A design method for an integrated communication and sensing waveform combining linear frequency modulation and OTFS technology

Abstract

This invention proposes a design method for an integrated communication-sensing waveform combining linear frequency modulation (LFM) and OTFS (Optical Time-Shift Keying) technology. The steps are as follows: acquiring the integrated communication-sensing signal; constructing a time-delay-Doppler domain information symbol matrix; performing OTFS modulation on each time-delay-Doppler domain information symbol; and obtaining the integrated communication-sensing waveform design result. This invention reduces the sensitivity of mobile communication to Doppler frequency shift in high-speed environments by performing orthogonal phase-shift keying modulation on the symbols generated at the communication end, and then performing OTFS modulation on the time-delay-Doppler domain information symbols in the matrix constructed from the modulated communication information symbols. Finally, the OTFS-modulated communication time-domain signal is fused with the corresponding LFM signal generated at the radar end. This ensures that the integrated communication-sensing system achieves both good radar sensing performance and improved communication performance.

Description

Technical Field

[0001] This invention belongs to the field of communication technology and relates to a design method for an integrated communication sensing waveform that combines linear frequency modulation and OTFS technology. Background Technology

[0002] The Integrated Communication and Sensing (ISAC) technology aims to create a complementary relationship between communication and sensing technologies through collaborative design, thereby reducing system costs, improving hardware utilization, and optimizing spectrum resource allocation. In ISAC, waveform design integrates waveforms with both sensing and communication functions while sharing signal resources.

[0003] Integrated waveform design for communication and sensing can be divided into three types: communication-centric integrated waveform design, sensing-centric integrated waveform design, and sensing-integrated integrated waveform design. Among them, the sensing-integrated integrated waveform design method provides efficient and reliable communication performance while having good sensing capabilities. For example, Zhao Zhongkai et al. from Harbin Engineering University disclosed an OFDM-LFM radar communication integrated waveform design method based on sensing-integrated integrated waveform design in the journal "Applied Technology" (2021, Vol. 3, pp. 73-77). This method first studies the feasibility of combining OFDM and LFM signals based on the properties of LFM signals, then derives the mathematical model of OFDM-LFM signals, and on this basis, studies and analyzes three common communication modulation methods in OFDM modulation: BPSK, MSK, and 16QAM, and designs three integrated waveforms. This method combines OFDM with linear frequency modulation signals to achieve communication and radar functions, and performs well in radar sensing. However, because the waveform design requires each subcarrier to be orthogonal in the frequency domain, different subcarriers will experience different Doppler frequency shifts in high-speed environments, which will lead to the destruction of the orthogonality between subcarriers, thereby causing interference between subcarriers and affecting the further improvement of the communication performance of the integrated communication and sensing. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the existing technology and propose a waveform design method for integrated communication and sensing that combines linear frequency modulation and OTFS. This method aims to ensure good radar sensing performance while reducing the impact of poor anti-Doppler frequency shift capability on communication performance in high-speed environments, thereby improving the overall performance of the integrated communication and sensing system.

[0005] To achieve the above objectives, the technical solution adopted by the present invention includes the following steps:

[0006] (1) Acquiring integrated communication and sensing signals:

[0007] In the integrated communication and sensing system, the linear frequency modulated signal f(t) generated at time t by the radar and the symbol a generated by the communication terminal are acquired. Q , where t∈[1,T] pulse ], T pulse T represents the duration of the pulse f(t). pulse ≥10μs, Q represents the number of symbols, Q≥50;

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

[0009] The code element a generated at the communication end Q Perform quadrature phase shift keying modulation and obtain the communication information symbol x through modulation. D Construct a time-delay-Doppler domain information symbol matrix X of dimension K×L. K×L , where X K×L The information symbol of the k-th time delay l-th Doppler unit is x[k,l], K≥4, L≥4;

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

[0011] OTFS modulation is performed on each time-delay-Doppler domain information symbol x[k,l] to obtain the communication time-domain signal s(t) at time t, where t∈[1,T] symbol ], T symbol T represents the period of the delay-Doppler domain information symbol. symbol ≥10μs;

[0012] (4) Obtain the waveform design results of the integrated communication and sensing system:

[0013] The communication time-domain signal s(t) and the linear frequency modulated signal f(t) are fused to obtain the integrated communication and sensing waveform z(t) at time t.

