Linear frequency modulation and OTFS technology combined communication perception integrated waveform design method

Abstract

The invention provides a linear frequency modulation and OTFS technology combined communication perception integrated waveform design method. The method comprises the implementation steps that a communication perception integrated signal is acquired; constructing a time delay-Doppler domain information symbol matrix; oTFS modulation is carried out on each time delay-Doppler domain information symbol; and obtaining a communication perception integrated waveform design result. According to the invention, quadrature phase shift keying modulation is carried out on code elements generated by a communication end, and OTFS modulation is carried out on time delay-Doppler domain information symbols in a time delay-Doppler domain information symbol matrix constructed by modulated communication information symbols. And the communication time domain signal modulated by the OTFS is fused with a linear frequency modulation signal generated by a corresponding radar end, so that the sensitivity of mobile communication to Doppler frequency shift in a high-speed environment is reduced, and the communication performance is improved while the communication perception integrated system has relatively good radar perception performance.

Description

Technical Field

[0001] The present invention belongs to the field of communication technologies, and relates to a design method for a communication and sensing integrated waveform combining linear frequency modulation and OTFS technologies. Background Art

[0002] The integrated communication and sensing (ISAC) technology aims to make communication and sensing technologies complement each other through co-design, so as to reduce system costs, improve hardware utilization, and thus optimize spectrum resource allocation. In ISAC, waveform design integrates waveforms with dual functions of sensing and communication on the premise of sharing signal resources.

[0003] The design of integrated communication and sensing waveforms is divided into three types: communication-centered integrated waveform design, sensing-centered integrated waveform design, and integrated waveform design combining communication and sensing. Among them, the integrated waveform design method combining communication and sensing has good sensing ability while providing efficient and reliable communication performance. For example, Zhao Zhongkai et al. from Harbin Engineering University published a radar-communication integrated waveform design method of OFDM-LFM in the journal "Applied Science and Technology", Volume 3, 2021, Pages 73-77. This method first studies the feasibility of combining OFDM and linear frequency modulation signals based on the properties of linear frequency modulation signals, then derives the mathematical model of OFDM-linear frequency modulation signals, and on this basis, conducts research and analysis on three relatively common communication modulation methods in OFDM modulation, namely BPSK, MSK, and 16QAM, and designs three integrated waveforms. This method combines OFDM and linear frequency modulation signals to achieve communication and radar functions, and performs excellently in radar sensing. However, since the designed waveforms require each subcarrier to be orthogonal in the frequency domain, different subcarriers will experience different Doppler frequency shifts in a high-speed environment, resulting in the destruction of orthogonality between subcarriers, thereby causing interference between subcarriers and affecting the further improvement of the communication performance of the integrated communication and sensing system. Summary of the Invention

[0004] The purpose of the present invention is to overcome the defects of the above-mentioned existing technologies, and propose a design method for a communication and sensing integrated waveform combining linear frequency modulation and OTFS, aiming to ensure good radar sensing performance while reducing the impact on communication performance due to poor anti-Doppler frequency shift ability in a high-speed environment, and further improving the overall performance of the integrated communication and sensing system.

[0005] To achieve the above purpose, the technical solutions adopted by the present invention include the following steps:

[0006] (1) Obtain an integrated communication and sensing signal:

[0007] Obtain the linear frequency modulation signal \(f(t)\) at the \(t\)-th moment generated by the radar end and the symbol \(a\) generated by the communication end in communication-sensing integration. Q , where \(t\in[1,T pulse \), \(T pulse represents the duration of the \(f(t)\) pulse, \(T pulse \geq10\ \mu s\), \(Q\) represents the number of symbols, \(Q\geq50\);

[0008] (2) Construct the delay-Doppler domain information symbol matrix:

[0009] Perform quadrature phase shift keying modulation on the symbol \(a\) generated by the communication end Q and obtain the communication information symbol \(x\) through modulation D Construct the delay-Doppler domain information symbol matrix \(X\) with dimensions \(K\times L\) K×L , where the information symbol of the \(k\)-th delay and the \(l\)-th Doppler cell in \(X K×L is \(x[k, l]\), \(K\geq4\), \(L\geq4\);

[0010] (3) Perform OTFS modulation on each delay-Doppler domain information symbol:

[0011] Perform OTFS modulation on each delay-Doppler domain information symbol \(x[k, l]\) to obtain the communication time-domain signal \(s(t)\) at the \(t\)-th moment, where \(t\in[1,T symbol \), \(T symbol represents the period of the delay-Doppler domain information symbol, \(T symbol \geq10\ \mu s\);

[0012] (4) Obtain the communication-sensing integration waveform design result:

[0013] Fuse the communication time-domain signal \(s(t)\) and the linear frequency modulation signal \(f(t)\) to obtain the communication-sensing integration waveform \(z(t)\) at the \(t\)-th moment.

