基于LDPC码与星座旋转准正交STBC的级联编译码方法

在4×4多输入多输出(multiple input multiple output, MIMO)系统中,为了同时达到全分集增益和全速率数据传输,进而达到降低系统误码率及提高系统可靠性的要求,提出将低密度奇偶校验(low density parity check, LDPC)码与基于星座旋转的准正交空时分组码级联的编码方案,并找出了在全数据传输速率的前提下能够获得满分集增益的最优旋转角度。仿真结果表明,该级联编码方案误码率低于传统的LDPC编码与空时分组码级联的编码方案,在误码率为10^-5的情况下,比LDPC码与正交空时分组码级联的编码方案有8 dB左右的增益。     

Efficient spread space-time block coding scheme in multiple antenna systems

1 .INTRODUCTIONRecently ,an intense interest has focused on wire-less systems that can provide good quality and highdata rate .Space-ti me coding is an i mportant tech-nique that can i mprove system performance at fa-ding environments by obtaining diversity gains andcoding gains in multiple antenna systems .To make multiple antenna system practical ,methods that can obtain diversity gains with mod-erate complexity and provide acceptable bit errorrate ( BER) performance are investigated i…     

基于STBC的双层预编码MIMO系统

提出一种结合空时分组码(space-time block coding, STBC)与双层预编码的方法。建立了基于STBC的双层预编码多输入多输出(multiple input multiple output, MIMO)系统模型,给出了预编码赋形权矢量的构造方法,利用预编码形成的两个虚拟子信道同时传输两个数据流,同时结合Alamouti STBC构成混合编码,带来分集增益;针对STBC双层预编码系统设计了一种低复杂度的译码方法。理论和仿真结果表明,新系统可以同时带来分集增益和复用增益,有效提高系统信道容量,与通常的MIMO系统相比,误码性能得到明显改善。     

基于四天线的并行空时分组编码方案

空时编码是一种结合信道编码和分集技术的新型的编码和信号处理方法,可以不需增加带宽而大幅度的提高无线通信系统的信道容量和传输速率,从而提供远高于传统单天线系统的频带利用率,空时分组码以其译码的简单性获得人们的广泛关注。为提高空时分组码的码元速率,在现有的空时分组编码方案的基础上,结合并行传输策略,提出了基于四天线的并行空时分组编码方案。与传统的空时分组编码方案相比,该方案能够在保证误码性能的同时提高码元速率,从而进一步提高了系统的性能。仿真结果验证了所提出的编码方案所具有的良好性能。     

基于OFDM系统的空时频分组编码方案

提出了一种空时频分组编码方案,其设计思路是:接收端通过子信道的相关特性确定不相关子载波组,并反馈给发射端;发射端基于反馈信息,利用星座旋转预编码矩阵和空时分组编码技术构建空时频分组编码。该方案只反馈子信道的相关性而无需反馈整个信道信息,可应用于任意数量的发射/接收天线,能获得极高的分集增益和带宽效率,且只有较低的解码复杂度。在瑞利衰落环境下的仿真结果证实了此方案的鲁棒性。     

Differential modulation based on space-time block codes

A differential modulation scheme using space-time block codes is put forward. Compared with other schemes, our scheme has lower computational complexity and has a simpler decoder. In the case of three or four transmitter antennas, our scheme has a higher rate a higher coding gain and a lower bit error rate for a given rate. Then we made simulations for space-time block codes as well as group codes in the case of two, three, four and five transmit antennas. The simulations prove that using two transmit antennas, one receive antenna and code rate of 4 bits/s/Hz, the differential STBC method outperform the differential group codes method by 4 dB. Useing three, four and five transmit antennas, one receive antenna, and code rate of 3 bits/s/Hz are adopted, the differential STBC method outperform the differential group codes method by 5 dB, 6. 5 dB and 7 dB, respectively. In other words, the differential modulation scheme based on space-time block code is better than the corresponding differential modulation     

基于AF-CDC-OFDM的差分网络编码

在多子载波、频率选择性衰落、双向中继转发信道中提出多中继协作的基于AF-CDC-OFDM的差分网络编码方法。通过多个协作中继的分布式循环延时编码及功率放大处理,两路终端发送的差分编码分组可获得完全的协作分集和频率分集增益。两路终端在检测对方的发送信号之前需要消除自干扰信号,为此,提出基于统计相关的自干扰分量估计方法。仿真结果表明,提出的差分网络编码能够获得完全的分集增益性能,对应的自干扰分量相关统计估计算法在慢衰落信道中与干扰分量完全消除的检测性能相比,仅有0.5 dB的信噪比损耗。     

基于Frobenius范数的正交空时多格形编码设计

基于Frobenius范数理论,提出了正交空时多格形编码(OST-MTCM)方法.新方法通过在编码网格图中的每个网格传输分支上引入正交码字矩阵,并采用Ungerboeck的星座图扩展和集分割思想,从而在获得满分集增益的同时,也获得优秀的编码增益.仿真结果表明,相对于原有的空时多格形编码方法,在相同的码速率和编码状态数的情况下,新方法可以获得大约1.5 dB左右的性能改善;并且,网格分支上传输码字矩阵正交性的确定极大简化了好码的搜寻过程,无需针对不同的信道衰落条件设计不同的编码方案.     

