SPC-APPM coded modulation for deep-space optical communications

A coded modulation scheme for deep-space optical communications is proposed,which is composed of an outer singleparity-check(SPC)-based product code,an interleaver,a bit-accumulator and a pulse-position modulation(PPM).It is referred as SPC-APPM code,which is decoded with an iterative demodulator-decoder using standard turbo-decoding techniques.Investigations show that the scheme has the advantages of low encoding and decoding complexities,good performance and flexible code rate for all rates above 1/2.Meanwhile,simulation results demonstrate that the SPC-APPM provides the performance similar to the low-density parity-check-APPM(LDPC-APPM),superior to the LDPC-PPM and product accumulate code-PPM(PA-PPM),although inferior to serially concatenated PPM(SCPPM).At the bit error rate(BER) of 10-5,the performance of SPC-APPM is about 0.7 dB better than LDPC-PPM and 1.2 dB better than PA-PPM.     

DNF-SC-PNC: a new physical-layer network coding scheme for two-way relay channels with asymmetric data length

To improve the bit error rate (BER) performance of physical-layer network coding (PNC) in data length asymmetric two-way relay channels (TWRC), a new PNC scheme named combined denoise-and-forward and superposition coded physical-layer network coding (DNF-SC-PNC) is proposed, and the decoding algorithm of the scheme is improved. In the new scheme, the mixed information is denoised and superposed at the relay node, which will be broadcasted to the destination nodes. The destination nodes can use successive interference cancellation (SIC) or likelihood rate (LLR) algorithm for decoding. Theoretical analysis and simulation results show that DNF-SC-PNC can provide better BER performance and better throughput rate performance when the data length is asymmetric. Furthermore, we also proved that LLR algorithm can provide better performance than SIC algorithm in data length asymmetric TWRC.

     

一种基于位反转置换的系统极化码的缩短方法

极化码作为 3GPP 标准制定中的一种信道编码技术方案,具有良好的纠错性能。为了进一步提高删余极化码的误码率性能,将极化码中基于位反转置换的缩短算法应用到系统极化码,提出一种系统极化码的缩短方法。仿真结果表明,在AWGN信道中,在高码率条件下,建议的系统极化码的缩短方法的误码率性能优于系统极化码的准均匀凿孔方法,也优于极化码的缩短方法。当码率为3/4、误码率为10^-4时,系统极化码的缩短方法比极化码的缩短方法约有0.5 dB的增益,比系统极化码的准均匀凿孔方法约有0.25 dB的增益。     

基于脉冲位置调制的无线光通信多级编码调制及其多阶段解调译码算法

针对无线光通信脉冲位置调制(PPM)与信道编码的结合应用,提出了一种多级编码调制方案,利用多级编码的多级标签结构,将PPM符号所对应的分组比特分拆到不同子码通道的码字中,同时结合PPM的信号集分割和极大似然检测解调方法,推导了方案的多阶段解调译码算法。在弱湍流大气条件下的仿真分析表明,PPM多级编码调制相对单级编码调制在误码率10-6下获得0.85 dB以上的增益,且可实现对不同重要程度信息段的不等差错保护。在分量码码型给定的条件下,按纠错能力逐级配置分量码并采用所推导的多阶段解调译码,可为系统提供更好差错性能,优于直接的并行译码方法。     

基于QC-LDPC的水下激光通信编码技术

针对水下蓝绿激光远距离可靠通信的需求,文中提出了PPM与QC-LDPC相结合的调制编码通信方法.通过对不同码长、码率与PPM调制阶数的组合方案进行仿真,找出在不同SNR条件下的最优QC-LDPC编码与PPM调制的组合方案.文中介绍了经典PPM信号的原理与QC-LDPC码的基本结构,并通过MATLAB软件模拟实现PPM信...     

Performance analysis of uplink spatial multiplexing MIMO MT‐CDMA over multipath fading channels

In this paper, we consider multiple‐input multiple‐output (MIMO) multi‐tone code division multiple access (MT‐CDMA) uplink transmission over multipath fading channels. The zero‐forcing vertical Bell Laboratories layered space‐time architecture (ZF V‐BLAST) algorithm and maximum ratio combining scheme are applied at the receiver. The average bit error rate (BER) expression is derived provided that the number of receive antennas is not less than that of transmit antennas. The BER expression is verified by simulations. Numerical results show that the numbers of transmit and receive antennas have significant effects on the BER performance of the considered system. Spatial and path diversity show different capabilities to improve the BER performance. The MIMO MT‐CDMA system based on the ZF V‐BLAST algorithm is capable of achieving a better BER performance and a higher capacity than the conventional MT‐CDMA system. Copyright © 2011 John Wiley & Sons, Ltd.     

