Abstract
Turbo coding is investigated for uninterleaved and partially interleaved Rayleigh fading channels. It is compared to ordinary convolutional coding with the same rate and memory 2, 4 and 8 best d/sub free/ encoders. When turbo frames are very long, turbo coding with a channel interleaver gets better bit error rates (BER) than ordinary convolutional coding with a channel interleaver. When the frames are shorter, lower complexity convolutional coding is as good as turbo coding. It is shown by experiment that only after a certain critical frame size does turbo coding get better BER than convolutional coding and the length of this threshold is linearly dependent on the inverse of the fading bandwidth, 1/BT. The effect of the constituent encoders on the error performance is also tested. Memory 2, 4 and 6 constituent encoders are compared. For short to moderate turbo frame size, the memory 2 constituent encoder is as good as the memory 4 and better than the memory 6 encoder. For very long block-lengths, the memory 4 encoder is the best. The memory 6 encoder is always the worst.
Published Version
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