In this paper,we design a spatial modulation based orthogonal time frequency space(SMOTFS)system to achieve improved transmission reliability and meet the high transmission rate and highspeed demands of future mobile ...In this paper,we design a spatial modulation based orthogonal time frequency space(SMOTFS)system to achieve improved transmission reliability and meet the high transmission rate and highspeed demands of future mobile communications,which fully utilizes the characteristics of spatial modulation(SM)and orthogonal time frequency space(OTFS)transmission.The detailed system design and signal processing of the SM-OTFS system have been presented.The closed-form expressions of the average symbol error rate(ASER)and average bit error rate(ABER)of the SM-OTFS system have been derived over the delay-Doppler channel with the help of the union bounding technique and moment-generating function(MGF).Meanwhile,the system complexity has been evaluated.Numerical results verify the correctness of the theoretical ASER and ABER analysis of the SM-OTFS system in the high signal-to-noise ratio(SNR)regions and also show that the SM-OTFS system outperforms the traditional SM based orthogonal frequency division multiplexing(SM-OFDM)system with limited complexity increase under mobile conditions,especially in high mobility scenarios.展开更多
Orthogonal time-frequency space(OTFS),which exhibits beneficial advantages in high-mobility scenarios,has been considered as a promising technology in future wireless communication systems.In this paper,a universal mo...Orthogonal time-frequency space(OTFS),which exhibits beneficial advantages in high-mobility scenarios,has been considered as a promising technology in future wireless communication systems.In this paper,a universal model for OTFS systems with generalized waveform has been developed.Furthermore,the average bit error probability(ABEP)upper bounds of the optimal maximum likelihood(ML)detector are first derived for OTFS systems with generalized waveforms.Specifically,for OTFS systems with the ideal waveform,we elicit the ABEP bound by recombining the transmitted signal and the received signal.For OTFS systems with practical waveforms,a universal ABEP upper bound expression is derived using moment-generating function(MGF),which is further extended to MIMO-OTFS systems.Numerical results validate that our theoretical ABEP upper bounds are concur with the simulation performance achieved by ML detectors.展开更多
Orthogonal Time Frequency and Space(OTFS) modulation is expected to provide high-speed and ultra-reliable communications for emerging mobile applications, including low-orbit satellite communications. Using the Dopple...Orthogonal Time Frequency and Space(OTFS) modulation is expected to provide high-speed and ultra-reliable communications for emerging mobile applications, including low-orbit satellite communications. Using the Doppler frequency for positioning is a promising research direction on communication and navigation integration. To tackle the high Doppler frequency and low signal-to-noise ratio(SNR) in satellite communication, this paper proposes a Red and Blue Frequency Shift Discriminator(RBFSD) based on the pseudo-noise(PN) sequence.The paper derives that the cross-correlation function on the Doppler domain exhibits the characteristic of a Sinc function. Therefore, it applies modulation onto the Delay-Doppler domain using PN sequence and adjusts Doppler frequency estimation by red-shifting or blue-shifting. Simulation results show that the performance of Doppler frequency estimation is close to the Cramér-Rao Lower Bound when the SNR is greater than -15dB. The proposed algorithm is about 1/D times less complex than the existing PN pilot sequence algorithm, where D is the resolution of the fractional Doppler.展开更多
