Research On Energy And Hotspot Aware Routing Protocols For Manet

A mobile ad hoc network (MANET) is a collection of mobile nodes connected by wireless links to form a temporary network without the use of any existing network infrastructure or centralized administration. The environment of an ad-hoc wireless network is characterized by unpredictable connectivity changes, unreliable wireless medium, resource-constrained nodes, and dynamic topology. These features make MANETs prone to numerous types of faults, including: transmission errors, node failures, link failures, route breakages, and congested nodes or links. Under these conditions, designing efficient and robust routing protocols and understanding their performance in various mobility and traffic conditions is an important and challenging task. While many routing protocols have been designed and evaluated for ad hoc network in literatures, none of them to our knowledge has demonstrated effective operation in a wide range of network states and scalability. This is because they lack efficiency, reliability and robustness. For example, ad hoc on-demand routing protocols, although has low routing overheads, they however, adopt flooding technique to find routes to destinations and use shortest path metrics to deliver data. Blind flooding and shortest path metrics leads to inefficiency and lack of robustness in ad hoc network.In this thesis, we design energy and hotspot aware routing techniques to ensure efficiency and robustness in mobile ad hoc network. Three techniques were proposed– one that efficiently discover route on-demand termed as Gradient broadcasting protocol, another that adapts routing based on the current state of the network termed'Network State Aware Routing Protocol', and a last one that can detect and remove any possible hotspot in the network. These three techniques combined together yields an efficient, reliable, and robust protocol for wireless ad hoc network. Each of these schemes was evaluated via extensive simulation using NS-2 simulator.The proposed gradient broadcasting protocol seeks to solve broadcast storm problem of redundant retransmissions, contention and collision caused by flooding in ad hoc networks. The main solution methodology combines the use of directional antenna and some intelligent location based algorithm. Directional broadcasting limits the area covered by a broadcast message, which also means limiting the number of nodes to rebroadcast and contend for the wireless channel. Another solution methodology used is border aware broadcasting. With border aware broadcasting, border nodes which are expected to cover more additional area are given priority to rebroadcast a broadcast message earlier over closer nodes. This could allow closer nodes to have more chances after receiving the same broadcast message several times to detect that they are redundant to rebroadcast the same message and cancel rebroadcast operation. Further more the relation used to give border nodes priority over closer nodes based on their distances from the source node also allows to differentiate the time rebroadcast nodes access the channel solving contention problem. Simulation result shows that the proposed gradient protocol has over other schemes high reachability, reduced retransmission and optimum utilization of network resources– bandwidth and power. This proposed gradient scheme is suitable for use with on-demand ad hoc routing protocols to limit the spread of query search during route discovery.The proposed network state aware routing protocol adapts routing based on the current state of the network. An ad hoc network can transit several states during it lifetime depending on nodes mobility, induce traffic load, and resource conditions. Each of these states requires unique routing schemes, but existing ad hoc routing protocols are only effective in one of these states. This implies that when the network enters any of the other states, these protocols runs in a sub optimal mode, degrading the performance of the network. To guarantee the requirements of various ad hoc network states, this thesis propose a network state aware routing protocol that adopts route selection metrics based on the current state of the network. Two versions of the Network State Aware Routing Protocol are proposed; one termed'Joint Load-Energy Balancing Protocol LEB'for non-ideal network states, and an extended version termed'Conditional Load-Energy Balancing Protocol CLEB'suitable for both ideal and non-ideal network states. These proposed joint load and energy aware schemes yield high efficiency, reliability, and robustness that best suits any dynamic and scalable ad hoc network environmentLastly a hotspot mitigation scheme was proposed to detect and remove any possible emergency of hotspot in an ad hoc network. Due to the dynamics and lack of central control, hotspots are intrinsic in ad hoc networks. This problem is further compounded by the use of shortest hop route selection metrics which have the tendency of concentrating traffic load on centrally located nodes. Under hotspot conditions a node will experience high contention, congestion and resources exhaustion, creating bottlenecks wherein demand for network resources exceeds that available for use. This if left unchecked will result in increased packet loss, end-to-end delay, transmission errors and faster battery power depletion. This phenomenon generally degrades the overall performance of the network. At a node, hotspot can be detected from high buffer occupancy, packet loss, and excessive MAC contention delay. No single one of these metrics alone can accurately detect hotspot. And monitoring these parameters independently and combining them to accurately detect hotspot would result in a complex scheme. To simplify issues, this thesis propose a simple and effective hotspot mitigation scheme termed HUNT, which utilizes a single node throughput metrics to accurately detect hotspot and maintain awareness of its relationship with other neighboring nodes to ensure connectivity. HUNT is capable of providing ad hoc networks with high degree of reliability, availability, flexibility and robustness, and is most effective for multimedia transmissions were high delay, delay jitter and out-of-sequence packet delivery are intolerable. It is also suitable for simultaneously transmitting real time and non-real data.This research work is part of Internet Technology and Engineering Research & Development Center's National Science Foundation NSF sponsor project; with the ultimate goal of ensuring efficiency, reliability and robustness in Mobile Ad hoc Wireless Network that would alleviate the problems that limit the wide spread usage of ad hoc networks.