EFFICIENT BIT ERROR PROBABILITY EXPRESSION AND VERY TIGHT BOUND FOR MAXIMAL RATIO COMBINING DIVERSITY SYSTEMS OVER RAYLEIGH FADING CHANNEL

Bit Error Probability (BEP) provides a fundamental performance measure for wireless diversity systems. This paper presents two new exact BEP expressions for Maximal Ratio Combining (MRC) diversity systems. One BEP expression takes a closed form, while the other is derived by treating the squared-sum of Rayleigh random variables as an Erlang variable. Due to the fact that the extant bounds are loose and could not properly characterize the error performance of MRC diversity systems, this paper presents a very tight bound. The numerical analysis shows that the new derived BEP expressions coincide with the extant expressions, and that the new approximation tightly bounds the accurate BEP.

Quantum Bit Error Avoidance

Qubit errors might be avoided by using the quantum Zeno effect to inhibit evolution.

Bit error probability of distributed Turbo coded relay systems over quasi-static Rayleigh fading channels

As is known, distributed Turbo coding （DTC） performs close to the theoretic outage probability bound of a relay channel when correct decoding is assumed at the relay. However, decoding error is inevitable in practical fading channels due to the error-prone feature of radio channels, and the decoding error propagation in DTC scheme will severely degrade the error performance of the relay system. As a result, it is necessary to evaluate the error performance of the DTC scheme in multi-hop relaying wireless systems in practical fading channels. Moreover, the theoretical method of analysis provides an effective tool for obtaining the error performance besides lengthy simulations. In this article, the concept of equivalent signal-to-noise ratio （SNR） of the two-hop relay channel and the method of computing equivalent SNR are developed, and then the upper bound on the bit error probability （BEP） of DTC relay systems is analyzed by use of Turbo code＇s distance spectrum, the concept of uniform interleaver, the limit-before-averaging technique, and the union bound method. Both theoretical analysis and numerical simulation are implemented for relay systems with DTC scheme over quasi-static Rayleigh fading channels. The results show that the upper bound approaches the simulation results in the medium to high SNR region.

CRC Look-up Table Optimization for Single-Bit Error Correction

Many communication systems use the cyclic redundancy code （CRC） technique for protecting key data fields from transmission errors by enabling both single-bit error correction and multi-bit error detection. The look-up table design is very important for the error-correction implementation. This paper presents a CRC look-up table optimization method for single-bit error correction. The optimization method minimizes the address length of the pre-designed look-up table while satisfying certain restrictions. The circuit implementation is also presented to show the feasibility of the method in the application specific integrated circuit design. An application of the optimization method in the generic framing procedure protocol is implemented using field programmable gatearrays. The result shows that the memory address length has been minimized, while keeping a very simple circuit implementation.

An independent but not identically distributed bit error model for heavy-tailed wireless channels

The error patterns of a wireless channel can be represented by a binary sequence of ones(burst) and zeros(run),which is referred to as a trace.Recent surveys have shown that the run length distribution of a wireless channel is an intrinsically heavy-tailed distribution.Analytical models to characterize such features have to deal with the trade-off between complexity and accuracy.In this paper,we use an independent but not identically distributed(inid) stochastic process to characterize such channel behavior and show how to parameterize the inid bit error model on the basis of a trace.The proposed model has merely two parameters both having intuitive meanings and can be easily figured out from a trace.Compared with chaotic maps,the inid bit error model is simple for practical use but can still be deprived from heavy-tailed distribution in theory.Simulation results demonstrate that the inid model can match the trace,but with fewer parameters.We then propose an improvement on the inid model to capture the 'bursty' nature of channel errors,described by burst length distribution.Our theoretical analysis is supported by an experimental evaluation.

Integrated coherent beam combining system for orbital-angular-momentum shift-keying-based free-space optical links

Orbital-angular-momentum(OAM)multiplexing technology offers a significant dimension to enlarge communication capacity in free-space optical links.The coherent beam combining(CBC)system can simultaneously realize OAM multiplexing and achieve high-power laser output,providing substantial advantages for long-distance communication.Herein,we present an integrated CBC system for freespace optical links based on OAM multiplexing and demultiplexing technologies for the first time,to the best of our knowledge.A method to achieve flexible OAM multiplexing and efficient demultiplexing based on the CBC system is proposed and demonstrated both theoretically and experimentally.The experimental results exhibit a low bit error rate of 0.47%and a high recognition precision of 98.58%throughout the entire data transmission process.By employing such an ingenious strategy,this work holds promising prospects for enriching ultra-long-distance structured light communication in the future.

