级联卷积码的性能评估

Performance Evaluation of the Concatenated Convolutional Codes

本文给出了三个采用卷积码的数字通信系统 ,并对其性能进行了评估 .其中两个系统采用了用两个短的卷积码进行级联的方式 (称为级联系统 ) .而另一个则是现在普遍使用的卷积编码方式 ,它采用一个长的卷积码 (称为基联系统 ) ,三个系统的编码效率和约束长度分别采用R =2 / 3和K =3 ,R =3 / 4和K =2 ,以及R =1/ 2和K =7.前两个系统在Viterbi译码器进行硬件判决之前采用了软判决 .两个级联系统中最为突出的特点是它们的译码器的复杂程度被大大降低 ,整个系统的复杂程度比基联系统改变了 2 5 %到 5 0 % .

Three systems using a concatenation of two short convolutional codes in place of a single long convolutional code are proposed and evaluated. Specifically, the systems use a R=2/3 with K=3, R=3/4 with K=2 and R=1/2 with K=7 code. The first two systems employ a soft decision followed by a hard decision Viterbi decoder. The most attractive feature of these systems is the reduction in the complexity of the decoders, and hence the complexity of the entire system, that varies from 25% to 50% of that of the baseline system.