CN113810325B - A multi-antenna OTFS modulation method and system based on spatial modulation - Google Patents

Abstract

The invention discloses a multi-antenna OTFS (optical transmission system) modulation method and a system based on spatial modulation, wherein the method comprises the following steps: carrying out spatial modulation on an original information sequence to be transmitted to obtain a modulated symbol sequence and a transmitting antenna index sequence; arranging the symbol sequence of each transmitting antenna into a time delay-Doppler domain signal matrix to obtain an OTFS symbol block, and transforming the OTFS symbol block into a time domain signal matrix; performing time domain channel transmission on the time domain signal matrix according to the sending antenna index sequence; performing OTFS demodulation on the time domain signal matrix at a receiving end, and recovering the time domain signal matrix into a symbol matrix on a delay-Doppler domain; and carrying out maximum likelihood detection on the symbol matrix recovered on each time slot by combining the antenna index sequence and the modulated symbol sequence, and recovering the original information sequence. According to the invention, only one sending antenna is activated in each time slot to transmit data information, so that the problems of mutual interference and synchronization among the antennas can be effectively avoided, and the complexity of a multi-antenna system receiver can be reduced.

Description

A multi-antenna OTFS modulation method and system based on spatial modulation

technical field

The invention belongs to the technical field of communication, and in particular relates to a multi-antenna OTFS modulation method and system based on spatial modulation.

Background technique

For next-generation wireless systems, such as post-5G and 6G, how to obtain high-reliability and high-throughput data transmission has become a hot issue in the design of multi-carrier signal transmission schemes. These solutions are expected to be efficiently transmitted in dual-dispersion channels in high-speed mobile scenarios such as high-speed rail communication and inter-vehicle communication. Orthogonal Time Frequency Space (OTFS) modulation technology is a multi-carrier transmission scheme proposed for this high Doppler channel. Compared with the Orthogonal Frequency Division Multiplexing (OFDM) scheme currently used in 4G and 5G for signal transmission in the time-frequency domain, OTFS uses the delay-Doppler domain for signal transmission and signal processing. Capture the time shift and Doppler shift in the actual physical channel, turn the time-varying multipath channel into a time-invariant channel in the delay-Doppler domain, and can be effective in the delay-Doppler domain It can estimate the channel state information accurately, which simplifies the design of the channel equalizer.

At present, the development of OTFS technology mainly has four major directions: simplifying the OTFS system structure, reducing the detection complexity, researching the performance of multi-antenna OTFS systems, and designing efficient channel estimation algorithms.

The research on MIMO (Multiple Input Multiple Output)-OTFS system mainly includes the vector of the input-output relationship of the general MIMO-OTFS system in the paper "MIMO-OTFS in high-Doppler fading channels: Signal detection and channelestimation" by M.K. Ramachandran and other scholars Research on derivation and low-complexity detection algorithm based on message passing. For the combination of specific MIMO technology and OTFS technology, there are also scholars such as R.M.Augustine researching the performance of STC-OTFS system in the paper "Space-time coded OTFS modulation in high-Dopplerchannels". The paper "Space-time coded OTFS modulation in high-Doppler channels" combines Space Time code (STC) with OTFS. The simulation results show that STC-OTFS can obtain full diversity gains in space, time and frequency, and it also shows that STC -OTFS has good bit error rate performance compared to single antenna system. However, the maximum spectral efficiency of the STC-OTFS system with full diversity can only be one symbol per time slot, and the spectral efficiency is low.

SUMMARY OF THE INVENTION

In order to solve the above problems in the prior art, the present invention provides a multi-antenna OTFS modulation method and system based on spatial modulation. The technical problem to be solved by the present invention is realized by the following technical solutions:

One aspect of the present invention provides a multi-antenna OTFS modulation method based on spatial modulation, including:

Perform spatial modulation on the original information sequence to be transmitted to obtain the modulated symbol sequence and transmit antenna index sequence;

Arrange the symbol sequence of each transmit antenna into a delay-Doppler domain signal matrix, obtain OTFS symbol blocks and modulate them into a time domain signal matrix;

performing time-domain channel transmission on the time-domain signal matrix according to the transmit antenna index sequence;

At the receiving end, OTFS demodulates the time-domain signal matrix received on each receiving antenna, and restores it to a symbol matrix in the delay-Doppler domain;

The maximum likelihood detection is performed on the demodulated and restored symbol matrix in each time slot, combined with the antenna index sequence and the demodulated symbol sequence, to restore the original information sequence.