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

[0015] This invention performs orthogonal phase shift keying modulation on the symbols generated at the communication end, 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, the OTFS-modulated communication time-domain signal is fused with the corresponding linear frequency modulated signal generated at the radar end. Since the information symbols are uniformly distributed in the time-delay-Doppler domain, the influence of Doppler frequency shift is also uniformly distributed in the time-delay-Doppler domain. Therefore, the resulting waveform reduces the sensitivity of mobile communication to Doppler frequency shift in high-speed environments, ensuring that the integrated communication and sensing system has both good radar sensing performance and improved communication performance. Attached Figure Description

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

[0017] Figure 2 This is a comparison of the bit error rate and signal-to-noise ratio curves of the waveforms of the present invention and the prior art under mobile communication environments of 30km / h and 120km / h. Detailed Implementation

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

[0019] Reference Figure 1 The present invention includes the following steps:

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

[0021] In the integrated communication and sensing system, the linear frequency modulated signal f(t) generated at time t by the radar and the symbol a generated by the communication terminal are acquired. Q ,in:

[0022]

[0023] Where A, f0, and B represent the amplitude, center frequency, and bandwidth of f(t), respectively; rect(·) represents a rectangular window function; t represents the time variable; j represents the imaginary unit; π represents pi; and t∈[1,T] pulse ], T pulse T represents the duration of the pulse f(t). pulse ≥10μs, Q represents the number of symbols, Q≥50.

[0024] In this embodiment, Q = 1000, T pulse =10000μs, B=10MHz, f0=0Hz, A=1.

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

[0026] The symbol a generated at the communication end is in units of two bits. Q The code is grouped, and when the number of code elements is odd, zeros are padded to the end of the code elements to make it an even length. In this embodiment, 1000 code elements are divided into 500 groups, each group containing two code elements. Each group of code elements is converted into a quaternary number as the delay-Doppler domain information symbol, resulting in the following: A set of communication information symbols x D Subsequently, the communication information symbol x is viewed along the time delay axis and the Doppler axis. DSampling is performed K times and L times respectively, and the information symbol x[k,l] of the l-th Doppler unit with the k-th time delay is placed at the corresponding position of the time delay-Doppler grid with dimension K×L, forming the time delay-Doppler domain information symbol matrix X. K×L , This indicates rounding up, where K≥4 and L≥4.

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

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

[0029] Perform a symplectic finite Fourier inverse transform on each time-delay-Doppler domain information symbol x[k,l] to obtain the signal X[k,l] at the k-th time and l-th frequency in the time-frequency domain grid. Then, perform a Heisenberg transform 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 time delay and l′-th Doppler unit corresponding to the k-th time and l-th frequency in X[k,l], k and l represent 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 time delay-Doppler domain, Δf represents the spacing of the OTFS subcarriers, and T symbol The period of the delay-Doppler domain information symbol, g tx (·) represents a rectangular window function, T symbol ≥10μs.

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

[0034] Step 4) Obtain the waveform design results of the integrated communication and sensing system:

[0035] By fusing the communication time-domain signal s(t) with the linear frequency modulated signal f(t), the integrated communication-sensing waveform z(t) at time t is obtained:

[0036]

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

[0038] This invention performs orthogonal phase shift keying modulation on the symbols generated at the communication end, 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, the OTFS-modulated communication time-domain signal is fused with the corresponding linear frequency modulated signal generated at the radar end. Since the information symbols are evenly distributed in the time-delay-Doppler domain, the influence of Doppler frequency shift is also evenly distributed in the time-delay-Doppler domain. Therefore, the resulting waveform reduces the sensitivity of mobile communication to Doppler frequency shift in high-speed environments, ensuring a balance between communication performance and sensing capability, thereby improving the overall performance of the integrated communication and sensing system.