A novel RS BTC coding scheme for optical communications

A novel Reed Solomon(RS) block turbo code(BTC) coding scheme of RS(63,58)×RS(63,58) for optical communications is proposed.The simulation results show that the net coding gain(NCG) of this scheme at the sixth iteration is more than that of other coding schemes at the third iteration for the bit error rate(BER) of 10-12.Furthermore,the novel RS BTC has shorter component code and rapider encoding and decoding speed.Therefore,the novel RS BTC coding scheme can be better used in high-speed long-haul optical communication systems,and the novel RS BTC can be regarded as a candidate code of the super forward error correction(super-FEC) code.Moreover,the encoding/decoding design and implementation of the novel RS BTC are also presented.     

Modified-rate-quantization algorithm for multiple-input multiple-output systems under imperfect channel knowledge

In this paper, a modified-rate-quantization algorithm for multiple input multiple output (MIMO) systems is proposed using singular-value decomposition (SVD). This low complexity scheme adapts the subchannel transmit power and spectral efficiency in the spatial and temporal domains under transmit power and instantaneous bit error rate (BER) constraints. It is shown that with five discrete-rate levels, the proposed scheme reaches a spectral efficiency performance similar to the scheme with a continuous rate. The robustness of the proposed scheme to channel state information (CSI) imperfections is also studied. The obtained results show that the spectral efficiency is unaffected up to a certain level, but the bit error rate (BER) performance is particularly sensitive to these imperfections, especially at high SNR levels. Indeed, this ideally designed MIMO system over-estimates the subchannels, which leads to a deterioration of the BER performance. A new version of this algorithm, which is suitable for vertical Bell Labs layered space–time (V-BLAST) systems, is also presented. Through simulation results, it appears that the extended algorithm allows to reach a better performance in terms of spectral efficiency than other known schemes, but it is more sensitive to imperfect CSI than the first version.     

PPM performance with BWT complexity: a fast and effective datacompression algorithm

This paper introduces a new data compression algorithm. The goal underlying this new code design is to achieve a single lossless compression algorithm with the excellent compression ratios of the prediction by partial mapping (PPM) algorithms and the low complexity of codes based on the Burrows Wheeler Transform (BWT). Like the BWT-based codes, the proposed algorithm requires worst case O(n) computational complexity and memory; in contrast, the unbounded-context PPM algorithm, called PPM*, requires worst case O(n²) computational complexity. Like PPM*, the proposed algorithm allows the use of unbounded contexts. Using standard data sets for comparison, the proposed algorithm achieves compression performance better than that of the BWT-based codes and comparable to that of PPM*. In particular, the proposed algorithm yields an average rate of 2.29 bits per character (bpc) on the Calgary corpus; this result compares favorably with the 2.33 and 2.34 bpc of PPM5 and PPM* (PPM algorithms), the 2.43 bpc of BW94 (the original BWT-based code), and the 3.64 and 2.69 bpc of compress and gzip (popular Unix compression algorithms based on Lempel-Ziv (LZ) coding techniques) on the same data set. The given code does not, however, match the best reported compression performance-2.12 bpc with PPMZ9-listed on the Calgary corpus results web page at the time of this publication. Results on the Canterbury corpus give a similar relative standing. The proposed algorithm gives an average rate of 2.15 bpc on the Canterbury corpus, while the Canterbury corpus web page gives average rates of 1.99 bpc for PPMZ9, 2.11 bpc for PPM5, 2.15 bpc for PPM7, 2.23 bpc for BZIP2 (a popular BWT-based code), and 3.31 and 2.53 bpc for compress and gzip, respectively     

Turbo码概率-代数联合解码算法

Turbo码采用修正的BAHL et al.算法实现解码.这是一种基于软值的概率迭代解码算法.本文在保持Turbo码迭代软解码算法优点的基础上,充分利用Turbo码编码器结构这一确知条件,结合代数解码原理,提出了一种Turbo码概率-代数联合解码算法.该算法结合了概率解码和代数解码的优点,又有效避免了误差传播的发生,使Turbo码的纠错性能在原经典算法的基础上得到进一步的提高.该算法不仅为降低Turbo码的比特误码率和误差地板值提供了一种新的研究途径,而且因其更好的纠错性能而具有十分明显的实用价值.仿真实验结果显示,在比特误码率(BER)为10^-3~10^-4时,与经典Turbo码解码算法相比,采用该算法能获得0.1dB左右的编码增益.     

