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Opportunistic Spatial Gossip over Mobile Social Networks

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  1. Opportunistic Spatial Gossip over Mobile Social Networks Augustin Chaintreau Pierre Fraigniaud Emmanuelle Lebhar Thomson CNRS CNRS Paris Universite Paris Diderot Universite Paris Diderot Paper Discussed by: Ranjeet Sangle

  2. Before we begin .. • Less than 6 Pages long • Out of which, Heavy Math on about 3 Pages. • Can’t really talk too much about the Mathematical Details. • Remaining Pages =3. • Not a single Figure !!

  3. An Outline • Review of Basic Terms • The Paper analyzed - Section-by-section • Applications • Questions/Comments

  4. Review of Basic Terms Random Walk a mathematical formalization of a trajectory that consists of taking successive random steps [1] Mates each static node maintains some privileged relationships with one or few mobile nodes that it has seen in the past. Mobile Social Networking A type of social networking where one or more individuals of similar interests or commonalities, conversing and connecting with one another using the mobile phone [2] Random Walk example Source: http://en.wikipedia.org/wiki/Random_walk

  5. The Abstract explained .. • The Paper investigates how the principles underlying online social network services could be used to take advantage of node mobility in an opportunistic manner. • The model includes static nodes, and mobile nodes which follow random walks. • A simple connection scheme enables to execute sophisticated tasks (e.g., routing) and mechanisms (e.g. spatial gossip) • Future online social networks can exploit mobility as long as they forget connections appropriately

  6. Introduction … • Online Social Networks (OSN) can take advantage of nodes mobility by appropriate connections maintenance. • Mates are forgotten and replaced by other nodes met in function of time and opportunistic encounters. • Two types of nodes • Static – positioned at vertices of lattice • Moving – perform random walks in lattice

  7. Introduction (Cont’d) … • A mobile node can be the mate of at most one static node, and a static node can have up to m mates, where m ≥ 1 is a parameter. • A static node can communicate with its mates at all times. • The proposed scheme simply requires the static nodes to reinitialize their mates according to a simple random process consisting in • (1) deciding when a mate should be forgotten, and • (2) how a forgotten mate should be replaced by a new one.

  8. Opportunistic Connection Scheme • ‘m’ Mates are acquired opportunistically by static nodes when they happen to meet mobile nodes. • If a static node x that has less than m mates happens to meet a free mobile node y, then y becomes the mate of x. • A forgetting process between the static nodes and their mates enables a renewal of the set of mate. • Forgetting process depends on age of the mate connection.

  9. Opportunistic Connection Scheme (Cont’d) • Assume that the mobile node y became the mate of the static node x at time t0. • Every Δt period of time, the static node x determines whether y should remain its mate. • More precisely, at time t0 + a · Δt, with a ≥ 1, node x forgets y independently from the past with probability φ(a).

  10. Opportunistic Connection Scheme • Setting the Forgetting function

  11. Opportunistic Connection Scheme (Cont’d) • Setting the Forgetting Function (Cont’d) …

  12. Opportunistic Routing • Opportunistic routing extends the idea of geographic routing, by using some node that is awake and available for routing at the time the packet needs to be transmitted[5]. • Greedy routing finds source-destination paths whose length grows polylogarithmically as a function of the distance between the source and the destination in the lattice

  13. Opportunistic Spatial Gossip • Spatial Gossip :– Gossip protocols in which the node selection mechanism uses the spatial distribution of the nodes. • Gossip protocol is based upon two mechanisms: a node selection mechanism and a message selection mechanism • every node u repeats infinitely the following: • Node selection: u selects q nodes v1, . . . , vq; • Message selection: u sends Mi to vi, i = 1, . . . , q; • Where Mi denotes a message prepared by u for node vi, and q ≥ 1 is a fixed parameter..

  14. Opportunistic Spatial Gossip(Cont’d) • Two node selection mechanisms: • 1. Geographic Gossip • Based upon the principle of flooding. • Uses links of the lattice and connections with the mates.

  15. Opportunistic Spatial Gossip(Cont’d) • 2. Social Gossip • Uses connections with the mates.

  16. Discussion • What if all nodes are mobile? • problem of using opportunistic shortcut even more complex. • Assuming that the movements of the nodes are mutually independent, the shortcut distribution would simply result from the forgetting mechanism applied to the combination of two independent random walks. • What if nodes follow other mobility processes?

  17. Applications • Gossip-based communication protocols are efficient methods for designing robust and scalable communication schemes in large distributed systems [3]. • Resource location • Construction of approximate spanning tree • In a variety of contexts, the use of randomization to propagate information has been found to provide better reliability and scalability than more regimented deterministic approaches. [4]

  18. References: • [1] http://en.wikipedia.org/wiki/Random_walk • [2] http://en.wikipedia.org/wiki/Mobile_social_network • [3] A. Demers, D. Greene, C. Hauser, W. Irish, J. Larson, S. Shenker, H. Sturgis, D. Swinehart, and D. Terry. Epidemic algorithms for replicated database maintenance. Proc. of ACM PODC, 1987. • [4] D. Kempe, J. Kleinberg, and A. Demers. Spatial gossip and resource location protocols. J. ACM 51(6):943–967, 2004.

  19. Questions / Comments??