In the context of satellite communications, random access (RA) methods cansignificantly increase throughput and reduce latency over the network. Therecent RA methods are based on multi-user multiple access transmission at thesame time and frequency combined with interference cancellation and iterativedecoding at the receiver. Generally, it is assumed that perfect knowledge ofthe interference is available at the receiver. In practice, the interferenceterm has to be accurately estimated to avoid performance degradation. Severalestimation techniques have been proposed lately in the case of superimposedsignals. In this paper, we present an improved channel estimation techniquethat combines estimation using an autocorrelation based method and theExpectation-Maximization algorithm, and uses Pilot Symbol Assisted Modulationto further improve the performance and achieve optimal interferencecancellation.
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