Error correction performance in digital subscriber looptransmission systems

The author describes an error correction system for digital subscriber loop transmission systems which use time compression multiplexing (TCM). An interleaved block code is used to correct the burst errors due to impulse noise from analog telephone circuits. This interleaving method requires no extra hardware and contributes no additional delay. To evaluate the transmission performance of this error correction system, the bit error rate after decoding is derived on the basis of a burst error model for 200 kb/s digital subscriber transmission using the alternate mark inversion (AMI) line code. The experimental results for a 200 kb/s TCM system show that burst errors are substantially reduced     

Progressive transmission of images over memoryless noisy channels

An embedded source code allows the decoder to reconstruct the source progressively from the prefixes of a single bit stream. It is desirable to design joint source-channel coding schemes which retain the capability of progressive reconstruction in the presence of channel noise or packet loss. Here, we address the problem of joint source-channel coding of images for progressive transmission over memoryless bit error or packet erasure channels. We develop a framework for encoding based on embedded source codes and embedded error correcting and error detecting channel codes. For a target transmission rate, we provide solutions and an algorithm for the design of optimal unequal error/erasure protection. Three performance measures are considered: the average distortion, the average peak signal-to-noise ratio, and the average useful source coding rate. Under the assumption of rate compatibility of the underlying channel codes, we provide necessary conditions for progressive transmission of joint source-channel codes. We also show that the unequal error/erasure protection policies that maximize the average useful source coding rate allow progressive transmission with optimal unequal protection at a number of intermediate rates     

256 QAM Modem for Multicarrier 400 Mbit/s Digital Radio

This paper describes the performance of a 256 QAM modem with 400 Mbit / s transmission capacity. A variety of novel techniques are introduced as ways to achieve good performance. Key techniques include 1) an accurate 256 QAM modulator employing a new monolithic multiplier IC, 2) a carrier recovery circuit which satisfies such requirements: good phase jitter performance and no false lock phenomenon, 3) a highly stable high-level decision circuit, and 4) a forward error correcting code. As an overall modem performance, BER characteristics and signatures are presented. The equivalent CNR degradations of 1 dB(at BER of 10^-4) and 2 dB (at BER of 10^-9)are obtained using a single Lee-error correcting code and a seven-tap baseband transversal equalizer. The residual bit errors are decreased below the order of 10^-10. The performance of a 256 QAM multicarrier modem has given prospect for the development of 400 Mbit/s digital microwave radio system.     

Design of parallel fault-secure encoders for systematic cyclic block transmission codes

In this paper, we consider the problem of designing parallel fault-secure encoders for various systematic cyclic linear codes used in data transmission. It is assumed that the data to be encoded before transmission are stored in a fault-tolerant RAM memory system protected against errors using a cyclic linear error detecting and/or correcting code. The main idea relies on taking advantage of the RAM check bits to control the correct operation of the cyclic code encoder as well. A slightly modified encoder allows not only for encoding the transmission data stream but also, independently and in parallel, to generate the reference check bits which allow for concurrent error detection in the encoder itself. The error detection capacity proves to be effective and grants good levels of protection as shown by error injection campaigns on encoders for various standard linear cyclic error detecting and error correcting codes. Moreover, the complexity evaluation of the FPGA implementations of the encoders shows that their fault-secure versions compare favorably against the unprotected ones, both with respect to hardware complexity and the maximal frequency of operation.     

