基于串行和并行级联Turbo思想的均衡算法

利用Turbo码在两个信道译码器之间的迭代，能够得到更加精确的信道编码器输入数据比特的概率，从而代替在一般Turbo均衡器中对于该概率的独立等分布（IID）的假设。同时，通过分析这两个不同级联Turbo思想在该算法中的关系，得到算法的收敛特性，并合理确定两者相应的迭代次数。     

基于串行和并行级联Turbo思想的均衡算法

利用Turbo码在两个信道译码器之间的迭代,能够得到更加精确的信道编码器输入数据比特的概率,从而代替在一般Turbo均衡器中对于该概率的独立等分布（IID）的假设. 同时,通过分析这两个不同级联Turbo思想在该算法中的关系,得到算法的收敛特性,并合理确定两者相应的迭代次数.     

改进的短波信道数据引导均衡算法研究(英文)

针对短波信道数据引导均衡算法(data-directed equalization algorithm,DDEA)存在的问题,即必须以一帧数据内信道恒定为前提假设,且在均衡器和译码器之间只能传递硬判决信息,提出两种改进的DDEA均衡算法,分别从不同角度对此加以解决。所提可变信道系数的DDEA算法无须假设一帧数据内信道系数恒定,而允许在每个采样间隔信道系数都是变化的。所提DDEA-Turbo均衡算法能通过在信道估计器、均衡器和译码器之间传递软判决信息,将均衡器和译码器联合起来进行迭代。仿真结果表明,两种改进算法相较于传统的DDEA算法在性能方面都有不同程度的提高,但有分析显示,这种性能的提高须以增加复杂度为代价。     

基于Renyi熵的正交小波盲均衡的快速算法

为解决在正交小波CMA盲均衡(WBCMA),收敛速度与计算量相对矛盾的问题,这里引入了一种最新的基于Renyi熵的随机梯度最陡下降的盲均衡算法．与以往的CBA算法相比,该算法不仅使得正交小波盲均衡算法的收敛速度显著增加,而且计算量也增加很小,仿真结果证明了此方法的优越性．另外对新算法的参数,α,N的各种情况进行了研究讨论,仿真表明当α=2,N=2时,能取得更好的效果。     

Variable step size multi-antenna diversity equalization algorithm using error feedback

Owning to the correlation of the error signal in multi-antenna diversity adaptive decision feedback equalization being not same with white noises', the equalization performance is constrained. This paper adds error feedback filters to the traditional multi-antenna diversity adaptive decision feedback equalizer. The proposed structure can decrease the correlation of the error signal to increase the performance under the mean square error criterion. However, the proposed structure lowers the algorithm's convergence speed. Consequently, a nonlinear function between step size and error signal by modifying the sigmoid function in order to make this variable step-size measure be adapted to decision feedback equalizers is proposed. The modified algorithm has a larger step size at beginning. Simulation results show that the proposed approach can increase the speed and lower mean square with only little increase in computation.     

空间分集均衡水声通信技术的研究与仿真

水声信道中的衰变多途特性使得水声数字通信比较困难，常引起难以克服的码间干扰(ISI)，为改善系统性能、减少误码率，对空间分集均衡技术(SDE)进行了研究讨论，将决策反馈均衡与空间分集技术相结合，给出了空间分集均衡器的结构，在理论上证明了该方法的有效性，并讨论了LMS和RLS算法的优缺点，对传统的均衡技术与空间分集技术的性能进行了对比，并通过计算机仿真来验证该方法可降低传输系统的误码率，从而提高水下通信的可靠性。     

BICM-ID中的一种复合型Turbo均衡

传统的接收机中均衡器和信道译码器是相互独立的,Turbo均衡是一种联合均衡和译码技术,通过迭代,在均衡器和译码器之间交换外信息,从而获得更好的性能.针对BICM-ID系统的均衡问题,将Turbo均衡中的SIC(软干扰抵消)算法做修正后应用到基于硬判决的BICM-ID系统中,并将其与MAP(最大后验概率)算法结合,提出一种复合型Turbo均衡算法.仿真结果表明,在不同衰落程度的ISI信道中算法均能有效收敛,且系统均衡后性能随着信噪比的增加越来越接近AWGN下性能.     

非理想信噪比估计对Turbo均衡性能的影响

在信噪比估计非理想条件下,给出了一种简单的先验信息模型,使用外信息转移图分析了信噪比估计对基于线性最小均方误差的Turbo均衡系统性能的影响。所给示例表明:在-3~6 dB条件下,长帧的渐进性能对估计偏差并不敏感,而中短帧的不敏感区间则会大大缩小,系统仿真验证了分析的准确性,最后提出了一种新的结合先验信息的噪声方差估计算法,同时应用到Turbo均衡中,并通过仿真验证了算法的有效性。     

外辐射源雷达参考通道多径干扰抑制方法

针对外辐射源雷达系统参考通道中含有多径干扰的问题,提出一种基于改进恒模算法的参考通道多径干扰抑制方法．参考通道中的多径干扰会影响后续的杂波相消和匹配滤波处理,形成虚假目标,影响雷达系统的探测性能．由于多径干扰与直达波信号具有很强的相干性,传统方法很难消除参考通道中的多径干扰成分．新方法根据机会照射源信号的恒模特点,运用改进恒模算法对参考通道进行盲均衡处理,在不需要任何训练序列的情况下,抑制参考信号中的多径干扰．与传统的盲均衡方法相比,新方法具有更好的收敛性,多径干扰抑制效果更好．     

