An Optimal Asynchronous IDMA Receiver

In this paper we develop an optimal receiver for an asynchronous IDMA system. A super-block structure is used to formulate the band diagonal matrix model for asynchronous IDMA. We show that the cost function for the ML decoder can be viewed as a path metric through a structured trellis. We use a dynamic programming algorithm to find the maximum likelihood transmitted bit sequence. We compare the performance of the optimal receiver with the conventional iterative receiver. Our results show that the optimal asynchronous IDMA receiver outperforms the iterative IDMA receiver for the IDMA systems with small block sizes that we simulated.