Reliable application layer multicast over combined wired and wireless networks

During the last several years, the Internet has evolved from a wired infrastructure to a hybrid of wired and wireless domains by spreading worldwide interoperability for microwave access (WiMAX), Wi-Fi, and cellular networks. Therefore, there is a growing need to facilitate reliable content delivery over such heterogeneous networks. On the other hand, application layer multicast (ALM) has become a promising approach for streaming media content from a server to a large number of interested nodes. ALM nodes construct a multicast tree and deliver the stream through this tree. However, if a node leaves, it cannot deliver the stream to its descendant nodes. In this case, quality-of-service (QoS) is compromised dramatically. Especially, this problem is exacerbated in wireless networks because of packet errors and handovers. In order to cope with this problem, multiple-tree multicasts have been proposed. However, existing methods fail to deliver contents reliably in combined wired and wireless networks. In this paper, we propose a method to ensure the robustness of node departure, while meeting various bandwidth constraints by using layered multiple description coding (LMDC). Finally, we evaluate the proposed method via extensive simulations by using the network simulator (ns-2). By comparing our proposed method with the existing ones, we demonstrate that our method provides better performance in terms of total throughput, relative delay penalty (RDP), and relative delay variation (RDV). The results indicate that our approach is a more reliable content delivery system when compared with contemporary methods in the context of heterogeneous networks containing wired and wireless environments.