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, p1, ...., pn) is called a Vickery-ClarkeGroves(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 itemIn 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
Experimental Results
Thank You