Analysis and verification of iterative estimation for joint random access satellite communications

Abstract

This paper investigates practical issues associated with ensuring high throughput in the random access satellite environment. In such situations it is typical for a large number of un-coordinated, mobile, low-cost, earth-based transmitters scattered over a large geographic area to connect intermittently to a single receiver over the satellite channel. This configuration fundamentally results in a random access scenario, where a large number of potential users contend for access to limited channel resources. Complexity is increased due to the geographic spread and localized weather effects which causes each user have its own independent channel that must be estimated to ensure a high level of system performance. This concept was explored previously, where joint detection and multiple packet reception (MPR) techniques were applied to show that it is theoretically possible to surpass the capacity of the current single-user random access channel. This was accomplished through adaptation of the concept of generalized modulation and the use of iterative estimation techniques to determine the channel response of each user. However, these results make a number of simplifying assumptions regarding the waveform processing required at the receiver. Under realistic conditions the proposed receiver is shown to be capable of surpassing the state of the art in satellite random access and achieve a system load of up to 2 bits/s/Hz in the high SNR region.