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Mobile Peer-to-peer Databases and Incentives for Participation. Bo Xu. Department of Computer Science University of Illinois at Chicago. Environment. query A report 1 report 2 report 3. Vehicles, smartphones, sensors, hotspots with short-range
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Mobile Peer-to-peer Databases and Incentives for Participation Bo Xu Department of Computer Science University of Illinois at Chicago
Environment query A report 1 report 2 report 3 Vehicles, smartphones, sensors, hotspots with short-range wireless capabilities report 8 query C Local query Local database query B report 4 report 5 Short-range wireless networks 802.11 bluetooth Why not simply use cellular? “Floating database” Resources of interest in a limited geographic area possibly for short time duration Applications coexist
Technical Challenges • Mobility and sparseness of peers • Bandwidth, energy, and memory constraints on mobile peers Even if there was a global coordination, the problem of determining whether a set of answers can be delivered to all the interested mobile peers is NP-complete.
Heuristic Solution 1 1 2 3 2 3 5 • Reports and queries are stored and forwarded • Ranking to decide which reports to store and forward • Ranking based on online machine learning from attributes such as age and distance of a report • Ranking considers demand and supply 6 B B 4 4 C C 5 6 A A 1 1 4 4 Ranked Store-and-forward
Incentive Mechanisms Mobile Peer Security Module Coin counter • Incentivize reports brokering • Based on virtual currency and security module • Who pays? • Producer, as in gas station advertisement • Consumer, as in parking slot discovery
Incentive Mechanisms (Cont’d) • Producer-paid • Logarithmic Dissemination Strategy (LDS) • Producer attaches a certain amount of initial credit to announced report • A broker earns a commission fee each time it transmits the report to another peer • The remaining budget is divided between the sender and receiver • How to set the initial credit in order to cover a target area? • Consumer-paid • Consumer pays a broker for receiving a report • Pricing based on expected benefit of report • Developed an analytical model for computing the expected reduction of discovery time based on age and distance of resource as well as resource valid duration
Incentive Mechanisms (Cont’d) • Transactional/Atomicity issue • Due to mobility, a transaction may not complete • Mobile Peer-to-peer Transaction (MOPT) mechanism • Mobile peer remembers unsuccessful transactions • Clearance center • Mobile peers submit transaction logs to clearance center for reconciliation • Compromising decentralization; data dissemination still decentralized Report, price = 6 coins Coin counter = 0 Coin counter = 10 Got it. Please charge 6 coins Coin counter = 0 Coin counter = 4
Research Issues • Centralized <-> decentralized economy • Reputation based incentives • Direct experience may be rare • Game theory