SCLDGM coded modulation for MIMO systems with spatial multiplexing and space‐time block codes

We analyze Multiple‐Input Multiple‐Output (MIMO) coded modulation systems where either Bit‐Interleaved Coded Modulation (BICM) with spatial multiplexing or concatenation of channel coding and Space‐Time Block Codes (STBCs) is used at transmission, assuming iterative Turbo‐like decoding at reception. We optimize Serially‐Concatenated Low‐Density Generator Matrix (SCLDGM) codes (a subclass of LDPC codes) for each system configuration, with the goal of assessing its ability to approach the capacity limits in either ergodic or quasi‐static channels. Our focus is on three relevant STBCs: the Orthogonal Space‐Time Block Codes (OSTBCs) for two transmit antennas (i.e., the Alamouti code), which enables optimum detection with low complexity; the Golden code, which provides a capacity increase with respect to the input constellation; and Linear Dispersion (LD) codes, which enable practical detection in asymmetrical antenna configurations (i.e., more transmit than receive antennas) for cases in which optimum detection is infeasible. We conclude that BICM without concatenation with STBCs is in general the best option, except for Alamouti‐coded 2×1 and Golden‐coded 2×2 MIMO systems. Copyright © 2009 John Wiley & Sons, Ltd.     

Gallager Exponent Analysis of Coherent MIMO FSO Systems over Gamma-Gamma Turbulence Channels

This paper studies the Gallager’s exponent for coherent multiple-input multiple-output (MIMO) free space optical (FSO) communication systems over gamma–gamma turbulence channels. We assume that the perfect channel state information (CSI) is known at the receiver, while the transmitter has no CSI and equal power is allocated to all of the transmit apertures. Through the use of Hadamard inequality, the upper bound of the random coding exponent, the ergodic capacity and the expurgated exponent are derived over gamma–gamma fading channels. In the high signal-to-noise ratio (SNR) regime, simpler closed-form upper bound expressions are presented to obtain further insights into the effects of the system parameters. In particular, we found that the effects of small and large-scale fading are decoupled for the ergodic capacity upper bound in the high SNR regime. Finally, a detailed analysis of Gallager’s exponents for space-time block code (STBC) MIMO systems is discussed. Monte Carlo simulation results are provided to verify the tightness of the proposed bounds.     

Space‐time block coding in millimeter wave large‐scale MIMO‐NOMA transmission scheme

In this paper, we introduce a new wireless system architecture using space‐time block coding schemes (STBC) and non‐orthogonal multiple access (NOMA) in millimeter wave (mmWave) large‐scale MIMO systems. The proposed STBC mmWave large‐scale MIMO‐NOMA system utilizes two MIMO subarrays, transmitting data over two channel vectors to mobile users. To reduce the communication overhead and latency in the system, we utilize random beamforming with optimal coefficients at the base station and random‐near random‐far user pairing in implementing the NOMA scheme. Our results show that the proposed STBC mmWave large‐scale MIMO‐NOMA technique significantly outperforms the previous counterparts.     

Blind carrier frequency offset mitigation in space–time block‐coded multicarrier code division multiple access uplink transmission

In this paper, a novel blind carrier frequency offset (CFO) estimation is proposed on the basis of the linearly constrained optimization for the uplink transmission of space–time block‐coded multicarrier code division multiple access systems. First, the full‐dimensional spatial‐and‐temporal data are formed to avoid violation of the second‐order statistics in the conventional receiver design. A set of weight vectors is then provided for acquiring each multipath signal from the desired user while the others get rejected. Finally, the estimated CFO is obtained in accordance with maximizing the well‐defined measurement function, which is formulated by collecting all the output powers of the receiver. A space–time averaging technique is also proposed to enhance the robustness to the finite sample effect. Simulation study confirms that with the proposed CFO estimator used in the preceding, the receiver can successfully achieve the same performance of the optimal receiver working in the absence of CFO. Copyright © 2014 John Wiley & Sons, Ltd.     

相关瑞利衰落信道下空时分组编码性能分析

目前对空时编码的研究大都是基于信道是独立的假设下进行的,然而在实际系统中独立性假设是不成立的。基于此,研究了信道的相关性对空时编码性能的影响。计算机仿真结果表明：由于衰落信道的相关性,系统性能有所下降,且系统性能关于相关系数存在“地板效应”,即相关系数小于某一数值时,对系统性能的影响较小;当大于此值时,系统性能就会急剧下降。     

Interference mitigation for asynchronous cooperative STBC-OFDM systems

This paper addresses the problem of interference mitigation in cooperative Space Time Block Coded Orthogonal Frequency Division Multiplexing (STBC-OFDM) systems in the presence of asynchronism. This scheme first preprocesses the received ST codewords to convert the equivalent fading matrix into a suboptimal ordering upper triangular form based on low complexity permutation QR decomposition, and then suppresses the InterCarrier Interference (ICI) and InterSymbol Interference (ISI) by exploiting Successive Interference Cancellation (SIC) technique. Simulation results show that the performance of the proposed algorithm slightly outmatches or asymptotically approaches to that of the existing Minimum Mean Square Error (MMSE) detector depending on the magnitude of the Carrier Frequency Offsets (CFOs) but with less complexity.     

一种改进的多符号反馈检测算法在快速瑞利衰落信道中的研究

针对多符号差分检测（MSDD）存在着和分组长度成指数级的高计算复杂度的问题,提出了一种改进的多符号反馈检测（IMDFD）算法,它除了具有低复杂度的性能外,还能克服多符号反馈检测（MDFD）的错误传播和低信噪比下性能恶化的问题．仿真结果表明这种算法通过增加观察间隔,能很好地填补差分检测和相关检测之间的性能间距,并且随着考虑的序列长度逐渐减小,IMDFD算法在复杂度稍微增大的基础上,系统的性能也在逐渐增强．     

一种新的基于脉冲超宽带系统的发送分集方案

本文针对UWB信道特点,提出了预瑞克(Pre-RAKE)与空时块码(STBC)结合的新的发送分集方案,采用了基于最小均方误差准则(MMSE)的Pre-RAKE参数估计算法.最后仿真结果表明,基于MMSE算法的发送分集方案对系统误码率性能有较大改善,尤其是多径衰落严重而且存在符号间干扰(ISI)和窄带干扰(NBI)的非视距(NLOS)信道性能改善明显.     

MIMO CDMA系统中一种新的循环空时分组编译码方法

该文提出了MIMO CDMA系统中一种新的空时分组编译码方法,称为循环空时分组码(Cyclic Space-Time Block Code,C-STBC),它是将输入信息进行分组循环编码,然后对循环编码后的码字通过不同的天线分别采用不同的扩频码扩频后发射出去。这种CDMA系统下的循环空时分组码对任意的发射天线数都能达到满编码速率和满分集度,且其译码与传统的空时分组码一样简单。仿真结果验证了这种循环空时分组码优于传统的空时分组码。     

TPC-based STBC multiuser detection with LSE-RLS algorithm

The Bit Error Rate （BER） performance of a Turbo Product Code （TPC） based Space-Time Block Coding （STBC） multiuser wireless system in the frequency-selective channels has been investigated. Both of the good error correcting capability of TPC and the large diversity gain of STBC can be achieved simultaneously. A Least Square Error-Recursive Least Square （LSE-RLS） algorithm is applied to estimate the channel and cancel the interference. Simulations show that the proposed system can obtain about 2.7dB gain in Es/N0 at the BER of 10^-3.