In an embodiment of the present invention, spatial modulation is performed on the original information sequence to be transmitted to obtain a modulated information symbol sequence and a transmit antenna index sequence, including:

Convert the original information sequence to be transmitted into a binary bit sequence, and group the binary bit sequence according to each m bits as a group, and each group is separated into a signal bit vector with a length of m _s and a length of Spatial bit vector of m _l , where m is the spectral efficiency of the modulation system, m _l =log ₂ N _t , N _t is the total number of transmitting antennas, m _s =mm _l ;

Carry out constellation mapping to the described signal bit vector whose length is m _s in each grouping, obtain the symbol after the constellation mapping, and then obtain the symbol sequence to be transmitted;

Perform antenna index mapping on the space bit vector with a length of _ml in each group to obtain a transmit antenna index, and then obtain a transmit antenna index sequence, wherein the transmit antenna index sequence is used to determine the activated data of each time slot. antennas, which in turn determine the sequence of symbols on each transmit antenna.

In an embodiment of the present invention, the symbol sequence of each transmit antenna is arranged into a delay-Doppler domain signal matrix, and an OTFS symbol block is obtained and transformed into a time domain signal matrix, including:

Set the OTFS modulation system parameters: set the number of subcarriers to M and the number of multi-carrier symbols to N;

Arranging the symbol sequence of each transmitting antenna into an M×N delay-Doppler domain signal matrix to form an OTFS symbol block;

Perform ISFFT transformation on the OTFS symbol block on each transmit antenna, and then perform Heisenberg transformation to obtain an M×N time-domain signal matrix.

In an embodiment of the present invention, performing time-domain channel transmission on the time-domain signal matrix according to the transmit antenna index sequence includes:

Convert the M×N time-domain signal matrix on each transmit antenna into an MN×1 time-domain signal vector through parallel-to-serial conversion;

Obtaining the transmit antenna index and activating the corresponding antenna in the time domain channel according to the transmit antenna index, so as to transmit the time domain signal vector.

In an embodiment of the present invention, the receiving end performs OTFS demodulation on the time-domain signal matrix received on each receiving antenna, and restores it to a symbol matrix in the delay-Doppler domain, including:

Perform serial-parallel conversion on the time-domain signal vector received on each receiving antenna into an M×N time-domain signal matrix;

Wigner transform and SFFT transform are performed on the M×N time-domain signal matrix on each receiving antenna, so as to restore the received signal of each receiving antenna to an M×N delay-Doppler-domain symbol matrix.

In an embodiment of the present invention, the maximum likelihood detection is performed on the demodulated and restored symbol matrix in each time slot in combination with the antenna index sequence and the demodulated symbol sequence to restore the original information sequence, including:

Perform parallel-to-serial conversion on the M×N delay-Doppler domain signal matrix recovered on each receiving antenna, and convert it into an MN×1 signal vector in the delay-Doppler domain;

The joint maximum likelihood detection of the antenna index sequence and the demodulated symbol sequence is performed according to the symbol vector composed of symbols received by different receiving antennas on each time slot, and the transmission information sequence on each time slot is recovered, and then the entire original information sequence.

Another aspect of the present invention provides a multi-antenna OTFS modulation system based on spatial modulation, comprising:

The spatial modulation module is used to spatially modulate the information sequence to be transmitted to obtain the modulated symbol sequence and the transmit antenna index sequence;

The OTFS modulation module is used to arrange the symbol sequence of each transmitting antenna into a delay-Doppler domain signal matrix, obtain OTFS symbol blocks and modulate them into a time domain signal matrix;

a time-domain channel module, configured to perform time-domain channel transmission on the time-domain signal matrix according to the transmit antenna index sequence;

The OTFS demodulation module is used at the receiving end to perform OTFS demodulation on the time-domain signal matrix received on each receiving antenna, and restore it to a symbol matrix in the delay-Doppler domain;

The signal detection module is used for performing maximum likelihood detection on the demodulated and restored symbol matrix combined with the antenna index sequence and the demodulated symbol sequence on each time slot to restore the original information sequence.

In an embodiment of the present invention, the spatial modulation module includes:

The signal separation unit is used to convert the original information sequence to be transmitted into a binary bit sequence, and group the binary bit sequence according to each m bits as a group, and each group is separated into a length of m _s . The signal bit vector and the space bit vector of length m _l , where m is the spectral efficiency of the modulation system, m _l =log ₂ N _t , N _t is the total number of transmitting antennas, m _s =mm _l ;

a constellation mapping unit, configured to perform constellation mapping on the signal bit vector with a length of m _s in each grouping to obtain a symbol after the constellation mapping, and then obtain a symbol sequence to be transmitted;

an antenna index mapping unit, configured to perform antenna index mapping on the space bit vector with a length of _ml in each group, to obtain a transmit antenna index, and then to obtain a transmit antenna index sequence, wherein the transmit antenna index sequence is used to determine The activated antennas for each time slot, in turn, determine the sequence of symbols on each transmit antenna.