[0014] Compared with the prior art, the present invention has the following advantages:

[0015] The present invention performs quadrature phase shift keying modulation on the symbol generated by the communication end, performs OTFS modulation on the delay-Doppler domain information symbols in the delay-Doppler domain information symbol matrix constructed by the modulated communication information symbols, and then fuses the OTFS-modulated communication time-domain signal and the corresponding linear frequency modulation signal generated by the radar end. Since the information symbols are evenly distributed in the delay-Doppler domain, the influence of Doppler frequency shift will also be evenly distributed in the delay-Doppler domain. Therefore, the formed waveform reduces the sensitivity of mobile communication to Doppler frequency shift in a high-speed environment, ensuring that the communication-sensing integration system improves the communication performance while having good radar sensing performance. Description of the Drawings

[0016] Figure 1 This is the implementation flowchart of the present invention.

[0017] Figure 2 This is a comparison graph of the relationship curves between the bit error rate and the signal-to-noise ratio of the waveforms of the present invention and the prior art in a mobile communication environment at 30 km / h and 120 km / h. Specific embodiments

[0018] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0019] Refer to Figure 1 , the present invention includes the following steps:

[0020] Step 1) Obtain the communication and sensing integrated signal:

[0021] Obtain the chirp signal f(t) at the t-th moment generated by the radar end in the communication and sensing integration and the symbol a generated by the communication end Q , where:

[0022]

[0023] Among them, A, f 0 , B respectively represent the amplitude, center frequency, and bandwidth of f(t), rect(·) represents the rectangular window function, t represents the time variable, j represents the imaginary unit, π represents the pi, t ∈ [1, T pulse , T pulse represents the duration of the f(t) pulse, T pulse ≥ 10 μs, Q represents the number of symbols, Q ≥ 50.

[0024] In this embodiment, Q = 1000, T pulse = 10000 μs, B = 10 MHz, f 0 = 0 Hz, A = 1.

[0025] Step 2) Construct the delay-Doppler domain information symbol matrix:

[0026] Group the symbol a generated by the communication end in units of two bits Q . When the number of symbols is odd, append 0 at the end of the symbol to make it an even length. In this embodiment, 1000 symbols are divided into 500 groups, each group includes two symbols, and each group of symbols is converted into a quaternary number as the delay-Doppler domain information symbol, obtaining a set x of communication information symbols, and then along the delay axis and the Doppler axis, the communication information symbol x D , and the communication information symbol x DPerform K samplings and L samplings respectively, and place the information symbol x[k, l] of the k-th delay and the l-th Doppler cell at the corresponding position of the delay-Doppler grid with dimensions K×L to form the delay-Doppler domain information symbol matrix X K×L , denotes rounding up, K≥4, L≥4.

[0027] In this embodiment, K = 128 and L = 128.

[0028] Step 3) Perform OTFS modulation on each delay-Doppler domain information symbol:

[0029] Perform the inverse symplectic finite Fourier transform on each delay-Doppler domain information symbol x[k, l] to obtain the signal X[k, l] at the k-th time and the l-th frequency in the time-frequency domain grid, and perform the Heisenberg transformation on X[k, l] to obtain the communication time-domain signal s(t):

[0030]

[0031]

[0032] where x[k′, l′] represents the information symbol of the k′-th delay and the l′-th Doppler cell corresponding to the k-th time and the l-th frequency in X[k, l], k and l represent the parameters in the time-frequency domain, and their maximum values are the same as the maximum values of the corresponding parameters k′ and l′ representing the delay-Doppler domain, Δf represents the interval of OTFS subcarriers, T symbol represents the period of the delay-Doppler domain information symbol, g tx (·) represents the rectangular window function, T symbol ≥10 μs.

[0033] In this embodiment, Δf = 100 kHz, T symbol = 10000 μs.

[0034] Step 4) Obtain the communication perception integrated waveform design result:

[0035] Fuse the communication time-domain signal s(t) with the chirp signal f(t) to obtain the communication perception integrated waveform z(t) at the t-th moment:

[0036]

[0037] Compared with the prior art, the present invention has the following advantages:

[0038] The present invention performs quadrature phase shift keying modulation on the symbols generated by the communication terminal, and performs OTFS modulation on the time-delay-Doppler domain information symbols in the time-delay-Doppler domain information symbol matrix constructed by the modulated communication information symbols. Then, it fuses the communication time-domain signal after OTFS modulation with the corresponding chirp signal generated by the radar terminal. Since the information symbols are uniformly distributed in the time-delay-Doppler domain, the influence of Doppler frequency shift will also be uniformly distributed in the time-delay-Doppler domain. Therefore, the formed waveform reduces the sensitivity of mobile communication to Doppler frequency shift in a high-speed environment, ensures the balance between communication performance and sensing ability, and further improves the comprehensive performance of the communication and sensing integrated system.

