Collaboration Mechanisms in SOA based MANETs. Introduction Collaboration implies the cooperation...
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Transcript of Collaboration Mechanisms in SOA based MANETs. Introduction Collaboration implies the cooperation...
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.
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 nodesE- 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 is a game-theory mechanism used to attract more and more nodes to participate in the collaboration
• A mechanism (f, p1, ...., pn) is called a Vickery-Clarke-Groves(VCG) mechanism if
f maximizes the social welfare: f(v1, ...., vn) ϵ argmaxaϵA Σi vi(a)
• The payment function is of the form:
pi(v1, ...., vn) = hi(v−i) − Σj≠i vj(a),
where a = f(v1, ...., vn) and hi(.) 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 + 1st 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