BICM-ID光通信系统中一种新颖星座映射方案的优化分析

针对传统Gray映射在中高信噪比区域内对迭代译码的比特交织编码调制(BICM-ID)光通信系统改善信道容量性能有限的问题,基于互信息准则和比特的不等保护度提出了一种新颖的16QAM星座映射方案.仿真分析表明:在中高信噪比下,所提出的新映射方案比传统Gray映射方案的信道容量最大改善值可达1.18 bit/channel.结合低密度奇偶校验(LDPC)码并借助外部信息传递(EXIT)图,该方案在光通信系统中具有很好的性能优势与应用前景.     

基于BICM的高效编码协作方案及性能分析

 提出一种基于比特交织编码调制(BICM)的高效编码协作(CC)方案,该方案中协作用户编码比特分为两帧,每一帧都通过BICM调制发送,通过结合比特交织器满足高阶调制星座符号的不同比特经历的衰落独立。一方面,论文分析了该协作方案在不同信道下的成对错误概率,并进一步推导了错误比特概率上界。理论分析以及仿真结果都表明：准静态衰落信道下,基于BICM的高谱效率编码协作方案仍然可以获得完全分集;而快衰落信道下,编码协作没有分集。另一方面,论文针对提出CC方案中映射方式以及交织器的设计进行研究,得出GRAY映射仍然是协作用户采用的最佳映射,且两帧的交织器不同更利于提高性能。     

NGB-W系统中基于星座旋转的BICM的实现与性能分析

下一代无线广播网(Next Generation Broadcast-Wireless,NGB-W)中,利用复平面星座点的星座旋转以及星座点的同相分量与正交分量的交织,提出了一种更为有效的比特交织编码调制(Bit Interleaved Coded Modulation,BICM)技术方案.发送端采用这种比特交织编码调制技术,接收端可以通过引入信号空间分集来提升系统性能.仿真结果表明:由星座旋转带来的系统性能增益随信道的不同、调制阶数的不同以及LDPC编码率的不同而产生差异.     

基于空时分组码的接收天线选择对MIMO系统性能的影响研究

对接收天线选择算法进行了研究,通过连续选择使出多输入多输出(MIMO)系统容量增加最大的天线的方法,用矩阵及行列式运算导出了一种接收天线选择算法,并基于空时分组编码(STBC),利用该算法对天线选择后的MIMO系统的容量和误比特(BER)性能进行了分析和仿真.结果表明,该算法在信噪比较小时,进行天线选择后,MIMO系统具有最大的遍历性容量(ergodic capacity);在BPSK调制和ML检测情况下,系统的误比特性能均明显优于无天线选择时的情况.     

比特交织编码协同方案及性能分析

在慢衰落信道条件下,为提高误码率性能,提出一种比特交织编码协同方案,用户或协同伙伴的编码数据,相邻两帧的打孔或者未打孔部分分别通过比特交织器进行交织,然后通过BPSK调制并按发送方案和划分时隙进行发送。推导了比特交织编码协同方案在慢衰落信道条件下的成对错误概率,仿真证明,此方案能够获得三阶完全分集。     

基于LDPC码的BICM系统性能分析和改进

将低密度奇偶校验码(LDPC)与比特交织编码调制(BICM)技术相结合,分别给出了不同码长LDPC码在16QAM调制方式下AWGN信道中的性能,并针对不同星座点对比特保护能力的差异,提出了一种有效的内置交织编码算法,即首先对LDPC编码后的码字进行相应的内置交织变换,然后将LDPC码中的信息位调制到星座点中保护能力强的比特位上,在译码端进行相应的矩阵变换译码,计算机仿真结果表明,新方案在信噪比较低时优于传统的16QAM调制方案。     

采用最大比率发射技术的天线选择系统性能研究

Alamouti方案(ALS)是仅有满速率的正交空时分组码(STBC),通过天线选择技术和优化发射功率提高其性能.若发射端知道全部的系统信道状态信息(CSI),文章提出在发射端混合最大比率发射(MRT)分集技术和发射天线选择(TAS)技术.基于信道增益系数大小的Frobenius范数最大的天线选择准则,系统选择瞬时输出信噪比(SNR)最大的天线子集{NT,2;mr}工作.采用MRT对Alamouti编码的双天线发射功率进行优化分配.仿真结果表明:采用混合MRT和TAS两技术后,基于ALS的多天线系统的比特误码率(BER)性能和信道容量均得到了明显改善.这一结论对有充足CSI的通信系统用于克服信道影响和提高系统传输速率具有借鉴意义.     

