针对目前基于正交时频空调制系统中使用脉冲导频进行信道估计会引入高均峰比和信道估计困难的问题,提出了一种基于双向长短期记忆网络(Bidirectional Long Short-term Memory,BiLSTM)的信道估计算法。该算法首先将低功率导频序列放置于...针对目前基于正交时频空调制系统中使用脉冲导频进行信道估计会引入高均峰比和信道估计困难的问题,提出了一种基于双向长短期记忆网络(Bidirectional Long Short-term Memory,BiLSTM)的信道估计算法。该算法首先将低功率导频序列放置于时频域中,再对发送信号添加功率放大器的非线性衰变模型,对接收信号导频部分的接收信号使用最小二乘法进行粗略信道的计算,之后通过BiLSTM结合卷积块注意力模块对完整信道进行拟合估计,从而得到时频域的完整信道矩阵。为进一步减少误差,通过神经网络对完整信道矩阵进行修正处理。仿真结果表明,该算法求得非线性衰变影响信号的信道矩阵的归一化均方误差提升了3~15 dB,均峰比下降了5~6 dB,误比特率性能提升3~8 dB。展开更多
正交时频空(Orthogonal Time Frequency Space, OTFS)信号调制过程中存在一定的带外(Out-of-Band, OOB)泄露,会导致相邻信道干扰,影响通信系统性能。针对这一问题,分析了OTFS系统功率谱特性,提出了一种新带外功率抑制方法。首先,理论推...正交时频空(Orthogonal Time Frequency Space, OTFS)信号调制过程中存在一定的带外(Out-of-Band, OOB)泄露,会导致相邻信道干扰,影响通信系统性能。针对这一问题,分析了OTFS系统功率谱特性,提出了一种新带外功率抑制方法。首先,理论推导出OTFS信号的精确功率谱密度(Power Spectral Density, PSD)数学表达式,明确影响OTFS带外功率的因素;其次,为抑制带外功率,提出了一种基于多项式抵消编码的正交时频空(Polynomial Cancellation Coding Orthogonal Time Frequency Space, PCC-OTFS)调制方案,利用PCC技术重构OTFS子载波,使相邻子载波以相互抵消的系数组成子载波对,加快子载波频谱旁瓣滚降,并给出矩形脉冲与升余弦脉冲PCC-OTFS的功率谱密度计算方法,探讨了其功率谱滚降特性。实验结果表明,相比矩形脉冲和圆形长脉冲形状(Circular-Prolate Pulse Shape, CPPS),升余弦脉冲PCC-OTFS可降低带外功率约117 dB和40 dB。展开更多
In view of the high computational complexity of traditional linear equalization algorithms in Orthogonal Time Frequency Space(OTFS)systems,a minimum mean square error(MMSE)channel equalization algorithm based on Matri...In view of the high computational complexity of traditional linear equalization algorithms in Orthogonal Time Frequency Space(OTFS)systems,a minimum mean square error(MMSE)channel equalization algorithm based on Matrix Chunking Lower and Upper Triangular Decomposition(CLU)is proposed.The proposed algorithm derives the structural properties of the chunked MMSE equalization matrix by leveraging the block diagonal structure of the Cyclic Prefix OTFS(CP-OTFS)time-domain channel matrix and the quasi-band structure of its constituent block matrices.On this basis,triangular decomposition combined with forward and backward substitution is used to avoid matrix inversion.This approach significantly reduces the complexity of the MMSE algorithm without sacrificing its performance.展开更多
The orthogonal time frequency space(OTFS)modulation is a novel modulation scheme that can effectively cope with the high Doppler expansion caused by high mobility.Since it modulates data on delay-Doppler(DD)domain and...The orthogonal time frequency space(OTFS)modulation is a novel modulation scheme that can effectively cope with the high Doppler expansion caused by high mobility.Since it modulates data on delay-Doppler(DD)domain and makes full use of the sparse characteristics of DD domain,it has been widely studied to design efficient channel estimation and signal detection schemes.In this paper,we design a novel superimposed pilot pattern with transition band,which replaces the traditional embedded pilot(EP)guard zero-symbols,and perform a two-stage channel estimation.In the first stage,we fully utilize the dispersion characteristics of OTFS signal in DD domain,and use threshold decision to make coarse channel estimation.In the second stage,we use the results of the coarse estimation for iterative signal detection and accurate channel estimation.During the second stage,we make full use of the sparsity of the channel in DD domain,remodel the received signal into the form of sparse channel vector multiplied by channel coefficient matrix,and introduce Doppler index segmentation factor(DISF)to subdivide the Doppler index to solve the problem of fractional Doppler.Simulations reveal that,the scheme proposed in this paper has higher spectral efficiency compared with traditional EP scheme and lower peak-to-average power ratio(PAPR)compared with traditional superimposed pilot scheme.展开更多
