Design of an Adaptive Communication System for Implementation on Board a Future Algerian LEO Satellite

Abstract

Understanding of the physical communications environment from low Earth orbits is the key to the successful implementation of the communications system. This already complex environment is further complicated by the constraints of the microsatellite platform. The small, low mass platform offers limited downlink power and a small antenna envelope and ground plane. This affects the performance of both uplink and downlink in the fading LEO environment. The 'little LEO' satellite systems must be designed to operate in the presence of this environment. The concept of adaptivity is of paramount importance in the design of future LEO satellite communication systems, in which a careful exploitation of the limited available resources (bandwidth, power, etc.) is required. An adaptive system, that can increase the rate of data transmission is desired. This system should be capable of changing its rate in response to the current signal conditions. An adaptive modulation scheme, which uses different constellation patterns with multi-level Turbo-coded modulation is proposed to be implemented on board the future Algerian Microsatellite. Basic concepts are highlighted and an overview of the achieved results is presented. The system is tested under AWGN noise and Rayleigh fading conditions. The system is found to provide good performance in AWGN and moderate fading conditions.