HDTV解调芯片中RS解码器的设计与实现

采用 Berlekamp-Massey(BM)算法设计了符合DVB-C标准的RS(204,188)解码器,同时采用SRAM作为缓存和时分复用等方法,减小了电路规模和硬件结构的复杂性,设计的电路能够对每帧数据(204字节)中不多于8个字节的错误进行检查和纠正,并且能达到28.8 MHz的工作频率,符合HDTV解调芯片的性能要求.     

一种具有检错功能的传输协议设计

针对不可靠的非连接网络传输,本文设计了一种具有检错功能的网络传输协议,协议中使用帧头检验和数据信息CRC校验,能有效检出传输中的数据错误,并综合运用发送、应答和错误重传等手段,保证了协议的可靠性和协议数据的正确性.文中重点介绍了该协议的帧格式和握手过程,详细讲述了数据发送接收过程和循环冗余校验.     

时空域自适应错误隐藏算法

由于解码器后处理错误隐藏技术主要在解码器端完成,不会在码流信息中加入冗余信息,所以解码器后处理错误隐藏技术在实践中得到广泛应用.目前解码器后处理错误隐藏方面已经提出了多种有效的方法,在对比现有的几种时空域错误隐藏的算法的基础上提出了针对视频流中I帧,P帧图像中不同的出错区域采用自适应的时空域错误隐藏算法来恢复原图像,模拟测试表明,该算法能够有效提高视频质量.     

液晶电视中系统参数的检纠错备份机制及检验方法

在液晶电视的嵌入武系统中,系统参数通常存放在主板芯片E2 PROM里,由于外界脉冲或其TA原因会使E2 PROM中的数据发生丢失或错误,从而导致液晶电视偏色或无法正常启动.为解决此问题,提出一种利用CRC检错码和RS纠错码的机制来实现对系统参数的备份,即使数据发生部分错误也能够即时纠正过来.同时,为了检验基于检错和纠错数据备份机制的可靠性,设计了一套能够针对液晶电视主板上E2 PROM芯片中数据的正确性进行测试的工具,在一线工厂应用价值较高.     

CRC循环冗余校验码并行算法的FPGA实现

CRC循环冗余校验是数字数据通信中最常用的差错控制编码方法之一。在多种通信协议的帧结构中有一个16位或32位的FCS(FrameCheckSequence),就是利用CRC编码保证数据帧的无误传输。本文阐述了CRC循环冗余校验码基本原理,根据实际系统需要,建立了并行处理算法的数学模型,并且在FPGA芯片中实现了该并行算法。     

一种高可靠性串口通信协议的设计

通常,在串口通信中协议数据帧在线路上的传输会受各种干扰而出错,其可靠性比较差,而且容错纠错能力低,而该串口通信协议却能够在基于串口的通信线路上保证了协议数据帧的高可靠性传输,并已经将此串口通信协议运用在一些装备中,实践中也进行了充分的验证。 本文讲述了该串口通信协议的协议数据帧格式,其协议数据帧格式中包含起始标志字段、长度字段、序列号字段、地址字段、应用数据字段、CRC16 校验字段、结束标志字段,这种协议数据帧格式设计保证了应用数据能够在线路中进行高可靠性地传输。本文还对该协议数据帧的组帧、收发和解析做了描述,并且还对该协议数据帧的丢失进行了判断与处理,大大提高了该串口通信协议的可靠性、实时性和容错性。     

CRC算法在以太网数据帧中的应用及其硬件实现

文章介绍了CRC校验算法的原理,在串行CRC实现的基础上,对电路结构提出了改进,提出了CRC的并行计算,并基于Verilog HDL语言以CRC8为例说明了硬件电路实现方法。CRC校验广泛应用于数据通信、数据存储领域,结合IEEE802．3标准,说明了CRC算法在以太网帧FCS字段中的应用,并给出了CRC32_D16仿真结果。     

浅谈波分设备误码处理

误码是指在传输过程中码元发生了错误，错误通常以bit位来表示。在SDH帧结构中，用于误码检测的字节是B1、B2、M1、B3、G1、V5。但在波分设备中，OTU单板只对B1、B2字节进行监测。     