正交时频空(Orthogonal Time Frequency Space,OTFS)调制因其在高速移动场景下优越的抗多普勒频移特性,被视为未来低地球轨道(Low Earth Orbit,LEO)卫星通信的关键候选技术。然而,OTFS信号固有的峰均功率比(Peak-to-Average Power Ratio...正交时频空(Orthogonal Time Frequency Space,OTFS)调制因其在高速移动场景下优越的抗多普勒频移特性,被视为未来低地球轨道(Low Earth Orbit,LEO)卫星通信的关键候选技术。然而,OTFS信号固有的峰均功率比(Peak-to-Average Power Ratio,PAPR)问题,会严重降低卫星高功率放大器(High-Power Amplifier,HPA)的效率,并引入显著的非线性失真,从而恶化误码率(Bit Error Rate,BER)性能。为解决此问题,提出了一种创新的混合自适应削波(Hybrid Adaptive Clipping,HAC)与神经网络预失真(Neural Network Predistortion)的方法——HAC-NNP。自适应削波(Adaptive Clipping,AC)模块根据实时信道质量或业务需求动态调整削波门限,在PAPR抑制和信号原始失真之间取得初步平衡;轻量级的神经网络(Neural Network,NN)预失真器在发射端对削波后的信号进行处理,训练后用于补偿由“削波处理”和“卫星HPA非线性效应”共同引入的复杂失真。仿真结果表明,在典型的LEO卫星信道和HPA非线性模型下,与传统削波方法相比,该HAC-NNP方法在将PAPR降低约3.5 dB的同时,能够显著改善由削波和HPA非线性共同导致的信号失真,将BER性能恢复至接近无HPA非线性影响的理想水平。展开更多
正交时频空(Orthogonal Time Frequency Space,OTFS)技术在高速移动环境下表现出对时延扩展和多普勒效应的强鲁棒性,显著提升了通信系统在移动场景下的可靠性。针对多用户OTFS系统,提出一种基于非正交多址接入(Non-Orthogonal Multiple ...正交时频空(Orthogonal Time Frequency Space,OTFS)技术在高速移动环境下表现出对时延扩展和多普勒效应的强鲁棒性,显著提升了通信系统在移动场景下的可靠性。针对多用户OTFS系统,提出一种基于非正交多址接入(Non-Orthogonal Multiple Access,NOMA)的信号检测器,该检测器利用共轭梯度法和OTFS正反变换实现OTFS-NOMA系统的信号检测。进一步,针对用户间干扰大和检测器梯度下降收敛慢的问题,提出一种模型驱动神经网络信号检测器。该检测器引入抑制用户间干扰的学习参数,并将执行过程中产生的中间变量嵌入到神经网络中作为学习参数。实验结果表明,相较于现有的信号检测器,所提的模型驱动神经网络信号检测器误比特率性能具有更优表现。展开更多
Orthogonal time frequency space(OTFS)has been broadly studied and applied in various fields due to its robustness in high dynamic scenes.In this paper,we investigate the application of OTFS in radarembedded communicat...Orthogonal time frequency space(OTFS)has been broadly studied and applied in various fields due to its robustness in high dynamic scenes.In this paper,we investigate the application of OTFS in radarembedded communication systems,and propose an OTFS-based radar-embedded communication model suitable for high-speed mobile scenarios.By comparing the communication reliability at different velocities,the benefits of OTFS-based radar-embedded communication systems over conventional linear frequency modulation(LFM)based systems are verified.The proposed algorithm also shows excellent radar detection performance,and compensates the channel state information according to the motion parameters of the target to achieve more accurate communication reception.Besides that,our algorithm exhibits superior covertness performance to that of LFM.展开更多
目前基于正交时频空(orthogonal time frequency space,OTFS)的雷达目标参数估计算法以在网估计为主,但在网估计算法无法有效应对现实应用中的离网现象。同时,现有离网估计算法的目标参数估计性能受建模误差的限制,也难以确保雷达系统...目前基于正交时频空(orthogonal time frequency space,OTFS)的雷达目标参数估计算法以在网估计为主,但在网估计算法无法有效应对现实应用中的离网现象。同时,现有离网估计算法的目标参数估计性能受建模误差的限制,也难以确保雷达系统在复杂环境下的有效应用。针对以上问题,提出了一种基于OTFS调制的动态稀疏贝叶斯(dynamic-sparse Bayesian learning,dynamic-SBL)算法。该算法在稀疏贝叶斯学习框架下引入动态虚拟网格,通过不断更新调整网格参数降低建模误差,提升目标参数估计性能。同时利用OTFS雷达信道特有的稀疏性对网格参数进行选择性局部更新,以降低算法的复杂度。仿真结果表明,所提算法估计的目标归一化时延和多普勒频率的均方误差较小,目标参数的估计性能优于传统离网估计方法的。该算法在实际雷达系统中具有较大应用潜力。展开更多
