基于非正规LDPC码的中继协作通信及其联合迭代译码的性能研究

 本文构造了一种适用于中继协作通信的非正规LDPC系统码,并将双非正规LDPC系统码应用于中继协作系统中. 提出了目的点接收机基于双LDPC码联合Tanner图的对多路接收信号进行联合迭代译码的新算法. 理论分析和数值模拟表明本文所提出的新方法将高效信道编码和协作技术有机地结合起来以充分实现编码协作所具有的潜在分集和编码增益,与非协作系统相比可显著地提高系统性能.     

基于有限域的QC-LDPC码编码协作通信及其联合迭代译码技术

为了提高系统的性能和易于工程实现,提出了基于有限域加群构造的QC-LDPC码,通过特殊的构造方法构造出满秩的QC-LDPC码并将之应用于编码中继协作通信系统的源节点和中继节点处,并由此构成了总体校验矩阵,导出了双层Tanner图,目的节点处采用基于双层Tanner图的联合迭代译码算法。仿真结果表明,误码率为10-5、迭代5次时,理想中继协作通信系统的性能好于非协作和非理想中继协作系统的性能,分别为1.3 dB和1 dB;并且S-D与R-D信道的信噪比相等时,S-R信道信噪比越高,非理想中继协作通信系统的性能越好。     

一种中继选择与分布式空时码相结合方案

针对一个发送端、接收端及每个中继都配置单根天线的无线中继网络,在假设中继不知道任何信道信息的条件下,为了提高系统性能,本文提出中继选择与分布式空时码相结合的方案.证明了选择2个中继与Alamouti正交空时码的结合方案成对错误概率的Chernoff上界要比对应的只选择2个中继参加协作不使用Alamouti正交空时码的情...     

基于联合迭代检测译码的多中继RA编码协作系统

为提高协作系统的性能,提出一种RA码多中继编码协作通信系统。首先,在系统的源和中继节点处采用RA编码,推导出与目的节点接收码字对应的多层Tanner图;然后,以多层Tanner图为基础,结合MAP算法给出一种联合迭代检测译码新算法译码,完成目的点的信号检测。理论分析和数值模拟表明,所提出的新方法能够充分实现多中继编码协作所具有的潜在分集和编码增益,随着内外迭代次数的增加,误比特率性能迅速提升,在相同条件下明显优于编码非协作系统。     

基于有限域网络编码的中继选择方法

针对采用有限域网络编码的多源多中继协作通信系统,提出一种以极大最小距离可分码作为网络编码的自适应中继选择方法,将网络编码技术与中继选择技术相结合来提高系统的复用增益。通过分析系统的中断概率性能,得到系统的分集复用折中,由此证明自适应中继选择方法能够在保持协作系统获得满分集增益的同时,使得系统的复用增益不低于1/2。仿真结果表明,自适应中继选择方法优于传统的网络编码协作方法。     

极化码在中继编码协作系统中的性能研究

极化码作为近年热门的编码方法,越来越受到人们的重视。对极化码的基本原理与编译码方法进行了简要介绍,分析了极化码的Plotkin结构的构造过程。在介绍传统中继协作通信系统和编码协作技术的基础上,提出基于Plotkin结构的极化码中继编码协作方案,具体分析了协作方案的实现过程,通过具体的理论分析和仿真结果说明,与非协作方式相比,在不同的中继信道条件下,该方案有不同程度的性能提升,同时,得出在中继节点不同的信息选取方式也可以带来不同的性能提升的结论。     

基于联合译码的RS码中继协作系统设计

协作通信技术是通过一定规则使单天线终端能够共享其他用户的天线,从而达到空间分集的效果,能够有效地减轻通信系统中信道衰落的不良影响。RS码在短码且信息位一定的条件下,其译码复杂度较低,且具有较强的应对突发错误的能力。基于此,提出了一种基于联合译码的缩短RS码的中继编码协作系统方案。该方案通过在源节点设置码长自由的缩短RS码,使得在误码性能不受影响的情况下,系统等效码率更为灵活,并在目的点设计了两种联合迭代译码算法。对设置缩短RS(43,31)和RS(63,31)的协作通信系统在AWGN信道和瑞利快衰落信道下进行仿真,仿真结果表明,与非协作系统相比,中继编码协作系统性能更优。此外,通过选用两种不同的联合迭代译码算法,实现了不同幅度的系统增益提升。     