MIMO—OFDM系统下基于频谱利用率的自适应发射方案选择

本文提出并分析了一种MIMO-OFDM系统下,考虑相关空间信道的自适应发射方案选择算法.采用比特交织卷积编码,在以下三种发射模式间进行选择:空间复用、空间分集和复用/分集的混合模式.我们通过对MIMO-OFDM系统中采用迫零(ZF)接收机在高信噪比条件下的错误概率的简化分析,得出空间相关的多天线系统下的自适应选择算法,在给定的误码率条件下可获得使频谱利用率最大化的编码速率、调制模式和发射模式,并反馈到发射端,有效改善了系统的性能.     

一种改进的麻雀搜索天线选择算法

为解决麻雀搜索算法在多输入多输出(Multiple-Input Multiple-Output, MIMO)系统中进行天线选择时,存在过早收敛导致系统容量非最优的问题,提出了一种改进的麻雀搜索天线选择算法。该算法首先结合0-1规划推导出信道容量函数,将其作为适应度函数。在天线选择子集寻优过程中,通过引入自适应变异,有效增加了个体变化的多样性。最后将禁忌搜索算法融入到算法中,并加速算法收敛。仿真结果表明,改进的麻雀搜索天线选择算法能够有效降低MIMO系统进行天线选择时的运算复杂度,在保证收敛速度的同时,最终得到的系统信道容量趋近于最优算法。     

STBC与VBLAST混合编码系统中一种新的天线选择算法

多输入多输出(MIMO)系统改善了误码率性能,同时为了减少对系统容量的影响,提出了空时分组码(STBC)与贝尔实验室垂直分层空时码(VBLAST)混合编码系统中的一种新的天线选择算法.对部分VBLAST层采用Alamouti STBC编码构成的混合编码,MIMO系统同时具有STBC与VBLAST两者的优点.基于天线子集最大容量准则,提出的天线选择算法选择那些对系统容量贡献较小的天线发送多层STBC信号,以便减少STBC编码所造成的系统容量损失.理论分析与仿真结果表明,提出的天线选择算法能够有效地提高STBC与VBLAST混合编码系统的容量,并且与VBLAST编码的MIMO系统相比其误码率性能得到明显改善.     

Turbo-BLAST系统中基于容量的天线选择和功率分配算法

在不完全信道状态信息条件下,提出了一种适用于Turbo BLAST系统的天线选择和功率分配算法。所提算法以信道容量最大化为准则,从所有天线中选取一组天线子集用于发射,并对选择的天线子集进行注水功率分配,以充分利用Turbo BLAST系统的空间复用增益并提高信道容量。在接收端,采用Turbo原理对接收信号进行迭代检测以改善系统的误比特率性能。仿真结果表明采用所提算法不仅可以显著提高系统的信道容量, 而且误比特率性能也得到明显的改善。      

Energy efficiency of massive MIMO wireless communication systems with antenna selection

Massive multiple-input multiple-output (MIMO) requires a large number (tens or hundreds) of base station antennas serving for much smaller number of terminals, with large gains in energy efficiency and spectral efficiency compared with traditional MIMO technology. Large scale antennas mean large scale radio frequency (RF) chains. Considering the plenty of power consumption and high cost of RF chains, antenna selection is necessary for Massive MIMO wireless communication systems in both transmitting end and receiving end. An energy efficient antenna selection algorithm based on convex optimization was proposed for Massive MIMO wireless communication systems. On the condition that the channel capacity of the cell is larger than a certain threshold, the number of transmit antenna, the subset of transmit antenna and servable mobile terminals (MTs) were jointly optimized to maximize energy efficiency. The joint optimization problem was proved in detail. The proposed algorithm is verified by analysis and numerical simulations. Good performance gain of energy efficiency is obtained comparing with no antenna selection.     

Turbo-BLAST系统中天线选择和功率分配算法

提出一种适用于Turbo-BLAST系统的自适应天线选择和功率分配算法,所提算法以误比特率为优化目标,并且考虑了信道估计误差的影响.在总功率约束条件下,采用所提算法进行天线选择和自适应功率分配,并利用软干扰抵消算法对接收信号进行迭代检测,以进一步改善系统性能.仿真结果表明:采用所提算法可以显著改善系统的误比特率性能.     

简明的联合收发端天线选择算法

For reducing the computational complexity of the problem of joint transmit and receive antenna selection in Multiple-Input- Multiple-Output (MIMO) systems, we present a concise joint transmit/receive antenna selec-tion algorithm. Using a novel partition of the channel matrix, we drive a concise formula. This formula enables us to augment the chan-nel matrix in such a way that the computational complexity of the greedy Joint Transmit/Receive Antenna Selection (JTRAS) algorithm is reduced by a factor of 4nL, where nL is the number of selected antennas. A de-coupled version of the proposed algorithm is also proposed to further improve the efficien-cy of the JTRAS algorithm, with some capacity degradation as a tradeoff. The computational complexity and the perform-ance of the proposed approaches are evalu-ated mathematically and verified by computer simulations. The results have shown that the proposed joint antenna selection algorithm maintains the capacity perormance of the JTRAS algorithm while its computational complexity is only 1/4nL of that of the JTRAS algorithm. The decoupled version of the proposed algorithm further reduces the computational complexity of the joint antenna selection and has better performance than other decoupling-based algorithms when the selected antenna subset is small as compared to the total number of antennas.     

