Prioritization-based Layered Multicast for Fixed/Mobile Networks with Fast Convergence and Inter-Session Fairness

Abstract

Multimedia streaming services are becoming popular in both wired and wireless networks. Layered multicast is a widely accepted approach for streaming multimedia data to a large number of users. Existing layered multicast approaches do not interact well with network dynamics. Indeed, upon a change in network conditions, they require a long time till they can appropriately adjust their data transmission rate. Additionally, they do not achieve fairness when users from different sessions share the bandwidth of a bottleneck link. In this paper, we propose a scheme that allows newly-arriving users to promptly converge their data transmission rates to the most optimal rate that best suit the current conditions of the network without degrading the system fairness. The proposed scheme is based on the fact that layered multicast uses prioritybased packet dropping policies. In the proposed scheme, two newly-defined packet messages are considered: “low priority join” and “normal join” messages. To join a session, a user first subscribes to all corresponding layers by issuing “low priority join” messages. It then computes packet drops experienced on each layer. If packets of a given layer experience a drop rate higher than a predetermined threshold, the user leaves that layer and all higher layers. The user then “officially” joins the remaining layers by transmitting “normal join” messages. This operation helps users to subscrive to only layers whose aggregate bandwidth fits the current network conditions. The performance of the proposed scheme is evaluated through computer simulations and is compared against the Receiverdriven Layered Multicast (RLM) scheme. The results show that the proposed scheme achieves appropriate bandwidth utilization from the start of the session. The results demonstrate also that the proposed scheme is effective in managing handover in mobile networks and achieves better Quality of Service (QoS) in heterogeneous mobile environments.

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