Soft-Bit Assisted Iterative AMR-WB Source-Decoding and Turbo-Detection of Channel-Coded Differential Space-Time Spreading Using Sphere Packing Modulation

Jointly optimised iterative source- and channel-decoding is invoked for enhancing the error resilience of the adaptive multi rate wideband (AMR-WB) speech codec. The resultant AMR-WB coded speech signal is protected by recursive systematic convolutional (RSC) codes and transmitted using a sphere packing (SP) aided differential space-time spreading-/(DSTS) assisted transceiver. The performance of the proposed scheme is evaluated when communicating over correlated non-dispersive Rayleigh fading channels. The proposed system exhibits an E_b/N₀ gain of about 1 dB in comparison to the benchmark scheme carrying out joint channel decoding and DSTS aided SP-demodulation, but separate AMR-WB decoding, when using I_out = 4 external iterations.