Best effort QoS support routing in mobile ad hoc networks

Abstract

In the past decades, mobile traffic generated by devices such as smartphones, iphones, laptops and mobile gateways has been growing rapidly. While traditional direct connection techniques evolve to provide better access to the Internet, a new type of wireless network, mobile ad hoc network (MANET), has emerged. A MANET differs from a direct connection network in the way that it is multi-hopping and self-organizing and thus able to operate without the help of prefixed infrastructures. However, challenges such dynamic topology, unreliable wireless links and resource constraints impede the wide applications of MANETs. Routing in a MANET is complex because it has to react efficiently to unfavourable conditions and support traditional IP services. In addition, Quality of Service (QoS) provision is required to support the rapid growth of video in mobile traffic. As a consequence, tremendous efforts have been devoted to the design of QoS routing in MANETs, leading to the emergence of a number of QoS support techniques. However, the application independent nature of QoS routing protocols results in the absence of a one-for-all solution for MANETs. Meanwhile, the relative importance of QoS metrics in real applications is not considered in many studies. A Best Effort QoS support (BEQoS) routing model which evaluates and ranks alternative routing protocols by considering the relative importance of multiple QoS metrics is proposed in this thesis. BEQoS has two algorithms, SAW-AHP and FPP for different scenarios. The former is suitable for cases where uncertainty factors such as standard deviation can be neglected while the latter considers uncertainty of the problems. SAW-AHP is a combination of Simple Additive Weighting and Analytic Hierarchical Process in which the decision maker or network operator is firstly required to assign his/her preference of metrics with a specific number according to given rules. The comparison matrices are composed accordingly, based on which the synthetic weights for alternatives are gained. The one with the highest weight is the optimal protocol among all alternatives. The reliability and efficiency of SAW-AHP are validated through simulations. An integrated architecture, using evaluation results of SAW-AHP is proposed which incorporates the ad hoc technology into the existing WLAN and therefore provides a solution for the last mile access problems. The protocol selection induced cost and gains are also discussed. The thesis concludes by describing the potential application area of the proposed method. Fuzzy SAW-AHP is extended to accommodate the vagueness of the decision maker and complexity of problems such as standard deviation in simulations. The fuzzy triangular numbers are used to substitute the crisp numbers in comparison matrices in traditional AHP. Fuzzy Preference Programming (FPP) is employed to obtain the crisp synthetic weight for alternatives based on which they are ranked. The reliability and efficiency of SAW-FPP are demonstrated by simulations.