Xavier Henocq

Application of DFT codes for robustness to erasures

Discrete Fourier transform (DFT) codes are used to provide robustness against packet losses in IP networks. First, the relationship between DFT codes and over-complete expansions using frames is established. It is shown that the message recovery by syndrome decoding of erasures and direct signal space projection from received samples are equivalent. The error performance analysis of DFT codes is used to develop packetization criteria in order to guarantee minimum reconstruction error.

TCP-compatible rate control for FGS layered multicast video transmission based on a clustering algorithm

This paper addresses the problem of rate and congestion control for video transmission in large multicast groups. A classification of the receivers is performed according to a predefined similarity measure (e.g. packet loss rate observed or TCP-friendly bandwidth share). The RTCP receiver reports are then filtered accordingly. The classification of receivers done by feedback aggregation agents helps in solving the feedback implosion problem in large multicast groups. The clustering and feedback aggregation mechanisms are coupled with an FGS layered video coding system in which the number of layers as well as their respective rates are adapted dynamically to aggregated feedback. The algorithm has been validated via NS 2 simulations.

Joint source and channel rate control in multicast layered video transmission

Delivering temporally-constrained multimedia streams in heterogeneous environments, offering no guarantee in terms of bandwidth, packet loss, or delay, is a very challenging problem faced today by both the networking and the coding community. Layered coding is often proposed as a solution for rate-based congestion control of video transmission in heterogeneous environments. The problem addressed more specifically here is the design of a responsive mechanism for rate allocation in each layer, that would guarantee the best bandwidth usage for all the receivers. After a review of solutions for congestion and loss control in unicast video communications, the paper describes a rate-based congestion control mechanism for multicast layered video transmission.