Irregular repetition slotted ALOHA with multiuser detection

Abstract

Irregular repetition slotted ALOHA is a random access scheme where users transmit multiple copies of a packet to the receiver to provide time-domain diversity; then, the receiver attempts to iteratively decode packets and cancel their interference contribution in other time slots, increasing the chance of resolving collisions and decoding more packets. This scheme was shown to support larger system loads compared to conventional slotted ALOHA. In the original scheme, collision resolution between l colliding packets is possible only when l - 1 of those packets are decoded in prior iterations, which is probable because of the other copies of each packet transmitted in other slots. However, although asymptotic analysis promises high efficiency of this scheme, the analysis relies on the large number of slots participating in the iterative collision resolution, which requires large receiver complexity and introduces delay. In this paper, we study this scheme for receivers capable of decoding multiple colliding packets jointly, which increases the chance of decoding more packets under large system loads. Asymptotic analysis for this generalized model is provided and it is shown by simulations that a multiuser detector supports larger loads for low number of slots jointly processed.