Marketplaces as Communication Patterns in mobile ad-hoc Networks* Daniel Görgen, Hannes Frey, Johannes K. Lehnert and Peter Sturm System Software and Distributed Systems Research Group University of Trier * This work is funded in part by DFG, Schwerpunktprogramm SPP1140 “Basissoftware für selbstorganisierende Infrastrukturen für vernetzte mobile Systeme”

Mobile multihop ad-hoc Networks Mobile devices  Wireless communication facility  Positioning Large scale ad-hoc networks  University campus, downtown area Communication mainly over many hops High mobility  Frequent topology changes  Network partitions  Permanent link failure

Communication Model Altruistic Demand and supply  Find a match  Make an agreement  Possible matches are unknown Applications with low time constraints  Digital ride boards, auction systems, … Trivial but impractical solutions  Flooding the entire network High network load Network partitions  Awaiting a matching counterpart In direct transmission range Low probability

The marketplace solution 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

Message Routing 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 Agents stay longer at market Discovery  Broadcast only in a small region Discard messages outside  Flooding or neighbor knowledge broadcasts Negotiation  Topology-based routing  Broadcasts as above Only simple solutions are implemented yet

UbiBay – A mobile auction system Auction at marketplaces  Low value goods  Direct neighborhood Agents  Auction agent Controls the auction  Discovery agent Lists all auctions at marketplace  Bid agent Bids on behalf of a user 15 10

Further Aspects Caretaker agents  Load Monitoring Splitting/Joining of marketplaces  Duplicate detection Primary at marketplaces Caching of information/data  Public bill-board Collecting information about device accumulation  Hotspot detection  enhanced position-based routing

Electronic Rideboard Lift offers and demands at marketplaces  Localized service  Non time-critical  Simple agreement protocol Splitting marketplaces  Classify agents by destinations postal code 01099…54290 on market A 54291…99998 on market B

Evaluation Own Simulation environment  Mobile MANETs Up to devices Up to 10 km x 10 km  High abstraction level  Visualization  One implementation for both simulation and real hardware Mobility Models  Exhibition, festival and campus

Simulation results Evaluated in simulations  Movement strategies Greedy routing, course information,…  Protocol quality Agent losses/duplication Correct/successful negotiations Simulation results  Course information to handle network partitions  Geographic routing depends on mobility model  No incorrect negotiation in simulated scenarios  Low agent duplication rate Well suited for non time-critical multihop ad- hoc network application

Status and further work Prototype implemented  Simulation and real-life Already implemented Applications  Electronic ride board  UbiBay - auction system Additional service agents Improved Message routing  Position based  Marketplace communication Integration in SOUL-Project  Self-organized ubiquitous learning Preparation for field trials  First tests with WLAN, GPS, PDAs and notebooks