Adaptive MLSE Equalizer with Per-Survivor QR Decomposition for Trellis-Coded MIMO Transmission

A trellis-coded multiple-input multiple-output (MIMO) transmission technique, which exploits multiple-antenna elements at both transmitter and receiver sides and employs trellis-coded modulations (TCMs), has potential to significantly increase spectral efficiency in wireless communications. At the receiver, an adaptive equalizer based on maximum-likelihood sequence estimation (MLSE) deals with intersymbol interference (ISI) incurred in wideband transmissions and jointly decodes multiplexed TCM signals. Recently, a sphere-constrained maximum-likelihood detection, so-called sphere decoding, has drawn much attention for reducing the computational burden in MIMO transmission systems. This paper describes the super-trellis structured Viterbi algorithm applying per-survivor sphere decoding, and evaluates the effect of the complexity reduction in branch metric computations. Toshiaki Koike received the B.S. degree in electrical and electronics engineering and M.S. degree in communications and computer engineering from Kyoto University, Kyoto, Japan, in 2002 and 2003, respectively. Since 2003, he has been working towards the Ph.D. degree in communications and computer engineering, Kyoto University. His current research interest includes digital signal processing for multiple-antenna systems and multi-user communications. He has been a Research Fellow of the JSPS since 2004. Hidekazu Murata received B.S., M.S., and Ph.D. degrees in electronic engineering from Kyoto University, Kyoto, Japan, in 1991, 1993, and 2000, respectively. In 1993, he joined the Faculty of Engineering, Kyoto University. Since 2002, he has been an associate professor of Tokyo Institute of Technology, Tokyo, Japan. His current research interests include signal processing and its hardware implementation, with particular application to multihop radio networks. He received the Young Researcher's Award from the IEICE of Japan in 1997 and the Ericsson Young Scientist Award in 2000. He is a member of the IEEE and SITA. Susumu Yoshida received the B.E., M.E. and Ph.D. degrees in electrical engineering from Kyoto University, Kyoto, Japan in 1971, 1973 and 1978, respectively. Since 1973, he has been with the Faculty of Engineering, Kyoto University and currently he is a full professor of the Graduate School of Informatics, Kyoto University. During the last two decades, he has been mainly engaged in the research of wireless personal communications. His current research interest includes wireless transmission technologies beyond IMT-2000 and wireless ad hoc networks. During 1990–1991, he was a visiting scholar at WINLAB, Rutgers University, U.S.A. and Carleton University in Canada. He served as an Executive Committee Chairperson of PIMRC'99, Osaka and also as a Technical Program Committee Chairperson of IEEE VTC 2000-Spring, Tokyo. He was a guest editor of IEEE J-SAC on Wireless Local Communications published in April and May 1996. He was a Director, Journal and Transactions of IEICE during 2002–2004 and has been a Fellow of the IEICE since 2004. He was awarded the Young Researcher's Award in 1978 and the Achievement Award in 1993 both from the IEICE.     

GSM公共信道中SCH自适应均衡解调算法研究

针对移动信道多径效应造成的严重的码间干扰(ISI)问题,研究了基于最大似然序列估计(MLSE)的GSM公共信道中SCH自适应均衡解调算法,并对这种自适应均衡解调算法在Jakes移动信道模型环境下的性能进行了分析和计算机仿真,仿真结果表明该自适应均衡解调算法能够很好地克服码间干扰(ISI)问题,性能良好。     

MLSE算法及其在智能天线中的应用

MLSE算法作为一种最优算法,能有效地抑制多径干扰,得到了比较广泛的应用。该文系统地介绍了MLSE算法原理和在智能天线中的应用。     

基于MLSE算法的GMSK均衡解调

为了克服高斯滤波最小频移键控(Gaussian Filtered Minimum Shift Keying,GMSK)调制信号经过移动通信传输后存在的码间干扰,利用信道中已知训练序列的伪随机性,进行信道同步和信道估计,经过匹配滤波和改进的Viterbi算法,使解调序列差错概率达到最小。以同步信道突发为例,研究基于最大似然序列估计(MaximumLikelihood Sequence Estimator,MLSE)均衡算法下的GMSK解调,并在JAKES信道下进行仿真,结果显示,这种MLSE均衡算法能很好的进行GMSK解调。     

