# Exploiting Mobility in Ad-Hoc Wireless Networks with Incentives

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```					Exploiting Mobility in Ad-Hoc
Wireless Networks with
Incentives

Daniel Figueiredo
Michele Garetto
Don Towsley
Outline
   Incentive mechanisms and Mobility
   System model
   Game model
   Simulation results
Incentives
   Incentive Problem:
   Battery power and bandwidth are scarce
resource
   Refuse to cooperate / relay traffic
   Solutions
   Reputation mechanisms
   Payments / Pricing mechanisms
Mobility
   Nodes are allowed to move strategically.

   Under different incentive mechanisms
   In reputation systems, nodes may want to
maintain high ―reputations‖.
   In payment mechanisms, nodes may want
to minimize their costs.
Outline
   Incentive and Mobility
   System model
   Game model
   Simulation results
System Model

S

B

r

D
System Model – relayed traffic
intensity R(x)

S

B

o   P       x
System Model
   Parameters:
   B rectangular width
   r transmission range
   Metrics
   R(x) relayed traffic intensity
   H(x) average path length
   H(x) =  D Dist(D,S(x)) /r dD
System Model – relationship
between R(x) and H(x)
    xR(x) dx =  xH(x) dx
   Represents the total amount of traffic
exchanged in the network.
   Two distribution have the same mean.
   Payment mech.  max R(x)-H(x)
   Reputation mech.  min R(x)
Outline
   Incentive and Mobility
   System model
   Game model
   Simulation results
Game Model
   Each node is a player.
   Players take turns to move.
   Assume at any time each node knows
the location of all other nodes.
Game Model
   Let pi=(xi ,yi) be the position of node i.
   P = (p1,p2,…,pN)
   P-i is P with i-th component removed.
   Redefine:
   R(pi,P-i) amount of relayed traffic by node i.
   H(pi,P-i) average # of hops from i to all
destinations
Game Model– I(pi,P-i)
   Let I(pi,P-i) be the noise produced by
other nodes’ transmissions.
   Assume signal power decay distance x
as 1/xa,with 2<a<4.
   I(pi,P-i) =jiN(j,i) / dist(pi,pj)a
   N(j,i) is the average # of transmissions
at j that interfere with the reception of a
useful signal at i.
Game Model—payoff function

   U(pi,P-i)= R(pi,P-i)+H(pi,P-i)+I(pi,P-i)
   For payment mech. =1, =-1
   For reputation mech. =-1, =0
    is negligible.
Subgame perfect equilibrium
& backward induction
1
L          R

2                    2
l        r          l         r

(0,0)           (3,2)(1,4)           (2,1)
Subgame perfect equilibrium
& backward induction
1
L          R

2                    2
l        r          l         r

(0,0)           (3,2)(1,4)           (2,1)
Subgame perfect equilibrium
& backward induction
1
L          R

2                    2
l        r          l         r

(0,0)           (3,2)(1,4)           (2,1)
Outline
   Incentive and Mobility
   System model
   Game model
   Simulation results
Key Observations
   Under reputation mech., nodes tends to
cluster together.
   Under payment mech., nodes tends to
scatter.
   By considering the interference, nodes
keep certain distance with each other.

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 views: 3 posted: 12/28/2011 language: pages: 19