In this paper, we propose a new differential space-time-frequency （DSTF） modulation for MIMOOFDM system with four transmit-antennas and arbitrary receive-antennas, which can improve the transmission rate since it ca...In this paper, we propose a new differential space-time-frequency （DSTF） modulation for MIMOOFDM system with four transmit-antennas and arbitrary receive-antennas, which can improve the transmission rate since it can adopt high order quadrature amplitude modulation （QAM） modulation. Our proposed DSTF scheme embeds some full diversity full rate （FDFR） quasi-orthogonal space-time codes （QOSTBC） with QAM modulation into the frequency intervals and adopts the differential modulation in both time and frequency domains. The simulation results demonstrate that the proposed DSTF scheme can improve transmission rate greatly. Compared with the conventional differential unitary space-time modulation （DUSTM）, it can get better transmission performance in high transmission rate for MIMO-OFDM system.展开更多
在未来的通信网络中,被广泛期待的第6代移动通信系统(The Sixth Generation of Mobile Communications System,6G)技术将面临诸多挑战,其中包括在高速移动场景下的超高可靠通信问题。正交时频空间(Orthogonal Time Frequency Space,OTFS...在未来的通信网络中,被广泛期待的第6代移动通信系统(The Sixth Generation of Mobile Communications System,6G)技术将面临诸多挑战,其中包括在高速移动场景下的超高可靠通信问题。正交时频空间(Orthogonal Time Frequency Space,OTFS)调制技术克服了传统通信系统在高速移动环境下多径和多普勒效应的影响,为实现6G超高可靠通信提供了新的可能性。该文首先介绍了OTFS的基本原理、数学模型、干扰与优势分析。然后,归纳分析了OTFS技术在同步、信道估计、信号检测技术上的研究现状。接着,从车联网、无人机、卫星通信、海洋通信4个典型应用场景分析了OTFS的应用趋势。最后,从降低多维匹配滤波器、相位解调和信道估计、硬件实现的复杂度和提高对时频资源的高度利用4个角度探讨了未来研究OTFS需要克服的困难和挑战。展开更多
车联网(Vehicle to Everything,V2X)通信被认为是未来无线通信网络最重要的应用之一。然而,车辆在高速移动时引起的高多普勒频移会严重恶化V2X通信链路的性能。正交时频空(Orthogonal Time Frequency Space,OTFS)调制技术可以将时间和...车联网(Vehicle to Everything,V2X)通信被认为是未来无线通信网络最重要的应用之一。然而,车辆在高速移动时引起的高多普勒频移会严重恶化V2X通信链路的性能。正交时频空(Orthogonal Time Frequency Space,OTFS)调制技术可以将时间和频率选择性信道转换为时延-多普勒(Delay-Doppler,DD)域的非选择性信道,从而显著提高无线通信系统在高移动性场景下的性能,在V2X通信中具有重要的应用价值。但OTFS调制技术极大地增加了系统接收端的复杂度,研究低复杂度信号检测算法成为了新一代无线通信系统采用OTFS调制的关键问题之一。为此,综述了面向车联网V2X通信的OTFS信号检测算法。首先介绍了OTFS系统模型,然后概述了现有的低复杂度OTFS信号检测算法,并将其分为线性检测算法、消息传递(Message Passing,MP)检测算法及其改进算法、基于神经网络的检测算法3类,最后探讨了V2X通信中OTFS信号检测目前所面临的技术挑战与未来的发展趋势。展开更多
The internet of things(IoT)has been widely considered to be integrated with high-speed railways to improve safety and service.It is important to achieve reliable communication in IoT for railways(IoT-R)under high mobi...The internet of things(IoT)has been widely considered to be integrated with high-speed railways to improve safety and service.It is important to achieve reliable communication in IoT for railways(IoT-R)under high mobility scenarios and strict energy constraints.Orthogonal time frequency space(OTFS)modulation is a two-dimensional modulation technique that has the potential to overcome the challenges in high Doppler environments.In addition,OTFS can have lower peak-to-average power ratio(PAPR)compared to orthogonal frequency division multiplexing,which is especially important for the application of IoT-R.Therefore,OTFS modulation for IoT-R is investigated in this paper.In order to decrease PAPR of OTFS and promote the application of OTFS modulation in IoT-R,the peak windowing technique is used in this paper.This technique can reduce the PAPR of OTFS by reducing the peak power and does not require multiple iterations.The impacts of different window functions,window sizes and clipping levels on PAPR and bit error rate of OTFS are simulated and discussed.The simulation results show that the peak windowing technique can efficiently reduce the PAPR of OTFS for IoT-R.展开更多
