HandVoD: A Robust and Scalable VoD Solution with Raptor Codes over GPRS/EDGE Network

Considering the high packet losses ,low bandwidth of GPRS/EDGE network and heterogeneity of mobile clients, we present and implement HandVoD: a robust and scalable VoD solution with raptor codes for hand-held devices, like PDAs, smartphones, over GPRS/EDGE network. It´s capable of providing 3GPP compliant end-to-end QoS support for each individual client with enhanced RTSP, RTCP, RTP protocols, priority_based encoding transmission(PET) and unequal error protection by Raptor FEC codes. Considering the high bandwidth jitter and heterogeneity of clients, we develop a PET rate adaptation scheme, which takes advantage of SVC 3-D scalability and RD optimization. To resist the high packet losses and low bandwidth of wireless link, we propose a priority_level based unequal error protection (PUEP) scheme. It uses raptor FEC codes for recovery, and protects unequally based on the NALU´s priority, namely its contribution to overall distortion. The overhead of raptor codes is quite low, compared with other retransmission based schemes, while it provides high recover probability. In addition, it allows on-the-fly encoding, and therefore can co-operate well with our PET rate adaptation mechanism without yielding any meaningless repair symbols. More importantly, an implementation of our system is realized and tested over existing GPRS/EDGE network deployed in China. The test results demonstrate that our system has performance advantage in terms of higher PSNR and lower overhead. Moreover, the clients can get relatively constant visual quality even in case of varying link bit rate, handover or temporal link outage. In addition, the system´s design concepts and results apply to wireless data system in general (i.e. CDMA, UMTS, etc).