Efficient Repair Mechanism of Real-Time Broadcast Services in Hybrid DVB-SH and Cellular Systems

摘要

In order to ensure good video quality and location-independent access to multimedia content, digital video broadcasting-satellite service to handhelds (DVB-SH) takes advantage of several innovative techniques. The major one is the forward error correction (FEC) scheme implemented at the link layer called multiprotocol encapsulation-inter-burst FEC (MPE-IFEC). MPE-IFEC supports reception in situations of long duration erasure spanning several consecutive time slice bursts (lasting several seconds) due to characteristics of the land mobile satellite channel which are easily hampered by obstacles such as trees, buildings, or overpasses. However, when deep signal fades last for larger durations, the MPE-IFEC correction capacity is insufficient and MPE-IFEC fails, causing a service interruption. In this paper, we propose a repair mechanism and a suitable architecture for real-time streaming service error handling with reduced degrading effects such as picture freeze, video frame degradation, and video lag. Based on an analytical model of the performance of the MPE-IFEC, an iterative algorithm is proposed where the probability of recovery of lost bursts is computed and updated. The proposed algorithm controls the retransmission request on the cellular network. Simulation results show that by recovering only some specific lost bursts via the cellular path, the quality of experience here expressed in terms of burst error rate is improved.