Digital Communications, in relation to wireless networks, have taken off in recent years due to the expanding need to communicate faster and more efficiently. A popular way to achieve this is by using wireless Multipl...Digital Communications, in relation to wireless networks, have taken off in recent years due to the expanding need to communicate faster and more efficiently. A popular way to achieve this is by using wireless Multiple Input Multiple Output (MIMO) communication systems. MIMO systems utilize Space Time Block Codes (STBC) as one of the leading ways to obtain higher data rates with limited bandwidth and power. With several STBC methods currently available, this paper analyzes simulations using Orthogonal Space Time Block Codes (OSTBC) in Rayleigh fading channels to evaluate the performance of MIMO systems. The selection to use a Rayleigh fading channel as a model for a non-line-of-sight (nLOS) environment is selected to mimic installations where a large number of signal paths and reflections are expected. All simulations are coded, generated and plotted using MATLAB resulting in graphical data representing the bit-error rate (BER) to signal-to-noise ratio (Eb/N<sub>0</sub>) or SNR. Each simulation captures how different configurations of key variables including code rate, diversity and antenna count can impact system performance. Four modulation schemes (BPSK, QPSK, 16-QAM and 64-QAM) are included in each simulation. Conclusive evidence based upon these simulations suggests higher diversity gains were achieved with a greater number of antennas. The most significant factor for increasing system performance was using a lower count of transmit antennas with a higher count of receive antennas.展开更多
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...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。展开更多
正交时频空(Orthogonal Time Frequency Space, OTFS)调制技术凭借对多普勒频移的优良抗性,保证了高动态场景下的可靠性通信。与大多数OTFS信号检测方案相比,基于深度学习(Deep Learning, DL)的OTFS检测器不需要耗费高额的导频能量,以...正交时频空(Orthogonal Time Frequency Space, OTFS)调制技术凭借对多普勒频移的优良抗性,保证了高动态场景下的可靠性通信。与大多数OTFS信号检测方案相比,基于深度学习(Deep Learning, DL)的OTFS检测器不需要耗费高额的导频能量,以此获得精确的信道状态信息。基于多维输入的卷积神经网络(Convolutional Neural Networks, CNN)和一维输入的深度神经网络(Deep Neural Networks, DNN),搭建了OTFS信号检测模型,并结合OTFS的输入输出关系,以模型驱动,提出一种部分输入方法。与数据驱动DL相比,该方法沿时延轴截断输入数据,仅向网络输入与待检测信号相关性强的部分接收信号。该方法不仅减小了数据驱动CNN和DNN的训练参数量,降低了训练复杂度,而且检测性能也不弱于传统的线性最小均方误差(Linear Minimum Mean Square Error, LMMSE)算法。展开更多
针对正交时频空(Orthogonal Time Frequency Space,OTFS)通信系统信号检测复杂度高的问题,提出一种改进的高斯近似消息传递(Gaussian Approximate Message Passing,GA-MP)检测算法。依据最大后验概率检测准则,对发送信号及隐变量进行逐...针对正交时频空(Orthogonal Time Frequency Space,OTFS)通信系统信号检测复杂度高的问题,提出一种改进的高斯近似消息传递(Gaussian Approximate Message Passing,GA-MP)检测算法。依据最大后验概率检测准则,对发送信号及隐变量进行逐符号高斯近似,基于置信传播算法与联合因子图进行消息传递,用边缘后验概率替代GA-MP中的外部信息以减少运算量,结合阻尼因子提升收敛速度,同时引入概率阈值减少后续更新的节点数,从而使运算复杂度得到有效降低。实验结果表明,改进后的GA-MP算法在保证误码率性能的前提下具有更低的复杂度。展开更多
利用正交时频空调制(OTFS,orthogonal time frequency space)作为传输波形的通信感知一体化(ISAC,integrated sensing and communication)系统具有更高的通信资源利用率,成为解决频谱资源短缺的关键技术。随着环境中感知目标数的增加,...利用正交时频空调制(OTFS,orthogonal time frequency space)作为传输波形的通信感知一体化(ISAC,integrated sensing and communication)系统具有更高的通信资源利用率,成为解决频谱资源短缺的关键技术。随着环境中感知目标数的增加,基站接收到的由多个感知回波信号叠加而成的信号功率差异不明显,采用传统多目标信道感知与目标探测算法会造成误差传递和累积,从而影响系统感知信道参数和目标探测的性能。针对以上问题,提出了一种基于最大似然估计器的多目标信道参数检测与目标探测算法,实现对感知参数估计和目标探测精确度的提升。具体而言,通过对接收到的叠加信号采用并行干扰消除(PIC,parallel interference cancellation)算法,利用从上一轮迭代中得到的结果重建信号,并从接收信号中减去重建的信号,从而提高在感知参数估计和目标探测时回波信号的信干噪比,实现最大似然估计器性能的提升。仿真结果表明,所提算法相较于传统算法能够实现更准确的信道估计和目标探测,并且所提算法具有较好的收敛性,能够有效减少时间开销。展开更多
随着无线通信技术的发展,雷达和通信频段逐渐相互重叠,使得雷达通信一体化成为了缓解频谱资源紧张的最好的实现方法之一。作为雷达通信一体化的主要载体之一,正交频分复用(Orthogonal Frequency Division Multiplexing,OFDM)的波形设计...随着无线通信技术的发展,雷达和通信频段逐渐相互重叠,使得雷达通信一体化成为了缓解频谱资源紧张的最好的实现方法之一。作为雷达通信一体化的主要载体之一,正交频分复用(Orthogonal Frequency Division Multiplexing,OFDM)的波形设计方法可分为两大类,一类是复用波形设计,另一类是共用波形设计。由于共用波形设计需要考虑雷达和通信性能之间的折中,且在雷达信号处理过程和通信接收端需要设计专门的处理流程,因此在频谱资源较为充足时,基于OFDM的复用波形设计比起共用设计优势更明显。由于OFDM对多普勒的敏感性高,基于OFDM的复用波形设计不适用于高速运动场景。针对这一问题,本文提出了一种基于正交时频空(Orthogonal Time Frequency Space,OTFS)的雷达通信一体化复用波形设计。这种设计利用OTFS多普勒容忍性高的特点,可实现高速运动场景下的雷达通信一体化。鉴于OTFS的时延-多普勒域和雷达的快时间慢时间概念相似,本文采用多普勒复用的方法实现了一体化复用信号设计,并提出了该波形下的通信和雷达接收端的处理流程。通信接收端通过OTFS解调可实现高速通信,雷达接收端无须进行波形分离,可直接利用常规雷达信号处理流程完成目标信息的估计。本文通过仿真验证了所提一体化复用波形的可行性,同时通过仿真验证了所提波形在高速运动场景上,相比于OFDM体制复用波形在雷达目标参数估计和通信误码率上的优势。展开更多
