Non-linear Turbo Codes for Interleaver-Division Multiple Access on the OR Channel

This paper presents an Interleaver-Division Multiple Access (IDMA) based architecture with single-user decoding using parallel concatenated non-linear trellis codes (PC-NLTCs). These PC-NLTCs are designed specifically for the Z-Channel that arises in a multiple-user OR channel when each user treats the other users as noise. Over the OR Multiple Access Channel (OR-MAC) single-user decoding permits operation at about 70% of the full multiple access channel sum capacity. In order to reach the sum capacity of the OR-MAC, these codes employ a ones density of much less than 50%. A union bound technique that predicts the performance of these codes under Maximum-Likelihood (ML) decoding is presented. The uniform interleaver analysis presented in this paper can be applied to any asymmetric channel, as long as an additive distance can be defined. Results for different numbers of users and a sum-rate of 60% are presented.