Fixed-point turbo decoder implementation suitable for embedded applications

Real-time decoders for turbo codes used in practical applications such as in the WCDMA (UMTS) 3GPP cellular standard are likely to be implemented using fixed-point arithmetic. Requirements for efficient turbo decoders include low-complexity algorithms and small word sizes. The implementation of such a decoder using a modified constant-Log-MAP decoding algorithm is described here. Simulation results demonstrate that the architectural decisions affecting this design lead to a BER performance that is within 0.1 dB of the performance of the baseline floating-point log-MAP algorithm. The low hardware cost offered by fixed-point turbo decoders make them suitable for use in embedded applications.