Design of non-systematic turbo codes for universal source controlled channel decoding

Non-systematic turbo codes have a large potential advantage over systematic codes when coding redundant sequences. However, to utilize this potential universally, when sequence statistics are unknown in advance, they need to be properly designed. We consider design criteria for non-systematic turbo codes that can allow universal utilization of redundancy in the encoded messages. We apply these criteria to decoding of independently identically distributed (i.i.d.) nonuniform sequences, and of piecewise stationary memoryless sequences. Simulation results are presented for both classes for rate 1/2 and 1/3 codes. They demonstrate that with proper designs, full (or almost full) utilization of the redundancy can be achieved for these source classes even universally, and the performance with unknown statistics is (almost) as good as that with initially known statistics.