In an embodiment of the present invention, the OTFS modulation module includes:

an OTFS symbol block generation unit, configured to arrange the symbol sequence of each transmitting antenna into an M×N delay-Doppler domain signal matrix to form an OTFS symbol block;

The ISFFT transform unit is used to perform ISFFT transform on the OTFS symbol block on each transmit antenna;

The Heisenberg transform unit is used to perform Heisenberg transform on the OTFS symbol block transformed by the ISFFT to obtain an M×N time-domain signal matrix.

In an embodiment of the present invention, the time domain channel module includes:

a parallel-serial conversion unit, configured to convert the M×N time-domain signal matrix into an MN×1-dimensional time-domain signal vector;

The antenna array unit obtains the transmit antenna index and activates the corresponding antenna in the time domain channel according to the transmit antenna index, so as to transmit the time domain signal vector.

Compared with the prior art, the beneficial effects of the present invention are:

1. The present invention applies the spatial modulation technology to the OTFS modulation system based on the multi-antenna OTFS modulation method of spatial modulation, utilizes the high spectral efficiency of spatial modulation and the diversity gain to the antenna, carries information through the antenna index, and improves the frequency spectrum of the system. It has high efficiency, reduces the bit error rate, and can also resist high Doppler well, and has good robustness in high-speed mobile and high-frequency communication scenarios.

2. The multi-antenna OTFS modulation method and system based on spatial modulation of the present invention uses one transmitting antenna to transmit data information, which can effectively avoid mutual interference and synchronization problems between antennas, and can reduce the complexity of the system receiver.

The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

Description of drawings

1 is a flowchart of a multi-antenna OTFS modulation method based on spatial modulation provided by an embodiment of the present invention;

2 is a schematic process diagram of a multi-antenna OTFS modulation method based on spatial modulation provided by an embodiment of the present invention;

3 is an example diagram of spatial mapping of a spatial modulation signal of a multi-antenna OTFS modulation method based on spatial modulation provided by an embodiment of the present invention;

4 is a schematic block diagram of a multi-antenna OTFS modulation system based on spatial modulation provided by an embodiment of the present invention;

FIG. 5 is a comparison diagram of simulation results between the method of the embodiment of the present invention and the existing STC-OTFS method.

Detailed ways

In order to further illustrate the technical means and effects adopted by the present invention to achieve the predetermined purpose of the invention, a multi-antenna OTFS modulation method and system based on spatial modulation proposed by the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

The foregoing and other technical contents, features and effects of the present invention can be clearly presented in the following detailed description of the specific implementation with the accompanying drawings. Through the description of the specific embodiments, the technical means and effects adopted by the present invention to achieve the predetermined purpose can be more deeply and specifically understood. However, the accompanying drawings are only for reference and description, and are not used for the technical description of the present invention. program is restricted.

It should be noted that, in this document, relational terms such as first and second are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any relationship between these entities or operations. any such actual relationship or sequence exists. Moreover, the terms "comprising", "comprising" or any other variation are intended to encompass a non-exclusive inclusion, whereby an article or device comprising a list of elements includes not only those elements, but also other elements not expressly listed. Without further limitation, an element qualified by the phrase "comprising a..." does not preclude the presence of additional identical elements in the article or device that includes the element.

Example 1

Please refer to FIG. 1. FIG. 1 is a flowchart of a multi-antenna OTFS modulation method based on spatial modulation provided by an embodiment of the present invention. The multi-antenna OTFS modulation method includes:

S1: Perform spatial modulation on the original information sequence to be transmitted to obtain the modulated symbol sequence and the transmit antenna index sequence.

Specifically, step S1 includes:

S11: Convert the original information sequence to be transmitted into a binary bit sequence, and group the binary bit sequence according to each m bits as a group, and each group is separated into a signal bit vector of length m _s and A spatial bit vector of length m _l , where m is the spectral efficiency of the modulation system, m _l =log ₂ N _t , N _t is the total number of transmitting antennas, m _s =mm _l ;

S12: Perform constellation mapping on the signal bit vector with a length of m _s in each group to obtain a constellation-mapped symbol, and then obtain a symbol sequence to be transmitted;

S13: Perform antenna index mapping on the spatial bit vector of length _ml in each packet to obtain a transmit antenna index, and then obtain a transmit antenna index sequence, where the transmit antenna index sequence is used to determine whether each time slot is The active antennas, in turn, determine the sequence of symbols on each transmit antenna.

S2: Arrange the symbol sequence of each transmit antenna into a delay-Doppler domain signal matrix, obtain an OTFS symbol block and modulate it into a time domain signal matrix.

Specifically, step S2 includes:

S21: Set OTFS modulation system parameters: set the number of subcarriers to M, the number of multi-carrier symbols to N, and an OTFS symbol block is an M×N matrix composed of MN symbol sequences;

S22: Arrange the symbol sequence of each transmitting antenna into an M×N delay-Doppler domain signal matrix to form an OTFS symbol block;

S23: Perform ISFFT transformation on the OTFS symbol block on each transmit antenna, and then perform Heisenberg transformation to obtain an M×N time-domain signal matrix.