一种 1x2x4分布式空时编码异步协作方案

协作分集技术可以有效提高移动通信系统的容量和可靠性。近年来,分布式空时码（DSTC）被广泛应用到协作分集系统以实现空间分集增益。然而,时间异步和频率异步会使正交DSTC的码字结构受到破坏,严重影响系统性能。本文针对时间异步的协作通信系统,提出一种基于分布式Alamouti STBC的1x2x4异步协作方案。对这种方案进行了理论分析和算法推导,并且重新定义了中继节点归一化后的发射信号幅度。仿真结果表明该方案的误比特率性能具有明显优势,能在时间异步的协作通信系统中很好地发挥多天线接收性能。     

基于率匹配Turbo码的协作通信验证系统

为提高短距离无线通信系统的可靠性,基于单片机C8051F120和射频芯片CC1101设计了采用率匹配Turbo码的协作通信验证系统。在该系统中,控制节点通过发送控制帧,实现系统中所有节点的同步。源节点和中继节点采用基于率匹配Turbo码的编码协作方案,目的节点通过迭代译码,同时获得了编码增益与分集增益。实际环境中的测试结果表明,与点对点传输相比,基于率匹配Turbo码的协作通信传输方案能显著降低误包率,提高通信系统的可靠性。     

中继编码协作系统等效点对点传输模型的研究

研究了LDPC编码中继协作通信系统及其编码协作系统目的点译码器基于双层Tanner图的LDPC联合迭代译码算法,通过在目的点接收机引入算术/几何平均信噪比的概念,将中继编码协作系统转换成等效的易于分析的点对点传输模型,利用点对点传输中的原理研究较复杂编码中继协作系统的性能。理论分析和模拟结果表明：在相同的条件下LDPC中继编码协作系统及其等效点对点编码传输系统的性能非常接近,从而证实了本文所提出的等效点对点传输模型的合理性,以及基于双层Tanner图的LDPC联合迭代译码算法的有效性。     

空时分组编码CDMA系统的性能分析

空时分组编码 ( STBC)可有效的应用于无线系统中 ,提高系统的容量。 STBC采用最大似然译码算法 ,译码过程中需要信道信息。本文利用导频辅助的方式获得信道信息 ,分析了Rayleigh信道下随着移动台速度的变化 STBC- CDMA系统的误码率性能     

基于Turbo码的机会编码协同策略

提出一种多中继协同无线网络的机会编码协同策略,该策略基于Turbo编码,利用信道条件信息机会选择最优协同节点。通过数学分析,给出了系统中断性能和瑞利衰落下的中断概率表达式,计算机仿真结果进一步揭示了机会编码协同相对于传统编码协同的优势。     

一种新的全极化雷达信号处理方案设计

Golay互补码和Alamouti空时编码相结合的极化测量方法,能有效地解决全极化测量波形自相关与互相关函数相互制约的矛盾。针对这种测量方法,设计了一种具有多普勒补偿能力的全极化雷达接收机信号处理方案,重点分析了多普勒频移对接收机性能的影响,仿真结果表明该方案在目标多普勒频移比较大的情况下,仍然具有比较好的性能。此外,该设计结构简单,易于工程实现。     

Interference‐resistant cooperative wireless networks based on complementary codes

Spatial diversity in wireless networks can be attained by exploiting the broadcast nature of wireless transmission without the need of multiple antennas in individual device, leading to the implementation of cooperative communication. While most prior works focused on the single source—destination scenario, it should be more realistic to consider how to induce cooperation among multiple source‐destination pairs assisted by multiple relays. In such a case, multiple access interference (MAI) may present due to asynchronous transmissions of the users and relays. In this paper, a cooperative network architecture based on orthogonal complementary (OC) codes inherently immune to MAI is proposed. To efficiently utilize the scarce radio spectrum and codes, a centralized medium access control (MAC) protocol is proposed to coordinate the code assignment and channel access among users and relays. We theoretically analyze the bit error rate (BER) performance of the proposed OC coded cooperative network over multipath Rayleigh fading channel. The performance gain resulted from different numbers of relays is investigated, and compared with a time division multiple access (TDMA) based cooperative scheme. We show that the proposed OC coded cooperative network performs well in the presence of timing offset, and thus is well suited for asynchronous uplink transmission with cooperative relaying. Copyright © 2009 John Wiley & Sons, Ltd.     

