الفهرس | Only 14 pages are availabe for public view |
Abstract A mobile ad hoc network (MANEr) is a collection of mobile platforms or nodes where each node is free to move about arbitrarily. Each node logically consists of a router that may have multiple hosts and that also may have multiple wireless communication devices. Ad hoc nodes should be able to detect the presence of other nodes and to perform the necessary handshaking to allow communications and sharing of information and services. A MANET is self-organizing, adaptive and infrastructureless; this means that a formed network can be deformed on-the-fly without the need for any system administration. Numerous protocols have been developed for MANET. These protocols deal with the typical limitations of these networks, which include high power consumption, low bandwidth, and high error rates. The MANET routing protocols may generally be categorized as: (a) table-driven, and (b) source-initiated on-demanddriven. The Ad Hoc On-Demand Distance Vector (AODV) routing protocol is one of the well-known and efficient on-demand MANET protocols. AODV currently does not support Quality of Service (QoS) and also has no load balancing mechanism. The QoS routing feature is important in a stand-alone multihop mobile network for realtime applications and also for a mobile network to interconnect wired networks with QoS support. The load balancing mechanism enables the protocol to choose routes in such a way that the data traffic can be more evenly distributed in the network. The thesis proposes some enhancements to the AODV protocol to provide QoS and load balancing features by adding two extensions to the messages used during route discovery. The first extension (named QoS extension) specifies the service requirements (maximum delay is chosen), which must be met by nodes rebroadcasting a Route Request or returning a Route Reply for a destination. When a node needs a route to a new destination with maximum delay requirements, it has to broadcast a new Route Request message to find a route that satisfies the delay requirements. A node, which receives such a request, must be able to meet the delay requirements in order to either rebroadcast the Route Request (if it does not already have a route to the destinationor unicast a RREP to the source. A route can be determined when the Route Request either reaches the destination with delay requirements satisfied, or reaches an intermediate node with a valid route (satisfying delay requirements) to that destination. The second extension (named cost extension) is used to determine the cumulative network load for a certain route in order to achieve load balancing. A node receiving a route request would update the cost extension by adding to its value the node’s average buffer usage. If several routes are available, that one with the minimum cost (satisfying QoS requirements if any) will be chosen. A detailed packet-layer simulation model with media access control (MAC) and physical layer models is used to study the performance of both the AODV and the QoS-AODV protocols. In this thesis, the ns-2 (network simulator version 2) has been extended to include the proposed QoS-AODV protocol, so that the two protocols can be compared accurately. Important performance measures such as average delay, packet delivery fraction and normalized routing load are used in the comparison. Simulations are presented for networks with 50 mobile nodes with different network loads, delay constraints, topological rate of change and mobility speeds. Simulation results show the efficiency of the proposed protocol especially in satisfying load balancing and QoS requirements |