Error Detecting Dual Basis Bit Parallel Systolic Multiplication Architecture over GF（2^m）

An error tolerant hardware efficient verylarge scale integration （VLSI） architecture for bitparallel systolic multiplication over dual base, which canbe pipelined, is presented. Since this architecture has thefeatures of regularity, modularity and unidirectionaldata flow, this structure is well suited to VLSIimplementations. The length of the largest delay pathand area of this architecture are less compared to the bitparallel systolic multiplication architectures reportedearlier. The architecture is implemented using Austria Micro System＇s 0.35 μm CMOS （complementary metaloxide semiconductor） technology. This architecture canalso operate over both the dual-base and polynomialbase.

Lower bound on BER performance for maximal ratio combining with weighting errors

The theoretical lower bounds on mean squared channel estimation errors for typical fading channels are presented by the infinite-length and non-causal Wiener filter and the exact closed-form expressions of the lower bounds for different channel Doppler spectra are derived. Based on the obtained lower bounds on mean squared channel estimation errors, the limits on bit error rate （BER） for maximal ratio combining （MRC） with Gaussian distributed weighting errors on independent and identically distributed （i. i. d） fading channels are presented. Numerical results show that the BER performances of ideal MRC are the lower bounds on the BER performances of non-ideal MRC and deteriorate as the maximum Doppler frequency increases or the SNR of channel estimate decreases.

水下舰艇扩频通信体制研究

水下舰艇通信采用的水声通信方式在长距离传输中信号衰减严重,且因为隐蔽性需求信号功率受限,叠加受到多径干扰和海洋背景噪声干扰,通信误码率较高。为此,提出水下舰艇扩频通信体制研究。设计扩频通信体制,利用扩频通信体制拓宽传输带宽,提升远距离衰减下的通信信噪比;采用类白噪声的伪随机码m序列和OPS序列作为扩频码组建编码序列集,解决白噪声干扰、多径干扰和码分多址的问题。测试结果表明:同等条件下,采用m序列的扩频通信结果更优,可以实现-25 dB下误码率低于1%的可靠通信。经过该方法调制后,剔除了噪声干扰和多径干扰,增强了衰减的高频信号,解决了水下通信远距离衰减、多径干扰、背景噪声干扰等问题。

32×10Gbit密集波分复用系统仿真

分析了DWDM技术及系统的设计原理,在此基础上,给出了基于Optisystem的DWDM光传输链路仿真模型的搭建,对复用及解复用后的光信号进行仿真得出光谱图,对链路传输性能及Q因子、误码率、眼图的等参数进行分析,并验证了波分复用系统的正确性和设计方案的可行性,近而得出相关结论。

2.5 Gbit/s光码分多址通信系统研究

以PTDS仿真实验平台为基础,对传输速率为2.5 Gbit/s的光码分多址通信系统性能进行了研究。仿真研究了传输信道和光功率对光码分多址系统性能的影响,分析了传输距离、光纤色散系数、光纤衰减、入纤光功率等与误码率和Q值的关系。

Multi-Bit Sliding Stack Decoding Algorithm for OVXDM

Overlapped x domain multiplexing(OVXDM) is a promising encoding technique to obtain high spectral efficiency by utilizing inter-symbol interference(ISI) intelligently. However, the computational complexity of maximum likelihood sequence detection(MLSD) increases exponentially with the growth of spectral efficiency in OVXDM, which is unbearable for practical implementations. In this paper, based on a novel path metric associating adjacent symbols, we propose a multi-bit sliding stack decoding(Multi-Bit SSD) algorithm to achieve multiple-bit decoding simultaneously in OVXDM. Theoretical analysis is provided for the algorithm, which indicates the relationship between the performance and parameters including multiplexing waveform, overlapping fold and sliding window size. Simulation results show that the proposed algorithm can achieve better decoding performance and higher spectral efficiency than conventional fast decoding algorithms.

