenarios, and providing strong support for the realization of actual communications.

[0058] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A space-time shift modulation method based on MIMO communication, characterized in that: The following steps are involved: Step 1: Divide the source bit information into two groups through the serial / parallel converter. The length of the first group of bits is log2 M , M is the modulation order, the length of the second group of bits is log2 R , R is the number of scattered matrices; Step 2: Modulate and map the first bit group to obtain modulation code elements , and construct a scattered matrix set based on the second group of bits, R , recorded as D 1 ,D 2 ,…，D R , m Indicates the number of combinations of corresponding modulation mode mapping; Step 3: According to the modulation code and the selected scatter matrix D r(1≤ r ≤ R ) Calculate the space-time matrix S , which extends both in space and time dimensions, r represents the index of the selected matrix; Step 4: Generate channel matrix using Rayleigh fading channel model , and superimposed with Gaussian white noise Interfere with the signal and obtain the received signal model: ;in, is the index of the transmitted signal, To transmit a signal; Step 5: Use the maximum likelihood detection algorithm to recover the received signal, vectorize the received signal and build an equivalent model; minimize the difference between the received signal and the expected signal to obtain the optimal combination.

2. The space-time shift modulation method based on MIMO communication according to claim 1, characterized in that In step 1, the step of dividing the source bit information into two groups through a serial / parallel converter includes: Log2 M bits as a first group, used for performing modulation mapping in step 2, wherein the modulation includes M-PSK modulation or M-QAM modulation; Log2 R bits as the second group, which are used to select the index of the scattered matrix in step 2.

3. The space-time shift modulation method based on MIMO communication according to claim 1, characterized in that In step 2; The step of modulating and mapping the first bit group is to map the first bit group into complex-valued modulation symbols according to the constellation diagram. ; The step of constructing a scattered matrix set according to the second group of bits is as follows: , 1≤ r ≤ R structure R A scatter matrix; where: , Nt is the number of transmitting antennas, T is the number of transmission time slots, Expressed as D The conjugate transposed matrix of r, tr ( ) is the trace of the matrix.

4. The space-time shift modulation method based on MIMO communication according to claim 3, characterized in that In step 3, the modulation code element and the selected scatter matrix D R calculates the space-time matrix S The steps include: Modulation code and the scattered matrix D r multiplied to obtain the space-time matrix S ; , , Nt is the number of transmitting antennas, T is the number of transmission time slots.

5. The space-time shift modulation method based on MIMO communication according to claim 4, characterized in that The step 5 comprises: For receiving signal Vectorize and get an equivalent model ; ； in, , ; , ; , , ; represents the Kronecker product; Represents vectorization; for Horizontal vectorization of is the identity matrix With channel matrix The Kronecker product, The scattered matrix D The set of r, is the vectorized Gaussian white noise; The transmitted signal predicted by the receiving end; By minimizing the received signal With expected signal The difference between combination; 。 6. The space-time shift modulation method based on MIMO communication according to claim 1, characterized in that: In order to improve the adaptability of the system in the actual channel environment, a joint channel estimation method based on training signals is proposed to solve the coherent communication scenario, including: Calculate the channel estimation matrix by the least squares method ; ； in: t represents the training data number, and represents the training signal matrix; Represents the training signal matrix The conjugate transposed matrix of ; The estimated channel matrix Substituting the actual channel matrix in step 4 , used for signal detection in step 5.

7. The space-time shift modulation method based on MIMO communication according to claim 6, characterized in that: Training signal matrix and The method of obtaining is: Assumed Configuration training blocks to generate the transmit signal matrix and received signal matrix , , t The receiving end vectorizes these matrices horizontally to obtain and ; Nt is the number of transmitting antennas, Nr is the number of receiving antennas, T is the number of transmission time slots.

8. The space-time shift modulation method based on MIMO communication according to claim 1, characterized in that: In order to overcome the difficulties in channel estimation and the high system overhead, a pulse space-time modulation based on Cayley transform is proposed to solve the non-coherent communication scenario, including: In step 2, the modulation is performed by M-PAM modulation to obtain a signal , generates the Hermitian matrix ; Generate a unitary matrix using Cayley transform , and obtain the space-time matrix , is the index of the transmitted signal, is the identity matrix, Reason The matrix obtained by differentially encoding the space-time matrix composed of and the unitary matrix; for The resulting unitary matrix; After linear processing through Cayley transform, the resulting matrix Instead of the transmit signal in step 4 , the maximum likelihood detection algorithm ML is used in step 5 to perform signal detection.

9. The space-time shift modulation method based on MIMO communication according to claim 8, characterized in that: The steps of performing signal detection using the maximum likelihood detection algorithm ML include: Will receive signal Linearization , that is, multiply both sides ; ； in: , , , ; j is an imaginary unit, is an M-PAM modulated signal; They are the equivalent received signal after linear processing, channel matrix, and Gaussian noise respectively; The optimal detection value is determined by minimizing the difference between the received signal and the expected signal after linearization.

10. A system used by the space-time shift modulation method based on MIMO communication according to any one of claims 1 to 9, characterized in that: include: The serial-to-parallel conversion unit is used to divide the source bit information into two groups through the serial-to-parallel converter. The length of the first group of bits is log2 M , M is the modulation order, the length of the second group of bits is log2 R , R is the number of scattered matrices; A modulation mapping unit is used to perform modulation mapping on the first bit group to obtain a modulation code element , and construct a scattered matrix set based on the second group of bits, R , recorded as D 1 ,D 2 ,…，D R , m Indicates the number of combinations of corresponding modulation mode mapping; The space-time mapping unit is used to map the modulation code elements according to the and the selected scatter matrix D r, 1≤ r ≤ R Compute space-time matrix S , which extends both in space and time dimensions, r represents the index of the selected matrix; A receiving signal generating unit is used to generate a channel matrix using a Rayleigh fading channel model , and superimposed with Gaussian white noise Interfere with the signal and obtain the received signal model: ;in, is the index of the transmitted signal, To transmit a signal; The detection optimization unit is used to recover the received signal using the maximum likelihood detection algorithm, vectorize the received signal and build an equivalent model; and obtain the optimal combination.

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