Average digit error probability in decoding a linear block code

An upper bound on the average digit error probability of a linear block code is given which is dependent only upon the minimum distance of the code. The tightness of this bound is also demonstrated, and an example is given where knowledge of the average digit error probability is important.     

Bayes error probability with inaccurate decision threshold

In a binary detection problem, the author derives an expression for the excess error probability caused by inaccurate setting of the threshold.<>     

低重分配概率的OVSF码重分配算法

在采用正交可变长扩频因子(OVSF)码作为信道化码的直接序列扩频码分多址系统中,提出用重分配概率作为重分配算法的一个新的评价指标,重分配概率越小,系统的计算复杂度越低。进而提出一种低重分配概率的、基于空码容量的重分配算法,在解决本次码阻塞的同时,兼顾对未来高数据速率的呼叫的支持能力,减少未来码阻塞发生。仿真证实,重分配概率比已有2种重分配算法都小。     

On the monotonic property of the probability of undetected errorfor a shortened code

The monotonic property of the probability of undetected error is considered when a shortened code of a linear code over GF(q) is used for error detection on a q-ary symmetric channel. Some conditions are presented under which the probability of undetected error is (or is not) monotonic with respect to the code length or the symbol error probability. It is shown that the probability of undetected error for a maximum distance separable code is monotonic with respect to the codelength. It is also shown that the probability of undetected error of a shortened code of any binary cyclic Hamming code generated by a trinomial is not monotonic with respect to the bit-error rate if the code length is short     

The probability of undetected error when a code is used for error correction and detection (Corresp.)

We study the probability of having an undetected error when a linear block code is used to correct up toterrors on a symmetric channel, and the remaining power of the code is used for error detection.     

On the threshold setting principles in code acquisition of DS-SSsignals

This paper compares the meaning of different threshold setting principles in the code acquisition process of a direct sequence (DS) spread spectrum (SS) receiver. The consideration is made mainly in one-path additive white Gaussian noise (AWGN) channel. A consideration to a fixed multipath channel is given to see its effect on the results. Also, a consideration for a certain type of fading is given in a case where the signal power is assumed to be considerably lower, i.e., faded, part of the time. For the possible performance measures of code acquisition, the main interest is in the mean acquisition time T_MA . The probability of the acquisition in a given observation interval P_acq is also considered to see if different measures have different demands. A matched filter (MF) acquisition is used with and without a verification mode using an active integration. In the comparisons, fixed thresholds, thresholds based on constant false alarm rate (CFAR) criteria, and optimal thresholds in the sense to give either the minimum T_MA or the maximum P_acq are used. The results, which are obtained by using a method of selecting the maximum value at the output of the MF, are compared to the threshold cases. The results can be summarized as follows: when the performance measure is T _MA, the best results are obtained by using CFAR-based threshold comparison. By a proper selection of the probability of a false alarm, the same performance is obtained as by using the optimal thresholds. When the performance measure is P_acq, the maximum-selection method is the best choice     

Estimation of the exponent of the decoding error probability for a special generalized LDPC code

A special construction of a generalized low-density parity-check (LDPC) code and a low-complexity algorithm for his code decoding are proposed. A lower estimate of the exponent of the decoding error probability is obtained for the considered code and the decoding algorithm. This estimate leads the conclusion that, in an ensemble of considered LDPC codes, there are codes with rates as high as the code capacity and the exponent of the decoding error probability exceeds zero.     

Outage probability analysis of a MC-DS-CDMA system with variable repetition code rate and spreading factor

In the multicarrier direct-sequence code-division multiple access with repetition code system, decreasing the code rate can result in greater frequency diversity. However, to keep the same transmit bit rate, the spreading factor in each subcarrier needs to be reduced. In this paper, we use the outage probability as a criterion for these two system parameters' design. We first examine the condition on code rate for the uncorrelated fading channel assumption. The system performance is derived and the outage probability is obtained in closed forms for equal and unequal transmit bit energy scenarios. The relation between the spreading factor and the rate of the repetition code is investigated by observing the outage probability equation.     

