Collaboration Mechanisms in SOA based MANETs

Introduction Collaboration implies the cooperation between the nodes to support the proper functioning of network. Collaboration is the sole of Mobile Ad-hoc Networks(MANETs) without which MANETs cannot be implemented.

Need of Collaboration in MANETs Nodes collaborate to: – Service Providing – Packet Forwarding By providing services a node introduces its information(data) or functionalities to the whole network By forwarding packets a node supports the network by acting as a router and forwarding packet to reach its destination.

Need of Collaboration in MANETs cont… Necessary in some environments such as disaster management. Example- – Flooding – Earthquake, etc When all known routes are supposed to be blocked/destroyed. MANETs can be used to find the available routes to rescue from the point of vicinity.

Traditional Assumption of Collaboration User’s cooperation is usually assumed Default cooperation is impractical in MANETs Sometimes user’s hesitate to collaborate

Why Nodes Hesitate to Collaborate? Lack of resources needed to collaborate example drowned battery, etc. To save their limited resources like – Battery – CPU – Memory – Sharable bandwidth Reliability issues They only wants to consume other’s services

Incentive Mechanisms Mechanisms to handle with selfish nodes To support collaboration in network Providing rewards for collaboration Rewards may be real or virtual currency

Types of Incentive Mechanisms They are of two types: – Credit-Payment Scheme – Game Theory Both mechanisms provide incentives or rewards on the basis of some event

Credit-Payment Scheme Mobile nodes providing service/ forwarding packets of others receive virtual currency or credit Mobile nodes/central coordinator benefiting from the service are charged for it.

Game Theory A branch of economics related to deriving the optimal strategy for every rational competitive player. Assumes all players are rational.

Objective of Game Theory Look for the Nash equilibrium point A player cannot increase his payoff by changing strategies while other players’ strategies remain fixed.

Traditional Approach of Incentive Mechanisms First-come-first-serve(FCFS) manner Requests arriving in the order will be served in the same manner The profit earned is fixed.

Drawbacks of Traditional Approach Incentives earned may not be sufficient to cover resources sacrificed Huge requests for service or packet forwarding will deplete resources in faster rate A node may refuse to provide service/ forward packet if it will not get the benefit

Proposed Approach When huge demand arrives, a node has the opportunity to maximize the profit Profit earned will follow the dynamic price Depends upon the number of requests a node have to serve or packets a node forwarded.

How to identify that a node would serve a huge demand ?

Articulation Point The concept of articulation point in graph theory can be used to determine the node which will forward maximum number of packets. Articulation point is a vertex in an undirected connected graph iff removing it disconnects the graph i.e. divides the graph in to two components.

Articulation Point cont… Considering network as a graph G(V,E) Where, V- Set of Vertices in G or set of Mobile nodes E- Set of Edges in G or set of connections between mobile nodes Snapshot of a network representing articulation point

Articulation Point cont… Removal of articulation point disconnects the graph in to two parts, therefore, every path between these two parts passes through the articulation point. Now, if a mobile node is the articulation point, it have to forward a large number of packets in the network which imposes a huge load on it. So, dynamic payment based packet forwarding can be used in this situation providing more benefit to the node forwarding large number of packets.

To determine which node will have to serve a large number of services, the sever node have to contact the central coordinator which is incharge of the payment based system.

Benefits of Using Dynamic Payment Scheme Nodes have opportunity to maximize their profit Nodes will not refuse to provide its services in case of high demand Nodes will try to give their maximum to earn more and more profit Selfish nodes will get attracted towards collaboration

Auction based VCG Algorithm

Auction is a game-theory mechanism used to attract more and more nodes to participate in the collaboration A mechanism (f, p 1,...., p n ) is called a Vickery-Clarke- Groves(VCG) mechanism if f maximizes the social welfare: f(v 1,...., v n ) ϵ argmax aϵA Σ i v i (a) The payment function is of the form: p i (v 1,...., v n ) = h i (v −i ) − Σ j≠i v j (a), where a = f(v 1,...., v n ) and h i (.) is any arbitrary function calculated without i’s participation.

Examples of VCG mechanism Auction of a single item- In the Vickery auction -There is a set of n agents denoted by I -The set of alternatives here is the set of possible winners. -Each agent is a possible winner here. Hence A = {i wins | iϵI} Multi-unit Auction- “Allocation Problem” addresses the issue of allocating “resources” among the different possible users of these resources.

Proposed Mechanism Based on dynamic payment multi-unit auction VCG mechanism Overall time complexity is Θ(nlgn)

Proposed Mechanism cont… This idea we now represent in the algorithm stated as follows: Sort the bids according to the bid price for the service Allocate the services to the k highest bidders, where k is the total number of requests that can be processed by providing node within the specified time frame For payment function, each bidder, getting a service, will pay the value of the k + 1 st bidder’s bid price

Benefits of Proposed Mechanism Attracts users in highly demanding environment Social benefits for the nodes which cannot afford providing huge demand Give opportunity to maximize the profit in high demand

Experimental Results

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