【作者】 陈玉婷；

【导师】 陈达；

【作者基本信息】 华中科技大学 ， 信息与通信工程， 2023， 硕士

【摘要】 正交时频空(Orthogonal Time Frequency Space,OTFS)技术引入了时延-多普勒域信道表示和信号调制,在高速移动场景下展现了良好的性能稳健性,在未来具有广阔的应用前景。但是OTFS通常采用时域矩形脉冲成形,这会使得信号的功率谱旁瓣衰减缓慢,从而造成频谱泄露,干扰相邻频带。信号旁瓣的关键在于成形滤波器的幅频特性,因此研究设计滤波器以抑制OTFS信号旁瓣具有重要意义。为降低OTFS信号旁瓣,本文提出了最小化阻带能量的OTFS成形滤波器优化方法。具体而言,本文首先分析了收发滤波器(即接收滤波器和成形滤波器)对系统正交传输的影响并推导出实现系统正交传输时二者需满足的条件,并发现滤波器长度与OTFS时频符号长度M的关系影响正交条件的具体表现形式。其次,以最小化成形滤波器阻带能量为目标,以推导出的正交条件为约束,分别建立长度小于等于M和长度大于M时OTFS收发滤波器的优化问题。最后,通过求解优化问题给出了优化后的收发滤波器系数。此外,提出了使用收发滤波器时OTFS系统的快速实现方法。仿真结果表明,优化所得的成形滤波器能够显著降低OTFS信号旁瓣,实现系统正交传输,且具有较低的实现复杂度。在上述滤波器优化方法中,每路子载波上的成形滤波器能量相同。为释放使用滤波器降低信号旁瓣的潜力,本文在不改变信号总功率的情况下,通过为不同子载波上的滤波器加权改变其能量,提出了收发滤波器加权优化方法。具体而言,首先推导得到使用加权滤波器时OTFS信号功率谱和系统均方误差性能。其次,为降低信号旁瓣,建立以最小化信号阻带能量为目标的滤波器权重优化问题并求解。最后,为权衡信号旁瓣和系统均方误差性能,以所得阻带能量最小值为参照,建立联合考虑系统均方误差和信号阻带能量的滤波器权重优化问题并求解。仿真结果表明所提滤波器加权技术能在滤波器优化基础上进一步抑制信号旁瓣,且联合考虑系统均方误差优化权重时能在抑制信号旁瓣的同时减少系统均方误差等传输性能的损失。更多还原

【Abstract】 Orthogonal Time Frequency Space(OTFS)technology introduces Delay-Doppler domain channel representation and signal modulation,which shows great performance robustness in high-speed mobile scenarios,and has broad application prospects in the future.However,OTFS usually adopts time-domain rectangular pulse shaping,which will make the sidelobe of the power spectrum of the signal attenuate slowly,resulting in spectrum leakage and interference with adjacent frequency bands.The key of the sidelobe of the signal is the amplitude-frequency characteristic of the shaping filter,so it is of great significance to study and design the filter to suppress the sidelobe of OTFS signal.In order to reduce the sidelobe of OTFS signal,an optimization method of OTFS shaping filter is proposed to minimize stopband energy.Specifically,this thesis first analyzes the influence of transceiver filters(receiving filter and shaping filter)on system orthogonal transmission and deduces the conditions to be satisfied when realizing system orthogonal transmission,and finds that the relationship between filter length and OTFS time-frequency symbol length affects the concrete expression of orthogonal condition.Secondly,with the objective of minimizing the stopband energy of the shaping filter and taking the derived orthogonal conditions as constraints,the optimization problems of OTFS transceiver filters are established when the length is less than or equal to M and the length is greater than M.Finally,the coefficients of the optimized transceiver filters are given by solving the optimization problem.In addition,a fast implementation method of OTFS system using transceiver filters is proposed.The simulation results show that the optimized shaping filter can significantly reduce the sidelobe of OTFS signal,realize the orthogonal transmission of the system,and has low implementation complexity.In the above filter optimization method,the shaping filter energy on each subcarrier is the same.In order to release the potential of using filters to reduce the sidelobe of signals,a weighted optimization method of transceiver filters is proposed by weighting filters on different subcarriers to change their energy without changing the total power of the signal.Specifically,firstly,the power spectrum of OTFS signal and the mean square error performance of the system using weighted filters are derived.Secondly,in order to reduce the signal sidelobe,the filter weight optimization problem aiming at minimizing the signal stopband energy is established and solved.Finally,in order to weigh the signal sidelobe and the system mean square error performance,with reference to the minimum stopband energy,the filter weight optimization problem considering the system mean square error and signal stopband energy is established and solved.The simulation results show that the proposed filter weighting technique can further suppress the signal sidelobe on the basis of filter optimization,and when jointly considering the system mean square error to optimize the weights,it can suppress the signal sidelobe and reduce the loss of transmission performance such as the system mean square error.更多还原