Fast Header Decoding Using Turbo Codes on Rayleigh Fading Channels

In this paper we present a modification of a typical turbo code to allow for the header bits to be decoded much faster than the other bits. This gives the decoder a possibility to discard data packets not addressed to it, and saves time and power since fewer iterations need to be performed to reliably decode the header. The proposed algorithm frequently terminates the first trellis of the turbo encoder by inserting tail bits into the data sequence. The bits surrounding the termination sequences have much lower bit error rate and higher reliability than the other bits and can be used to store header information. Moreover, a tailored interleaver and puncturer design can increase the reliability of the header decoding even further. The algorithm is shown to decode the header bits at bit error rate of approximately 0.002 (at Eb/N0=3dB) after only one iteration. In addition, the proposed algorithm has lower memory requirements than the non-modified turbo decoding algorithm.