[0039] The technical effects of the present invention will be explained below with reference to simulation experiments:

[0040] 1. Simulation conditions and content:

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

[0042] 2. Simulation Result Analysis:

[0043] Reference Figure 2 , Figure 2 (a) and Figure 2 (b) Comparison of the bit error rate and signal-to-noise ratio curves of the present invention and the prior art under mobile communication environments of 30km / h and 120km / h, respectively. Figure 2 (a) is a comparison of the bit error rate and signal-to-noise ratio curves of the waveforms of the present invention and the prior art under a 30km / h mobile communication environment. Figure 2 (b) is a comparison graph showing the relationship between bit error rate and signal-to-noise ratio of the waveforms of the present invention and the prior art under a 120km / h mobile communication environment. Figure 2 (a) It can be seen that the bit error rate of the present invention decreases significantly faster with increasing signal-to-noise ratio than the prior art, and the bit error rate decreases to 10 at high signal-to-noise ratios (SNR > 15dB). -3 The following is significantly lower than existing technologies, by Figure 2 (b) It can be seen that in a high-speed (120km / 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 Doppler frequency shift in mobile communication under high-speed conditions and improves communication performance better than the prior art.

Claims

1. A communication sensing integrated waveform design method combining linear frequency modulation and OTFS, characterized in that, Includes the following steps: (1) Acquiring integrated communication and sensing signals: Acquiring the first generation generated by the radar end in the integrated communication and sensing system linear frequency modulation signal at time 1 Symbols generated by the communication end ,in: ； in, , express The duration of the pulse, , Indicates the number of code elements. ; , , They represent The amplitude, center frequency, and bandwidth, Represents a rectangular window function. Represents a time variable. Represents the imaginary unit. Represents pi; (2) Construct the time-delay-Doppler domain information symbol matrix: Symbols generated at the communication end Perform quadrature phase shift keying modulation and obtain communication information symbols through modulation. Construction dimension Delay-Doppler domain information symbol matrix ,in The Middle The delay is the first The information symbol of each Doppler unit is , , ; (3) OTFS modulation is performed on each time-delay-Doppler domain information symbol: For each time-delay-Doppler domain information symbol Perform OTFS modulation to obtain the first Communication time-domain signal at each moment ,in, , The period of the delay-Doppler domain information symbol is represented. ; (4) Obtain the waveform design results of the integrated communication and sensing system: For communication time domain signals With linear frequency modulation signal By merging, we obtain the first... Integrated waveform for communication and sensing at any given moment : ； in, Represents the corresponding first in the time-frequency domain grid. The first time A signal of a frequency, Indicates the spacing of OTFS subcarriers. The period of the delay-Doppler domain information symbol is represented.

2. The method according to claim 1, characterized in that, The code elements generated at the communication end in step (2) The method for performing quadrature phase shift keying modulation is as follows: Symbols are represented in units of two bits. The code is grouped, and each group of code elements is converted into a quaternary number as a communication information symbol, resulting in a set including... A set of communication information symbols .

3. The method according to claim 2, characterized in that, The construction dimension mentioned in step (2) is Delay-Doppler domain information symbol matrix The implementation method is as follows: Communication information symbols along the time delay axis and Doppler axis Perform separately Subsequent The second sampling, and the first The delay is the first Information symbols of a Doppler unit Placed in dimension The positions corresponding to the time-delay-Doppler grids form a time-delay-Doppler domain information symbol matrix. .

4. The method according to claim 3, characterized in that, The steps for performing OTFS modulation on each time-delay-Doppler domain information symbol as described in step (3) are as follows: For each time-delay-Doppler domain information symbol Performing a symplectic finite Fourier inverse transform yields the corresponding th element in the time-frequency domain grid. The first time Signal of frequency and to By performing the Heisenberg transformation, the communication time-domain signal is obtained. : ； ； in, Indicates and The Middle The first time The frequency corresponding to the first The delay is the first Information symbols of each Doppler unit Indicates the spacing of OTFS subcarriers. The period of the delay-Doppler domain information symbol is represented. Represents a rectangular window function. .

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