SC-FDE系统的一种新型判决反馈均衡器

针对单载波频域均衡系统MMSE均衡器存在残留码间干扰的缺点,提出MMSE-RISIC判决反馈均衡器消除残留码间干扰.MMSE-RISIC均衡器采用传统MMSE均衡后的判决数据,对残留码间干扰进行估计并消除.残留码间干扰的估计主要采用FFT和IFFT运算,与其他方法相比计算量较小.对该均衡器在不同信道下进行了计算机仿真,结果表明,在频率选择性衰落信道条件下,系统性能有了较为明显的提高.     

A Multiple Input-Multiple Output (MIMO) Adaptive Decision Feedback Equalizer (DFE) with Cancellation for Wideband Space-Time Communications

A new receiver structure able to deliver high data rates in a multiple input-multiple output (MIMO) frequency selective wireless environment is proposed and investigated in this paper. The optimal solution for the finite-length MIMO decision feedback equalizer (DFE) with cancellation is derived and used to illustrate the potential of this architecture for space-time communications. LMS and RLS adaptive algorithms are also presented for the MIMO architecture. The convergence and performance of these adaptive algorithms is analyzed through simulation results. The proposed adaptive solutions do not require channel identification, are less computationally intensive than their optimal solution counterpart, and allow the proposed MIMO receiver to seamlessly adapt to channel changes.     

基于快速信道捕获与系数映射均衡的流星通信接收机

针对流星余迹通信原理及信道特点,构造了基于自适应编码调制的变速率通信机制,提出了有效利用传输帧结构的快速信道估计及系数映射均衡的流星余迹通信接收机.在利用时域相关运算快速捕获流星信道冲击响应的基础上,推导出信道参数与均衡器系数之间的映射关系,直接计算出判决反馈均衡器的抽头系数,从而实现流星余迹通信自适应编码调制方式数据的可靠接收.该接收机在信道变化的情况下具有较快的收敛速度,和较好的抗噪声性能.仿真结果和复杂度分析验证了算法的有效性.     

室内可见光通信信道估计的研究

要:建立了室内可见光通信系统模型,针对其信道冲击响应,分别采用最小二乘(LS)估计方法和最小均方差(MMSE)估计方法对信道进行了理论分析,并且通过计算机仿真,对两种不同的估计方法性能进行了比较,最后在此基础上,分别对抽头长度和训练序列长度对信道估计的性能影响进行了仿真验证。实验结果表明:在相同信噪比下,MMSE方法的性能优于LS方法,但是计算量比LS方法复杂,而且LS方法性能依赖于噪声的影响,信噪比越高,LS估计方法的性能越好。同时抽头数越多,训练序列越长,信道估计的性能越好,但也会增加计算的复杂度。     

40Gb/s光纤通信系统中自适应判决反馈均衡器的补偿性能

数值仿真了40Gbit/s 非归零码(NRZ)光纤通信系统中,基于最小均方差算法的非线性自适应判决反馈均衡器对系统传输损伤的补偿性能.仿真结果表明,对于单信道40 Gbit/s NRZ系统,在同时考虑色散和自相位调制情况下,自适应判决反馈均衡器的引入可以使系统色散容限(1 dB眼图张开度代价)得到明显改善.在信号丢失率为10-3条件下,PMD容限由补偿前的0.17/单位比特周期,可提高到补偿后的0.22/单位比特周期.     

多天线双向中继转发的优化方法研究

本文对多天线双向中继放大转发方案进行了研究。首先,基于最小化均方误差的准则,通过对上行链路和下行链路进行联合优化,推导出了相应的中继优化方法,该优化方法能够实现最优的链路可靠性。然后,基于该优化方法,利用部分信道状态信息和信道统计信息,针对固定中继和移动中继两种不同的通信场景,分别设计了不同参数控制下的鲁棒性实现。理论分析和计算机仿真都表明所提方案具有明显的性能增益。      

MMSE准则下近似最优MIMO分组并行检测算法

在采用多天线高阶QAM的MIMO通信系统中,现有基于信道分组并行检测算法虽然接近最优检测性能但以牺牲计算效率为代价.针对这一问题,本文提出一种MMSE准则下基于信道分组的并行检测算法,不但有效降低计算复杂度,而且仍保证检测性能.该算法采用MMSE准则下格归约算法改进分组后条件较好子信道矩阵特性,并在消除参考信号基础上利用改进的子信道矩阵对剩余信号以非线性方式进行检测.仿真结果表明:对4×4和6×6MIMO系统,该算法检测性能达到最优,对于8×8 MIMO系统,比最优算法所需信噪比提高约1dB.复杂度分析表明:相比现有信道分组检测算法,相同检测性能下该算法在6×6 MIMO系统中复杂度降低90%以上,在8×8 MIMO系统中复杂度降低98%以上.     

