The Digital Video Broadcasting Satellite services to Handhelds (DVB-SH) is a hybrid satellite/terrestrial system for the broadcasting of multimedia services to mobile receivers. To mitigate deep signal fading events occurring mainly in the land-mobile satellite channel, a Multi-Protocol-Encapsulation Inter-burst Forward Error Correction (MPE-IFEC) technique has been recently introduced. It is based on a clever organization of data and parities offering long interleaving. Two decoding modes have been proposed: the late decoding mode and the early decoding mode. In this paper, we propose to discuss and to analyse the impact of these decoding strate-gies on the channel change delay, known as the key issue of DVB-SH system. Based on an end-to-end DVB-SH network simulator, two criteria: the channel change delay and the cu-mulative freeze time, are computed by considering different MPE-IFEC parameters and typical DVB-SH propagation environments. These two criteria are sufficient to give us the subjective video quality of the newly joined channel.

This paper presents an enhanced permeable layer mechanism useful for highly robust packetized multimedia transmission. Packet header recovery at various protocol layers using MAP estimation is the cornerstone of the proposed solution. The inherently available intra-layer and inter-layer header correlation proves to be very effective in selecting a reduced set of possible header configurations for further processing. The best candidate is then obtained through soft decoding of CRC protected data and CRC redundancy information itself. Simulation results for WiFi transmission using DBPSK modulated signals over AWGN channels show a substantial (4 to 12 dB) link budget improvement over classical hard decision procedures. We also introduce a sub-optimal and hardware realizable version of the proposed algorithm.

The DVB-SH system relies on a hybrid satellite/terrestrial infrastructure. A complementary solution using the interworking with a bi-directional path offered by cellular network is under investigation in DVB-Convergence of Broadcast and Mobile Services Group. This aims to provide good QoS of DVB-SH service anywhere anytime. Due to the strict reception conditions and the severe satellite channel propagation, many time-sliced bursts are lost impacting negatively the subjective video quality because the new link layer : inter-burst FEC, fails to recover the burst losses even with an adequate coding rate. In this paper, we propose a repair mechanism and a suitable architecture for real-time streaming service error handling. By recovering only some specific lost information of the broadcasted stream, the quality of TV service is improved.