Channel Estimation for a Multi-User System with Iterative Interference Cancelation

To allow multiple-access between small earth terminals and a satellite hub in a fully unsynchronized manner, the authors present a hub receiver which uses iterative interference cancelation on the physical-layer to separate the traffic. Instead of approaches like Contention Resolution Diversity Slotted ALOHA, which operates on the data-link layer, the receiver presented allows for interference cancelation within one time slot. While the general structure of the hub receiver was already introduced in [7] and [8], the estimation and equalization of channel impairments like sampling-clock offsets as well as carrier frequency offsets are targeted here. The system model is introduced briefly and channel estimation and equalization approaches are presented. For channel estimation the authors recommend a correlation-based channel tap estimator which uses the preamble as well as received and corrected data as pilots for better channel estimation in subsequent iterations. To equalize channel impairments two kinds of single-tap equalizers are investigated. The impact of the estimation and equalization approaches on the bit error rate performance of the system in comparison to previous investigated scenarios where the channel was assumed known are studied [8].