Nonbinary error detection codes for data retransmission and biterror rate monitoring

The author discusses the use of (n, n-1) polynomial codes for data retransmission and bit error rate (BER) monitoring in nonbinary data transmission systems. For a particular type of polynomial code, called a simple polynomial code, a simple error detection scheme which exploits the Gray coding commonly employed in nonbinary data transmission systems can be devised. Even though its algebraic structure is the same as that of general (n, n -1) polynomial code, the simple polynomial code's performance, when using this detection algorithm, is either equal to or better than that of the corresponding general polynomial code, for data retransmission and BER monitoring. The improvement in the BER monitoring performance of the simple code relative to that of the corresponding general code increases as the data alphabet size becomes larger     

An integrated FEC coding scheme for ATM transmission over regenerative satellite networks

The application of asynchronous transfer mode (ATM) on both wireless and satellite networks requires system adaptation. This adaptation has to improve the overall system's performance, and achieve high quality‐of‐service classes approaching that for fibre‐optic communications. In this paper, a new integrated forward‐error‐correction (FEC) coding scheme is introduced for ATM transmission over regenerative satellite networks. The proposed FEC scheme is a concatenation of two Reed–Solomon codes tailored for the header and payload parts of the ATM cell. This integrated coding scheme is shown to significantly improve the cell loss ratio as compared to the standard CRC code used in the ATM cell header. We obtain both upper and lower performance bounds for the concatenated code and check their accuracy when compared to exact system's performance. Both analytical and simulation results show that a cell loss ratio and bit‐error rate (BER) of 10^?25 and 10^?7 can be, respectively, achieved with minimum delay requirements on the SATCOM link. Finally, an approximation for the system's throughout is obtained. It is shown that using a hybrid selective‐repeat automatic‐repeat‐request (SR‐ARQ) with the RS code, a large throughput of approximately 0.843 can be achieved at BERs lower than 10^?7 for data services. Copyright © 2005 John Wiley & Sons, Ltd.     

Time Synchronization for Cooperative Communication in Wireless Sensor Networks

Time synchronization is crucial for the implementation of cooperative communication in wireless sensor networks. In this paper, we explore the effect of synchronization error on cooperative communication utilizing distributed Alamouti code. The analysis and simulation results show that small synchronization error has negligible effect on bit error rate (BER) performance. In order to synchronize the distributed sensor nodes within an acceptable error, we propose a physical layer synchronization scheme. This scheme consists of an initial synchronization of the cooperative transmitters, synchronization error estimation at the cooperative receiver and finally a feedback phase. A maximum likelihood method is proposed to make the synchronization error estimation. It achieves better performance than the matched filter method at the price of moderate increase in computational complexity and memory space. Two strategies after synchronization error estimation have been analyzed. They provide better BER performance in the existence of initial synchronization error. They are practical to be implemented in the sensor nodes before the Alamouti decoding.     

Analysis of error performance for Turbo coded pulse position width modulation

To lower the bit error rate （BER） of the pulse position width modulation （PPM＋PWM）, which is the improved scheme of the pulse position modulation （PPM）, correcting coding technique is necessary. After setting up the analytic model, the Turbo decoder and iterative algorithm for PPM＋PWM are studied, and the system error performance ofuncoded and Turbo coded PPM＋PWM under the Gaussian channel is simulated and analyzed, as well as the effects of the number of iterations and frame size on the bit error rate. The results show that the introduction of Turbo code can get the encoding gain of 4.0-6.9dB, which improves the error performance of system effectively and has advantage in military communications.     

QAM调制下基于卷积码与累加编码调制级联的纠错码性能研究

基于卷积码与累加编码的PPM调制级联码(SCPPM)在泊松信道光PPM调制下具有极优异的性能。文章将这种累加编码结构引入到QAM调制中,分析其性能。将卷积码+累加编码+QAM调制串行级联(SCAQAM)纠错方案与常规基于卷积码、并行级联卷积码(Turbo)以及低密度奇偶校验码(LDPC)的比特交织编码调制迭代译码(BICM-ID)系统进行比较,并进一步比较了SCAQAM系统的自然、格雷、反格雷星座映射方式。结果表明,在高阶QAM调制下,这种纠错结构具有极优异的误码性能。对于16QAM及64QAM调制,SCAQAM相对于另外几种纠错码结构的BICM-ID系统分别有约0.3和0.5 dB的性能提升,只有卷积码与累加码结合才更具性能优势。并且SCAQAM将累加后的比特流以反格雷方式映射具有更优异的性能。     

Low‐complexity energy efficient power allocation scheme for DAS with maximum power constraint

