基于MMSE准则的改进型并行迭代ICI消除算法

无线信道的时变性破坏了OFDM系统各子载波间的正交性,造成子载波间功率泄漏,从而产生子载波间干扰(ICI).ICI的产生严重影响了OFDM系统的性能.本文首先从ICI的特性出发,对MMSE准则进行了修正,在此基础上,提出一种改进的并行迭代(PIC)均衡算法消除ICI的影响.Jakes谱瑞利衰落信道上的仿真结果表明,该方...     

A bandwidth‐efficient cooperative relaying scheme with hard interference cancellation and iterative decoding

This paper considers a coded cooperative relaying scheme in which all successfully decoded signals from multiple sources are simultaneously forwarded by a multi‐antenna relay to a common multi‐antenna destination to increase bandwidth efficiency. Iterative decoding with hard interference cancellation is used at destination to recover user information. By using orthogonal transmission from sources to avoid their mutual interference, the multi‐antenna relay offers receive space diversity that greatly enhances the decoding performance at the relay. This makes the source‐relay transmission more robust, less sensitive to the source‐relay link SNR, and hence increases the contribution of the relay in cooperative transmission. Simulation results show that the proposed scheme significantly outperforms direct transmission under the same transmit power and bandwidth efficiency. Copyright © 2009 John Wiley & Sons, Ltd.     

时变信道下OFDM系统中基于载频间干扰抑制的迭代检测算法

为了有效地抑制OFDM系统载频间干扰（ICI），提出一种并行干扰消除的迭代检测算法。基于检测信号的信干噪比最大化的准则，通过对接收信号进行判决、重构、干扰抵消处理，建立了ICI抑制的迭代检测算法，给出了信号检测流程。通过对时变信道的分析，研究了时变信道中归一化频偏对系统陛能的影响，给出了性能仿真结果。仿真结果表明所建议的算法可有效地利用时变信道的时间分集特性来提高系统性能，计算复杂度从O（N^3）降低到O（N）。     

频率选择性衰落下一种基于迭代干扰抵消的空时分组码译码算法

针对频率选择性衰落下空时分组码的正交性由于多径干扰而遭到严重破坏,提出一种基于迭代干扰抵消的最大似然序列估计(MLSE)译码方案;并结合最大比合并方法对所提方案进行改进和提高,以进一步降低计算复杂度。这些方案能很好地弥补通常空时分组码在频率选择性衰落下译码时的不足,它们不仅能抵消正交性没有破坏的在偶次项上的多径干扰,还能抵消正交性受到破坏的在奇次项上的多径干扰;有着非常好的性能。而且与直接对长序列信号进行MLSE译码相比,有着非常低的译码复杂度;从而以低复杂度实现了较好的空时分组码译码性能。     

An efficient hybrid decoding algorithm for Reed-Solomon codes based on bit reliability

The paper presents a computationally efficient hybrid reliability-based decoding algorithm for Reed-Solomon (RS) codes. This hybrid decoding algorithm consists of two major components, a re-encoding process and a successive erasure-and-error decoding process for both bit and symbol levels. The re-encoding process is to generate a sequence of candidate codewords based on the information provided by the codeword decoded by an algebraic decoder and a set of test error patterns. Two criteria are used for testing in the decoding process to reduce the decoding computational complexity. The first criterion is devised to reduce the number of re-encoding operations by eliminating the unlikely error patterns. The second criterion is to test the optimality of a generated candidate codeword. Numerical results show that the proposed decoding algorithm can achieve either a near-optimum error performance or an asymptotically optimum error performance.     

MIMO系统中基于混合干扰消除的低复杂度迭代接收

针对MIMO(多输入多输出)通信系统中传统的基于软干扰消除和MMSE(最少均方误差)滤波器的迭代接收方案对信道相关性较敏感的问题。提出了一种基于混合干扰消除(软干扰消除和硬干扰消除)以及MMSE滤波器的检测算法,并引入一个确信机制来控制错误传播问题。仿真结果表明,新算法相比传统的算法在相关信道环境下有明显的性能增益。定性的计算复杂度分析表明新算法在恰当的系统配置下比传统算法具有更低的计算复杂度。     

An efficient decoding algorithm for block turbo codes

An efficient soft-input soft-output iterative decoding algorithm for block turbo codes (BTCs) is proposed. The proposed algorithm utilizes Kaneko's (1994) decoding algorithm for soft-input hard-output decoding. These hard outputs are converted to soft-decisions using reliability calculations. Three different schemes for reliability calculations incorporating different levels of approximation are suggested. The algorithm proposed here presents a major advantage over existing decoding algorithms for BTCs by providing ample flexibility in terms of performance-complexity tradeoff. This makes the algorithm well suited for wireless multimedia applications. The algorithm can be used for optimal as well as suboptimal decoding. The suboptimal versions of the algorithm can be developed by changing a single parameter (the number of error patterns to be generated). For any performance, the computational complexity of the proposed algorithm is less than the computational complexity of similar existing algorithms. Simulation results for the decoding algorithm for different two-dimensional BTCs over an additive white Gaussian noise channel are shown. A performance comparison of the proposed algorithm with similar existing algorithms is also presented     

