Peer-to-peer Communications to Prevent Broadcast Diffusion from Feedback Implosion

Nowadays low cost UMTS and soon HSDPA network developments lead to an increase in multimedia broadcasted services. The new standard for broadcast over mobiles, DVB-H, needs service reliability. This issue is tricky, because in a broadcast transmission, the sender may not be able to receive all acknowledgements from all users like in TCP. In this paper, we evaluate the performance and benefits of using a separate return channel for quality of service control of a broadcast diffusion. Peer-to-peer links between the receivers are used in order to allow diffusion of the information losses with low risk of feedback implosion on the central server. Index Terms—Video broadcast, DVB-H, UMTS, Peer-to-peer networks, Quality of Service, Service reliability, Mobility. I. INTRODUCTION ulticast over IP packet-switched networks become more and more commonly used. The algorithm described here can be used to diffuse a lot of data types, especially multimedia contents, with a guaranty of quality of service. The standard which will probably get the largest market share is DVB-H, a special adaptation of the DVB broadcast systems for broadcasting content on handset terminals. It is a video- broadcasting standard, but it uses IP encapsulation. It is difficult to ensure a given quality of service over such diffusion systems, because there is no return channel basically designed in these standards. When diffusing by broadcast, it may be useful for the sender to receive a feedback from the receiver, in order to evaluate the quality of the transmission. This requires that a return channel is capable of carrying the feedback from the user to the sender. It is possible to use a mobile data channel, like 3G mobile, but if there is no mechanism to prevent feedback implosion, a feedback implosion may happen on the central server in case of peaks of losses. The algorithm proposed here uses peer-to-peer communications between the receivers in order to prevent feedback implosion: when a user notes a loss, he waits for a random delay before reporting the loss to the server and saying to his neighbours that this loss has been reported, in order to allow them not to send a message to the server.