初始判决指导下的DS/CDMA最大似然检测算法

本文首先给出了多径异步多用户ＤＳ／ＣＤＭＡ系统的一种数学模型，得出了恒参信道下最大似然检测（ＭＬＳＥ）算法的一种新的表示形式。然后作者具体分析了以ＲＡＫＥ接收机作为衰落信道的匹配滤波器时，最大似然检测器的算法设计问题。分析指出，在多径环境下ＭＬＳＥ算法的复杂度和计算量与多径时延的分布有关，如果用户时延扩散在一个信息码元之内，算法复杂度和恒参信道下相同，而其实现可以用状态数可变的Ｖｉｔｅｒｂｉ算法来实现。最后，本文用传统判决方法得出的初始判决信息缩减Ｖｉｔｅｒｂｉ算法的搜索空间，在保证一定性能的前提下，算法的计算复杂度大大降低。     

一种基于最大似然序列估计的均衡算法

本文利用编码的思想,在Viterbi算法的基础上提出了一种改进的准MLSE均衡算法.此算法能大大降低计算的复杂度,并具有对信道冲激响应波形的敏感性较低、和软输出的Viterbi 算法兼容等特点.本文利用计算机对算法进行了性能仿真,并和NMLSE等算法进行了比较,模拟结果表明,该算法具有良好的抗ISI性能.     

短波通信中的低复杂度时域均衡

提出了一种基于Chase算法的低复杂度时域均衡技术.首先通过传统的自适应均衡器获取软值,再利用Chase算法计算可信度找到不可靠位,同时构造测试序列,然后进行滑动窗搜索和逐比特译码.此算法在减小计算量的同时消除了译码时延,并且误码率逼近最大似然序列估计,实现了复杂度和性能的折衷.     

将空时MLSE算法用于判决反馈检测器的研究

提出了一种将空时MLSE算法用于判决反馈检测器的方案，它无须功率控制即可实现抗远近效应，其误码性能比广泛应用的多用户检测中的判决反馈器理想，它可用于CDMA移动通信系统中。经计算机仿真可以看出，这种方案确实对系统的接收性能有一定的改善。     

Demodulation with a Multichannel Estimation Method Using a Reduced Rank Constraint

This paper deals with the Maximum Likelihood Estimation of the multichannel impulse response in a mobile communication system whose base stations are equipped with antennas arrays. The following problem is solved: using the training sequence, find the maximum likelihood multichannel impulse response from one mobile to the base station under a reduced rank constraint in the presence of gaussian noise and jammers with unknown covariance matrix. This method finds applications in demodulation (the reduced rank channel estimate can be used in a Viterbi Algorithm), and experimental results using real signals demonstrate its high performance compared with the standard Minimum Mean Square Error (MMSE) multichannel estimate.     

ADAPTIVE EQUALIZATION WITH RLS-MLSE ASSISTED BY FEC BLOCK CODING FOR FADING MOBILE RADIO CHANNELS

In this paper, we propose an adaptive maximum-likelihood (ML) sequence estimator with RLS channel estimation, which is assisted by forward error control (FEC) coding. The reliable symbols reconstructed in the FEC decoder are used as the feedback signal to the RLS channel estimator. The scheme is compared with decision feedback equalization (DFE) with RLS algorithm, which is assisted by FEC coding. Computer simulations show that in frequency-selective fast fading mobile radio channels, the proposed scheme performs better at moderate Doppler frequencies. It is suitable for four-phase modulation data transmission at the rate of several 10 kb/s in 900 MHz band or in the 1800 MHz band.