QoS Preemptive Routing with Bandwidth Estimation for Improved Performance in Ad Hoc Networks

Ad hoc networks are collection of mobile nodes which communicate using wireless media without any fixed infrastructure. Each mobile host acts both as a network router and an end point as packets are forwarded over multiple hops. Node mobility being the distinguishing feature of the mobile ad hoc network, makes routing an important challenge. Hence, Quality of Service (QoS) is not easily achieved in ad hoc networks. To provide QoS routing in Ad hoc networks, it is not just sufficient to provide a basic routing functionality where only a feasible route is found, other aspects like the bandwidth constraints due to shared media, dynamic topology due to continuously changing topology and the power consumption due to limited battery powers must also be considered. The nodes in the Ad hoc network move randomly, hence, the topology changes continuously resulting in route breakage. Thus, the route breakage must first be detected and a new route should be found to the destination in advance. This paper proposes a QoS Preemptive Routing protocol with Bandwidth estimation (QPRB) that computes the available bandwidth in the route and then sets up the route based on the network traffic and maintains the route using preemptive routing procedure. This protocol provides QoS support to the real time applications by providing a feedback about the network status. The algorithm improves network performance and performs well in route breakage conditions as better routes are found in advance to route breakage. The cost incurred to detect the route breakage and to find a new route is avoided. Simulation results show that the protocol significantly improves the packet delivery ratio and reduces the end-to-end delay in the route breakage conditions.