Near-Optimal Multiuser Detection in Asynchronous MC-CDMA via the Ant Colony Approach

In this paper, we present a novel multiuser detection (MUD) structure for asynchronous multi-carrier code division multiple access (MC-CDMA) systems. Previously proposed MUDs assume a desired user while performing joint demodulation. As a result, multiple runs of the demodulation process become necessary to obtain all users' information. In this paper, we present a MUD structure that detects all users' symbols simultaneously in one run. The proposed structure is based on extending the integration time at the receiver to capture the energy scattered in two consecutive symbol durations. We derive the optimal receiver structure and implement it using a low-complexity ant colony optimization (ACO) approach. The proposed ACO-MUD is based on the cooperative foraging strategy of real ants and is shown to converge to the optimal MUD BER performance in relatively few iterations with a 97.7% saving in complexity over an exhaustive search technique