The use of on-demand techniques in routing protocols for multi-hop wireless ad hoc networks has been shown to have significant advantages in terms of reducing the routing protocol's overhead and improving its ability to react quickly to topology changes in the network. A number of on-demand multicast routing protocols have been proposed, but each also relies on significant periodic (non-on-demand) behavior within portions of the protocol. This paper presents the design and initial evluation of the Adaptive Demand-Driven Multicast Routing protocol (ADMR), a new on-demand ad hoc network multicast routing protocol that attemps to reduce as much as possible any non-on-demand components within the protocol. Multicast routing state is dynamically established and maintained only for active groups and only in nodes located between multicast senders and receivers. Each multicast data packet is forwarded along the shortest-delay path with multicast forwarding state, from the sender to the receivers, and receivers dynamically adapt to the sending pattern of senders in order to efficiently balance overhead and maintenance of the multicast routing state as nodes in the network move or as wireless transmission conditions in the network change. We describe the operation of the ADMR protocol and present an initial evaluation of its performance based on detailed simulation in ad hoc networks of 50 mobile nodes. We show that ADMR achieves packet delivery ratios within 1% of a flooding-based protocol, while incurring half to a quarter of the overhead.

A number of different routing protocols proposed for use in multihop wireless ad hoc networks are based in whole or in part on what can be described as on-demand behavior. By on-demand behavior, we mean approaches based only on reaction to the offered traffic being handled by the routing protocol. In this paper, we analyze the use of on-demand behavior in such protocols, focusing on its effect on the routing protocol's forwarding latency, overhead cost, and route caching correctness, drawing examples from detailed simulation of the dynamic source routing (DSR) protocol. We study the protocol's behavior and the changes introduced by variations on some of the mechanisms that make up the protocol, examining which mechanisms have the greatest impact and exploring the tradeoffs that exist between them.

An ad hoc networkis a collwtion of wirelessmobile nodes dynamically forminga temporarynetworkwithouttheuse of anyexistingnetworkirrfrastructureor centralizedadministration.Dueto the limitedtransmissionrange of ~vlreless nenvorkinterfaces,multiplenetwork"hops"maybe neededfor onenodeto exchangedata ivithanotheracrox the network.In recentyears, a ttiery of nelvroutingprotocols~geted specificallyat this environment have been developed.butlittle pcrfomrartwinformationon mch protocol and no ralistic performancecomparisonbehvwrrthem ISavailable.~Is paper presentsthe results of a derailedpacket-levelsimulationcomparing fourmulti-hopwirelessad hoc networkroutingprotocolsthatcovera range of design choices: DSDV,TORA, DSR and AODV.\Vehave extended the /~r-2networksimulatorto accuratelymodelthe MACand physical-layer behaviorof the IEEE 802.1I wirelessLAN standard,includinga realistic wtrelesstransmissionchannelmodel, and present the resultsof simulations of net(vorksof 50 mobilenodes.This work was supported in