Distributive High-Rate Space–Frequency Codes Achieving Full Cooperative and Multipath Diversities for Asynchronous Cooperative Communications

In user-cooperative communications, relay nodes are usually asynchronous. By realizing that the processing in the frequency domain is insensitive to the errors in the time domain, Mei and Shin recently applied the space-time-coded orthogonal frequency-division multiplexing (OFDM) technique to achieve full cooperative diversity for asynchronous cooperative communications, where orthogonal space-time block codes (particularly the Alamouti code) were used for relay nodes. In this paper, we consider asynchronous cooperative communications, and the channels from one node to another node are frequency-selective fading. We propose a high-rate space-frequency coding method and prove that it can achieve both cooperative and multipath diversities. Simulation results are shown to verify the performance of the constructed codes.     

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.     

BER analysis and power allocation for cooperative diversity networks with distributed Alamouti code

In this paper, we consider the distributed Alamouti code for a cooperative diversity network consisting of a source, a non‐regenerative relay, and a destination. While in the first time phase, the source radiates signals to both relay and destination; in the second time phase, the source and the relay cooperatively send signals to the destination by using an Alamouti code. Considering the amplify‐and‐forward protocol and independent Rayleigh fading, we first derive the exact average bit error rate performance in a single integral expression so that the system performance can be numerically evaluated. Then, based on a new approximation method of the Marcum Q‐function, we also give a tight upper bound for the system performance with a summation of a number of series components. We demonstrate through simulation that, in various operation scenarios with different channel quality and types of modulation, the results of the exact bit error rate expression accurately matches the simulation results, and the bound is tighter and more robust than existing approximation methods. Finally, we show that the analytic work also provides a method for the optimal allocation of power between the source and the relay in the second time phase. Copyright © 2013 John Wiley & Sons, Ltd.     

基于STBC的无线认知NOMA系统物理层安全性能研究

基于非正交多址接入（NOMA,Non-Orthogonal Multiple Access）的认知无线电（CR,Cognitive Radio）网络物理层传输面临主用户干扰和第三方窃听双重干扰威胁.本文提出利用空时编码（STBC,Space Time Block Coding）技术提高认知用户物理层安全性能,推导了任意认知用户的安全中断概率闭合表达式.通过蒙特卡洛仿真进行验证,结果表明,所提STBC-CR-NOMA相比未采用STBC编码方案的CR-NOMA可以明显提高用户的安全中断概率,且随着认知发射功率的增大,近端用户安全中断性能提高越大,而远端用户安全中断性能提升受认知基站发射功率的影响较小.仿真结果还表明,通过调整功率分配系数对远端用户和近端用户的安全中断性能影响不同.     

协同通信中的分布式线性疏散码

该文提出一种分布式线性疏散码解决无线网络中协同节点不能确定时的空时编码问题。参与协同的节点采用独立的疏散矢量进行编码,推导协同节点减少时分布式线性疏散码的互信息损失,并以此建立一种分布式疏散码的编码准则。仿真结果验证了这种分布式线性疏散码的误比特性能及编码准则的可行性。     

基于信道编码及空时编码级联的两用户协同分集

传统协同分集通过使网络中各单天线用户共享彼此天线,形成虚拟多天线阵列来实现空间分集,使得体积和功耗受限的网络终端也能获得分集增益,然而这并没有将信道编码和空时编码结合起来以使系统得到编码增益。为了能够获得编码增益来进一步改善系统性能,本文提出了一种基于信道编码和分布式空时分组码级联方式下的两用户协同分集方案,并且在准静态的瑞利衰落信道下对系统误码性能进行了理论推导和系统仿真,给出了误比特率的上限解析表达式。在协同用户间信道存在噪声的情况下,我们分别对CRC-DSTBC和CC-DSTBC级联下的发射方案进行了性能分析和系统仿真。仿真结果表明:即使协同用户间的信道存在噪声,本文所提出的协同分集方案与传统协同分集相比,不但获得了分集增益,同时也得到了编码增益,系统误比特率大大降低,从而显著提高了系统性能,并且这也和理论分析相吻合。