A low-complexity superorthogonal turbo-code for CDMA applications

Turbo-codes are parallel concatenated convolutional codes (PCCC) whose performance in an AWGN channel has been shown to be near the Shannon limit. We describe a low rate superorthogonal turbo-code that outperforms the ordinary turbo-code at the expense of bandwidth expansion both in AWGN and especially in fading channels. Thus superorthogonal turbo-codes are suited mainly for e.g. CDMA applications. We concisely describe the soft output Viterbi (1995) algorithm using a priori inputs (APRI-SOVA) with connection to optimal maximum a posteriori (MAP) symbol estimation. Simulation results in AWGN and fading channels are also presented.

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