Research On Load-Balance Based Key Technologies And Algorithms For Ad Hoc Networks

The mobile ad-hoc network, which is quick deployable and self-organized, plays a critical role in places where a wired backbone is neither available nor economical to build, such as tactical battlefield, civilian emergency communication, and so on. Due to its special operation mode, many protocols used in networks with pre-configured and centrally controlled infrastructure, cannot be directly applied to mobile ad-hoc networks. Thus protocols need to be carefully designed for this kind of networks. The design of MAC and routing protocols are the most difficult parts, on which the performances such as throughput, delay and power consumption of the networks depend. This dissertation focuses on the problem of traffic load balancing in mobile ad-hoc networks and mainly investigats several aspects listed as: the load-balancing based multi-channel MAC protocols, the load-balancing based single path routing protocol, and protocols combined with the robustness and scalability of the network, such as the load-balancing based alternate path routing and probability routing protocols.Multi-channel in mobile ad-hoc networks is a novel research field and the tendency of applications. The asymmetric distribution of traffic load and the network resources leads to the degradation of the utilization of network resources as well as the capacity of the network. Thus, how to dynamic distribute resources and traffic among different channels according to their load status must be considered in the design of multi-channel MAC protocol to avoid severe congestion and packet loss due to heavy load, as well as the waste of resources of idle channels with light load. The chapter 2 investigates the load-balancing based MAC protocol in multi-channel mobile ad-hoc networks. A load-balance among multiple channels of network nodes based MAC layer protocol is presented to be deployed in places where node density is high and each node equipped with only one pair of half duplex transmitter and receiver. Simulation results showed good performances in the network throughput as well as the average packet delay.During the design of routing protocols for mobile ad-hoc networks, the status of node traffic and congestion degree need to be considered to achieve load balance while route selection. Thus optimizes the integrated performance of packet successfully delivered ratio, the end-to-end packet delay and additional overhead. Chapter 3 investigates the important load-balance based single path routing protocols, and presents a novel Cross-layer Load-aware and Bidirectional path re-selection based Load-balanced Routing for ad-hoc networks (CLBLR). By presenting and analyzing simulation results, the CLBLR is shown to result in good performance of packet delivery ratio, average end-to-end delay and routing overhead, exhibiting many attractive features of distributed control to adapt to the dynamic ad hoc networks.By restricting the flooding scope, CLBLR in chapter 3 reduces the routing overhead and improves the throughput and delay performances at the same time. However, it doesn't investigate the problem of link break and the route recovery after link break. Based on chapter 3, chapter 4 presents two methods to solve the link break. One is the optimization of local repair to restrict flooding scope of route rebuilt to improve the network performances such as routing overhead and delay as well as throughput, named as CLBLR-LR. The other method based on the expansion of CLBLR with alternate path, which named as CLBLR-AP, aims at the decrease of the flooding frequency. Simulation results of both methods show improvement in packet successfully delivered ratio and the end-to-end packet delay in a certain extent.In order to reduce the flooding overhead of alternate path construction, most existed alternate path routing protocols builds their alternate path routes during route discover period, which leads to two limitations. As the topology of ad hoc network evolves, links will be created and destroyed, resulting in route reduction or route failure. Additionally, changes in network traffic (including the traffic introduced by the source itself) will have a significant effect on traffic-dependent route metrics. This motivates the need for a route-probing mechanism that could periodically re-assess the status of the APR route set. The results of those route...