RDMAR: A bandwidth-efficient Routing Protocol for Mobile Ad hoc Networks George Aggelou Rahim Tafazolli Center for Communication Systems Research (CCSR) Center for Communication Systems Research (CCSR) University of Surrey University of Surrey UK UK Tel: +44 1483 300800 ext. 2292 Tel: +44 1483 300800 ext. 9834 G.Aggelou@ee.surrey.ac.uk R.Tafazolli@ee.surrey.ac.uk ABSTRACT (MAN) is an autonomous system of mobile hosts which are free to move around randomly and organise themselves arbitrarily; thus, We present a loop-free routing protocol for ad hoc mobile the network's wireless topology may change rapidly and networks. The protocol is highly adaptive, efficient and scaleable; unpredictably. In a mobile ad hoc network, mobile hosts share the and is well-suited in large mobile networks whose rate of same frequency channel, like IEEE 802.11 [6], thus limiting the topological changes is moderate. A key concept in its design is network capacity. In many packet-radio networks the packet that protocol reaction to link failures is typically localised to a radios do not have direct radio links to all other packet radios in very small region of the network near the change. This desirable the network and thus store-and-forward routing of the packets is behaviour is achieved through the use of a novel mechanism for required. Therefore, nodes are acting also as routers (also called route discovery, called Relative Distance Micro-discovery Mobile Routers) and dynamically establishing routing patterns (RDM). The concept behind RDM is that a query flood can be among themselves to form an infrastructure-less network. localised by knowing the relative distance (RD) between two terminals. To accomplish this, every time a route search between Recently, several adaptive routing protocols for ad hoc networks the two terminals is triggered, an iterative algorithm calculates an have been proposed to solve the multi-hop routing problem in ad estimate of their RD, given an average nodal mobility and hoc networks, each based on different assumptions and concepts. information about the elapsed time since they last communicated In general, these protocols can be classified either as proactive or and their previous RD. Based on the newly calculated RD, the reactive . In proactive protocols, nodes continuously search for query flood is then localised to a limited region of the network routing information within the network, so that when a route is centred at the source node of the route discovery and with needed, the route is already known. In reactive approach, a need maximum propagation radius that equals to the estimated relative for route triggers a route search. Here, nodes evaluate the network distance. This ability to localise query flooding into a limited area on as-needed basis. The existing routing schemes ([1], [3], [10] of the network serves to minimise routing overhead and overall [14] [16], [17] and [18]) have both advantages and disadvantages. network congestion. Simulation results illustrate its performance We summarise hereafter some of the drawbacks of the existing and demonstrate its good behaviour comparing to other protocols proposals: In [1] (AODV) and [3,8] (DSR) nodes make use of proposed by IETF Working Group. We refer to the protocol as their routing caches to reply to route queries. This mechanism, the Relative Distance Micro-discovery Ad Hoc Routing however, results to a storm of replies and repetitive updates in (RDMAR) protocol. hosts’ caches, yet early query quenching cannot stop the propagation of all query messages which are flooded all over the Keywords network. Furthermore, AODV uses periodic beaconing to keep Multihop Networks, Dynamic Routing, Mobile Terminal. routing tables updated thus adding a significant overhead to the protocol. DSR, on the other hand, requires hosts to operate in promiscuous mode, which could present an even higher routing 1. INTRODUCTION and processing overhead as it will have to process every packet heard. Finally, both protocols do not guarantee shortest path Today’s wireless networking technologies can be broadly routes. In TORA [16], nodes maintain multiple routes to classified into single-hop and multi-hop, depending on the hop destinations, thus additional cost of maintenance is implied, albeit distance (i.e., wireless links) a packet travels through the air no protocol reaction may be required in the face of topological interface. A well-known representative paradigm of single-hop changes. In addition, TORA makes use of the so-called technology, is today’s wireless cellular networks [9]. Single-hop “advantaged” nodes. These are nodes that may provide a route networks, support nomadic host "roaming" [2,9], where a roaming that is shorter, in hops, to other possible routes. We argue that host may be connected through various means to the fixed advantages nodes may adversely affect the performance of TORA infrastructure other than its well known fixed-address domain because a big number of paths will pass through the advantaged space. node, thus leading to situations where some parts of the network Multi-hop wireless networks, on the other hand, also called “ ad turn to be highly congested whereas other remain undiscovered hoc” networks [11], serve the need to establish an instant wireless and hence unloaded. Hass [18] attempts to combine proactive and infrastructure when is needed. A “Mobile Ad Hoc Network” reactive approaches in the Zone Routing Protocol (ZRP) by
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