在OTFS(Orthogonal Time Frequency Space,正交时频空间)调制中,Zak变换是将时域信号转换为关于DD(Delay-Doppler,时延-多普勒)域信号,DD域能够将时变的无线信道转换为二维的准静态信道表示,进而提升通信的可靠性,但同时增加了信号检测...在OTFS(Orthogonal Time Frequency Space,正交时频空间)调制中,Zak变换是将时域信号转换为关于DD(Delay-Doppler,时延-多普勒)域信号,DD域能够将时变的无线信道转换为二维的准静态信道表示,进而提升通信的可靠性,但同时增加了信号检测的复杂度。目前对OTFS的研究主要考虑Ts-OTFS(Two step-OTFS,两步方法),即首先将DD域信号转换为时频域,然后将其转换为时域进行传输。与两步方法相比,Zak变换方法更为简洁且性能更优。文章研究了基于Zak变换的OTFS(Zak-OTFS)传输,并在不同参数下误码性能进行了研究。首先通过Zak变换的原理推导了Zak-OTFS的传输过程,然后利用MRC(Maximal Ratio Combining,最大比合并)进行信号检测,最后通过对Zak-OTFS、Ts-OTFS、OFDM(Orthogonal Frequency Division Multiplexing,正交频分复用)的误码率对比,验证了Zak-OTFS的优势。仿真结果表明:Zak-OTFS和两步OTFS均优于OFDM。展开更多
基金supported by ZTE Industry-University-Institute Cooperation Funds under Grant No.KY10800230005。
摘要In view of the high computational complexity of traditional linear equalization algorithms in Orthogonal Time Frequency Space(OTFS)systems,a minimum mean square error(MMSE)channel equalization algorithm based on Matrix Chunking Lower and Upper Triangular Decomposition(CLU)is proposed.The proposed algorithm derives the structural properties of the chunked MMSE equalization matrix by leveraging the block diagonal structure of the Cyclic Prefix OTFS(CP-OTFS)time-domain channel matrix and the quasi-band structure of its constituent block matrices.On this basis,triangular decomposition combined with forward and backward substitution is used to avoid matrix inversion.This approach significantly reduces the complexity of the MMSE algorithm without sacrificing its performance.
基金supported by National Natural Science Foundation(NNSF)of China under Grant 62001351the Foundation of National Key Laboratory of Electromagnetic Environment(6142403220202)the Stability Support Fund for Basic Military Industrial Research Institutes(A240104130).
摘要The orthogonal time frequency space(OTFS)modulation is a novel modulation scheme that can effectively cope with the high Doppler expansion caused by high mobility.Since it modulates data on delay-Doppler(DD)domain and makes full use of the sparse characteristics of DD domain,it has been widely studied to design efficient channel estimation and signal detection schemes.In this paper,we design a novel superimposed pilot pattern with transition band,which replaces the traditional embedded pilot(EP)guard zero-symbols,and perform a two-stage channel estimation.In the first stage,we fully utilize the dispersion characteristics of OTFS signal in DD domain,and use threshold decision to make coarse channel estimation.In the second stage,we use the results of the coarse estimation for iterative signal detection and accurate channel estimation.During the second stage,we make full use of the sparsity of the channel in DD domain,remodel the received signal into the form of sparse channel vector multiplied by channel coefficient matrix,and introduce Doppler index segmentation factor(DISF)to subdivide the Doppler index to solve the problem of fractional Doppler.Simulations reveal that,the scheme proposed in this paper has higher spectral efficiency compared with traditional EP scheme and lower peak-to-average power ratio(PAPR)compared with traditional superimposed pilot scheme.
