Information Dissemination in P artitionable Mobile Ad Ho c Net w orks Goutham Karumanc hi Sriniv asan Muralidharan Ra vi Prak ash Departmen t of Computer Science Univ ersit y of T exas at Dallas Ric hardson, TX 75083-0688. f goutham,msrini,ra vip g @utdallas.edu E-mail: Abstract imp ortan t to determine: 1. When to up date information? A d-ho c wir eless networks have no wir e d c omp onent, and may have unpr e dictable mobility p attern. Such 2. Where to send up dates? networks c an get p artitione d and r e c onne cte d sever al 3. Whic h no des to query for information? times. One p ossible appr o ach for information dissem- ination in such networks is to r eplic ate information 1.1 Problem Description and System Model at multiple no des acting as r ep ositories, and employ quorum b ase d str ate gies to up date and query informa- Let us consider a building on �re. A large n um b er, tion. We pr op ose thr e e such str ate gies that also use sa y N , of �re�gh ters ha v e b een assigned to extinguish lo c al know le dge ab out the r e achability of r ep ositories to the �re. Among the N �re�gh ters are a small n um b er, judiciously sele ct quorums. The primary go al is high sa y n , of o�cers whose job is to collectiv ely manage availability of information in the fac e of network p ar- the en tire op eration. All the o�cers need to b e able to titioning. We also c onsider four p olicies to determine comm unicate amongst themselv es. Also, an o�cer can the appr opriate time to p erform up dates. Exp erimental act as a pro xy for all ordinary �re�gh ters with whom r esults indic ate that a hybrid information management it can comm unicate. str ate gy and an absolute c onne ctivity-b ase d up date trig- T o increase the e�ciency of the op eration, and for ger p olicy ar e most suite d for p artitionable ad-ho c net- the safet y of the �re�gh ters, it is imp ortan t to: works. 1. trac k the lo cation of eac h �re�gh ter, and 2. gather information ab out the surroundings of eac h 1 In tro duction �re�gh ter. Existing solutions for dissemination of information in static or cellular net w orks ma y not b e applicable to A �re�gh ter is resp onsible for up dating his/her lo cation ad-ho c net w orks. First, these solutions usually do not and state information. Also ev ery �re�gh ter should consider c hanging top ology of the net w ork bac kb one b e able to retriev e the latest information ab out ev ery that con tains the information serv ers. Second, the p os- other �re�gh ter. Let eac h �re�gh ter ha v e a small, ligh t- sibilit y of partitioning means that some no des ma y not w eigh t wireless comm unication device with the same b e able to comm unicate up dates to other no des and/or range to send and receiv e information. The devices of all the �re�gh ters collectiv ely form a connected m ulti- ma y b e unable to retriev e the latest information on queries. Third, earlier solutions that do consider net- hop wireless net w ork. The o�cers ha v e additional w ork partitioning approac h the problem from the di- memory in their devices to main tain the state infor- rection of replica consistency in distributed databases. mation. Th us, the o�cers' devices collectiv ely act as 1 While the problems are similar, sev eral instances of in- information serv ers for other �re�gh ters. formation dissemination problem in ad-ho c net w orks The m ulti-hop wireless net w ork formed b y the �re- are simpler in nature. Emplo ying the sophisticated �gh ters ma y get partitioned in to disjoin t comp onen ts. replica consistency solutions w ould result in reduced The duration for whic h the net w ork sta ys partitioned, the iden tities of no des in eac h partition, and the w a ys a v ailabilit y of data, while also incurring unacceptably high comm unication o v erheads. F ourth, unlik e tradi- in whic h partitions merge are non-deterministic. tional distributed database systems where the timing 1 While it is p ossible to add more memory to ev ery �re�gh ter's of up dates is indep enden t of net w ork top ology , in ad- device without signi�can tly increasing the w eigh t, broadcasting ho c net w orks lo cation sensitiv e information should b e ev ery up date to ev ery no de w ould incur high comm unication up dated as a function of net w ork top ology . So, it is costs and drain the batteries quic kly .
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