MIMO blind equalization algorithm based on successive interference cancellation

Modified Constant Modulus Algorithm (MCMA) is widely used in the SISO blind equalization for its simplicity. For MIMO systems MCMA can only equalize one of the source signals. Through the combination of channel estimation and successive interference cancellation, source signals can be equalized in turn. However the recovery of the first source and the channel estimation are the key points, which directly affects the recovery of the subsequent sources. This paper proposes a channel estimation method with a small amount of calculation, and can accurately estimate the channel vector. Meanwhile, a new blind equalization algorithm is put forward to reliably recovery the first source signal. Simulation results verify the effectiveness of the proposed algorithm.     

LDPC码的改进迭代比特翻转译码算法

为提高低密度奇偶校验(LDPC)码的低复杂度硬判决译码算法的性能,提出了一种改进的比特翻转(BF)译码算法,在迭代时利用一个交替的门限模式对多个比特进行翻转,降低了每次迭代时比特被错误翻转的概率,从而有效提高了译码性能.仿真结果表明,与BF算法相比,该算法在保持低复杂度的基础上获得了更好的译码性能和更快的收敛速度.     

基于博弈论功率控制的串行干扰消除算法

无线网络实现串行干扰消除算法可以提高网络吞吐量,在采用串行干扰消除算法的无线网络系统中,如何控制节点间传输功率使系统效用最大化是一个NP-Hard难题。针对此问题提出非合作博弈算法来解决节点间的传输功率控制,提出了串行干扰消除算法功率控制的非合作博弈,证明了纳什均衡,所提算法可以获得较高的无线网络吞吐量,仿真实验证实了分析结果并展示了算法的优越性。     

一种联合星座和伴随式信息的迭代译码算法

针对构造性的大数逻辑可译低密度奇偶校验(LDPC)码,联合信号星座和伴随式信息,提出一种基于可靠度的迭代大数逻辑译码算法。在校验节点,直接使用伴随式信息进行传递和处理;在变量节点,结合信源端的星座映射和伴随式进行译码信息收集和处理。理论分析和仿真实验结果表明,所提出的算法在保持优良译码性能的同时,具有更低的译码复杂度。     

基于SSCANL译码器的联合迭代检测译码算法

为了提升基于极化码的稀疏码多址接入（sparse code multiple access,SCMA）系统接收机性能,提出了基于简化软消除列表（simplify soft cancellation list,SSCANL）译码器的循环冗余校验（cyclic redundancy check,CRC）辅助联合迭代检测译码接收机方案。该方案中极化码译码器使用SSCANL译码算法,采用译码节点删除技术对软消除列表（soft cancellation list,SCANL）算法所需要的L次软消除译码（soft cancellation, SCAN）进行简化,通过近似删除冻结位节点,简化节点间软信息更新计算过程,从而降低译码算法的计算复杂度。仿真结果表明,SSCANL算法可获得与SCANL算法一致的性能,其计算复杂度与SCANL算法相比有所降低,码率越低,算法复杂度降低效果越好;且基于SSCANL译码器的CRC 辅助联合迭代检测译码接收机方案相较基于SCAN译码器的联合迭代检测译码（joint iterative detection and decoding based on SCAN decoder, JIDD-SCAN）方案、基于SCAN译码器的CRC辅助联合迭代检测译码（CRC aided joint iterative detection and decoding based on SCAN decoder,C-JIDD-SCAN）方案,在误码率为10^-4时,性能分别提升了约0.65 dB、0.59 dB。     

基于CRC纠错与迭代干扰消除的星载AIS接收机

为了提升星载船舶自动识别系统( AIS)的卫星接收性能,提出了一种采用4 b循环冗余校验( CRC)纠错与迭代干扰消除算法的星载AIS接收方案。针对星载AIS系统中多路信号碰撞明显的情况,首先,通过分析星载AIS系统中CRC错误类型,采用比特反转的方式进行纠错;其次,对纠错后的序列进行AIS数据重构,采用迭代干扰消除方法消除重构信号,并将余下信号作为输入信号再次进入系统进行解调。仿真结果表明,和传统的CRC纠错系统相比,针对典型的两路信号碰撞情况,基于4 b CRC校验与迭代干扰消除的星载AIS系统能够带来1~2 dB的误码率增益,对星载AIS系统的性能提升有重要指导意义。     

