Application-layer FEC erasure codes and cellular multicast/broadcast

Speaker: Dr Michael Luby , Digital Fountain.


There has recently been and continues to be a large amount of work in cellular commercial standards that is focused on multimedia delivery using broadcast and multicast channels. The reasons for these standardization efforts are self-evident: while cellular services become ever more popular and as cellular multimedia applications grow richer, the available bandwidth for delivering these services remains fairly limited, and thus broadcast/multicast delivery is the only viable solution operators see to this obvious revenue-threatening bottleneck. Examples of such commercial standardization efforts include 3GPP MBMS, DVB-H IPDatacast, 3GPP2 BCMCS and DMB. One of the primary challenges in using broadcast/multicast channels for delivering multimedia is to provide a reliable solution that efficiently uses the channel. For cellular unicast delivery, there are a number of methods to assure reliability and efficiency, including automatic modulation and error-correction adjustments at the physical layer, automatic retransmission of lost radio packets, and automatic adjustments of transmit power, all based on continual feedback from each individual receiver.

For cellular broadcast/multicast delivery, none of these methods are applicable, and the primary method of providing reliability instead is the use of application-layer FEC codes. In this talk we describe some of the broadcast/multicast services to be offered and specifically how application-layer FEC codes provide reliability and channel efficiency for each of the services. We also describe in some detail Raptor R10, the application-layer FEC code that has been chosen by 3GPP MBMS and DVB-H IPDatacast, and that is under consideration in all of the remaining cellular standards that have not yet made a selection.

Full presentation