A Study On Replication-based Routing Algorithms For Opportunistic Networks

As the increased application and the enlarged scale of wireless networks, it is moreimportant to handle networks'fragmentation and interruption. So it promotes the birthand development of Opportunistic networks. As a new kind of networks, opportunisticnetworks can complete communication when the wireless links are broken or thenetworks are divided, which are different from the traditional single hop and multi hopwireless networks. Even when the end to end path from source to destination does notexist, it can also transmit information smoothly. Thus they are applied in the harsh anddemanding environmental conditions, such as wildlife monitoring, wireless Internetaccess, Interplanetary Internet and vehicle sense information system. Opportunisticnetworks are not only the special network forms but also new challenging techniques innetwork communication. Opportunistic networks are considered as an importantdevelopment direction of mobile ad hoc networks, and they have great significance forubiquitous computing in the future.In this paper, firstly, a survey of opportunistic networks is presented, and the routingalgorithms are classified, introduced, and compared based on their different principles.This paper takes the replication based routing algorithm as the main researching object,and realizes a typical routing algorithm epidemic routing algorithm.In the following, the sensing of the encountered nodes and the packet exchanging inthe epidemic routing algorithm are deeply analysed. It proposes ERBEI, an efficientlow delay routing algorithm based on exchange of increments of packet indexes, ERBEItransmits only the increments of packet indexes in the process of packet exchange, deletesthe packets reaching destinations from nodes'memory, utilizes only the Hello messagesto sense the encountered nodes, and sends the packets approaching their destinationsfirstly, thereby reduces overhead and end to end delay. The algorithm is simulated andcompared with other interrelated algorithms based on OPNET platform. Both theoreticalanalysis and simulation results show that ERBEI outperforms others in the performanceof control overhead, end to end delay, memory overhead and so on.Additionally, this paper studies the impact of the information of network topology onthe epidemic routing algorithm. It proposes LDREN, a low delay routing algorithm basedon exchange of neighborhood information. It exchanges two hop Neighborhood information in the process of packet indexes exchange, and sends the packets approachingtheir destinations last two hops firstly, thus reducing the delay of packets. Moreover, inthe process of sensing encountered nodes, it uses Echo messages to delete the packets thathave reached destinations from nodes'buffer. The OPNET is also used to simulate thealgorithm and compare with other interrelated algorithms. Performance results show thatLDREN is the best in terms of delivery rate, end to end delay, and memory overhead.Finally this paper gives the conclusion and proposes the future research directions ofrouting algorithms for opportunistic networks.