FPGA自主刷新技术研究

FPGA自主刷新技术是一种有效减缓FPGA单粒子翻转效应的措施,有利于提高FPGA空间应用时的可靠性。以Xilinx公司Virtex-7系列FPGA为例,研究基于内部配置访问接口(Internal Configuration Access Port,ICAP)对配置存储器的回读和刷新技术、基于帧纠错码(Frame Error Correction Code,FRAME_ECC)对配置存储器的检错和纠错技术等关键技术,使FPGA在空间应用时能够自主检测并纠正由于单粒子翻转造成的FPGA配置存储器位翻转错误,实现对每帧回读配置存储器数据中1比特位翻转错误的纠正及2比特位翻转错误的检测。     

基于VHDL语言的CRC信道编解码电路设计与实现

CRC码由于其具有良好的检纠错能力在现代通信中得到了非常广泛的应用.文中讨论了CRC码的原理,详细分析了编码,解码及纠正一个码元错误的设计思路,并用VHDL实现了CRC(15,6)码的编解码电路.     

Huffman code based error screening and channel code optimization for error concealment in perceptual audio coding (PAC) algorithms

The class of perceptual audio coding (PAC) algorithms yields efficient and high-quality stereo digital audio bitstreams at bit rates from 16 kb/sec to 128 kb/sec (and higher). To avoid "pops and clicks" in the decoded audio signals, channel error detection combined with source error concealment, or source error mitigation, techniques are preferred to pure channel error correction. One method of channel error detection is to use a high-rate block code, for example, a cyclic redundancy check (CRC) code. Several joint source-channel coding issues arise in this framework because PAC contains a fixed-to-variable source coding component in the form of Huffman codes, so that the output audio packets are of varying length. We explore two such issues. First, we develop methods for screening for undetected channel errors in the audio decoder by looking for inconsistencies between the number of bits decoded by the Huffman decoder and the number of bits in the packet as specified by control information in the bitstream. We evaluate this scheme by means of simulations of Bernoulli sources and real audio data encoded by PAC. Considerable reduction in undetected errors is obtained. Second, we consider several configurations for the channel error detection codes, in particular CRC codes. The preferred set of formats employs variable-block length, variable-rate outer codes matched to the individual audio packets, with one or more codewords used per audio packet. To maintain a constant bit rate into the channel, PAC and CRC encoding must be performed jointly, e.g., by incorporating the CRC into the bit allocation loop in the audio coder.     

Multirate 3-D subband coding of video

We propose a full color video compression strategy, based on 3-D subband coding with camera pan compensation, to generate a single embedded bit stream supporting multiple decoder display formats and a wide, finely gradated range of bit rates. An experimental implementation of our algorithm produces a single bit stream, from which suitable subsets are extracted to be compatible with many decoder frame sizes and frame rates and to satisfy transmission bandwidth constraints ranging from several tens of kilobits per second to several megabits per second. Reconstructed video quality from any of these bit stream subsets is often found to exceed that obtained from an MPEG-1 implementation, operated with equivalent bit rate constraints, in both perceptual quality and mean squared error. In addition, when restricted to 2-D, the algorithm produces some of the best results available in still image compression.     

Error characteristics of fiber distributed data interface (FDDI)

An analysis is made of the impact of various design decisions on the error detection capability of the fiber distributed data interface (FDDI), a 100-Mb/s fiber-optic LAN standard being developed by the American National Standards Institute (ANSI). In particular, the frame error rate, token loss rate, and undetected error rate are quantified. Several characteristics of the 32-b frame check sequence (FCS) polynomial, which is also used in IEEE 802 LAN protocols, are discussed. The standard uses a nonreturn to zero invert on ones (NRZI) signal encoding and a 4-b to 5-b (4b/5b) symbol encoding in the physical layer. Due to the combination of NRZI and 4b/5b encoding, many noise events are detected by code (or symbol) violations. A large percentage of errors are detected by FCS violations. The errors that escape these three violations remain undetected. The probability of undetected errors due to creation of false starting delimiters, false ending delimiters, or merging of two frames is analyzed. It is shown that every noise event results in two code bit errors, which in turn may result in up to four data bit errors. The FCS can detect up to two noise events. Creation of a false starting delimiter or ending delimiter on a symbol boundary also requires two noise events. This assumes enhanced frame validity criteria. The author justifies the enhancements by quantifying their effect     

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.     

