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UCLA COMSCI 218 - yj-ngc02

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Scalable Team Multicast in Wireless Ad hoc NetworksExploiting Coordinated Motion∗Yunjung YiComputer ScienceUniversity of California, LosAngelesLos Angeles California, [email protected] HongComputer ScienceUniversity of California, LosAngelesLos Angeles California, [email protected] GerlaComputer ScienceUniversity of California, LosAngelesLos Angeles California, [email protected] this paper, we study a new multicast paradigm for largescale mobile ad hoc networks, namely team multicast. Inteam multicast the multicast group does not consist of in-dividuals, rather, of member teams. For example a teammay be a special task force that is part of a search andrescue operation. The message must be broadcast to eachmember of each team in the multicast group. Team multi-cast is very common in ad hoc networks set up to accom-plish some collective tasks, such as for emergency recoveryor battlefield applications. A key problem in several of theab ove applications is scalability to large membership size aswell as network size. Our approach exploits motion affinity(more precisely, team members’ coordinated motion) whichis typically present when the set of nodes has a commonalityof interests. Each team can be viewed as a logical subnet.Within the team a landmark node is dynamically elected.The addresses of and the paths to the chosen landmarks arepropagated into the whole network so that a source of amulticast group can route to the landmark of a subscribedteam.Our protocol, Multicast-enabled Landmark Ad Hoc Rout-ing (denoted as M-LANMAR), uses tunneling from multi-cast sources to each landmark of the subscrib ed team and re-stricted flooding within the motion group. Simulation studyshows that M-LANMAR provides efficient and reliable mul-ticast compared with the application of a “flat” multicastscheme (e.g., ODMRP) that does not exploit team coordi-nated motion.This paper contains three contributions: a new model forteam multicast, with the definition of team dynamics (join,merge, split); the exploitation of team mobility and of land-marks in order to achieve scalable multicast, and; the im-∗This work is supported in part by ONR “MINUTEMAN”project under contract N00014 - 01 - C - 0016Permission to make digital or hard copies of all or part of this work forpersonal or classroom use is granted without fee provided that copies arenot made or distributed for profit or commercial advantage and that copiesbear this notice and the full citation on the first page. To copy otherwise, torepublish, to post on servers or to redistribute to lists, requires prior specificpermission and/or a fee.Copyright 2002 ACM 1-58113-619-6/02/0010 ...$5.00.plementation and performance evaluation of M-LANMAR,a landmark based team multicast scheme.Keywordsteam multicast, MANET multicast protocol, LANMAR, scal-ability, team-oriented, multicast, mobile ad hoc networks1. INTRODUCTIONMobile ad hoc networks (MANETs) are self-organizingnetworks that do not need a wired/wireless infrastructure.Two nodes communicate directly if they are in the trans-mission range of each other. Otherwise, they reach via amulti-hop route. Each MANET node must therefore be ableto function as a router, forwarding data packets on behalfof other nodes. Because of their unique benefits and ver-satilities, MANETs have a wide range of applications suchas collaborative, distributed mobile computing (e.g., sen-sors, conferences), disaster relief (e.g., flo od, earthquake),war front activities, and communication between automo-biles on highways.In many MANET scenarios (e.g., warfront activities, searchand rescue, disaster relief operations, etc.), the mobile nodesare often organized in teams with different tasks and, cor-respondingly, different functional and operational charac-teristics. In particular, no des in the same team will havecoordinated motion. We call this model the “affinity teammodel”. For example, attendees of a major conference canbe subdivided into teams based on their topic interests forthe purpose of organizing birds of a feather sessions; vari-ous units in a division can be organized into companies andthen further partitioned into task forces based on their as-signments in the battlefield.One of the main challenges of MANET protocol design isthe fact that unlike in Internet nodes are moving continu-ously. In particular, it is difficult to keep track of individualnode movements and to route packets to them especiallywhen the network grows large. The “affinity team” model,considerably simplifies the mobility management problemand allows us to design a routing protocol that scales. Infact, it suffices for a source to know the path to one of nodesin the team (say, a landmark) in order to route a packet toany other destination within that team.Scalable routing in an team situation with coordinatedmotion has already been addressed in [3] [12]. Here we ex-tend that concept to team multicast. First, we will makesome assumptions about team multicast. Nodes in the sameteam share the same interest, and thus all the members inthe team participate in the same multicast group(s). Forexample, all the members of a search and rescue task forcereceive situation updates from other teams. Moreover, mul-ticast dynamics are on a per team basis - and entire teamjoins or withdraws from a multicast group. Two or moreteams may merge into one; or a team may split in sub-teams,dep ending on the operational needs.Since MANETs function under severe constraints suchas limited bandwidth and energy, group communicationsshould be performed efficient and at low control overheadcost. Several MANET multicast protocols already exist(e.g., ODMRP [8], MAODV [13], CAMP [7]). Anyone ofthese protocols could be used in a brute force, “flat” ap-proach by treating each node in the team as an individualunit without exploiting the group mobility feature. How-ever, these schemes require periodic or event-driven controlpacket updates for each member in the multicast group inorder to maintain the multicast structure (e.g., membershipinformation, routes, etc.). Those protocols work effectivelywith small-scale multicast groups (e.g., less than 100 nodes).However, they suffer from severe communications overheadcaused by control packet floods (e.g., Join Query or Requestpacket flooding in ODMRP and MAODV) in a large-scalenetwork with a large number of multicast groups. Such over-head would be unsustainable in a battlefield


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UCLA COMSCI 218 - yj-ngc02

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