S3: Perform time-domain channel transmission on the time-domain signal matrix according to the transmit antenna index sequence.

Specifically, the M×N time-domain signal matrix on each transmit antenna is converted into an MN×1 time-domain signal vector through parallel-serial conversion; the corresponding antenna in the time-domain channel is activated according to the transmit antenna index, so as to The time domain signal vector is used for transmission.

S4: Perform OTFS demodulation on the time-domain signal matrix received on each receiving antenna at the receiving end, and restore it to a symbol matrix in the delay-Doppler domain.

Specifically, serial-to-parallel conversion is performed on the time-domain signal vector received on each receiving antenna into an M×N time-domain signal matrix; then Wigner transform and SFFT transform are performed on the M×N time-domain signal matrix on each receiving antenna. , so that the received signal of each receiving antenna is restored to an M×N delay-Doppler domain symbol matrix.

S5: Perform maximum likelihood detection on the demodulated and restored symbol matrix in each time slot in combination with the antenna index sequence and the demodulated symbol sequence to restore the original information sequence.

Specifically, perform parallel-to-serial conversion on the M×N delay-Doppler domain signal matrix recovered on each receiving antenna, and convert it into an MN×1 signal vector in the delay-Doppler domain; The symbol vector composed of symbols received by different receiving antennas on the slot is subjected to joint maximum likelihood detection of the antenna index sequence and the demodulated symbol sequence, and the transmission information sequence on each time slot is recovered, and then the entire information sequence is recovered.

In this embodiment, the receiving end uses the optimal detection algorithm—maximum likelihood sequence detection to perform maximum likelihood detection on the symbol matrix recovered by demodulation in each time slot, combined with the antenna index sequence and the modulated symbol sequence, Antenna demapping and signal demapping are then performed to obtain the entire information sequence transmitted.

In this embodiment, the multi-antenna OTFS modulation method based on spatial modulation applies the spatial modulation technology to the OTFS modulation system, utilizes the high spectral efficiency of spatial modulation and the diversity gain to the antenna, and carries information through the antenna index, thereby improving the spectral efficiency of the system , reduces the bit error rate, and can also resist high Doppler well, and has good robustness in high-speed mobile and high-frequency communication scenarios.

Embodiment 2

On the basis of the foregoing embodiment, this embodiment provides another multi-antenna OTFS modulation method based on spatial modulation. Referring to FIG. 2 , the multi-antenna OTFS modulation method in this embodiment includes:

(1) Allocate the required number of space bits to the transmitting antenna space: set the total number of transmitting antennas N _t to the power of 2, perform logarithmic operation on the total number of transmitting antennas N _t , and obtain the number of space bits as m _l =log ₂ N _t ; it is assumed that the activation probability of each transmit antenna is equal, then a spatial bit vector and an antenna index form a one-to-one mapping.

In this embodiment, the total number of transmitting antennas N _t is set to be 2, and the number of space bits is m _l =log ₂ N _t =1. That is, space bit 0 corresponds to antenna index 1, and space bit 1 corresponds to antenna index 2.

(2) Allocate the required number of signal bits to the signal space mapping: set the spectral efficiency that the system needs to achieve as m=3, and use the spectral efficiency formula to calculate the number of bits required for the signal space mapping m _s =mm _l =2.

(3) Set the parameters of the OTFS modulation module: set the number of OTFS modulated subcarriers to M=2, representing the delay dimension; the number of multi-carrier symbols to N=2, representing the Doppler dimension; then an OTFS symbol A block consists of a 2x2 matrix containing MxN=4 modulation symbols.

(4) Group the information sequence to be transmitted:

Specifically, the original information sequence to be transmitted is represented by a binary bit sequence, and then every m bit sequence in the binary bit sequence is separated, that is, each group includes m bit sequences, and each group is separated is a signal bit vector of length _ms and a space bit vector of length _ml .

In this embodiment, every 3 bits in the binary bit vector are divided into a group, and then the group of bits is separated into a signal bit vector of length 2 and a space bit vector of length 1, as shown in FIG. 2 . Show.