摘要正交时频空(Orthogonal Time Frequency Space,OTFS)技术在高速移动环境下表现出对时延扩展和多普勒效应的强鲁棒性,显著提升了通信系统在移动场景下的可靠性。针对多用户OTFS系统,提出一种基于非正交多址接入(Non-Orthogonal Multiple Access,NOMA)的信号检测器,该检测器利用共轭梯度法和OTFS正反变换实现OTFS-NOMA系统的信号检测。进一步,针对用户间干扰大和检测器梯度下降收敛慢的问题,提出一种模型驱动神经网络信号检测器。该检测器引入抑制用户间干扰的学习参数,并将执行过程中产生的中间变量嵌入到神经网络中作为学习参数。实验结果表明,相较于现有的信号检测器,所提的模型驱动神经网络信号检测器误比特率性能具有更优表现。
基金supported by the Key Project of National Natural Science Foundation of China under Grant 62531019the National Natural Science Foundation for Distinguished Young Scholar under Grant 62425103.
摘要Orthogonal time frequency space(OTFS)has been broadly studied and applied in various fields due to its robustness in high dynamic scenes.In this paper,we investigate the application of OTFS in radarembedded communication systems,and propose an OTFS-based radar-embedded communication model suitable for high-speed mobile scenarios.By comparing the communication reliability at different velocities,the benefits of OTFS-based radar-embedded communication systems over conventional linear frequency modulation(LFM)based systems are verified.The proposed algorithm also shows excellent radar detection performance,and compensates the channel state information according to the motion parameters of the target to achieve more accurate communication reception.Besides that,our algorithm exhibits superior covertness performance to that of LFM.
摘要目前基于正交时频空(orthogonal time frequency space,OTFS)的雷达目标参数估计算法以在网估计为主,但在网估计算法无法有效应对现实应用中的离网现象。同时,现有离网估计算法的目标参数估计性能受建模误差的限制,也难以确保雷达系统在复杂环境下的有效应用。针对以上问题,提出了一种基于OTFS调制的动态稀疏贝叶斯(dynamic-sparse Bayesian learning,dynamic-SBL)算法。该算法在稀疏贝叶斯学习框架下引入动态虚拟网格,通过不断更新调整网格参数降低建模误差,提升目标参数估计性能。同时利用OTFS雷达信道特有的稀疏性对网格参数进行选择性局部更新,以降低算法的复杂度。仿真结果表明,所提算法估计的目标归一化时延和多普勒频率的均方误差较小,目标参数的估计性能优于传统离网估计方法的。该算法在实际雷达系统中具有较大应用潜力。
摘要在OTFS(Orthogonal Time Frequency Space,正交时频空间)调制中,Zak变换是将时域信号转换为关于DD(Delay-Doppler,时延-多普勒)域信号,DD域能够将时变的无线信道转换为二维的准静态信道表示,进而提升通信的可靠性,但同时增加了信号检测的复杂度。目前对OTFS的研究主要考虑Ts-OTFS(Two step-OTFS,两步方法),即首先将DD域信号转换为时频域,然后将其转换为时域进行传输。与两步方法相比,Zak变换方法更为简洁且性能更优。文章研究了基于Zak变换的OTFS(Zak-OTFS)传输,并在不同参数下误码性能进行了研究。首先通过Zak变换的原理推导了Zak-OTFS的传输过程,然后利用MRC(Maximal Ratio Combining,最大比合并)进行信号检测,最后通过对Zak-OTFS、Ts-OTFS、OFDM(Orthogonal Frequency Division Multiplexing,正交频分复用)的误码率对比,验证了Zak-OTFS的优势。仿真结果表明:Zak-OTFS和两步OTFS均优于OFDM。