Joint control of delay and packet drop rate in satellite systems using network coding

Abstract

Mobile terminals communicating through satellite suffer from low channel quality due to the combination of slow and fast fading and limited battery power. Moreover, the advanced applications proliferating over such terminals forbids the use of feedback based packet retransmission schemes over satellite due to their high latency, exceeding three times the round trip time. These feedback based packet retransmission schemes also suffer from large throughput degradations to reduce packet drop rates, especially for the large receiver population. In this paper, we propose a joint delay and packet drop rate control protocol over lossy mobile satellite channels using network coding. The suggested protocol employs random network coding at the mobile terminals, within and across different sessions, to generate efficient proactive retransmission packets, without prior knowledge of lost packets at the different users. It also allows the satellite to transmit random network coding combinations of all received packets, to fill the gaps left by packet losses on the uplink channel. By adjusting the timing of these network coded transmissions, the protocol can control packet recovery at any desired delay above one round trip time. The protocol can also control the packet drop rate level by adjusting the network coding rate. The protocol is able to achieve these gains at a much higher system throughput compared to conventional ARQ protocols. Moreover, the protocol do not suffer from the lack of throughput scalability for larger user populations.