Multiuser soft interference canceler via iterative decoding for DSLapplications

This paper presents a method to mitigate interference on a transmission system by another system with an overlapping frequency band. The systems are uncoordinated so that they cannot be made to transmit in orthogonal coding space. The transmission environment is an interference channel rather than the multiaccess channel often considered in other multiuser detection problems, for instance at the base station of a code division multiple access wireless system. Using the fact that the inputs are all from discrete constellations, it is possible to use a multiuser maximum-likelihood (ML) detector to decode the signals from the system of interest with low probability of error. However, the ML detector often requires impractical computation. A soft linear canceler is instead used to reduce the interference with a small loss of bandwidth in the system of interest. The method has a much lower complexity than a full-blown ML detector, and the soft canceler performance is close to an ML detector. The method is demonstrated on a very-high-speed digital subscriber lines system with a home local area network interference. The system of interest is using a multicarrier modulation transmission scheme such as discrete multitone, while the interfering system transmits using quadrature amplitude modulation     

一种改进的数字同频直放站自适应反馈干扰抑制算法

基于数字地面电视广播(Digital Terrestrial Television Broadcasting,DTTB)同频直放站的回波干扰抑制,提出了一种变步长块LMS(Variable Step- size Block Normalized Least Mean Square,VSSBNLMS)自适应算法.此算法的目的是为了提高传统回波干扰抑制的自适应算法的收敛速度和降低计算复杂度.其将输入信号分为长度相等的块,在每一个数据块内,权值向量只更新一次,有效地降低了计算复杂度.另外,该算法通过输出误差控制更新步长的变化,与传统的归一化LMS(NLMS)和块LMS(BLMS)算法相比,提高了收敛速度.仿真结果表明,该算法具有良好的收敛速度和回波干扰抑制性能.     

一种自适应快速SSCL极化码译码算法

极化码的简化串行抵消列表(Simplified Successive Cancellation List,SSCL)译码提出了R1(Rate-1)、R0(Rate-0)等多种特殊节点的快速译码算法,一定程度改善了SCL译码复杂度高和时延大的问题,但当节点信息比特数量较大时仍存在大量的冗余计算.针对R1等信息比特较多的节点,提出了一种基于路径度量(Path Metric,PM)的自适应路径选择策略,无需先验信息设置阈值,在不降低SSCL译码性能的条件下能有效降低排序复杂度,减少所需时间步数,提升Polar码译码效率.仿真和实验结果表明,在保证纠错性能的前提下,该算法针对R1节点译码所需的时间步数相对传统SCL译码降低了约83％,相对SSCL降低了约47％,相对快速SSCL降低了约18％.同时,相对基于搜索集和决策函数的SCL译码算法译码效率也有较大提高,其所需时间步数受码字结构及信道环境自适应改变,但不大于快速SSCL译码算法所需时间步数.     

基于时变步长最小均方算法的射频干扰对消

针对同时同频全双工系统中射频域干扰对消收敛速度与对消比相互制约的问题,提出基于时变步长最小均方算法的射频自干扰对消方法.该方法在正交两路合成干扰对消方案基础上,利用Logistic函数非线性关系实时改变步长因子,在最小均方准则下实现两路衰减器的快速精确调整,完成自干扰信号的有效对消.最后,理论分析了该对消方法的收敛性和稳态失调误差,给出了收敛状态下能够获得对消比的闭合表达式.理论分析和仿真表明,该方法的收敛时间缩短为已有变步长对消方法的1/4,最终达到的对消比与已有方法相比提高了约5 dB.     

Joint iterative interference cancellation and parameter estimation for cdma systems

This letter proposes a unified approach to joint iterative parameter estimation and interference cancellation (IC) for uplink CDMA systems in multipath channels. A unified framework is presented in which the IC problem is formulated as an optimization problem of an IC parameter vector for each stage and user. We also propose detectors based on a least-squares (LS) joint optimization method for estimating the linear receiver filter front-end, the IC, and the channel parameters. Simulations for the uplink of a synchronous DS-CDMA system show that the proposed methods significantly outperform the best known IC schemes.     

Successive interference cancellation with SISO decoding and EMchannel estimation

We derive a low-complexity receiver scheme for joint multiuser decoding and parameter estimation of code division multiple access signals. The resulting receiver processes the users serially and iteratively and makes use of soft-in soft-out single-user decoders, of soft interference cancellation and of expectation-maximization parameter estimation as the main building blocks. Computer simulations show that the proposed receiver achieves near single-user performance at very high channel load (number of users per chip) and outperforms conventional schemes with similar complexity