无线传感器网络中的异步协作通信方案

为了改善多跳传感器网络的性能,提出了一种基于三种空间分集技术的异步协作传输模式.该模式是考虑非同步网络传输,多个传感器通过共享天线,形成虚拟多天线发送/多天线接收(MIMO)的协作通信,并利用空时编码、发射天线选择和信号空间分集三种空间分集技术,有效抵制传输信道的衰落,提高了系统的分集增益.通过蒙特卡罗仿真,结果表明,对比传统的单发单收传输模式和异步空时协作传输模式,该传输模式获得了更高的分集增益,提高了系统的性能,从而节省了网络的能量损耗.     

Raptor码在下行协作无线蜂窝系统中的研究

不同于传统的采用固定码率编码的协作中继系统,在发送端不知道信道状态信息(channel state in formation,CSI)时,提出协作蜂窝系统下行链路中使用无限码率Raptor码及分布式空时分组码(distributed space-time block code,DSTBC)的新方案,并研究该方案有效性、可靠性和健壮性的问题。理论分析和仿真结果证明,当发送端不知道CSI时,结合应用Raptor码和DSTBC,即使在低信噪比(signal-to-noise ratio,SNR)环境中仍能降低总传输时间及能量消耗,给无线蜂窝系统带来显著的性能增益。     

Power control scheme for multiple antenna systems with space-time coding in Rayleigh fading channels

Two optimal power control(PC) schemes under the power constraint for space-time coded multiple input multiple output systems over the flat Rayleigh fading channel with the imperfect channel state information(CSI) are presented.One is based on the minimization of a bit error rate(BER),and the other is based on the maximization of a fuzzy signal-to-noise ratio.In these schemes,different powers are allocated to individual transmit antennas rather than equal power in the conventional one.For the first scheme,the optimal PC procedure is developed.It is shown that the Lagrange multiplier for the constrained optimization in the power control does exist and is unique.A practical iterative algorithm based on Newton’s method for finding the Lagrange multiplier is proposed.In the second scheme,some existing schemes are included,and a suboptimal PC procedure is developed by means of the asymptotic performance analysis.With this suboptimal scheme,a simple PC calculation formula is provided,and thus the calculation of the PC will be straightforward.Moreover,the suboptimal scheme has the BER performance close to the optimal scheme.Simulation results show that the two PC schemes can provide BER lower than the equal PC and antenna selection scheme under the imperfect CSI.     

Symbols detection for frequency-selective V-BLAST OFDM systems

1.INTRODUCTION TheverticalBellLabslayeredspace time(V BLAST)architecture[1]isonemostpromisingspace timecoding(STC)technique.Theprovisioningca pacityoftheV BLASTarchitecturecanmorenear thetheoreticalupper limitofchannelcapacity[2].Therefore,quiteanumberofresearchersproposedto deploytheV BLASTarchitectureinwirelesslocal loop(WLL)andwirelesslocalareanetwork(WLAN)[3].Conventionally,themultiple inputmultiple out put(MIMO)wirelesschannelsintheV BLASTar chitectureareassumedtobefl…     

Lattice-reduction-aided MMSE precoding for correlated MIMO channels and performance analysis

The lattice-reduction (LR) has been developed to improve the performance of the zero-forcing (ZF) precoder in multiple input multiple output (MIMO) systems. Under the assumptions of uncorrelated flat fading channel model and perfect channel state information at the transmitter (CSIT), an LR-aided ZF precoder is able to collect the full transmit diversity. With the complex LenstraLenstra-Lova′sz (LLL) algorithm and limited feedforward structure, an LR-aided linear minimum-mean-square-error (LMMSE) precoder for spatial correlated MIMO channels and imperfect CSIT is proposed to achieve lower bit error rate (BER). Assuming a time division duplexing (TDD) MIMO system, correlated block flat fading channel and LMMSE uplink channel estimator, it is proved that the proposed LR-aided LMMSE precoder can also obtain the full transmit diversity through an analytical approach. Furthermore, the simulation results show that with the quadrature phase shift keying (QPSK) modulation at the transmitter, the uncoded and coded BERs of the LR-aided LMMSE precoder are lower than that of the traditional LMMSE precoder respectively when E b / N0 is greater than 10 dB and 12 dB at all correlation coefficients.     

