Reduced Complexity Iterative Multi-user Detector for IDMA-based Satellite Communication System

Interleave-Division Multiple Access (IDMA) is a multi-user scheme, in which user-specific interleavers are the only means for user separation. Its receiver involves a chip-by-chip iterative multi-user detector (MUD). In IDMA-based satellite systems, due to the high distance from the satellite to the ground and the large coverage area, the distances between the user ends (UEs) and the satellites are greatly different, which will cause serious asynchronous transmission. In this case, the complexity of MUD is approximately linear with the square of the maximum of users chip delays. Some simplified algorithms were proposed, such as the Simplified Gaussian Chip Detector (sGCD), the MUD with Probabilistic Data Association (PDA) algorithm and the simplified ESE algorithms. But these algorithms are all based on the assumption that the IDMA system is synchronous (without users chip delays). In this paper, two novel reduced complexity MUDs, based on the simplified ESE algorithms and the PDA algorithm, will be proposed for the asynchronous IDMA. We compare the performance of our detectors with the sGCD, the MUD with PDA algorithm and tow simplified ESE algorithms, in terms of Bit Error Rate (BER) and complexity with respect to the number of operations of these detectors for (Additive White Gaussian Noise) AWGN channel. The proposed detectors presents the effective trade-off between performance and complexity. Simulation results show that the proposed detectors have better BER performance than simplified ESE algorithms. Further, results show that one of our detectors outperforms the sGCD when large users chip delays exist in a satellite communication system.