基金in part by the National Natural Science Foundation of China under Grant 61771291,Grant 61671278in part by the Key Research and Development Project of Shandong Province under Grant 2018GGX101009,Grant 2019TSLH0202,Grant 2020CXGC010109+1 种基金in part by the National Nature Science Foundation of China for Excellent Young Scholars under Grant 61622111in part by the Project of International Cooperation and Exchanges NSFC under Grant 61860206005.
文摘In this paper,we design a spatial modulation based orthogonal time frequency space(SMOTFS)system to achieve improved transmission reliability and meet the high transmission rate and highspeed demands of future mobile communications,which fully utilizes the characteristics of spatial modulation(SM)and orthogonal time frequency space(OTFS)transmission.The detailed system design and signal processing of the SM-OTFS system have been presented.The closed-form expressions of the average symbol error rate(ASER)and average bit error rate(ABER)of the SM-OTFS system have been derived over the delay-Doppler channel with the help of the union bounding technique and moment-generating function(MGF).Meanwhile,the system complexity has been evaluated.Numerical results verify the correctness of the theoretical ASER and ABER analysis of the SM-OTFS system in the high signal-to-noise ratio(SNR)regions and also show that the SM-OTFS system outperforms the traditional SM based orthogonal frequency division multiplexing(SM-OFDM)system with limited complexity increase under mobile conditions,especially in high mobility scenarios.
基金supported in part by the National Key Research and Development Program of China under Grant 2021YFB2900502the National Science Foundation of China under Grant 62001179the Fundamental Research Funds for the Central Universities under Grant 2020kfyXJJS111。
文摘Orthogonal time-frequency space(OTFS),which exhibits beneficial advantages in high-mobility scenarios,has been considered as a promising technology in future wireless communication systems.In this paper,a universal model for OTFS systems with generalized waveform has been developed.Furthermore,the average bit error probability(ABEP)upper bounds of the optimal maximum likelihood(ML)detector are first derived for OTFS systems with generalized waveforms.Specifically,for OTFS systems with the ideal waveform,we elicit the ABEP bound by recombining the transmitted signal and the received signal.For OTFS systems with practical waveforms,a universal ABEP upper bound expression is derived using moment-generating function(MGF),which is further extended to MIMO-OTFS systems.Numerical results validate that our theoretical ABEP upper bounds are concur with the simulation performance achieved by ML detectors.
文摘Orthogonal Time Frequency and Space(OTFS) modulation is expected to provide high-speed and ultra-reliable communications for emerging mobile applications, including low-orbit satellite communications. Using the Doppler frequency for positioning is a promising research direction on communication and navigation integration. To tackle the high Doppler frequency and low signal-to-noise ratio(SNR) in satellite communication, this paper proposes a Red and Blue Frequency Shift Discriminator(RBFSD) based on the pseudo-noise(PN) sequence.The paper derives that the cross-correlation function on the Doppler domain exhibits the characteristic of a Sinc function. Therefore, it applies modulation onto the Delay-Doppler domain using PN sequence and adjusts Doppler frequency estimation by red-shifting or blue-shifting. Simulation results show that the performance of Doppler frequency estimation is close to the Cramér-Rao Lower Bound when the SNR is greater than -15dB. The proposed algorithm is about 1/D times less complex than the existing PN pilot sequence algorithm, where D is the resolution of the fractional Doppler.