[0039] The technical effects of the present invention are described below in combination with simulation experiments:

[0040] 1. Simulation conditions and content:

[0041] The relationship between the bit error rate and the signal-to-noise ratio of the present invention and the waveforms of the prior art in mobile communication environments of 30 km / h and 120 km / h is simulated through a 64-bit operating system and MATLAB R2023b, and the results are as Figure 2 shown.

[0042] 2. Analysis of simulation results:

[0043] Referring to Figure 2 , Figure 2 (a) and Figure 2 (b) are respectively the comparison diagrams of the relationship curves between the bit error rate and the signal-to-noise ratio of the waveforms of the present invention and the prior art in mobile communication environments of 30 km / h and 120 km / h. Among them, Figure 2 (a) is the comparison diagram of the relationship curve between the bit error rate and the signal-to-noise ratio of the waveforms of the present invention and the prior art in a 30 km / h mobile communication environment, Figure 2 (b) is the comparison diagram of the relationship curve between the bit error rate and the signal-to-noise ratio of the waveforms of the present invention and the prior art in a 120 km / h mobile communication environment. It can be seen from Figure 2 (a) that the bit error rate of the present invention decreases significantly faster than that of the prior art as the signal-to-noise ratio increases, and the bit error rate drops to 10 -3 or less at high signal-to-noise ratios (SNR > 15 dB), which is significantly lower than that of the prior art. It can be seen from Figure 2 (b) that in a high-speed (120 km / h) mobile communication environment, the bit error rate of the present invention is significantly lower than that of the prior art as the signal-to-noise ratio increases, indicating that the present invention reduces the sensitivity of mobile communication to Doppler frequency shift in a high-speed environment and improves the communication performance better than the prior art.

Claims

1. A communication perception integrated waveform design method combining linear frequency modulation and OTFS, characterized in that: The following steps are involved: (1) Obtaining integrated communication and perception signals: Obtain the linear frequency modulation signal f(t) generated by the radar end at the tth moment and the code element a generated by the communication end in the communication perception integration Q , where t∈[1,T pulse ], T pulse represents the duration of the f(t) pulse, T pulse ≥10μs, Q represents the number of code elements, Q≥50; (2) Constructing the delay-Doppler domain information symbol matrix: The code element a generated by the communication end Q Orthogonal phase shift keying modulation is performed, and the communication information symbol x obtained by modulation is D Construct a K×L delay-Doppler domain information symbol matrix X K×L , where X K×L The information symbol of the kth time delay and the lth Doppler unit is x[k,l], K≥4, L≥4; (3) Perform OTFS modulation on each delay-Doppler domain information symbol: Perform OTFS modulation on each delay-Doppler domain information symbol x[k,l] to obtain the communication time domain signal s(t) at the tth moment, where t∈[1,T symbol ], T symbol represents the period of the delay-Doppler domain information symbol, T symbol ≥10μs; (4) Obtain the communication perception integrated waveform design results: The communication time domain signal s(t) and the linear frequency modulation signal f(t) are fused to obtain the communication perception integrated waveform z(t) at the tth moment.

2. The method according to claim 1, characterized in that The linear frequency modulation signal f(t) described in step (1) is expressed as: Where A, f0, and B represent the amplitude, center frequency, and bandwidth of f(t), respectively; rect(·) represents the rectangular window function; t represents the time variable; j represents the imaginary unit; and π represents the circumference of a circle.

3. The method according to claim 2, characterized in that The code element a generated by the communication end in step (2) Q Perform quadrature phase shift keying modulation, the implementation method is: The code element a is calculated in units of two bits. Q Group them and convert each group of code elements into quaternary numbers as communication information symbols, and get The set of communication information symbols x D ,in Indicates rounding up.

4. The method according to claim 3, characterized in that The delay-Doppler domain information symbol matrix X constructed in step (2) with a dimension of K×L is K×L , the implementation method is: The communication information symbol x along the delay axis and Doppler axis D Perform K and L samplings respectively, and place the information symbol x[k,l] of the kth delay and lth Doppler unit to the corresponding position of the delay-Doppler grid with dimension K×L to form the delay-Doppler domain information symbol matrix X K×L .

5. The method according to claim 4, characterized in that The OTFS modulation of each delay-Doppler domain information symbol in step (3) is implemented by: Perform a symplectic finite inverse Fourier transform on each delay-Doppler domain information symbol x[k,l] to obtain the corresponding signal X[k,l] at the kth time and the lth frequency in the time-frequency domain grid, and perform a Heisenberg transform on X[k,l] to obtain the communication time domain signal s(t): Where x[k′,l′] represents the information symbol of the k′th time delay and l′th Doppler unit corresponding to the kth time and lth frequency in X[k,l], Δf represents the spacing of OTFS subcarriers, T symbol represents the period of the delay-Doppler domain information symbol, g tx (·) represents the rectangular window function, T symbol ≥10μs.

6. The method according to claim 5, characterized in that The communication-sensing integrated waveform z(t) described in step (4) is expressed as:

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