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Power control under best response dynamics for interference mitigation in a two-tier femtocell network

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Title: Incentive Based Power Control in Wireless Networks of Autonomous Entities with Various Degrees of Cooperation Last modified by: vaggelis – PowerPoint PPT presentation

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Title: Power control under best response dynamics for interference mitigation in a two-tier femtocell network


1
Power control under best response dynamics for
interference mitigation in a two-tier femtocell
network
Vaggelis G. Douros Stavros Toumpis George C.
Polyzos
_at_ RAWNET 2012 Paderborn, Germany, 18 May 2012
2
Motivation (1)
This is urgent!
Deadline is today!
The food is delicious
Fantastic shirt!
The problem Some couples may not communicate
efficiently ?
3
Motivation (2)
  • N pairs of wireless nodes (e.g., BSs-MNs,
    FBSs-FMNs) transmit their data sharing the same
    wireless medium
  • Each pair aims at achieving a (different) QoS
    target
  • Interference among wireless devices may prevent
    an efficient communication
  • N couples of friends discuss in the same
    cafeteria
  • Each couple aims at achieving a (different)
    minimum quality of discussion
  • Discussions of other couples may prevent an
    efficient communication

Competition for resources among players
Non-Cooperative Game Interference mitigation
through power control
4
Which is the wireless network?
A two-tier femtocell network
Chandrasekhar et al., IEEE Comm. Mag., 2008
5
Why Femtocells? (1)
  • Femtocells
  • low-power access points
  • connect to the service providers network via
    broadband
  • provide voice and broadband services
  • allow a small number of simultaneous calls and
    data sessions

http//www.smallcellforum.org
6
Why Femtocells? (2)
  • () dense deployment? increase spectrum reuse
  • () better indoor coverage? superior indoor
    reception
  • () low(er) cost (than macrocell deployment)
  • () plug and play installation
  • (-) interference This is the challenge!
  • Source Informa Telecoms Media, October 2011

7
A two-tier femtocell network power control game
(1)
  • Players ??N transmitters share the same portion
    of the spectrum (CDMA Network)
  • N1 Macrocell Mobile Nodes (MNs)
  • N2 Femtocell Mobile Nodes (FMNs)
  • Strategy ??Selection of the transmission power
  • MN Pi ? 0,Pmax
  • FMN Pi ? 0,FPmax
  • Utility (Payoff)

8
A two-tier femtocell network power control game
(2)
  • N1 MNs
  • will be mostly used for voice, inelastic traffic
  • high(er) priority to be served by the operators
  • low(er) QoS demands (than FMNs)
  • N2 FMNs
  • are deployed by indoor users for their self
    interest
  • should not create high interference to MNs
  • focus on data services?high(er) QoS demands
  • Conclusion Difficult to describe their needs and
    restrictions with the same utility function

9

A two-tier femtocell network power control game
(3)
  • Our choices
  • MN Utility Function
  • FMN Utility Function

10
A two-tier femtocell network power control game
(4)
  • N1 MNs
  • will be mostly used for voice, inelastic traffic
  • high(er) priority to be served by the operators
  • use any transmission power up to Pmax without
    pricing
  • low(er) QoS demands (than femtocells)
  • SINRmax
  • N2 FMNs
  • FMNs should not create high interference to MNs
  • pricing is used to discourage them from creating
    high interference to the macrocell users
  • focus on data services?high(er) QoS demands
  • No SINRmax

11
Nash Equilibrium Existence
  • Q1 Has the game G at least one NE?
  • Yes!
  • Debreu-Fan-Glicksberg (1952)

12
Best Response Dynamics Power Control (1)
  • Q2 How can we devise an algorithm that converges
    to a NE?
  • The two-tier femtocell game G is a collection of
    N parallel optimization problems
  • each (F)MN aims at maximizing its own utility
    function Ui
  • Best Response Dynamics Scheme

13
Best Response Dynamics Power Control (2)
  • MN Optimization problem
  • which leads to
    (1)
  • See also Foschini Miljanic, TVT93 Grandhi
    et al., WPC94
  • So, the best response dynamics scheme is

  • (2)

14
Best Response Dynamics Power Control (3)
  • FMN Optimization problem
  • which leads to
    (3)
  • See also Alpcan, Basar, Srikant, Altman,
    Wireless Netw.02
  • So, the best response dynamics scheme is

  • (4)

15
Best Response Dynamics Power Control (4)
  • Equations (2) and (4) form a best response
    dynamics power control scheme
  • () simple scheme
  • () distributed algorithm

16
Uniqueness of the Nash Equilibrium (1)
  • Q3 Does the best response dynamics power control
    scheme based on equations (2) and (4) converge to
    the NE that is defined by equations (1) and (3)
    respectively?
  • In general, there are games where the best
    response dynamics do not always lead to a NE
  • from every initial strategy

17
Uniqueness of the Nash Equilibrium (2)
  • Q4 Is this the unique NE of the game G?
  • Answers Yes Yes!
  • Theorem Let L be the spread factor of the system
    and be the maximum SINR target
    among all the MNs. If
    , then
  • The two-tier femtocell network game has a unique
    NE
  • The power control scheme under best response
    dynamics for FMNs and MNs converges to this NE

18
Topology/Scenarios
  • Topology parameters are based on an extensive
    study by the smallcellforum
  • Symmetric topologies, vary (F)MN-(F)BS positions
    and/or SINR targets

19
Some Results (1)
  • Fixed positions
  • The target SINR of each MN increases with a step
    equal to 0.5 dB

Voice is feasible
20
Some Results (2)
  • Each FMN gradually moves away from its associated
    FBS. All other parameters are fixed

21
Some Results (3)
  • Each FMN gradually moves away from its associated
    FBS. All other parameters are fixed

Voice is feasible
22
The Meat
  • Two-tier femtocell networks
  • heterogeneous needs
  • heterogeneous targets
  • interference remains a big challenge
  • We show the existence and uniqueness of a NE and
    devise an algorithm based on best response
    dynamics that converges to it
  • Interference mitigation in various scenarios is
    achieved
  • Things to do Stackelberg game formulation,
    maximize total revenue, maximize social welfare

23
? Danke schön! ?
  • Vaggelis G. Douros
  • Mobile Multimedia Laboratory
  • Department of Informatics
  • Athens University of Economics and Business
  • douros_at_aueb.gr
  • http//mm.aueb.gr/douros
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