不等长信源的符号约束MAP联合译码算法  

Symbol-constrained joint source-channel MAP decoding of VLCs

作　　者：周丹丹[1] 邹艳[1] 陆佩忠[1] 

机构地区：[1]复旦大学计算机科学与工程系,上海200433

出　　处：《计算机工程与应用》2008年第6期39-41,61,共4页Computer Engineering and Applications

基　　金：国家自然科学基金(the National Natural Science Foundation of Chinaunder Grant No.90204013)。

摘　　要：由于不等长编码信源(VLCs)所固有的易于误码扩散的弱点,传统的纠错编码并不能高效地解决其差错控制问题。提出了一种新的针对不等长编码信源的符号约束MAP联合译码算法,利用VLCs双树信源的构造方法,有效地抑制了VLCs的错误扩散;同时,通过将"符号约束"的思想应用于最大后验概率(MAP)译码算法,不仅充分利用了信源先验信息,而且极大地降低了误符号率。实验结果表明,在误符号率为1%时,对于在高斯加性白噪声(AWGN)信道传输情况下的JPEG信源,提出的算法比传统的"比特约束"MAP译码算法有将近0.8dB的性能增益。Since Variable-Length Codes （VLCs） are inherently vulnerable to channel errors,traditional error-correcting codes are unable to solve the propagation-error problem efficiently.A new symbol-constrained joint source-channel decoding algorithm for VLCs is presented.By constructing double-tree VLCs sources,the propagation-error problem is evidently alleviated.Meanwhile,by applying symbol-constrained method to MAP algorithm,not only the a priori probability of VLCs sources is efficiently utilized,but also the Symbol Error Rate （SER） is reduced enormously.Compared with traditionally bit-constrained MAP algorithm,simulation results demonstrate that for JPEG source over AWGN channels,the gain in SNR of the method is around 0.8dB when SER reaches 1%.

关 键 词：联合译码 不等长编码 符号约束 MAP译码 

分 类 号：TP39[自动化与计算机技术—计算机应用技术]