MIMO空间复用系统的最小BER比特分配

该文基于最小误比特率(BER)准则,提出了多输入多输出(MIMO)空间复用系统的贪婪比特分配算法和基于二分法的比特分配算法。在总比特速率和每个发射天线分配相等功率的约束条件下,通过比特分配优化每个发射天线的调制方式,改善了系统的BER性能。仿真结果表明,与传统的MIMO系统相比,比特分配的MIMO系统可获得显著的信噪比(SNR)增益;与功率分配相比,比特分配在性能损失很小的情况下减少了每个发射天线的功率放大器的动态范围。     

基于分布式天线选择的TD—SCDMA动态小区覆盖技术

分布式M IMO天线结构可以降低发射功率,减少小区干扰,而天线选择技术在保持了M IMO系统优点的同时降低成本。TD-SCDMA有独特的时隙结构,可将不同时隙用于不同的天线组来覆盖不同的小区。基于此,提出了一种分布式天线选择的动态小区覆盖技术,采用两级天线选择,第一级可根据用户的具体位置选择天线组并确定覆盖范围,有效减少小区干扰,同时采用了预分配天线组方法,避免了通用天线选择算法的复杂性;第二级在选定的天线组内确定具体的天线,仿真结果说明该方法具有与一般天线选择相同的性能但更简单。     

Asymptotic performance of space-time block codes with imperfect transmit antenna selection

The asymptotic bit error performance of the Alamouti scheme with transmit antenna selection is investigated for imperfect selection of antenna subset. It is shown that the transmit diversity order is equal to the largest ordinal number of the antenna within the selected antenna subset.     

Robust Transmit Antenna Selection with Phase Feedback Over Correlated Fading Channels

A new transmit antenna selection (TAS) scheme with phase feedback for multiple-input multiple-output systems is proposed in this paper. This scheme allows two or more transmit antennas to simultaneously use one radio frequency chain. By grouping the transmit antennas according to their similarities in instantaneous channel coefficients into two subsets and treating each subset as a single antenna, both hardware complexity reduction and antenna array gain can be achieved. Compared with the transmit antenna selection combined with space-time block code (TAS/STBC) scheme, the proposed TAS scheme provides excellent robustness, in terms of symbol error rate performance, against spatially correlated fading channels. Moreover, the proposed TAS scheme need not use STBC encoder and decoder which used in the TAS/STBC schemes. Therefore, the proposed TAS scheme is simpler than the TAS/STBC schemes in practical hardware implementation.     

Adaptive transmit antenna selection with pragmatic space-time trellis codes

We consider the problem of selecting a subset of transmit antennas in MIMO systems to minimize error probability when only partial channel information is available at the transmitter. An upper bound for error probability of space-time coded transmit antenna selection scheme conditioned on the channel state information is presented. Based on the performance analysis, a criterion of selecting a subset of available transmit antennas to minimize the upper bound on the PEP is proposed. In contrast to other transmit antenna selection schemes for uncoded transmission or with a fixed number of antennas within the selection subset in the literature, the proposed scheme can adaptively select both a variable number of transmit antennas and their corresponding space-time codes for transmission. Furthermore, we present pragmatic space-time trellis coding schemes for slow Rayleigh fading channels. The principal advantage of the schemes is that a single encoder and decoder can be used for systems with a variable number of transmit antennas. The performance of the pragmatic space-time codes with adaptive antenna selection and the effect of the imperfect channel estimation on performance are evaluated by simulations. It is shown that the adaptive selection offers considerable antenna selection gain relative to the antenna selection system with a fixed number of antennas within the selection subset     

Loading Algorithm for Multicarrier Spatial Diversity Systems with Antenna Selection

In this paper, a novel loading algorithm consisting of four variants is proposed for a multicarrier transceiver employing multiple antennas configured for spatial diversity. The primary objective of the proposed algorithm is to increase the overall throughput while ensuring the mean bit error rate (BER) is below a specified limit. To achieve this, spatial diversity is employed to improve the subcarrier signal-to-noise ratio (SNR) values. Simultaneously, (uniform or non-uniform) bit allocation, which is a function of subcarrier SNR, is performed to increase throughput. To reduce power consumption, spatial processing complexity, and hardware costs, antenna subset selection is also performed by the proposed algorithm to choose a set of active transmit/receive antennas. The results show that combining bit allocation with spatial diversity (employing antenna subset selection) can yield substantial throughput increases.