Pre-detection Combining of Small Satellite Downlink's Replicas

Abstract

This study contributes to the reception quality improvement of small satellites' signals. Traditionally, the data from a satellite is downloaded through single radio link to the related steerable ground station. This single communication is problematic as it is highly exposed to outages when the channel is deeply affecting the signal or when the steering engine fails. Instead, this paper proposes a terrestrial solution by combining multiple raw replicas of the same downlink received by separate multiple receiving sites. The individual stations are networked to collect multiple raw versions and send them to a virtual ground station for processing and combining. The suggested receive-diversity combining of the raw symbols is promising to improve the performance of the ground stations and reduce the probability of singular site failures. The proposed receive diversity scheme offers the replacement of the conventional expensive steerable antenna by much affordable omnidirectional antenna where the diversity gain compensates the lesser antenna gain. To achieve this diversity payoff, a simple yet efficient pre-detection combining algorithm is also developed in this article. The results show that the diversity mode, under different testing scenarios, can achieve lesser bit error rate (BER) than every other BER in the network. Furthermore, the cooperative reception scheme reduces system outages and exhibits to track more than a satellite at once.