Modelling the mobile satellite channel for communication system design

In the overall design of a mobile communication network, the propagation channel characteristics must be taken into account in order to develop robust and efficient modulation, multiple access, speech and forward error correction (FEC) coding techniques. Also for any power control system to operate reliably on a mobile satellite link, typical channel information is essential for its design. Adequate technical solutions to these subsystems are significant in terms of cost, capacity and therefore viability of a satellite-based mobile communication system. In general the channel information is grouped into narrowband and wideband characterisation. The two classes in fact refer to the different types of signalling formats involved in propagation measurements, and hence the information extracted from them. The basic information, related to the mobile-satellite channel, and required for the system design is a quantity called the 'propagation link margin'. The propagation link margin is provided in the link budget in order to support adequate link quality under fading conditions and which is estimated to be sufficient to achieve the desired network service availability. Provision of a specific link margin has direct consequences on the space and ground segment design and cost. A review of various channel measurements and models is presented from a systems engineering viewpoint.