In this paper, a low‐complexity optimal power allocation (PA) scheme is developed to maximize energy efficiency (EE) in a distributed antenna system (DAS) under maximum power constraint and target bit error rate (BER) requirement. Composite Rayleigh fading, multiple receive antennas, and dynamic circuit power consumption are all considered in the system. Unlike conventional schemes, the presented scheme provides a closed‐form expression of PA. Firstly, the optimization problem is formulated according to the definition of EE. Using the Karush‐Kuhn‐Tucker conditions, a general form of the optimal PA, in which the number of active antennas and corresponding power allocation are required only, is then proposed. With this general form, an effective algorithm is presented to yield the closed‐form PA. The proposed scheme can be applied to the system with static circuit power consumption and/or without target BER constraint to obtain optimal PA. Simulation results corroborate the effectiveness of the developed scheme, and the scheme can achieve the same EE performance as the existing optimal schemes with lower complexity. Moreover, the distributed antenna system with multiple receive antennas has higher EE than that with single receive antenna.     

A novel QC-LDPC code based on the finite field multiplicative group for optical communications

A novel construction method of quasi-cyclic low-density parity-check(QC-LDPC) code is proposed based on the finite field multiplicative group,which has easier construction,more flexible code-length code-rate adjustment and lower encoding/decoding complexity.Moreover,a regular QC-LDPC(5334,4962) code is constructed.The simulation results show that the constructed QC-LDPC(5334,4962) code can gain better error correction performance under the condition of the additive white Gaussian noise(AWGN) channel with iterative decoding sum-product algorithm(SPA).At the bit error rate(BER) of 10-6,the net coding gain(NCG) of the constructed QC-LDPC(5334,4962) code is 1.8 dB,0.9 dB and 0.2 dB more than that of the classic RS(255,239) code in ITU-T G.975,the LDPC(32640,30592) code in ITU-T G.975.1 and the SCG-LDPC(3969,3720) code constructed by the random method,respectively.So it is more suitable for optical communication systems.     

Development of a new code family based on SAC-OCDMA system with large cardinality for OCDMA network

We have proposed a new Multi-Diagonal (MD) code for Spectral Amplitude – Coding Optical Code Division Multiple Access (SAC-OCDMA). Although this new MD code has many properties, one of the important properties of this code is that the cross correlation is always zero. Simplicity in code construction and flexibility in cross correlation control has made this code a compelling candidate for future OCDMA applications. The Multiple access interference (MAI) effects have been successfully and completely eliminated. Based on the theoretical analysis MD code is shown here to provide a much better performance compared to Modified Quadratic Congruence (MQC) code and Random Diagonal (RD) code. Proof-of-principle simulations of encoding with 5 and 10 users with 622 Mb/s data transmission at a BER of 10⁻¹² have been successfully demonstrated together with the DIRECT detection scheme.     

Multi-user receiver scheme and uplink performance of space–time-coded CDMA system in Rician fading channels

The uplink performance of multi-user space–time-coded code-division multiple access (STC-CDMA) system in Rician fading channel is presented. A simple and effective multi-user receiver scheme is developed for STC-CDMA system. The scheme has linear decoding complexity when compared to the existing scheme with exponential decoding complexity, and thus implements low-complexity decoding. Based on the bit error rate (BER) analysis and moment generation function, theoretical BER expressions are derived for STC-CDMA with orthogonal and quasi-orthogonal spreading code, respectively. It is shown that these expressions have more accuracy. Using these expressions and the approximation of error function, closed-form approximate BER expressions are obtained, which can simplify the calculation of the derived theoretical BER. Simulation results show that the developed low-complexity decoding scheme can achieve almost the same performance as the existing scheme. The theoretical BER are in good agreement with the corresponding simulated values. Moreover, the presented approximate expressions are also close to the simulated values due to the better approximation. Under the same system throughput and concatenation of channel code, the presented full-rate STC-CDMA system has lower BER than the corresponding full-diversity STC-CDMA systems.     

A novel BTC decoding algorithm based on the genetic algorithm in optical communication systems

Combining the advantages of both the genetic algorithm （GA） and the chase decoding algorithm, a novel improved decoding algorithm of the block turbo code （BTC） with lower computation complexity and more rapid decoding speed is proposed in order to meet the developing demands of optical communication systems. Compared with the traditional chase decoding algorithm, the computation complexity can be reduced and the decoding speed can be accelerated by applying the novel algorithm. The simulation results show that the net coding gain （NCG） of the novel BTC decoding algorithm is 1.1 dB more than that of the traditional chase decoding algorithm at the bit error rate （BER） of 10^-6. Therefore, the novel decoding algorithm has better decoding correction-error performance and is suitable for the BTC in optical communication systems.