纠错码在M元扩频通信系统中的应用

研究了一种将M元扩频和纠错码相结合的通信方案。由于采用了M元扩频,在带限信道中获得了较高的数据传输速率;同时采用纠错编码,增强了系统的可靠性。两者的结合,较好地解决了通信系统有效性与可靠性两大问题。仿真结果表明该系统具有很好的性能。     

Performance analysis of time-hopping spread-spectrum multiple-access systems: uncoded and coded schemes

An ultra-wide bandwidth time-hopping spread-spectrum code division multiple-access system employing a binary PPM signaling has been introduced by Scholtz (1993), and its performance was obtained based on a Gaussian distribution assumption for the multiple-access interference. In this paper, we begin first by proposing to use a practical low-rate error correcting code in the system without any further required bandwidth expansion. We then present a more precise performance analysis of the system for both coded and uncoded schemes. Our analysis shows that the Gaussian assumption is not accurate for predicting bit error rates at high data transmission rates for the uncoded scheme. Furthermore, it indicates that the proposed coded scheme outperforms the uncoded scheme significantly, or more importantly, at a given bit error rate, the coding scheme increases the number of users by a factor which is logarithmic in the number of pulses used in time-hopping spread-spectrum systems.     

RS（16,12）缩短码编译码原理及性能分析

在各类数字通信系统以及计算机存储和运算系统经常利用差错控制编码降低误码率,提高通信质量,满足对数据传输通道可靠性的要求。RS码是一种性能优良的前向纠错码,具有同时纠正随机错误和突发错误的能力,它的构造特点决定了其非常适合于纠正突发性错误。文中在阐述RS系统码编译码原理的基础上,提出了RS（16,12）缩短码的编译码方法,利用MATLAB对R S（16,12）缩短码在高斯信道和瑞利信道条件下的纠错能力进行仿真,并分析其纠错性能。     

状态网格图的LDPC码在OFDM系统中的应用

介绍了LDPC码的编译码技术,提出了一种新颖的2状态网格图译码算法,研究了该码在OFDM系统中的性能,对不同的译码算法进行了比较.仿真结果表明,LDPC码在OFDM基带传输系统中用2状态网格图对其译码能够更好的对错误码进行纠错,提高码字性能,信息传输速率会大大提高.     

401 km, 622 Mb/s and 357 km, 2.488 Gb/s IM/DD repeaterlesstransmission experiments using erbium-doped fiber amplifiers and errorcorrecting code

Record repeaterless transmission distances of 401 km at 622 Mb/s and 357 km at 2.488 Gb/s on nondispersion-shifted fiber are demonstrated. The transmission format is intensity modulation/direct detection (IM/DD), and a forward error correcting code scheme is implemented. Erbium-doped fiber amplifiers are used at the transmit and receive end of the system as postamplifier, preamplifier, and remotely pumped amplifier     

8B/10B编码对高速传输的影响分析

研究了8B/10B编码的编码原理以及其内在特性。同时结合8B/10B编码的主要特点分析了其对PCIE等高速串行总线数据传输特性的影响。分析了利用编码的不一致性检测数据传输中的任意单个错误,并通过CRC校验提高系统的多错误纠检错能力。通过仿真PCIE于2.5Gb/s的时钟下传输不同类型的数据来分析8B/10B编码利用DC平衡特点,解决AC耦合工作模式下低频数据失真与传输速度之间的矛盾。     

An Iteratively Decodable Tensor Product Code with Application to Data Storage

The error pattern correcting code (EPCC) can be constructed to provide a syndrome decoding table targeting the dominant error events of an inter-symbol interference channel at the output of the Viterbi detector. For the size of the syndrome table to be manageable and the list of possible error events to be reasonable in size, the codeword length of EPCC needs to be short enough. However, the rate of such a short length code will be too low for hard drive applications. To accommodate the required large redundancy, it is possible to record only a highly compressed function of the parity bits of EPCC?s tensor product with a symbol correcting code. In this paper, we show that the proposed tensor error-pattern correcting code (T-EPCC) is linear time encodable and also devise a low-complexity soft iterative decoding algorithm for EPCC?s tensor product with q-ary LDPC (T-EPCC-qLDPC). Simulation results show that T-EPCC-qLDPC achieves almost similar performance to single-level qLDPC with a 1/2 KB sector at 50% reduction in decoding complexity. Moreover, 1 KB T-EPCC-qLDPC surpasses the performance of 1/2 KB single-level qLDPC at the same decoder complexity.     

