Study of two 1/4 turbo codes in non-frequency selective and doppler fading channels

In this paper, we investigate the coding, decoding methods and the performance of two turbo codes with code rate of 1/4 in the 3 ^rd generation HSDPA (high-speed downlink packet access) system. The first way to get a % turbo code is puncturing from a 1/5 turbo code, while the second way is repeating the output bits of a 1/3 turbo code. In the second method, in addition to a bit repeater, an inter-leaver is adopted at transmitter to further spread the distance between two identical bits. At receiver, decoding with diversity processing is proposed. This paper shows, in channels with both AWGN arid Doppler fading, the performance of combining the diversity gain and coding gain in the second method is at least comparable to the performance of the first method with only a higher coding gain. Moreover, the second method has less decoding complexity, which is highly desired since the existing standardized 1/3 turbo codes can be utilized directly with only minor changes at the transmitter and receiver.