一种基于FPGA的Viterbi译码器的研究与设计

针对通信系统中传统维特比(Viterbi)译码器结构复杂、译码延时大、资源消耗大的问题,提出了一种新的基于FPGA的Viterbi译码器设计。结合(2,1,7)卷积编码器和Viterbi译码器的工作原理,设计出译码器的核心组成模块,具体采用3比特软判决译码,用曼哈顿距离计算分支度量,32个碟型加比选子单元并行运算,完成幸存路径和幸存信息的计算。幸存路径管理模块采用Viterbi截短译码算法,回溯操作分成写数据、回溯读和译码读,以改进的流水线进行并行译码操作,译码延时和储存空间分别降低至和。     

Performance evaluation and implementation of convolution coded OFDM modem in wireless underwater acoustic communication

High‐data transmission rate and reliable communication in underwater acoustic channel is challenging because of limited bandwidth, multipath propagation, and Doppler shift, which results in poor bit error performance. Under this constraint, this paper explains the simulation results of underwater wireless acoustic data transmission system by using quadrature phase shift keying modulation with convolution encoder at the transmitter and proposed Viterbi decoder at the receiver. The decoder algorithm in comparison with MATLAB inbuilt function shows asserting improved results. This paper evaluates the performance of convolution coded orthogonal frequency division multiplexing modem, which is studied over typical underwater channel through an extensive computer simulation and a semirealistic experimentation. The performance of convolution coded orthogonal frequency division multiplexing system is measured in time domain plots, bit error rate curves, and number of bit errors per frame over additive white Gaussian noise and Rayleigh channel conditions.     

市级台站无人值守机房光纤信号的搭建与思考

针对市级台站无人值守机房光纤信号源相关问题的解决,结合目前市级台站布局及光纤路由现状,在综合考虑业务发展并利用现有资源的基础上,以扬州台“江苏健康广播”光纤信号源的搭建为例,阐述市级台站无人值守机房光纤信号源的设计思路,并对相应的交换机、解码器的具体配置进行简单介绍,同时对该方案进行分析与思考,证明此设计方案的可靠性及稳定性,将其应用在市级台站无人值守机房光纤信号源上是行之有效的.     

CMOS三值译码器

本文探讨了在常规CMOS集成电路基础上设计三值逻辑电路的方法。从三值倒相器入手,结合常规CMOS门电路,给出了CMOS三值译码器的设计方案及应用电路。     

一种新的未知信道参数下的次最优分集合并接收机

本文推导了衰落信道中未知信道参数情况下相移键控信号多信道分集合并的最大似然序列估计算法,并在此最优方案的基础上提出了两新的次最优维持比算法,将该算法用于扩系统的ＲＡＫＥ接收机的模拟结果表明,对ＤＱＰＳＫ和编码的ＱＰＳＫ信号的接收民理想接收十分接近。     

Metric‐based node synchronization of the Viterbi decoder in satellite applications

Convolutional codes are used in digital communication systems to correct errors that occur during transmission. Their use is now commonplace, particularly in power‐limited satellite and deep space communication systems. Before the decoder can correctly decode the received continuous bit sequence, however, it must establish where codewords begin and end in this sequence. The process of determining codeword boundaries is called node synchronization. In this paper we develop a node synchronization algorithm based on metric difference values with the objectives of simple implementation and reliable performance. Focusing on satellite applications, we consider the constraint length 7, rate ½ convolutional code standardized by the National Aeronautics and Space Administration (NASA) and the European Space Agency (ESA); the approach we develop can be extended to other convolutional coding systems. Through simulation, we investigate the statistics of the received sequence, and highlight correlation in the sequence of the decoder metric values. In the light of these observations, we propose a synchronization algorithm, and develop a first‐order analysis of this simple up/down counter framing technique. We recommend framing parameters based on both the analytical results and the expected response of the framing algorithm to correlated metric values. Development of a simple node synchronization algorithm that accommodates correlated metric values has not been reported previously in the literature. Simulation results confirm that reliable node synchronization is possible with this very simple approach. Copyright © 2000 John Wiley & Sons, Ltd.     

Performance analysis and simulation of OCDMA system based on FBGs encoder/decoder

The encoding/decoding scheme based on Fiber Bragg Grating （FBG） for Optical Code Division Multiple Access （OCDMA） system is analyzed and the whole process from transmitting end to receiving end is researched in detail. The mathematical mode including signal transmission, summing, receiving and recovering are established respectively. One of the main sources of Bit Error Rate （BER） of OCDMA system based on FBGs is the unevenness of signal power spectrum, which leads to the chip powers unequal with each other. The Signal to Interfere Ratio （SIR） and BER performance of the system are studied and simulated at the case with uneven distribution of chips＇ powers.     

Instance-optimality in probability with an -minimization decoder

Let Φ(ω), ωΩ, be a family of n×N random matrices whose entries _i,j are independent realizations of a symmetric, real random variable η with expectation and variance . Such matrices are used in compressed sensing to encode a vector by y=Φx. The information y holds about x is extracted by using a decoder . The most prominent decoder is the ℓ₁-minimization decoder Δ which gives for a given the element which has minimal ℓ₁-norm among all with Φz=y. This paper is interested in properties of the random family Φ(ω) which guarantee that the vector will with high probability approximate x in to an accuracy comparable with the best k-term error of approximation in for the range kan/log₂(N/n). This means that for the above range of k, for each signal , the vector satisfies

with high probability on the draw of Φ. Here, Σ_k consists of all vectors with at most k nonzero coordinates. The first result of this type was proved by Wojtaszczyk [P. Wojtaszczyk, Stability and instance optimality for Gaussian measurements in compressed sensing, Found. Comput. Math., in press] who showed this property when η is a normalized Gaussian random variable. We extend this property to more general random variables, including the particular case where η is the Bernoulli random variable which takes the values with equal probability. The proofs of our results use geometric mapping properties of such random matrices some of which were recently obtained in [A. Litvak, A. Pajor, M. Rudelson, N. Tomczak-Jaegermann, Smallest singular value of random matrices and geometry of random polytopes, Adv. Math. 195 (2005) 491–523].     

复杂环境下低信噪比WCDMA信号接收系统总体设计

根据区域内移动通信网信号接收的需求,提出了一种复杂环境下 低信噪比WCDMA移动通信信号接收系统的总体设计方案,针对关键环节小区搜索采用了差分 相干累积和RS译码判决等改进措施,提高了低信噪比WCDMA信号的处理性能。仿真和实验证 明了改进措施的有效性。     

一种提高AIS信号检测性能的设计方法及其应用

提出了一种提高船舶自动识别系统(AIS)信号检测性能的设计方法,主要包括两部分算法:一部分是针对AIS系统的码间串扰,采用基于GMSK调制方式的Viterbi解调算法;另一部分是针对AIS报文长度的不固定,采用报文自动检测算法.在设计过程中,依据软件无线电设计思想,将基于GMSK调制方式的Viterbi解调算法和报文自动检测算法组合成的设计方法,应用在Spartan-6系列的FPGA和简单外围电路组成的双通道AIS中频数字化接收机中,从而提高了AIS信号检测性能,使得中频信号载噪比大于10 dB时,误码率小于10-4.