基于4 bit-CRC反馈网络的高速LVDS传输优化设计

针对低压差分信号在恶劣环境中高速度、长距离传输链路中的丢数与误码问题,硬件关键电路设计采用高速LVDS芯片搭建,并增加发送端信号预加重与接收端均衡器处理;逻辑上,应用Verilog HDL构建了一种简单、实用的向前纠错反馈编解码方法,数据收发端以每包数据8 KB采用4bit-CRC生成校验结果,接收端判断校验结果一致与否发送重传与非重传RS-422指令,配合收发端使用乒乓缓存,保证数据可靠高效传输。经验证,系统在长度94 m LVDS专用屏蔽双绞电缆中实现了240 Mbit/s零误码传输。

Error Probability Analysis for Ultra-Massive MIMO System and Near-Optimal Signal Detection

In this paper,average bit error probability(ABEP)bound of optimal maximum likelihood(ML)detector is first derived for ultra massive(UM)multiple-input-multiple-output(MIMO)system with generalized amplitude phase modulation(APM),which is confirmed by simulation results.Furthermore,a minimum residual criterion(MRC)based lowcomplexity near-optimal ML detector is proposed for UM-MIMO system.Specifically,we first obtain an initial estimated signal by a conventional detector,i.e.,matched filter(MF),or minimum mean square error(MMSE)and so on.Furthermore,MRC based error correction mechanism(ECM)is proposed to correct the erroneous symbol encountered in the initial result.Simulation results are shown that the performance of the proposed MRC-ECM based detector is capable of approaching theoretical ABEP of ML,despite only imposing a slightly higher complexity than that of the initial detector.

8 bit量化误差对正弦参数拟合影响的误差界

针对量化误差对四参数正弦拟合带来的误差影响,分别在有效位数、幅度、频率、初始相位和直流分量5项参数上进行了拟合误差界的搜索。选取的条件变量分别是幅度、序列所含波形的周波数、初始相位、直流分量以及序列数据点数。以两两联动的双条件组合方式进行误差界搜索,获得了上述5项参数的误差界随不同条件变化而变化的曲线规律,筛分出了显著影响量和不显著影响量,以及明确的误差上界和下界。该结果可用于拟合参数的误差和不确定度估计,也可以在设定拟合误差和不确定度情况下,选择测量条件。

BER Performance Analysis of Asynchronous NOMA with Arbitrary Phase Offset

An asynchronous transmission scenario for non-orthogonal multiple access(NOMA)user signals with arbitrary phase offset is investigated in this paper.To improve the system performance in the user power-balanced conditions,we adopt a synthetic detection method at the receiver,i.e.,the jointly optimal maximal likelihood detection aided triangular successive interference cancellation(JO ML-TSIC)method.Analytical bit error rate(BER)solutions are obtained for a two-user case with the optimal,intentional onehalf symbol period time delay implemented between the user signals.Furthermore,closed-form BER solutions for the case using the triangular successive interference cancellation(TSIC)detection method are also derived for comparisons.Numerical results show that the JO ML-TSIC receiver for the asynchronous system outperforms the TSIC receiver as well as the synchronous successive interference cancellation(SIC)receiver in all the conditions concerned.The results also show that the superiority of the JO ML-TSIC receiver is strengthened when the signals experience flat Rayleigh fading channels compared to the TSIC and the synchronous SIC receivers.

同步数字体系中155Mbit/s净荷的误码测试

本文基于光纤传输同步数字体系(SDH)系统的开发背景,较为详细地总结了155Mbit/s速率下的净荷误码测试机理。最后给出了净荷的误码测试方法以及误码测试系统的信号流程。

用于调制频率合成器的5bit 4阶误差反馈ΔΣ调制器设计

针对频率合成器的高速数据调制应用 ,采用误差反馈结构 ,设计了一个用于直接 ΔΣ调制频率合成器的 5 bit4阶 ΔΣ调制器 .该结构能简化多 bit量化器的设计 ,不会对调制输入信号产生采样延迟 .通过在传递函数中引入两个极点 ,获得了比多环路级联结构更好的系统噪声性能 .在电路实现上 ,采用 CSD方法实现滤波器的系数相乘 ,并通过对系数共同项的优化 ,减少了系统的硬件消耗和功耗 。

基于FPGA的64 kbit/s通信误码生成仪

介绍了利用FPGA实现64 kbit/s通信误码生成仪的具体实现方法,即为减轻CPU的工作负担,利用FPGA和SDRAM芯片IS61LV5128实现64 kbit/s信号的时延、在64 kbit/s信号中添加随机误码、连续误码的实现方法,利用FPGA实现从信号中提取时钟的锁相环电路的设计方法。利用ARM7的数据处理能力和FPGA并行处理能力相结合,适用于实时性要求高的场合,是一种实时信号处理新的实现方法的探索。