OTFS Communication-Sensing Integrated Signal Technology Based on a Prototype Filter
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摘要:
随着无线技术的快速发展,无线设备呈现爆炸式增长趋势,导致频谱资源日益稀缺,雷达和通信频段不断重叠。为了避免无线通信和雷达感知之间的相互干扰,学术界广泛研究了通信感知一体化(Integrated Sensing and Communication,ISAC)技术,并且重点关注了正交时频空(Orthogonal Time Frequency Space, OTFS)信号。OTFS信号具备实现无线通信与雷达感知一体化的潜力。然而,分数多普勒会抬高OTFS多普勒旁瓣,引起多普勒弥散效应,不仅在通信数据与通信数据之间、通信数据与雷达数据之间产生严重干扰,还将导致微弱目标被强目标旁瓣淹没,进而影响雷达探测概率和通信信道估计精度,恶化整体性能。针对分数多普勒导致的OTFS性能下降问题,提出了基于原型滤波器的OTFS通感一体化信号设计方法。通过原型滤波器调理多普勒旁瓣,在不显著损失多普勒分辨率的同时,抑制多普勒弥散效应,提升检测概率,降低误码率。针对OTFS互相关匹配滤波信道估计算法计算复杂度高等问题,进一步提出了利用恒虚警率(Constant False Alarm Rate,CFAR)检测进行信道估计的思路,在降低计算复杂度的同时,稳健检测出了同一时延、不同多普勒的多个目标,保障了信道估计和目标检测性能。依据理论分析和仿真实验可知,本文可将分数多普勒条件下的通信误码率降低2个数量级。
Abstract: With the rapid development of wireless technology, wireless devices have shown an explosive growth trend, resulting in increasingly scarce spectrum resources and continuous overlap of radar and communication bands. To avoid the mutual interference between wireless communication and radar sensing, integrated sensing and communication technology has been widely studied in the academic community, and the orthogonal time frequency space (OTFS) signal has been a research hot spot. This signal has the potential to realize the integration of wireless communication and radar sensing; however, it is particularly sensitive to fractional Doppler. Nevertheless, fractional Doppler elevates the OTFS Doppler sidelobe and causes a Doppler dispersion effect, which not only generates major interference between communication data and radar data, but also leads to the flooding of weak targets by the strong target sidelobe. This then affects the radar probability of detection and the estimation accuracy of the communication channel, and deteriorates the overall performance. Aiming at solving the problem of OTFS performance degradation caused by fractional Doppler, a design method of OTFS integrated signal based on a prototype filter is proposed. The Doppler sidelobe is adjusted by the prototype filter, to suppress the Doppler dispersion effect and reduce the communication error rate without significant loss of Doppler resolution. Aiming at solving the problem of high computational complexity of the OTFS cross-correlation matched filter channel estimation algorithm, the idea of using constant false alarm rate (CFAR) detection for channel estimation is further proposed. While reducing the computational complexity, multiple targets with the same delay and different Doppler are robustly detected, which ensures the performance of channel estimation and target detection. According to theoretical analysis and simulation experiments, the technique presented in this paper can reduce the bit error rate of communication under fractional Doppler conditions by two orders of magnitude.
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表 1 原型滤波器频域参数
Table 1 Frequency domain parameters of the prototype filter
K H0 H1 H2 H3 2 1 √2/2 ‒ ‒ 3 1 0.911438 0.411438 ‒ 4 1 0.971960 √2/2 0.235147 表 2 目标参数
Table 2 Objective parameters
目标 1 2 3 4 5 6 距离/ m 4.31 4.31 8.62 12.91 17.24 21.55 速度/ (m/s) 5 125 25 35 45 60 增益 1 0.2 0.5 0.8 0.45 0.66 表 3 仿真参数
Table 3 Simulation parameters
参数 参数值 子载波间隔/kHz 30 单个符号时宽/μs 33.33 载波频率/GHz 6 子载波个数 512 本文方法符号数 64 OTFS符号数 256 总带宽/MHz 30.72 通信调制 256-QAM 信道模型 EVA 分数多普勒分辨率倒数 10 MRC检测最大迭代次数 15 表 4 参数估计结果
Table 4 Parameter estimation results
目标 1 2 3 4 5 6 估计距离/ m 4.31 4.31 8.62 12.91 17.24 21.55 估计速度/ (m/s) 4.6875 124.8536 25.1953 35.1562 45.1172 59.7656 -
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