Research On Fountain Encoding-based Multicast Routing Mechanisms For Opportunistic Networks

There is no central node and fixed infrastructure in MANETs(Mobile Ad-hoc Networks), where nodes transmit data through the end-to-end path. However, the low node density, unpredictable node mobility and other factors in practical applications lead to the intermittently connected network, which consumes massive network resources to recover and reconstruct routes. Targeting at the communication requirements in this special environment, researchers proposed the architecture of opportunistic networks. Different from MANETs, the “store-carry-forward” mode and communication opportunities between nodes are exploited for the data forwarding in opportunistic networks. And the flexible communication means of opportunistic networks have facilitated the development of opportunistic networks.In many communication scenarios, data have to be transmitted to a group of nodes in opportunistic networks, namely the multicast communication. Due to the intermittent network connectivity, traditional multicast routing mechanisms are not suitable for opportunistic networks. In order to achieve the reliable multicast communication in opportunistic networks, this thesis is intended to study the multicast routing mechanisms in opportunistic networks.Firstly, the basic concepts, characteristics, typical application scenarios and current hot spots of opportunistic networks are introduced. Then the presentation of multicast communication in opportunistic networks and the characteristics of existing multicast routing mechanisms are provided minutely. Finally, the summary is given at the end of this chapter.Secondly, the relationship between nodes is studied in this thesis, and combined with fountain codes, a social relation-aware multicast routing mechanism for opportunistic networks is proposed. The relationship between nodes and data forwarding capability of node can be learned from the running state of nodes for a reasonable relay node selection. Besides, redundancy detection is proposed to reduce the unnecessary data forwarding based on the characteristic of fountain codes. The simulation results show that the proposed mechanism can achieve high delivery ratio with low network overhead.Next, an optimal matching multicast routing mechanism with controlled code rate is proposed to balance the loads between nodes. Based on the connectivity degree, service degree and diffusion degree, the forwarding utility of node can be obtained. And to involve as many useful nodes as possible in the multicast communication, the optimal matching algorithm is utilized to select relay nodes. Furthermore the code rate can be controlled according to the multicast communication capacity. The simulation results show that the proposed mechanism can achieve the higher communication efficiency by balancing the node forwarding load.Finally, the research works are concluded and the future works are presented.