Method and apparatus for detecting a packet error in a wireless communications system with minimum overhead using embedded error detection capability of turbo code

摘要

The need for separate CRC bits is eliminated by taking advantage of what has been determined to be an embedded error detection capability in a turbo code itself to perform error detection following turbo decoding. Specifically, since the two constituent encoders of a turbo encoder that are used to encode a data packet produce two systematic codes that share the same systematic bits one code, one is used to serve as the parity check for the other. The sign of the log likelihood ratio (LLR) of each systematic bit in a block of decoded data calculated at the end of a turbo decoding cycle is compared with the sign of the LLR of each corresponding bit that was calculated at a previous turbo decoding cycle. If the signs of the LLRs for each comparison do not agree, then a packet error is determined to have occurred; otherwise no packet error is detected.