基金This work was supported in part by the National Natural Science Foundation of China under grant No. 60572117the Natural Science Foundation of Hubei Province under grant No. 2005ABA244.
文摘In this paper, we propose a new differential space-time-frequency （DSTF） modulation for MIMOOFDM system with four transmit-antennas and arbitrary receive-antennas, which can improve the transmission rate since it can adopt high order quadrature amplitude modulation （QAM） modulation. Our proposed DSTF scheme embeds some full diversity full rate （FDFR） quasi-orthogonal space-time codes （QOSTBC） with QAM modulation into the frequency intervals and adopts the differential modulation in both time and frequency domains. The simulation results demonstrate that the proposed DSTF scheme can improve transmission rate greatly. Compared with the conventional differential unitary space-time modulation （DUSTM）, it can get better transmission performance in high transmission rate for MIMO-OFDM system.
文摘在未来的通信网络中,被广泛期待的第6代移动通信系统(The Sixth Generation of Mobile Communications System,6G)技术将面临诸多挑战,其中包括在高速移动场景下的超高可靠通信问题。正交时频空间(Orthogonal Time Frequency Space,OTFS)调制技术克服了传统通信系统在高速移动环境下多径和多普勒效应的影响,为实现6G超高可靠通信提供了新的可能性。该文首先介绍了OTFS的基本原理、数学模型、干扰与优势分析。然后,归纳分析了OTFS技术在同步、信道估计、信号检测技术上的研究现状。接着,从车联网、无人机、卫星通信、海洋通信4个典型应用场景分析了OTFS的应用趋势。最后,从降低多维匹配滤波器、相位解调和信道估计、硬件实现的复杂度和提高对时频资源的高度利用4个角度探讨了未来研究OTFS需要克服的困难和挑战。
文摘车联网(Vehicle to Everything,V2X)通信被认为是未来无线通信网络最重要的应用之一。然而,车辆在高速移动时引起的高多普勒频移会严重恶化V2X通信链路的性能。正交时频空(Orthogonal Time Frequency Space,OTFS)调制技术可以将时间和频率选择性信道转换为时延-多普勒(Delay-Doppler,DD)域的非选择性信道,从而显著提高无线通信系统在高移动性场景下的性能,在V2X通信中具有重要的应用价值。但OTFS调制技术极大地增加了系统接收端的复杂度,研究低复杂度信号检测算法成为了新一代无线通信系统采用OTFS调制的关键问题之一。为此,综述了面向车联网V2X通信的OTFS信号检测算法。首先介绍了OTFS系统模型,然后概述了现有的低复杂度OTFS信号检测算法,并将其分为线性检测算法、消息传递(Message Passing,MP)检测算法及其改进算法、基于神经网络的检测算法3类,最后探讨了V2X通信中OTFS信号检测目前所面临的技术挑战与未来的发展趋势。
基金supported by the National Key R&D Program of China under Grant 2022YFF0608103the National Natural Science Foundation of China under Grant 62001519 and 62271037。
文摘The internet of things(IoT)has been widely considered to be integrated with high-speed railways to improve safety and service.It is important to achieve reliable communication in IoT for railways(IoT-R)under high mobility scenarios and strict energy constraints.Orthogonal time frequency space(OTFS)modulation is a two-dimensional modulation technique that has the potential to overcome the challenges in high Doppler environments.In addition,OTFS can have lower peak-to-average power ratio(PAPR)compared to orthogonal frequency division multiplexing,which is especially important for the application of IoT-R.Therefore,OTFS modulation for IoT-R is investigated in this paper.In order to decrease PAPR of OTFS and promote the application of OTFS modulation in IoT-R,the peak windowing technique is used in this paper.This technique can reduce the PAPR of OTFS by reducing the peak power and does not require multiple iterations.The impacts of different window functions,window sizes and clipping levels on PAPR and bit error rate of OTFS are simulated and discussed.The simulation results show that the peak windowing technique can efficiently reduce the PAPR of OTFS for IoT-R.