Further, please refer to FIG. 3 . FIG. 3 is an example diagram of spatial mapping of a spatial modulation signal of a multi-antenna OTFS modulation method based on spatial modulation provided by an embodiment of the present invention. Specifically, FIG. 3 shows an example of spatial modulation. First, the binary bit sequence is grouped according to m=3, and after each group is obtained, the binary bit vector in each group is separated into a length of m _l =1 The antenna index bits and the signal vector bits of m _s = 2, as shown in the shaded part in the figure, in the first time slot, 011 is separated into 0 and 11 to represent the antenna index bits and signal vector bits respectively, and then according to the mapping table, the antenna Index bit 0 maps to antenna index 1, and signal vector bit 11 maps to complex number -1-j. At this time, in the first time slot, the first transmit antenna is activated, and the transmit vector V ₁ of the first time slot indicates that the first antenna transmits a signal -1-j, and the second antenna transmits a value of 0. In the figure, x ₁ and x ₂ represent the transmitted symbol sequences on the first antenna and the second antenna.

(5) Mapping the grouped signal bit vector and the space bit vector respectively.

Specifically, a signal bit vector with a length of 2 and a space bit vector with a length of 1 are respectively mapped, and the signal bit vector is mapped to a QPSK (Quadrature Phase Shift Keying) constellation point through a constellation mapping method to obtain The symbol sequence after constellation mapping; perform antenna index mapping on the space bit vector with the length of m _l =1 in each group to obtain a transmit antenna index sequence, wherein the transmit antenna index sequence is used to determine each time slot The activated antennas in turn determine the sequence of symbols on each transmit antenna.

(6) Construct an OTFS symbol block: Arrange the symbol sequence of each transmit antenna after constellation mapping into a 2×2 delay-Doppler domain signal matrix, that is, an OTFS symbol block.

(7) OTFS modulation: The OTFS symbol block is first subjected to ISFFT transformation and then Heisenberg transformation to obtain a 2×2 time-domain signal matrix.

(8) Channel transmission: First, convert the 2×2 time-domain signal matrix into a 4×1 time-domain signal vector through parallel-serial conversion, and then determine the location of each information symbol according to the transmit antenna index in step (5). The corresponding transmitting antenna is activated, and the time domain signal is sent out. At this time, the spatial bit vector information is contained in the index of the transmitting antenna.

(9) The receiving antenna receives the time-domain signal vector: the receiving end converts the time-domain received signal vector into a 2×2 time-domain received signal matrix through serial-to-parallel conversion.

(10) OTFS demodulation: The 2×2 time-domain received signal matrix is first subjected to Wigner transform and then SFFT transform to obtain a 2×2 received signal matrix in the delay-Doppler domain.

(11) Maximum likelihood detection in the delay-Doppler domain: The receiving end adopts the optimal detection algorithm - maximum likelihood sequence detection, and performs the detection according to the symbol vector composed of symbols received by different receiving antennas on each time slot. The joint maximum likelihood detection of the antenna index sequence and the demodulated symbol sequence restores the transmission information sequence on each time slot, and then restores the entire original information sequence.

Embodiment 3

On the basis of the foregoing embodiments, this embodiment provides a multi-antenna OTFS modulation system based on spatial modulation. Referring to FIG. 4, FIG. 4 is a schematic block diagram of a multi-antenna OTFS modulation system based on spatial modulation provided by an embodiment of the present invention. The signal modulation system includes:

The spatial modulation module 1 is used to perform spatial modulation on the information sequence to be transmitted to obtain the modulated symbol sequence and the transmit antenna index sequence;

The OTFS modulation module 2 is used for arranging the symbol sequence of each transmitting antenna into a delay-Doppler domain signal matrix, obtaining an OTFS symbol block and modulating it into a time domain signal matrix;

a time-domain channel module 3, configured to perform time-domain channel transmission on the time-domain signal matrix according to the transmit antenna index sequence;

The OTFS demodulation module 4 is used at the receiving end to perform OTFS demodulation on the time domain signal matrix received on each receiving antenna, and restore it to a symbol matrix in the delay-Doppler domain;

The signal detection module 5 is used for performing maximum likelihood detection on the demodulated and restored symbol matrix in each time slot in combination with the antenna index sequence and the modulated symbol sequence, to restore the original information sequence.

Further, the spatial modulation module 1 of this embodiment includes:

The signal separation unit is used to convert the original information sequence to be transmitted into a binary bit sequence, and group the binary bit sequence according to each m bits as a group, and each group is separated into a length of m _s . The signal bit vector and the space bit vector of length m _l , where m is the spectral efficiency of the modulation system, m _l =log ₂ N _t , N _t is the total number of transmitting antennas, m _s =mm _l ;

a constellation mapping unit, for performing constellation mapping on the signal bit vector with a length of m _s in each grouping, to obtain a symbol sequence after the constellation mapping;

an antenna index mapping unit, configured to perform antenna index mapping on the space bit vector with a length of _ml in each group to obtain a transmit antenna index sequence, wherein the transmit antenna index sequence is used to determine that each time slot is activated antennas to determine the sequence of symbols on each transmit antenna.

