Multi-metric routing decisions for ad hoc networks using fuzzy logic

Routing is an essential function for traffic management in ad hoc networks. Table-based routing algorithms used in proactive protocols are computationally intensive and require periodic transmission of status information amongst all network nodes. Also, routing table volume swells with network size and can be large for dense networks. Therefore to cope with possibly rapidly changing topology reactive protocols such as Dynamic Source Routing (DSR) generate routes for unknown destination paths on an as needs be basis. So as to avoid the continual demand for route discovery in DSR, network nodes record previously determined routes in either path or link caches. A route discovery attempt can possibly result in several paths being uncovered for a single destination. As nodes often have a finite capacity path cache, it may not be possible to store all paths. So as to influence productive caching decisions a fuzzy logic system is applied to the route discovery technique to curb non-optimal network floods. This action causes a cessation in the generation of low quality routes as only paths with good routing metrics are selected for the rebroadcast of route discovery packets. Consequently, route query packets arriving at the necessary destination node, or at some intermediate node with knowledge of the destination node, generate high quality route replies. This paper presents a fuzzy logic based decision algorithm that weighs individual links as a path to the necessary destination is being constructed if this link is deemed suitable by the fuzzy logic system it is added to the path and route construction continue. The fuzzy controller is used to instruct caching decisions and to optimise route selection as only good quality links are recorded in source destination paths.