文摘Digital Communications, in relation to wireless networks, have taken off in recent years due to the expanding need to communicate faster and more efficiently. A popular way to achieve this is by using wireless Multiple Input Multiple Output (MIMO) communication systems. MIMO systems utilize Space Time Block Codes (STBC) as one of the leading ways to obtain higher data rates with limited bandwidth and power. With several STBC methods currently available, this paper analyzes simulations using Orthogonal Space Time Block Codes (OSTBC) in Rayleigh fading channels to evaluate the performance of MIMO systems. The selection to use a Rayleigh fading channel as a model for a non-line-of-sight (nLOS) environment is selected to mimic installations where a large number of signal paths and reflections are expected. All simulations are coded, generated and plotted using MATLAB resulting in graphical data representing the bit-error rate (BER) to signal-to-noise ratio (Eb/N<sub>0</sub>) or SNR. Each simulation captures how different configurations of key variables including code rate, diversity and antenna count can impact system performance. Four modulation schemes (BPSK, QPSK, 16-QAM and 64-QAM) are included in each simulation. Conclusive evidence based upon these simulations suggests higher diversity gains were achieved with a greater number of antennas. The most significant factor for increasing system performance was using a lower count of transmit antennas with a higher count of receive antennas.
文摘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。
文摘针对正交时频空(Orthogonal Time Frequency Space,OTFS)通信系统信号检测复杂度高的问题,提出一种改进的高斯近似消息传递(Gaussian Approximate Message Passing,GA-MP)检测算法。依据最大后验概率检测准则,对发送信号及隐变量进行逐符号高斯近似,基于置信传播算法与联合因子图进行消息传递,用边缘后验概率替代GA-MP中的外部信息以减少运算量,结合阻尼因子提升收敛速度,同时引入概率阈值减少后续更新的节点数,从而使运算复杂度得到有效降低。实验结果表明,改进后的GA-MP算法在保证误码率性能的前提下具有更低的复杂度。
文摘利用正交时频空调制(OTFS,orthogonal time frequency space)作为传输波形的通信感知一体化(ISAC,integrated sensing and communication)系统具有更高的通信资源利用率,成为解决频谱资源短缺的关键技术。随着环境中感知目标数的增加,基站接收到的由多个感知回波信号叠加而成的信号功率差异不明显,采用传统多目标信道感知与目标探测算法会造成误差传递和累积,从而影响系统感知信道参数和目标探测的性能。针对以上问题,提出了一种基于最大似然估计器的多目标信道参数检测与目标探测算法,实现对感知参数估计和目标探测精确度的提升。具体而言,通过对接收到的叠加信号采用并行干扰消除(PIC,parallel interference cancellation)算法,利用从上一轮迭代中得到的结果重建信号,并从接收信号中减去重建的信号,从而提高在感知参数估计和目标探测时回波信号的信干噪比,实现最大似然估计器性能的提升。仿真结果表明,所提算法相较于传统算法能够实现更准确的信道估计和目标探测,并且所提算法具有较好的收敛性,能够有效减少时间开销。
文摘随着无线通信技术的发展,雷达和通信频段逐渐相互重叠,使得雷达通信一体化成为了缓解频谱资源紧张的最好的实现方法之一。作为雷达通信一体化的主要载体之一,正交频分复用(Orthogonal Frequency Division Multiplexing,OFDM)的波形设计方法可分为两大类,一类是复用波形设计,另一类是共用波形设计。由于共用波形设计需要考虑雷达和通信性能之间的折中,且在雷达信号处理过程和通信接收端需要设计专门的处理流程,因此在频谱资源较为充足时,基于OFDM的复用波形设计比起共用设计优势更明显。由于OFDM对多普勒的敏感性高,基于OFDM的复用波形设计不适用于高速运动场景。针对这一问题,本文提出了一种基于正交时频空(Orthogonal Time Frequency Space,OTFS)的雷达通信一体化复用波形设计。这种设计利用OTFS多普勒容忍性高的特点,可实现高速运动场景下的雷达通信一体化。鉴于OTFS的时延-多普勒域和雷达的快时间慢时间概念相似,本文采用多普勒复用的方法实现了一体化复用信号设计,并提出了该波形下的通信和雷达接收端的处理流程。通信接收端通过OTFS解调可实现高速通信,雷达接收端无须进行波形分离,可直接利用常规雷达信号处理流程完成目标信息的估计。本文通过仿真验证了所提一体化复用波形的可行性,同时通过仿真验证了所提波形在高速运动场景上,相比于OFDM体制复用波形在雷达目标参数估计和通信误码率上的优势。