Investigation of 9.6 kb/s data transmission via a pcm link at 64 kb/s with and without link errors

The problem of pulse code modulation (PCM) bit errors causing voice frequency (VF) modem errors has been studied in detail. The error mechanism consists of the addition of an impulse response type error signal added to the reconstructed VF data signal waveform at the digital-to-analogue (D/A) output of the PCM decoder. This error signal may cause a burst of errors registering in the VF modem receiver, depending on which PCM bit is in error. Numerous data have been collected in a laboratory experiment and analysed in various ways. The average bit error rate (BER) enhancement factor of VF data over PCM is between 10 and 20. For each PCM bit in error, an average of two VF data bits are in error. The analysis leads to suggestions for possible solutions to the problem.     

Variable rate data transmission with blind rate detection forcoherent DS-CDMA mobile radio

A variable rate data transmission scheme with blind rate detection is described for pilot-symbol-assisted coherent DS-CDMA mobile radio. Cyclic redundancy check (CRC) coding and decoding is used for blind rate detection. Computer simulations of eight-rate variable rate data transmission demonstrate that when 16 bit CRC is used, the loss in required total E_b/N₀ at a frame error rate of 10 ^-2 under two-path Rayleigh fading, is only ~0.1 dB from the known rate case     

Low-complexity maximum-likelihood detection of coded signals sentover finite-state Markov channels

We propose a decision-feedback decoder for coded signals transmitted over finite-state Markov channels. The decoder achieves maximum-likelihood sequence detection (in the absence of feedback errors) with very low complexity by exploiting previous bit decisions and the Markov structure of the channel. We also propose a similar decoder, the output-feedback decoder, that does not use previous bit decisions and therefore does not suffer from error propagation. The decoder performance is determined using a new sliding window analysis technique as well as by simulation. Both decoders exhibit excellent bit error rate performance with a relatively low complexity that is independent of the channel decorrelation time     

Error concealment techniques for digital TV

Compressed video bitstreams are intended for real-time transmission over communication networks. Most of the video coding standards employ the temporal and spatial prediction structure to reduce the transmitted video data. Therefore, the coded video bitstreams are highly sensitive to information loss and channel errors. Even a single bit error can lead to disastrous quality degradation in both time and space. This quality deterioration is exacerbated when no error resilient coding mechanism is employed to protect coded video data against the error prone environments. Error concealment is a data recovery technique that enables the decoder to conceal effects of transmission errors by predicting the lost or corrupted video data from the previously reconstructed error-free information. Motion vector recovery and motion compensation with the estimated motion vector is a good approach to conceal the corrupted macroblock data. In this paper, we develop various error concealment algorithms based on motion vector recovery, and compare their performances to those of conventional error concealment methods.     

Performance of Error-Correcting Codes on Channels with Memory

Most magnetic recording and many other digital communication channels exhibit statistical dependencies among errors. The design of error-control schemes for such channels .requires proper models and tools that can be used to evaluate error performance after decoding. In this paper a simplified partitioned model of a channel with memory suggested by B. D. Fritchman is considered. This model is used to derive expressions for block and bit error probability bounds for major block burst-error-correcting codes: interleaved, single burst-correcting, and nonbiuary codes. The model-based bounds are compared to the experimental ones using the data obtained for helical scan magnetic tape recorders. The comparison showed an agreement between experimental and analytical data within one order of magnitude, with the average difference being as small as 16 percent in some cases. A simple and effective implementation of a multiple burst-error-correcting scheme based on the majority-logic decoding of interleaved binary codes is suggested. The scheme requires about ten off-the-shelf IC's for both encoder and decoder with the interleaving degree up to 512.     

Improving the performance of turbo codes with a simple protection scheme for error-prone bit positions

It is well known that turbo codes provide highly unequal error protection within a transmitted frame. Previous attempts to exploit this fact focused mainly on adding additional redundancy to provide extra protection for the error-prone bit positions. Here, instead, we use the error-detection capability of the cyclic redundancy check (CRC), which is almost always employed in practical systems. Once a frame is declared uncorrectable by the CRC, a process termed the error-prone bit processing procedure is activated in an attempt to correct the probable error patterns which are a priori identified as being error-prone.