共查询到20条相似文献,搜索用时 125 毫秒
1.
MD5加密算法的研究及应用 总被引:3,自引:0,他引:3
针对当前网站建设和系统开发中用户信息等重要数据的安全问题,提出了一种MD5加密算法,可以对用户密码进行加密。MD5加密算法是一种比较常用的单向加密算法,通过对该算法的深入研究,介绍了MD5算法的特性、算法原理及其算法流程,并给出MD5算法在一个具体系统中的实际应用,得出MD5算法是一种非常安全和易用的加密算法。 相似文献
2.
误码掩盖是在无线信道进行低速率视频传输的一种抗误码技术。本文在比较和分析了现有几种误码掩盖方法优劣势后,提出了一种混合误码掩盖法。该算法在没有过多增加解码端运算复杂度的同时,大大提高了恢复图像的质量。 相似文献
3.
4.
5.
为解决传统H.264时域误码掩盖算法中丢失块的相邻运动矢量在无线环境下极易丢失的问题,结合部分误码掩盖算法研究成果,提出了一种利用相邻参考帧和丢失块相邻运动矢量,运用投影加权的方法估计出最优丢失块运动矢量用于误码补偿的改进误码掩盖算法.实验证明,运用改进算法掩盖后的图像质量有所提高,并且抑制了误码的错误积累和扩散,具有一定实际应用意义. 相似文献
6.
LZ算法在文本压缩领域应用广泛。LZ译码以先前接收码字的译码结果形成字典,后续译码依赖于先前的重构数据,一旦压缩码字出现误码将会引起严重的误码扩散。分析了主流的LZ77算法编译码原理,讨论了输入误码对译码字典和解压数据的影响,研究了误码传播问题。在此基础上提出一种用于文本压缩数据的容错译码算法,指出容错处理对抑制误码传播及保证LZ77解压数据的完整性具有重要意义。 相似文献
7.
本文主要讨论DES加密算法和RSA算法两大加密算法类中的两个算法的性能比较和改进,以决定用哪一种算法作为本VoIP系统的加密算法的基础算法。 相似文献
8.
一种防误码的自适应预测算法及其应用 总被引:1,自引:0,他引:1
本文给出了一种能防误码的自适应预测算法——防误码简化符号相关梯度算法.该算法是从研究自适应差分编码(ADPCM)系统导出的.本文对该算法进行了详细的理论推导及证明,并对该算法的防误码特性以及应用在ADPCM系统中存在的问题进行了讨论.最后给出了计算机模拟结果. 相似文献
9.
本文主要讨论DES加密算法和RSA算法两大加密算法类中的两个算法的性能比较和改进,以决定用哪一种算法作为本VolP系统的加密算法的基础算法。 相似文献
10.
11.
针对范德蒙阵列纠删码算法,介绍了纠删码编译码过程,重点论述了范德蒙码编码算法和译码算法,提出了适合在嵌入式系统实现时的快速算法;在Matlab软件中构建了数字卫星广播系统(DVB-S)模型并进行了信道误码分布仿真,获得了DVB-S系统的误码分布,分析了在系统中使用范德蒙纠删码的可行性;提出了纠删码与系统中的纠错码级联使用模型,并对算法的纠错性能进行仿真,仿真结果表明级联模型能大大提高无线传输系统的可靠性。 相似文献
12.
13.
A robust error control coding system is presented. This system is a cascaded FEC (forward error control) scheme supported by parity retransmissions for further error correction in the erroneous data words. The error performance and throughput efficiency of the system are analyzed. Two specific examples of the error control system are studied. The first example does not use an inner code, and the outer code, which is not interleaved, is a shortened code of the NASA standard RS code over GF(28). The second example, as proposed for NASA uses the same shortened RS code as the base outer code C2, except that it is interleaved to a depth of 2. It is shown that both examples provide high reliability and throughput efficiency even for high channel bit-error rates in the range of 10-2 相似文献
14.
15.
以光存储应用为背景,针对盘片记录信息固有的高原生误码率问题,从目前CD,DVD的纠错编码方案出发,设计并实现一种合适的差错控制方法来保证数据读写的正确性。分析了实现Reed Solomon(RS)纠错编码的Berlekamp Massey(BM)算法和Peterson Gorentstein-Zierler(PGZ)算法的原理和各自的实现途径,比较了这两种算法的优缺点,得出了它们的不同应用条件。采用高速硬件描述语言(VHDL)成功实现了PGZ算法,并得到了理想的仿真结果。 相似文献
16.
17.
El-Khamy M. Jilei Hou Bhushan N. 《Selected Areas in Communications, IEEE Journal on》2009,27(6):965-973
In this paper, families of rate-compatible protograph-based LDPC codes that are suitable for incrementalredundancy hybrid ARQ applications are constructed. A systematic technique to construct low-rate base codes from a higher rate code is presented. The base codes are designed to be robust against erasures while having a good performance on error channels. A progressive node puncturing algorithm is devised to construct a family of higher rate codes from the base code. The performance of this puncturing algorithm is compared to other puncturing schemes. Using the techniques in this paper, one can construct a rate-compatible family of codes with rates ranging from 0.1 to 0.9 that are within 1 dB from the channel capacity and have good error floors. 相似文献
18.
Error-resilient image and video transmission over the Internet using unequal error protection 总被引:1,自引:0,他引:1
This paper presents a new bit-plane-wise unequal error protection algorithm for progressive bitstreams transmitted over lossy networks. The proposed algorithm protects a compressed embedded bitstream generated by a 3-D SPIHT algorithm by assigning an unequal amount of forward error correction (FEC) to each bit-plane. The proposed algorithm reduces the amount of side information needed to send the size of each code to the decoder by limiting the number of quality levels to the number of bit-planes to be sent while providing a graceful degradation of picture quality as packet losses increase. We also apply our proposed algorithm to transmission of JPEG 2000 coded images over the Internet. To get additional error-resilience at high packet loss rates, we extend our algorithm to multiple-substream unequal error protection. Simulation results show that the proposed algorithm is simple, fast and robust in hostile network conditions and, therefore, can provide reasonable picture quality for video applications under varying network conditions. 相似文献
19.
Joint spatial-frequency blind multiuser detection based on LCCMA 总被引:1,自引:0,他引:1
ZHAO Fa-yong FENG Guang-zeng Department of Communication Information Engineering Nanjing University of Posts Telecommunications Nanjing China 《中国邮电高校学报(英文版)》2007,14(2):19-22
Multicarrier code division multiple access (MC-CDMA) has the ability to combat with frequency selective fading and antenna array can enhance the performance of system. The paper proposes a novel joint spatial-frequency blind multiuser detection for antenna array MC-CDMA based on linear constraint constant modulation algorithm (LCCMA), which has robust performance and can ensue the weight vectors to converge to that of the desired user. Simulation indicates the proposed algorithm has better bit error ratio (BER) performance than that of the traditional beamforming-based two-step algorithm. 相似文献
20.
本文分析了JPEG压缩中的DCT变换和量化过程,根据量化的特性提出了一种半脆弱水印方案,并将水印信息调制为纠错码嵌入JPEG压缩过程的量化系数中,实验证明,此水印方案鲁棒性较强,虚警率低,能较好的检测图像是否被篡改并对篡改定位。 相似文献