The Research On Routing Issues In Wireless Ad Hoc Network

Next Generation telecommunication Network (NGN) requires not only high-speed data delivery at low cost, but also structural flexibility, adaptability and stability. Wireless Ad-hoc Network is an infrastructure-free, self-reconfigurable multi-hop wireless network. Different from other traditional wireless network, it can support temporarily-organizing, dynamic topology and computation capability of each node is limited. Therefore, Wireless Ad-hoc Network should be the right data delivery solution for a group of nodes scattered in a certain area, in which each node may reach some other nodes but not all nodes via wireless communication. Within Wireless Ad-hoc Network, considering limited wireless communication radius, normally data delivery between a pair of nodes may have to be done by means of multi-hop forwarding and as a result, routing protocol is the key player for data delivery. However, because of the characteristics of Wireless Ad-hoc Network, traditional routing protocol can not be applied to achieve expected performance. Therefore, routing protocols become hot topics. Although now there are some achievements, they have various limitations and only apply to specific scenarios. More research should be done for more generic and comprehensive routing solutions.This paper analyzes and summarizes Wireless Sensor Network (WSN), Vehicular Ad hoc Network (VANET) and Opportunistic Network, evolved from Mobile Ad Hoc Network (MANET) recent years systematically and comprehensively. Based on the result as well as the characteristics of Wireless Ad-hoc Network, dedicated research has been done on more generic and efficient routing protocols for Wireless Ad hoc Network and three novel solutions have been proposed:SICR for WSN data collection, MDA for VANET data delivery and PICD for Opportunistic Network data delivery. Here are details for these three routing protocols as follows:1. Based on both Self-Organised Mapping (SOM) and Immunity Clonal Selection algorithm, this dissertation proposes a novel clustering routing solution SOM and Immune Clonal Selection Based Clustering Routing Scheme for Wireless Sensor Networks (SICR) for data collection in WSN. There are two phases in SICR:clustering and maintenance. Unlike existing research, during clustering phase, SICR takes key factors such as node density, residual energy and distance to the sink into account. Based on self-mapping theorem, SICR adopts an innovative cluster head competition algorithm to establish energy consumption-balanced cluster structure. This structure can be effectively applied to heterogeneous energy scenario. Meanwhile, in order to reduce the reconstruction cost, self-adaptive mechanism has been introduced to maintenance phase:cluster head estimates current stability of the cluster based on each node's residual energy and then adjusts cluster size accordingly to maintain the stability. Routing scheme can be divided into intra-cluster and inter-cluster communication: intra-cluster communication should be done based on topology inside the cluster while inter-cluster communication should be done based the minimum spanning tree, constructed by clone-selection algorithm. Simulation shows that, compared with several existing algorithms, SICR can lead to more balanced energy consumption among nodes and prolonged network life.2. The dissertation proposes a novel data delivery solution:Mobile Distribution-Aware Data Dissemination (MDA) based Publish/Subscribe mechanism for VANET. MDA takes advantage of VANET'self-organization and self-stabilization: firstly, establish appropriate Publish/Subscribe model for the VANET; then, predict the subscribers'distribution by calculating the delivery probabilities between vehicles and corresponding mobile subscribers; thirdly, based on the predicted subscribers' distribution, adjust notification token's real-time deployment and schedule the token forwarding to achieve effective distribution of notification brokers(notification-token holder) in the VANET and thus ensure efficient data delivery accordingly. Compared with existing solutions, a novel heuristic algorithm is introduced to alter notification broker distribution dynamically to adapt to real-time node topology in this VANET. Furthermore, MDA adopts an effective notification token control algorithm based on probability prediction density:dynamically adjust the number of notification tokens to control the number of notification broker. As a result, MDA can also reduce overall network load of VANET by restricting the occurrences of broadcasting. Simulation results based on a real city map and realistic traffic situations show that the MDA performs much better in terms of delivery ratio and delay with less network load over other solutions. 3. The dissertation proposes an innovative data delivery solution Periodic Intermittently Connected-Based Data Delivery in Opportunistic Networks (PICD) for Opportunistic Network. By effectively utilizing periodic intermittent connectivity between any two nodes, PICD can lead to better data delivery:Firstly, for a certain node, based on its periodic intermittently-connected paths to the sink and its data delay tolerance, PICD establishes its delay probability model by means of random dynamic programming. Then, PICD will calculate the node's periodic delay probability distribution matrix within a certain cycle by multi-hop based function space iteration. Next, according to the node's delay probability distribution matrix, current data delivery probability for a certain data within its tolerable delay can be calculated by specifying current cycle and the tolerable delay and this will become key-player of next-hop choosing. In brief, this probability forwarding mechanism is delay-relevant and can increase data delivery probability within tolerable delay. Simulation shows that compared with existing algorithms, which only take advantages of single-hop delivery probability, PICD can lead to better data delivery and lower delay.