适于高速无线通信系统的空时分组码组合QAM调制方案

空时分组码 (STBC)利用多输入 多输出 (MIMO)无线通信系统的本质特性 ,通过提供发射天线分集和接收端的信号处理 ,从本质上提高了无线通信系统的容量 ,并以其编译码算法简单的特点获得了广泛关注和应用。在介绍了空时码和多输入 多输出无线通信系统的系统模型后 ,以基本的两天线空时分组码C2 为例给出了其编码和解码算法 ,并基于此提出了适于高速无线通信系统的空时分组编码结合正交调制 (QAM)的通信方案。最后给出了该方案在 16 QAM调制条件下几种典型空时分组码的误符率和误码率的性能仿真结果。结果表明 ,该方案是一种适于高速无线通信系统的优选方案     

Efficient coding schemes with power allocation using space-time-frequency spreading

1 .INTRODUCTIONOver the last few years , space-ti me coding[1]hasreceived a lot of attention among communicationand information theory community , which in-tegrates the technique of antenna array spatial di-versity and channel coding,and can effectivelyi m-prove capacity gains and spectral efficiency . Mostwork on space-ti me coding has focused on the nar-row-band flat fading channels . However , non-flatfading channels such as frequency selective mul-tipath fading channels are the typical…     

基于线性弥散空时码的有限反馈干扰对齐算法

干扰对齐(interference alignment,IA)作为极具潜力的干扰管理策略,能获得与用户数量成线性关系的自由度增益,但因其需要全局实时信道状态信息(channel state information,CSI)才能有效实现,使得IA理论向实用的转化将面临众多挑战。针对该问题,本文基于多小区蜂窝系统,提出了一种基于线性弥散空时码的有限反馈干扰对齐算法,该算法将预编码和线性弥散空时码编码进行级联,在只需反馈单个用户CSI的条件下,通过合理地设计预编码矩阵、线性弥散空时码块以及接收端的接收矩阵,来实现干扰的完全消除。仿真结果表明,相比已有研究,新IA算法在实现干扰完全消除的情况下,能够极大地降低系统CSI反馈开销。     

复数域符号相乘的差分网络编码

传统差分网络编码在解码转发方式下编码环节繁杂、中继检测复杂度高。基于此,文中提出复数域符号相乘的差分网络编码,并构建了中继检测方法一和中继检测方法二,能显著降低中继的检测和编解码复杂度。同时,将提出的编码方法拓展到多中继协作方式以获取高阶协作分集增益,并得到随机差分空时网络编码,其能获得的分集增益阶数为解码正确的中继个数。仿真实验和理论分析均验证了提出的复数域符号相乘的差分网络编码方法在单中继和多中继协作方式下的有效性。     

Resource allocation for multiuser STBC-BF MIMO-OFDM downlink with imperfect channel information

To improve the performance of a multiuser MIMO-OFDM system with imperfect channel status information, a downlink adaptive resource allocation algorithm which combines space-time block coding and beam forming (STBC-BF) is proposed. The algorithm allocates the subcarriers with a shared manner. A zero forcing processing with joint Rx-Tx is used to suppress the co-channel interference (CCI) and to construct uncorrelatedchannels for STBC. An adaptive power allocation for the STBC equivalent channels can increase signal to interference and noise ratio at the receiver. Simulation results show that under the condition of an imperfect CSI, the proposed algorithm improves the system performance and reduces the number of BS transmit antennas required.     

Throughput-based mode switching for MIMO ARQ systems in presence of transmit correlation

The mode switching between spatial multiplexing(SM) and space-time block code(STBC) diversity is investigated for the multiple-input multiple-output(MIMO) automatic repeat request (ARQ) system.Five important practical factors are considered in the proposed switching scheme:transmit correlation,ARQ technique, packet loss probability(PLP) constraint,discrete rate transmission (DRT) and channel coding.Under the spatially correlated channel,the distributions of the post signal-to-interference-plusnoise ratio(SINR) for the SM mode and the STBC mode are obtained by using Gamma approximations.Then this paper derives the closed-form expressions of the PLP and the throughput for different modes when the ARQ technique is employed,based on which the mode switching algorithm is proposed to improve the spectral efficency.In the simulation,the correction of the expressions is first verified.Then,the significant gain observed by the proposed algorithm is presented.Since the switching point is the key parameter to implement the mode switching,this paper also shows how the switching point is affected by the practical factors considered.     

基于低密度格码的编码协作中继系统

提出一种联合低密度奇偶校验码(low density parity check,LDPC)的低密度格码编码协作(low density lattice code coded cooperation,LDLC-CC)改进方案。中继对源节点广播的LDLC码字进行译码,并向目的节点转发基于LDPC和LDLC编码的增强校验信息。通过利用校验矩阵下三角结构特性,源节点和中继节点可以简单地通过各自的校验矩阵进行整形和编码,且采用的LDLC校验矩阵可以构成高维下三角结构校验矩阵。此外,设计了目的节点联合迭代软译码算法。该算法建立了LDLC联合译码与LDPC软译码之间的联系,相比LDPC硬译码可以获得显著的编码增益。仿真结果显示,在瑞利慢衰落信道下提出的联合LDPC的LDLC-CC系统相比传统无协作直传LDLC系统最大可以取得近5 dB性能增益。