Machine Learning Algorithms for Predicting Electricity Consumption of Buildings

Inter-satellite optical wireless communication (IsOWC) is a developing free-space optical technology used to communicate among satellites in space. At the same time, SAC-OCDMA (spectral amplitude coding optical code division multiple access) is an encouraging research area in the domain of optical communication because of its high bandwidth, speed, huge capacity, and ability to carry bursty and asynchronous information transmission. The present paper is concerned with the hybrid IsOWC non-coherent SAC-OCDMA system based on PM-ZCC (Permutation Matrix Zero Cross-Correlation) code for long-range high data rate transmission. The advanced modulation format (CSRZ) and direct detection (DD) techniques have been used to design the proposed system. The system is designed for five stations (each carrying 10 Gb/s). The system's performance is investigated for pointing error (with and without) over a space distance up to 12000 km in terms of Q factor, eye diagrams, BER and SNR. Moreover, the performance of a single IsOWC link has also been compared with multiple IsOWC links for a distance of 6500 km at 10 Gb/s data rate. The results show that system performance improves by using CSRZ format and multiple ISL links.

     

BER performance comparison of single code and multicode DS/CDMAchannelization schemes for high rate data transmission

The bit error rate (BER) performance of single code and multicode channelization schemes for high rate data transmission in direct-sequence code division multiple access (DS/CDMA) systems is compared. The multipath interference (MPI) effects, which become significant as the data rate increases, are accurately included in the analysis. It is shown that notable performance improvement can be achieved by using multicode scheme in the multipath fading channel     

A 0.18-$muhbox m$CMOS Analog Min-Sum Iterative Decoder for a (32,8) Low-Density Parity-Check (LDPC) Code

Current-mode circuits are presented for implementing analog min-sum (MS) iterative decoders. These decoders are used to efficiently decode the best known error correcting codes such as low-density parity-check (LDPC) codes and turbo codes. The proposed circuits are devised based on current mirrors, and thus, in any fabrication technology that accurate current mirrors can be designed, analog MS decoders can be implemented. The functionality of the proposed circuits is verified by implementing an analog MS decoder for a (32,8) LDPC code in a 0.18-mum CMOS technology. This decoder is the first reported analog MS decoder. For low signal to noise ratios where the circuit imperfections are dominated by the noise of the channel, the measured error correcting performance of this chip in steady-state condition surpasses that of the conventional floating-point discrete-time synchronous MS decoder. When data throughput is 6 Mb/s, loss in the coding gain compared to the conventional MS decoder at BER of 10^-3 is about 0.3 dB and power consumption is about 5 mW. This is the first time that an analog decoder has been successfully tested for an LDPC code, though a short one     

时隙ALOHA DS/CDMA系统与多载波时隙ALOHA系统吞吐性能的比较研究

该文对同样带宽下时隙 ALOHA DS/CDMA系统和多载波时隙 ALOHA系统的吞吐量进行了理论计算、比较和仿真。结果表明,在总负载较大时,采用高纠错能力的时隙 ALOHA DS/CDMA系统可以在吞吐量上有更好的性能。但若网络负载过重,时隙ALOHA DS/CDMA系统的吞吐性能较多载波时隙ALOHA的系统下降快;码字总数受限会带来码字选择的冲突,从而降低系统的吞吐性能。     