Further, the OTFS modulation module 2 includes an OTFS symbol block generation unit, an ISFFT transform unit and a Heisenberg transform unit, wherein the OTFS symbol block generation unit is used to arrange the symbol sequence of each transmit antenna into an M×N delay- Doppler domain signal matrix to form OTFS symbol blocks; ISFFT transform unit is used to perform ISFFT transform on the OTFS symbol blocks on each transmit antenna; Heisenberg transform unit is used to perform Heisenberg transform on the OTFS symbol blocks after ISFFT transformation to obtain M ×N time-domain signal matrix.

Further, the time-domain channel module 3 in this embodiment includes a parallel-serial conversion unit and an antenna array unit, wherein the parallel-serial conversion unit is used to convert the M×N time-domain signal matrix into an MN×1 time-domain signal matrix. domain signal vector; the antenna array unit is configured to acquire the transmit antenna index and activate the corresponding antenna in the time domain channel according to the transmit antenna index, so as to transmit the time domain signal vector.

The OTFS modulation module 4 in this embodiment includes a serial-to-parallel conversion unit, a Wigner conversion unit, and an SFFT conversion unit, wherein the serial-to-parallel conversion unit is used to convert the received MN×1 time-domain signal vector into an M×N time-domain signal matrix, where M is the number of subcarriers, and N is the number of multi-carrier symbols; the Wigner transform unit is used to transform the M×N time-domain signal matrix into a signal matrix in the time-frequency domain; the SFFT transform The unit is used to transform a signal matrix in the time-frequency domain into a symbol matrix in the delay-Doppler domain.

Further, the signal detection module 5 includes a signal conversion unit and a maximum likelihood detection unit, wherein the signal conversion unit is used to perform parallel-serialization on the M×N delay-Doppler domain signal matrix recovered on each receiving antenna. Converted into an MN×1 signal vector in the delay-Doppler domain; the maximum likelihood detection unit is used to perform antenna index sequence and modulation according to the symbol vector composed of symbols received by different receiving antennas on each time slot After joint maximum likelihood detection of the symbol sequence, the transmission information sequence on each time slot is recovered, and then the entire original information sequence is recovered.

This embodiment is based on a multi-antenna OTFS modulation system based on spatial modulation, applies spatial modulation technology to the OTFS modulation system, utilizes the high spectral efficiency of spatial modulation and the diversity gain for antennas, and carries information through antenna indices, thereby improving the spectral efficiency of the system , reduces the bit error rate, and can also resist high Doppler well, and has good robustness in high-speed mobile and high-frequency communication scenarios. The system uses one transmitting antenna to transmit data information, which can effectively avoid mutual interference and synchronization problems between antennas, and can reduce the complexity of system detection.

The technical effects of the SM-OTFS-based signal modulation method and system in the embodiment of the present invention are described below in conjunction with simulation experiments:

1. Simulation conditions and content:

The embodiment of the present invention uses Visual Studio 2013 to refer to the simulation parameters in Table 1, and compares and simulates the transmission bit error rate between the existing STC-OTFS method and the method of the embodiment of the present invention under the Windows 10 system, wherein the signal bit vector and the modulation constellation The point mapping relationship is shown in Table 2, and the mapping relationship between the space bit vector and the antenna index is shown in Table 3. The results are shown in Figure 5:

Table 1. Simulation Parameters Table

parameter Numerical value Carrier frequency (GHz) 4 Subcarrier spacing (kHz) 3.75 The number of subcarriers M 2 The number of multi-carrier symbols N 2 Multiple Antenna Configurations 2T4R Constellation modulation QPSK, 8PSK channel estimation ideal The number of paths P=2, (τ_i,υ_i) (0,0), (1,1) Maximum speed (km/h) 506.2 receiver Maximum Likelihood Sequence Detection

Table 2. Signal bit vector and modulation constellation point mapping table

binary signal bit vector QPSK modulation symbols 00 +1+j 01 -1+j 10 +1-j 11 -1-j

Table 3. Spatial bit vector and transmit antenna index mapping table

binary space bit vector Antenna Index 0 1 1 2

2. Analysis of simulation results:

Please refer to FIG. 5 . FIG. 5 is a comparison diagram of simulation results between the method of the embodiment of the present invention and the existing STC-OTFS method, wherein the horizontal axis represents the signal-to-noise ratio of the transmission channel, and the vertical axis represents the bit error rate of each transmission. The "SM-OTFS-QPSK" line represents the bit error rate curve of the SM-OTFS method of the embodiment of the present invention under QPSK modulation, and the "STC-OTFS-8PSK" line represents the bit error rate of the existing STC-OTFS method under 8PSK modulation The “SM-OTFS-8PSK” line represents the bit error rate curve of the SM-OTFS method according to the embodiment of the present invention under 8PSK modulation.

