Effect of Nodes Mobility on Density-Based Probabilistic Routing Algorithm in Ad-hoc Networks

Density-based probabilistic routing algorithm (AODV–Probabilistic) has been introduced for mobile ad hoc networks. Under ideal settings, it has been proven to provide drastic performance improvement over AODV and OLSR routing protocols. In this paper, the authors study the effect of inaccurate location information caused by node mobility under a rich set of scenarios. They identify three different environments: a high density, a variable density and a sparse density. Simulation results show noticeable improvement under the three environments. Under the settings the authors examine, their proposed algorithm achieve up to 22% longer links lifetime than AODV and 45 percent longer links lifetime than OLSR at the three environments, on average, without incurring any additional routing overheads or intense computation. DOI: 10.4018/ijwnbt.2012010103 30 International Journal of Wireless Networks and Broadband Technologies, 2(1), 29-48, January-March 2012 Copyright © 2012, IGI Global. Copying or distributing in print or electronic forms without written permission of IGI Global is prohibited. distribution of nodes imposes a problem for MANET since the nodes are required to be near each another in order to communicate. This scenario was discussed in HeimLicher et al. (2009) to determine the necessary scenarios studying partially connected networks. The uneven distribution of nodes in an area was identified as a contributive factor for poor or limited connectivity in a multi-hop wireless network such as MANET. Frequent solicitation of routing information via broadcasts performed by MANET nodes in densely populated areas exposes the network to a problem known as “broadcast storm”. This event occurs when a high number of broadcast activities are performed simultaneously at a certain point in time and trigger torrents of redundant broadcast requests and replies that will eventually lead the contention based link layer of MANETs to suffer a blackout (Ni et al., 1999). In networks with varying node densities, such problems are expected to occur more frequently since MANET nodes will be forced to retransmit broadcasts whenever there is a broken link or when the destination could not be found after a certain period of time. The performance of the communications link in the network would eventually decline due to aggressive broadcast activity (Siddique et al., 2007). In short, the problems found in MANET networks with varying node distributions are the following: low packet delivery ratio, low data throughput rate, high end to end delays and potential “broadcast storm” problems due to an unmanaged network broadcast generating a high number of retransmissions. The research objective of this work was to study the behavior of MANET protocols encountering non-uniform node distribution in a given area and to address the issues caused by non-uniformity. A suitable quantitative estimate of node density in a given area was found to be dense with the assumption that all of the nodes had an identical transmission range. This estimate was used to provide node density awareness for nodes within this network. In addition, an enhanced MANET routing protocol was developed to address the problems arising from node density variations. The performance of the enhanced protocol was compared with existing MANET protocols for different levels of node density to determine the effectiveness of the new protocol. The rest of this paper is organized as follows: Section 2 summarizes related work on the nodes density effects; then, the proposed density based probabilistic algorithm, performance analyses of the proposed algorithm, simulation results and evaluations, and finally, the conclusions will be presented. 2. NODE DENSITY ISSUES The nature of our proposed scheme is a combination of the issues of nodes connectivity (density) and broadcast management. In this section, we conducted a survey for both issues. 2.1. DENSE and SPARSE Regions The optimum density of MANET was studied in Royer et al. (2001), which discussed the tradeoffs between network density and node connectivity in the face of increasing node mobility. This study also proposed a search for an optimal node density value in order to maintain connectivity in a stationary network. However, the results were inconclusive regarding the optimal density for maintaining connectivity in highly mobile environments. When neighbor nodes were saturated, they yielded very similar results. Nonetheless, Royer et al. (2001) concluded that both transmission power and the node densities needed to increase when the nodes experience increasing mobility in order to maintain connectivity. The node density for an entire network can be identified as the number of nodes that populate over a certain area or region of a MANET. Therefore, the node density can be equated to: ρ Node Density n Number of nodes A Size of Network Area 18 more pages are available in the full version of this document, which may be purchased using the "Add to Cart" button on the product's webpage: www.igi-global.com/article/effect-nodes-mobility-densitybased/75526?camid=4v1 This title is available in InfoSci-Journals, InfoSci-Journal Disciplines Communications and Social Science. Recommend this product to your librarian: www.igi-global.com/e-resources/libraryrecommendation/?id=2