Turbo编码系统中信噪比盲估计算法

针对盲估计算法复杂度高、运算量大,研究了TURBO译码器中两个成员译码器输出的外部信息与信道信噪比的关系,提出一种基于译码器外部信息量的信噪比盲估计算法。仿真结果说明,采用此信噪比盲估计算法,在较小的系统性能恶化的前提下,大大简化了信道估计器的复杂度。分析了信噪比盲估计算法的误差性能,理论分析表明,发生误判的几率很小,均在1-0 3量级以下,可以认为信噪比估计值十分可靠。     

Combination of interference alignment and beamforming in cellular networks

In this paper, we propose two joint transmit-receive iterative algorithms without the cooperation between different base stations based on the idea of interference alignment (IA) to improve the throughput of relay backhaul links in cellular networks for the case of imperfect channel knowledge,which can be implemented with small changes to existing TD-LTE standards. Unlike the previous interference alignment algorithms’ only reducing the sum interference to the other receivers at the transmitter or the sum received Multi-user interference (MUI) at the receiver, our algorithm shapes the transmission of each data stream at transmitters in order not only to minimize interference to the other users, but also to minimize the interference between different streams objected to the same user, suppressing the MUI and Multi-stream interference (MSI) at receivers. The proposed algorithm I is to maximize the SINR at receivers. But the complexity is relatively high. Algorithm II only needs linear operations and sacrifices a little performance for much lower complexity compared to the Maximize SINR iterative algorithm which needs the inversion operation of matrix. It is also proved that the algorithm converges monotonically. The simulation results show that the techniques have considerable performance gain compared with the previous algorithms. Further research about power allocation is also discussed.     

Factor-graph-based iterative channel estimation and signal detection algorithm over time-varying frequency-selective fading channels

The problem of soft-input soft-output (SISO) detection for time-varying frequency-selective fading channels is considered. Based on a suitably-designed factor graph and the sum-product algorithm, a low-complexity iterative message passing scheme is proposed for joint channel estimation, equalization and decoding. Two kinds of schedules (parallel and serial) are adopted in message updates to produce two algorithms with different latency. The computational complexity per iteration of the proposed algorithms grows only linearly with the channel length, which is a significantly decrease compared to the optimal maximum a posteriori (MAP) detection with the exponential complexity. Computer simulations demonstrate the effectiveness of the proposed schemes in terms of bit error rate performance.     

用基于LMMSE-PIC算法消除OFDMA上行链路多用户干扰

提出了一种消除载波频偏引起的多用户接入干扰的LMMSE-PIC算法.首先,采用线性最小均方误差(LMMSE)来估计各用户的频偏干扰,然后根据这些估计值采用一种迭代的并行干扰消除(PIC)算法来消除多用户接入干扰.仿真结果表明,所采用的算法对载波频偏的估计精度较高,消除MUI干扰的效果明显.     

一种OFDM系统的自适应配置干扰抵消方法

分析了目前OFDM系统中当信道时延大于保护间隔时,采用信道压缩方法后存在的问题,指出了信道压缩后目标信道某些频点产生深衰落的可能性,提出了一种OFDM传输系统中双重自适应配置的多径干扰抵消方法。通过自适应配置与信道压缩相结合的方法克服了压缩后由目标信道频率深衰落产生的较低信噪比的子载波在频域均衡时的影响,在减少系统保护间隔开销的同时进一步改善了误码率;通过蒙特卡洛(MONTE CARLO)方法在无线信道条件下对算法进行了模拟,模拟结果显示该方法能有效改善系统性能。     

单音干扰下相干扩频系统早迟门延迟锁定环路性能分析

研究了单音干扰下扩频接收机延迟锁定环路（delay lock loop, DLL）的性能，提出在每个码元符号间隔内有整数个码片扩频序列的相干扩频系统中，单音干扰对DLL环路产生一个离散正弦波，而不是通常认为的高斯噪声.单音干扰下DLL环路的稳态误差，在无高斯噪声干扰的情况下，以离散正弦波形态振荡；在有高斯噪声干扰的情况下，为离散正弦波叠加高斯噪音.离散正弦波的频率、幅度和单音干扰与本地接收机的频率之差、接收信号的信息速率，以及码速率有关.     

基于小波包变换的直接序列扩频通信窄带干扰抑制技术

为了进一步提高直接扩频通信系统抑制大功率窄带干扰的能力,分别利用多进制小波包和复小波包分解将信号与干扰分离,然后再对滤波处理后的分解结果进行小波包合成.试验结果证明,这两项技术的误比特率性能优于二进制小波包噪声抑制技术     

Enhanced EM-based channel estimation for MIMO-OFDM in highly mobile channels

An enhanced expectation-maximization(EM)-based iterative channel estimator for coping with channel time variation is proposed for mobile multiple-input multi-output orthogonal frequency division multiplexing(MIMO-OFDM)systems.In the proposed scheme,the recursive least squares(RLS)algorithm is applied to track the time-varying channel impulse response(CIR)within several symbols.By using the tracked time-varying CIR,the ICI are constructed and then cancelled from the received signal,thus reducing their impactions on the channel estimation.Moreover,based on an over-sampled complex exponential basis expansion model(OCE-BEM),an improved channel predictor is derived in order to improve the initial channel estimates accuracy of the iterative estimator.Simulation results show that the proposed scheme outperforms the classic counterpart in time-varying scenarios with a smaller cost of complexity.