It can be seen from FIG. 5 that under the 2×4 antenna configuration, the spectral efficiency of the SM-OTFS method according to the embodiment of the present invention under both QPSK modulation and 8PSK modulation is 3 bits per time slot. When the bit error rate is 10 ⁻⁴ , the SM-OTFS method according to the embodiment of the present invention can obtain a performance gain close to 9 dB in the QPSK modulation communication system compared with the existing transmission scheme STC-OTFS-8PSK. It is shown that under the same antenna configuration and the same spectral efficiency, the SM-OTFS method according to the embodiment of the present invention can reduce the bit error rate compared with the existing STC-OTFS method, which is mainly achieved by using lower-order constellation mapping, and each Even if only one antenna is activated in a time slot, the method of the embodiment of the present invention can effectively avoid multi-antenna interference and obtain better bit error rate performance.

In addition, under the same 2×4 antenna configuration, the SM-OTFS method of the embodiment of the present invention and the existing STC-OTFS method both use 8PSK constellation mapping, and the spectral efficiency of the SM-OTFS-8PSK of the embodiment of the present invention is 4 bits per slot, while the spectral efficiency of the existing STC-OTFS-8PSK transmission method is 3 bits per slot. It can be seen from FIG. 5 that the SM-OTFS-8PSK of the embodiment of the present invention not only has higher spectral efficiency than the existing transmission method STC-OTFS-8PSK, but also has a bit error rate performance higher than that of the STC-OTFS-8PSK. The bit error rate performance of OTFS-8PSK is good.

To sum up, the embodiment of the present invention applies the spatial modulation technology to the OTFS modulation system based on the multi-antenna OTFS modulation of spatial modulation, utilizes the high spectral efficiency of the spatial modulation and the diversity gain of the antenna, carries information through the antenna index, and improves the system performance. The spectral efficiency is low, the bit error rate is reduced, and it can also resist high Doppler well, and has good robustness in high-speed mobile and high-frequency communication scenarios. The signal modulation method and system employs activating one transmitting antenna to transmit data information, which can effectively avoid mutual interference and synchronization problems between antennas, and can reduce the complexity of system detection.

The above content is a further detailed description of the present invention in conjunction with specific preferred embodiments, and it cannot be considered that the specific implementation of the present invention is limited to these descriptions. For those of ordinary skill in the technical field of the present invention, without departing from the concept of the present invention, some simple deductions or substitutions can be made, which should be regarded as belonging to the protection scope of the present invention.

Claims (10)

