SELMA: A middleware platform for self- organizing distributed applications in mobile multi-hop ad-hoc networks Daniel Görgen, Hannes Frey, Johannes K. Lehnert, Peter Sturm System software and distributed systems University of Trier Germany

 Metropolitan sized networking  Mobile devices Wireless communication facilities Localized location computation  Direct communication only within transmission range  Unpredictable network topology changes due to mobility Network partitions Permanent link failures Mobile multi-hop ad-hoc networks

Marketplace communication  Fixed geographic regions High device density Known position  Devices at market acting on behalf of a user  Geographic routing of agents/data To and from marketplaces  Negotiation at a marketplace Geographic limited broadcast Topology-based Routing  Definition of home zones Negotiation results are sent back to a defined home zone R O O O R R O R Request Offer R R R O O O

UbiBay – A mobile auction system  Auction at marketplaces Intended for low value goods Direct neighborhood  Agents Auction agent  Controls the auction Discovery agent  Discovers all auctions at marketplace Bid agent  Bids on behalf of a user 15 10

Middleware platform overview positioninglocal unicast local broadcast neighbor discovery agent movement agent transport hotspot detection marketplace commu- nication marketplace localization map computation geographic routing A1A1 A2A2 A3A3 ticket agent duplicate elimination load monitoring …… Application AgentsService Agents Agent Platform Hardware abstraction

Agent movement  To and from marketplaces  Geographic routing e.g. greedy algorithm Additional: course information  Messages can be carried over network partitions  Message duplication to avoid message losses Sender keeps messages until reception is acknowledged Duplicated messages can be detected on the marketplace  Losses are still possible Device crash S D

Communication at Marketplaces  More reliable communication High device density Network partitions are rare Message loss can be detected  Discovery Broadcast only in a small region  Discard messages outside Flooding or neighbor knowledge broadcasts  Negotiation Topology-based routing Broadcasts as above

Homezones  Sending Messages to User User is mobile Possibly hours later  Homezone Agent knows homezone High visit probability Faculty building, apartment Long waiting times  Links to current position Sequence of homezones Updates after movement Other devices needed

Services at marketplaces  Mobile service at marketplace Self organized creation Tries to stay at marketplace  Load monitoring High network load Not enough resources Splitting and joining of marketplaces Geographical disjoined regions with high device density  Duplication detection Duplication due to permanent link failures Duplicates ask service first

Summary  Prototype implemented Simulative, Emulative & real hardware  Already implemented Applications UbiBay, Electronic ride board, Distributed Newsgroup,…  Application Domain Based on Offer and Demand No hard time constraints  Future Work Improved version is planned Increase probability to communicate over partitions Learning network topologies