Error Sensitivity of CCITT Standard Facsimile Coding Techniques

The CCITT has defined Group 3 facsimile apparatus as that which digitally transmits an ISO A4 document over a switched telephone circuit in approximately one minute. Data compression is employed to achieve the reduced transmission time. Study Group XIV of the CCITT has drafted Recommendation T.4 to achieve compatibility between Group 3 facsimile devices. The standard data compression technique specified by T.4 is a one-dimensional coding scheme in which runlengths are encoded using a modified Huffman code (MHC). The recommendation also includes an optional twodimensional compression technique known as the modified READ code (MRC). It is recognized that the switched telephone network is prone to error when transmitting digital data at the standard T.4 data rate of 4800 bits/s. This paper evaluates the error sensitivity of the MHC and MRC when operating over a typical telephone circuit. The error sensitivity analysis is accomplished by means of computer simulation. The error performance of the two coding techniques is analyzed both quantitatively and qualitatively. The quantitative analysis is accomplished using the error sensitivity factor which represents the average number of incorrect pels in the output document caused by a transmission error. The qualitative analysis is based upon viewing actual error-contaminated images generated in the simulation process. Two separate analyses have been performed. First, error sensitivity data for both the MHC and MRC are developed under identical operational conditions, and their relative performance is discussed. In the second part four different techniques for processing the received facsimile signal (MRC), to minimize the subjective effect of transmission errors, are analyzed.     

高速数据通信及其差错控制研究

提出一种基于嵌入式时钟的高速数据通信方案及其差错控制编译码算法,并分析了性能。采用信道编码调制技术将时钟信息嵌入到高速串行数据流中,实现自同步传输,突破了外同步方式下传输距离和传输速率的上限,使远程传输带宽达3Gbps以上。针对高速调制信道的特点,在经典汉明码基础上引入交织技术,把可能存在的连续误码转为单个随机错误,简化了差错控制算法的复杂度,提高了编码效率和纠错性能。其编译码电路延时小、易实现、码率易控,方便高速数据通信系统应用,且能显著改善低信噪比条件下传输的可靠性。     

LDPC码在OFDM通信系统中的应用与仿真

介绍了OFDM基带传输系统及其模型；概述LDPC的编译码方法，研究了其在OFDM系统中的性能，并与卷积码进行了比较。仿真表明，LDPC码在OFDM基带传输系统中具有更好的纠错能力。LDPC码可实现完全并行的编译码操作，译码简单，吞吐量大，因而将在下一代移动通信中得到广泛应用。     

An embedded transmission scheme using PPM signaling with symmetric error-correcting codes for optical CDMA

An embedded transmission (ET) scheme is proposed to easily apply error-correcting codes into optical code-division multiple-access (CDMA) systems for immunity from multiple-access interference (MAI). The ET scheme offers high transmission capability over the traditional scheme using pulse position modulation (PPM) signaling, because a 2/sup J/-ary symbol of each user is embedded in the signature sequence with 2/sup J/ weighted positions. Furthermore, the ET scheme with 2/sup J/-ary PPM signaling makes the optical CDMA system J parallel transmission systems, because J bits consisting of 2/sup J/-ary symbol are separately decided. Since such a separate decision is a comparison decision, the effect of MAI added in the optical channel is converted to symmetric errors in the individual parallel transmission systems. Using the symmetric error-correcting (SEC) code immunizes the individual parallel transmission systems against MAI more easily than the embedded-modulation scheme described in because the ET scheme avoids using the asymmetric error correcting code, which is difficult to implement. We analyze the bit error rate under Poisson photon counting channel and show that the ET scheme has an advantage of good energy efficiency over the traditional scheme in applying SEC codes.     

Analysis of the interaction between linear cyclic error correcting codes and self-synchronous payload scramblers

In order to protect public network data transmission from potential Layer 1 attacks by malicious users, selfsynchronous scramblers have come into widespread use. Such networks include those using ATM, Packet over SONET (POS), and the new Generic Framing Procedure (GFP). Unfortunately, feedback taps inherent in self-synchronous descramblers cause multiplication of transmission errors, which in turn degrades the performance of most linear cyclic error detection/correction codes. This paper analyzes this scrambler/code interaction with respect to the resulting probability of undetectable errors and transmission error correction capability. The theoretical criteria are derived for a linear cyclic code to maintain its error detection and correction performance in the presence of the scramblers. A novel approach for improving the error correction capabilities is also presented.