1. a multi-antenna OTFS modulation method based on spatial modulation, is characterized in that, comprises: Perform spatial modulation on the original information sequence to be transmitted to obtain the modulated symbol sequence and transmit antenna index sequence; Arrange the symbol sequence of each transmit antenna into a delay-Doppler domain signal matrix, obtain OTFS symbol blocks and modulate them into a time domain signal matrix; performing time-domain channel transmission on the time-domain signal matrix according to the transmit antenna index sequence; At the receiving end, OTFS demodulates the time-domain signal matrix received on each receiving antenna, and restores it to a symbol matrix in the delay-Doppler domain; The maximum likelihood joint detection is performed on the demodulated and restored symbol matrix combined with the antenna index sequence and the demodulated symbol sequence on each time slot to restore the original information sequence. 2. The multi-antenna OTFS modulation method based on spatial modulation according to claim 1, is characterized in that, carries out spatial modulation to the original information sequence that needs to transmit, obtains the information symbol sequence after modulation and transmit antenna index sequence, comprising: Convert the original information sequence to be transmitted into a binary bit sequence, and group the binary bit sequence according to each m bits as a group, and each group is separated into a signal bit vector with a length of m _s and a length of Spatial bit vector of m _l , where m is the spectral efficiency of the modulation system, m _l =log ₂ N _t , N _t is the total number of transmitting antennas, m _s =mm _l ; Carry out constellation mapping to the described signal bit vector whose length is m _s in each grouping, obtain the symbol after the constellation mapping, and then obtain the symbol sequence to be transmitted; Perform antenna index mapping on the space bit vector with a length of _ml in each group to obtain a transmit antenna index, and then obtain an antenna index sequence, wherein the transmit antenna index sequence is used to determine the activated antenna in each time slot , and then determine the symbol sequence on each transmit antenna. 3. The multi-antenna OTFS modulation method based on spatial modulation according to claim 1, is characterized in that, the symbol sequence of each transmitting antenna is arranged into a time delay-Doppler domain signal matrix, obtains OTFS symbol block and transforms is the time-domain signal matrix, including: Set the OTFS modulation system parameters: set the number of subcarriers to M and the number of multi-carrier symbols to N; Arranging the symbol sequence of each transmitting antenna into an M×N delay-Doppler domain signal matrix to form an OTFS symbol block; Perform ISFFT transformation on the OTFS symbol block on each transmit antenna, and then perform Heisenberg transformation to obtain an M×N time-domain signal matrix. 4. The multi-antenna OTFS modulation method based on spatial modulation according to claim 3, wherein the time-domain channel transmission is performed on the time-domain signal matrix according to the transmit antenna index sequence, comprising: Convert the M×N time-domain signal matrix on each transmit antenna into an MN×1 time-domain signal vector through parallel-to-serial conversion; Obtaining the transmit antenna index and activating the corresponding antenna in the time domain channel according to the transmit antenna index, so as to transmit the time domain signal vector. 5. The multi-antenna OTFS modulation method based on spatial modulation according to claim 3, is characterized in that, at the receiving end, the time domain signal matrix received on each receiving antenna is subjected to OTFS demodulation, and is restored to time delay-Dopp Symbolic matrices over the Le field, including: Perform serial-parallel conversion on the time-domain signal vector received on each receiving antenna into an M×N time-domain signal matrix; Wigner transform and SFFT transform are performed on the M×N time-domain signal matrix on each receiving antenna, so as to restore the received signal of each receiving antenna to an M×N delay-Doppler-domain symbol matrix. 6. The multi-antenna OTFS modulation method based on spatial modulation according to claim 5, is characterized in that, carrying out maximum likelihood on the symbol matrix of demodulation recovery on each time slot in combination with the antenna index sequence and the demodulated symbol sequence Detect and restore the original sequence of information, including: Perform parallel-to-serial conversion on the M×N delay-Doppler domain signal matrix recovered on each receiving antenna, and convert it into an MN×1 signal vector in the delay-Doppler domain; The joint maximum likelihood detection of the antenna index sequence and the demodulated symbol sequence is performed according to the symbol vector composed of symbols received by different receiving antennas in each time slot, and the transmission information sequence on each time slot is recovered, and then the entire original information sequence. 7. a multi-antenna OTFS modulation system based on spatial modulation, is characterized in that, comprises: The spatial modulation module is used to spatially modulate the information sequence to be transmitted to obtain the modulated symbol sequence and the transmit antenna index sequence; The OTFS modulation module is used to arrange the symbol sequence of each transmit antenna into a delay-Doppler domain signal matrix, obtain OTFS symbol blocks and modulate them into a time domain signal matrix; a time-domain channel module, configured to perform time-domain channel transmission on the time-domain signal matrix according to the transmit antenna index sequence; The OTFS demodulation module is used at the receiving end to perform OTFS demodulation on the time-domain signal matrix received on each receiving antenna, and restore it to a symbol matrix in the delay-Doppler domain; The signal detection module is used for performing maximum likelihood detection on the demodulated and restored symbol matrix combined with the antenna index sequence and the demodulated symbol sequence on each time slot to restore the original information sequence. 8. The multi-antenna OTFS modulation system based on spatial modulation according to claim 7, wherein the spatial modulation module comprises: The signal separation unit is used to convert the original information sequence to be transmitted into a binary bit sequence, and group the binary bit sequence according to each m bits as a group, and each group is separated into a length of m _s . The signal bit vector and the space bit vector of length m _l , where m is the spectral efficiency of the modulation system, m _l =log ₂ N _t , N _t is the total number of transmitting antennas, m _s =mm _l ; a constellation mapping unit, configured to perform constellation mapping on the signal bit vector whose length is m _s in each group, to obtain a symbol after the constellation mapping, and then obtain a symbol sequence to be transmitted; an antenna index mapping unit, configured to perform antenna index mapping on the space bit vector with a length of _ml in each group, to obtain a transmit antenna index, and then to obtain a transmit antenna index sequence, wherein the transmit antenna index sequence is used to determine The activated antennas for each time slot, in turn, determine the sequence of symbols on each transmit antenna. 9. The multi-antenna OTFS modulation system based on spatial modulation according to claim 7, wherein the OTFS modulation module comprises: The OTFS symbol block generation unit is used to arrange the symbol sequence of each transmitting antenna into an M×N delay-Doppler domain signal matrix to form an OTFS symbol block, wherein the OTFS modulation system parameters are: subcarriers The number is M, and the number of multi-carrier symbols is N; The ISFFT transform unit is used to perform ISFFT transform on the OTFS symbol block on each transmit antenna; The Heisenberg transform unit is used to perform Heisenberg transform on the OTFS symbol block transformed by the ISFFT to obtain an M×N time-domain signal matrix. 10. The multi-antenna OTFS modulation system based on spatial modulation according to claim 9, wherein the time domain channel module comprises: a parallel-serial conversion unit, configured to convert the M×N time-domain signal matrix into an MN×1-dimensional time-domain signal vector; The antenna array unit is configured to acquire the transmit antenna index and activate the corresponding antenna in the time domain channel according to the transmit antenna index, so as to transmit the time domain signal vector.

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