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Self-Organized Aggregation of Wi-Fi Networks Elias C. Efstathiou, Advisor: George C. Polyzos Mobile Multimedia Laboratory, Department of Computer Science Athens University of Economics and Business Abstract: We present a peer-to-peer (P 2 P) scheme that could fuel the deployment of free public wireless networks in cities; we call it P 2 P Wireless Network Confederation (P 2 PWNC). Unlike existing approaches, P 2 PWNC does not rely on central planning. In P 2 PWNC, wireless service is provided to those who provide service to others based on an algorithm that runs in isolation on every peer. 1 5 Motivation Incomplete Information • Teams have partial view of receipt graph • Private Wi-Fi networks, connected to the Internet, cover major metropolitan areas • Teams do not cooperate in a distributed storage scheme and there is no central repository of receipts • We could use one another’s networks to access the Internet • Must rely on members to disseminate receipts: – members carry a subset of the receipts their team knows about – before requesting service, members transmit these receipts to Plus, Wi-Fi phones are now available the prospective provider Motorola CN 620 2 6 Evolutionary Learning Framework • Assume cost c when providing a unit of service and The Problem • How to encourage Wi-Fi connection sharing? benefit b when receiving one • For various b/c ratios (>1): – “Give to those who give” • – – – 3 – let each team follow one of various predefined sharing strategies – let teams interact at random – allow teams to learn, i. e. switch to better-performing strategies Design a reciprocity scheme that is fully self organized collusion proof easy to join When do cooperative strategies outperform non-cooperative ones? Example of a conditionally cooperative strategy from  (black) outperforming “never share” (blue) and “always share” (red) 7 Solution Architecture • Participants form small teams, typical teams = households • Team IDs are uncertified, no need for authorities • Teams operate one or more Wi-Fi access points (APs) 4 • Simple text-based protocol : • – Blue team – – Green team – : Wi-Fi access point : team member Wi-Fi network view Team view member PK team PK RCPT: Client transmits a stored or a newly signed Y 5 consult receipt graph: UPDT: Client requests latest receipts from own team Summary, Contact, References Z G 6 timestamp – We design, simulate, and implement [2, 3, 4, 5] a self-managed solution for Wi-Fi aggregation, which can be deployed spontaneously X B signed by team SK consumer cert. Additional information: the Peer-to-Peer Wireless Network Confederation section at http: //mm. aueb. gr/research/ and via e-mail to efstath@aueb. gr (Elias Efstathiou) • receipt graph contains the community’s history volume of traffic signed by consumer SK 4 Decision function: ? Keys and certificates based on Elliptic Curve Cryptography (Receipt size: 150 bytes) RREQ: AP requests an updated receipt for the current 8 W providing team PK • receipt 1 All IDs = unique public/private key (PK/SK) pairs 3 Receipt: CACK: Positive/negative response from AP AP code runs on the Linux-based Linksys WRT 54 GS AP session (thus splitting consumer/provider risk) Receipt Graph, When to Cooperate? 2 Member certificate: CONN: Client requests service from access point (AP) (request includes member certificate) White team • Team members sign receipts whenever they access another team’s APs Protocol, Implementation Green team AP: “Should I cooperate with the member from the Blue team who is requesting service? ” • graph arrows encode the owes to relationship • we study collusion-proof reciprocity strategies  that allow the evolution of cooperation White team PK Green member cert timestamp Timestamp volume of traffic Weight Signed by Green member SK  Feldman, Lai, Stoica, Chuang, Robust Incentive Techniques for Peer-to-Peer Networks, Proc. ACM EC’ 04.  Efstathiou, Polyzos, Self-Organized Peering of Wireless LAN Hotspots, European Transactions on Telecommunications (special issue on Self-Organization in Mobile Networking, in press).  Efstathiou, Frangoudis, Polyzos, in preparation.  Antoniadis, Courcoubetis, Efstathiou, Polyzos, Strulo, Peer-to-Peer Wireless LAN Consortia: Economic Modelling and Architecture, Proc. IEEE P 2 P’ 03.  Efstathiou, Polyzos, A Peer-to-Peer Approach to Wireless LAN Roaming, Proc. ACM Mobi. Com WMASH’ 03.