Device-Free Through-the-Wall Activity Recognition Using Bi-Directional Long Short-Term Memory and WiFi Channel State Information

Activity recognition plays a key role in health management and security. Traditional approaches are based on vision or wearables, which only work under the line of sight (LOS) or require the targets to carry dedicated devices. As human bodies and their movements have influences on WiFi propagation, this paper proposes the recognition of human activities by analyzing the channel state information (CSI) from the WiFi physical layer. The method requires only the commodity: WiFi transmitters and receivers that can operate through a wall, under LOS and non-line of sight (NLOS), while the targets are not required to carry dedicated devices. After collecting CSI, the discrete wavelet transform is applied to reduce the noise, followed by outlier detection based on the local outlier factor to extract the activity segment. Activity recognition is fulfilled by using the bi-directional long short-term memory that takes the sequential features into consideration. Experiments in through-the-wall environments achieve recognition accuracy >95% for six common activities, such as standing up, squatting down, walking, running, jumping, and falling, outperforming existing work in this field.     

An MMSE Decoding Algorithm without Matrix Inversion in QSTBC

The matrix inversion operation is needed in the MMSE decoding algorithm of orthogonal space-time block coding （OSTBC） proposed by Papadias and Foschini. In this paper, an minimum mean square error （MMSE） decoding algorithm without matrix inversion is proposed, by which the computational complexity can be reduced directly but the decoding performance is not affected.     

Simplified transmitter design for MIMO systems with channel uncertainty

This article investigates transmitter design in Rayleigh fading multiple input multiple output (MIMO) channels with spatial correlation when there are channel uncertainties caused by a combined effect of channel estimation error and limited feedback. To overcome the high computational complexity of the optimal transmit power allocation, a simple and suboptimal allocation is proposed by exploiting the transmission constraint and differentiating a bound based on Jensen inequality on the channel capacity. The simulation results show that the mutual information corresponding to the proposed power allocation closely approaches the channel capacity corresponding to the optimal one and meanwhile the computational complexity is greatly reduced.     

SVD-based MIMO Precoding and Equalization Schemes for Realistic Channel Knowledge: Design Criteria and Performance Evaluation

Multiple-input multiple-output (MIMO) based communication systems with precoding, bit-loading and equalization procedures are considered in this paper. Applications of precoding schemes, which are based on Singular Value Decomposition (SVD) of the channel matrix H assume almost always ideal channel knowledge at the transmitter and/or receiver site. This paper investigates an SVD based MIMO approach considering non ideal radio channel estimation results. In any case the MIMO channel matrix H is decomposed into Eigenmodes. In case of an ideal radio channel knowledge the SVD based precoding procedure, which is applied at the transmitter site, is going to consider all possible Eigenmodes which results in a perfect separation of all signals at the receive antenna output and into a minimum bit-error-rate (BER). It will be shown in this paper that in case of non ideal channel knowledge and a limited accuracy in the channel matrix H estimation a reduced number of Eigenmodes in the precoding process will become an optimum and will lead into an increased BER performance.

基于冲激响应加窗法的CO-OFDM系统信道估计研究

针对相干光正交频分复用(CO-OFDM)系统中光纤的色散和信号传输过程中噪声对系统可靠性的降低,提出了信道的冲激响应加窗(IRM,impulse response processed with window)算法,在最小二乘(LS)算法的基础上,通过时域加窗将信道冲激响应长度以外的噪声滤除,保证了信道冲激响应长度在OFDM保护间隔之内。在算法复杂度提高并不大的前提下,IRW算法系统误码率(BER)比LS算法降低了近1个数量级。仿真结果表明,在256个子载波的CO-OFDM系统中,BER为10-4时,IRW算法对系统信噪比(SNR)的要求比LS算法低了近2.5dB,而只比线性最小均方误差(LMMSE)算法高0.7dB;并且,IRW算法的复乘次数仅比LS算法高8倍,而比LMMSE算法的复乘次数低32倍。     

An Achievable Rate Region for the Asynchronous Multiple Access Channel with Feedback

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