Efficient Interlayer Network Codes for Fair Layered Multicast Streaming

Multilayer video streaming allows to provide different video qualities to a group of multicast receivers with heterogeneous receive rates. The number of layers received (and thus the receive rate) determines the quality of the decoded video stream. For such layered multicast streaming, network coding provides higher capacity than multicast routing. Network coding can be performed within a layer or across layers, and in general, interlayer coding outperforms intralayer coding. An optimal solution to a network-coded layered multicast problem may require decoding of the network code at interior nodes to extract information to be forwarded. However, decoding consumes resources and introduces delay, which is particularly undesirable at interior nodes (the routers) of the network. In this paper, we thus focus on the interlayer network coding problem without decoding at interior nodes. We show that the problem is NP-hard and propose a heuristic algorithm for rate allocation and coding based on the Edmonds-Karp maximum flow algorithm. We prove that our algorithm ensures decodability of the information received and provides some fairness properties. Finally, we perform extensive simulations and show that our algorithm may even outperform other heuristics that do require decoding at interior nodes.