Wireless multi-hop ad hoc networks: evaluation of radio disjoint multipath routing

A wireless multi-hop ad hoc network consists of a collection of nodes, which can communicate without any fixed base stations or networking infrastructure. Multi-hop ad hoc networks are ideally suited in areas such as sensor networking, community networking and networking used in emergency situations. Since transmission is wireless and nodes could be mobile, ad hoc networks bring about new challenges to be considered when designing routing algorithms. Multipath routing discovers more than one route between a source node and a destination node in a wireless multi-hop ad hoc network. These routes can be used simultaneously to distribute traffic among several paths or used as backup paths. Multipath routing can provide benefits such as load balancing, bandwidth aggregation, fault tolerance and improvement in QoS. The work done in this thesis investigates the simultaneous use of multipath routes in wireless multi-hop ad hoc networks. In wireless multi-hop ad hoc networks, the simultaneous use of multiple routes may degrade the performance of applications due to mutual interference of discovered paths, irrespective of whether paths are physically node disjoint or link disjoint. Therefore, the selection of noninterfering routes is the main criterion to be addressed when using multiple routes simultaneously. This thesis introduces a new metric to select multiple routes by reducing the effect of interference between paths as far as possible and also selecting the least congested paths. The proposed protocol is named Radio Disjoint Multipath (RDM). The concept of the RDM protocol which can be applied to both reactive and proactive ad hoc protocols is developed and feasibility of the protocol is proven by an implementation and also through an analytical model. Furthermore, this thesis introduces a novel mechanism to distribute multiple flows as well as packets of a single flow based on the properties of the discovered path, which is computed considering the Background Traffic Load (BTL) of each path and the mutual interference between paths. The single flow distribution is further investigated by replicating packets among the RDM paths. This distribution is used to enhance the reliability in adverse environments such as a fire-fighting scenario. The evaluation of results is done considering the non-interfering RDM routing, the interfering RDM routing and the single path routing. When using the RDM routes, two distribution methods, viz., the single flow and the multiple flow distribution methods are considered. The performance of the applications is compared using real application flows consisting of audio conferencing, video transmissions, HTTP web accessing and FTP downloads that use different scenarios with and without mobility. The analysis shows that the use of non-interfering RDM routes simultaneously to distribute application flows significantly outperforms the use of single path routing for most of the scenarios investigated. In summary, all investigations presented in this thesis can help to enhance the application performance in different kinds of wireless multi-hop ad hoc networks of Mobile Ad hoc NETworks (MANET), Wireless Sensor Networks (WSN) and Wireless Mesh Networks (WMN), by discovering RDM routes and using them simultaneously.