Detection and false alarm probability of PN code acquisition inDS-CDMA system

The authors present the performance of double dwell acquisition using a continuous integration detector. One performance measure in an acquisition system is the mean acquisition time, which depends on detection and false alarm probability. The detection and false alarm probability of double dwell acquisition using continuous integration detector is derived     

Reliability of Hamming code transmission versus error probability on message bits

The paper presents an algorithm for the determination of the reliability of Hamming Code transmission against the error probability on message bits incurred during transmission. It establishes that Hamming Code is effective as long as the error probability of transmission line is less than 3%. The accuracy of Hamming Code drops to 90% when the error probability of the line is 8%. The algorithm is useful in adaptive communication circuits and is suitable for VLSI implementation.     

Bounds on the bit error probability of a linear cyclic code overGF(2l) and its extended code

An upper bound on the bit-error probability (BEP) of a linear cyclic code over GF(2^l) with hard-decision (HD) maximum-likelihood (ML) decoding on memoryless symmetric channels is derived. Performance results are presented for Reed-Solomon codes on GF(32), GF(64), and GF(128). Also, a union upper bound on the BEP of a linear cyclic code with either hard- or soft-decision ML decoding is developed, as well as the corresponding bounds for the extended code of a linear cyclic code. Using these bounds, which are tight at low bit error rate, the performance advantage of soft-decision (SD) ML and HD ML over bounded-distance (BD) decoding is established     

一种PN码自适应捕获门限的改进算法

文献[1]提出了一种用于直扩系统的PN码自适应门限算法。但该文献也指出,此算法对门限总数十分敏感。当门限总数设置不当时,系统的平均捕获时间将显著增加。这限制了该算法在实际中的应用。本文就此提出了改进,给出了算法及电路框图。仿真结果表明,与原方案相比,改进算法改善了对门限总数的敏感性,降低了PN码平均捕获时间。     

Effects of multiple threshold values for PN code acquisition inDS-CDMA systems

A decision method using multiple threshold value for PN code acquisition in DS-CDMA systems is describe. This technique is applied to a conventional hybrid search algorithm and analysis in terms of the probability of detection and false alarm. Simulation results show that the proposed scheme outperforms the conventional scheme in terms of detection probability because multiple threshold values mitigate any possible decline in performance caused by the used of a single threshold     

Acquisition of PN code with adaptive threshold for DS/SScommunications

An adaptive acquisition scheme of PN sequences is presented for DS/SS communications. The basic idea of the scheme is to apply the radar CFAR technique to the acquisition of PN sequences. The detection performance is analysed and an example of adaptive thresholding for multipath Rayleigh fading channels is given     

基于码重分布概率方差的循环码识别方法

提出循环码的一种盲识别方法。在码字起点已知的条件下,分析循环码码重分布特点,基于码重分布概率方差识别码长;根据码重分布统计结果选择最佳的码字,求其循环移位后码多项式的公因式,最后通过判决关系识别生成多项式完成循环码的盲识别。仿真实验表明该方法对误码率在10-2时的循环码具有较好的识别效果。     

Optimum threshold for double-dwell DS-SS code acquisition system inPCS channel mode

A method for selecting the optimum threshold for a double-dwell direct-sequence spread-spectrum (DS-SS) code acquisition system in the JTC PCS channel model is presented. A modified expression for the mean acquisition time is derived, along with a set of optimum threshold values. Simulation is performed on VHDL to verify the acquisition system     

双门限自适应调整PN码捕获及其性能分析

基于双重驻留搜索策略提出了一种双门限自适应调整的直接序列扩频伪随机(PN)码捕获方法，并分析了其主要性能。理论分析和计算机仿真结果表明：此方法的性能优于恒虚警概率(CFAR)检验，可以适应通信环境的变化。     

IP码与子网掩码

网际协议（IP）的规范是在1982年由RFC791建立的。这些规范的部分内容规定了IP地址的结构。这个结构为每个主机和路由器接口提供了32位逻辑地址。一个IP地址用0—255之内的4个十进制数表示，数之间用句点分开。这些十进制数中的每一个都代表32位地址的其中8位，即所谓的八位位组。这称为点分表示法。     

An algorithm for calculating the exact bit error probability of a binary linear code over the binary symmetric channel

An efficient algorithm for calculating the ith bit error probability of a binary linear code over the binary symmetric channel (BSC) is presented. It is proved that the exact ith bit error probability of maximum-likelihood (ML) decoding, bounded distance decoding, and symbol-wise maximum a posteriori probability (MAP) decoding can be obtained with time complexity O(n2/sup n-k/), where n and k denote the length and the dimension of the target code. The proposed methods are applicable to any binary linear code with redundancy up to nearly 25-30 bits with a typical personal computer.