Dual satellite path diversity and practical channel management for non-geostationary satellite systems

In non-geostationary satellite systems dual satellite path diversity has been proposed to improve the link quality when the network load is low. The expense is one channel realised for the price of two, as each diversity branch is broadcast through different satellites. This paper discusses how this cost can be reduced when the network reaches congestion. In essence, allocated and engaged diversity branches are regarded as a stand-by resource group available through preemption, such that quality experienced by individual links can be traded for capacity. The reliability of such a mechanism is dependent on the system´s ability to clear a diversity branch, and then re-allocate it for the new connection in a timely fashion. The paper therefore also considers a mechanism suitable for reducing the call set-up delay. The paper concludes that preemption is a suitable mechanism for designing a satellite system with soft degradation that is also robust to channel impairments due to obstruction of the line of sight path between a user and a satellite