MAP译码器嵌入式状态信息存储机制设计

Embedded state metric storage used in MAP decoder implementation

嵌入式状态信息存储机制(ESMS)是一种用于turbo码的MAP译码算法以减少其状态信息对存储器容量需求的方法。对于LOG_MAP译码器,本文提出的ESMS从前向和后向状态信息更新过程中各取一个嵌入式状态信息,并用更新后的状态信息减掉嵌入式状态信息,从而减少对存储器的需求和计算复杂度。在状态信息更新过程中不保存的嵌入式状态的似然比信息通过网格中各状态的相对关系来保持。这样,嵌入式状态信息不用存储,且与用嵌入式状态信息相关的计算也可以省略。嵌入式状态存储机制可以使MAP译码器VLSI实现过程中减小面积和时延。

A method, embedded state metric storage, is used for MAP decoder of turbo codes to reduce the memory requirement of state metrics information calculation. For log MAP decoder, this method includes selecting an embedded metrics from the updated state metric in each direction, forward and reverse, and subtracting the embedded metric from the state metrics. The contribution of an embedded metric during state metric updating and likelihood ratio calculation is embedded in the relationship among the state metrics. Thus, the embedded metric need not be kept in the state metrics memory, and calculation using the embedded metric can be omitted. Therefore, the latency and area in the implementation will be reduced with embedded state metric storage.