Power Control in WLANs for Optimization of Social Fairness

1. Power Control in WLANs for Optimization of Social Fairness Vaggelis Douros Pantelis Frangoudis Konstantinos Katsaros George Polyzos {douros06,pfrag,ntinos,polyzos}@aueb.gr PCI 2008, 28/08/2008, Samos, Greece

2. Motivation • Some friends stay in the same neighborhood • Each one has an AP • Should they use Power Control for a fair and efficient distribution of their incomes?

3. Outline • Prerequisites - Methodology • Proposed Algorithms • Performance Evaluation • Variations • Conclusions

4. Prerequisites • 2 APs (3 APs) • Using the same channel interference • Transmit at Pmax (i.e. maximum coverage radius) • Each AP belongs to a different owner • Goal: APs fully cooperate* for a fair and efficient distribution of their incomes • Ν users (N=10,30,50,100) • Uniformly randomly distributed • Static – Noarrivals/ volunteersdepartures

5. Methodology • Custom simulator: C/Matlab • 10000 simulationsfor each scenario • Income computation for each useriand eachAP k

6. Algorithm FirstMax • APs apply power control • They simultaneously reduce their transmission power to the same level • If, in the new state, the income for each AP is larger (worst case … equal) than the income in the previous state, power decrease continues • Otherwise, they choose to transmit at the exact previous state • Algorithm stops First time there is a decrease to an AP’s income • Find the first local maximum

7. Algorithm BestMax (1) • APs apply power control • They simultaneously reduce their transmission power to the same level • Each AP computes its income • Algorithm stops APs have no common coverage area

8. AlgorithmBestMax (2) • Find the value of the transmission power (Pmax) that maximizes the income of an AP, independently of the income of all other APs. • Repeat the previous step for all APs of the topology. • Find the value of the transmission power that the sum of the percentage losses from the maximum feasible incomes of each AP is minimized.

9. Income Comparison between FirstMax - BestMax

10. Mean % Improvementof FirstMax and BestMax with 2 ΑPs - 3 APs

11. Variations • All APs of the neighborhood belong to me!.. • Should I use power control? • Non strict (not fully compliant) versions of these power control algorithms … • “Bliss or curse?” • Add a type of bargaining mechanism

12. Conclusions • Back to the start… • Some friends stay in the same neighborhood • Each one has an AP • Should they use Power Control for a fair and efficient distribution of their incomes? • Of course! BestMax is a brilliant choice! • Full and honest cooperation is rewarded!

13. Thank You! Vaggelis Douros Mobile Multimedia Laboratory Department of Informatics Athens University of Economics and Business douros06@aueb.gr http://mm.aueb.gr/~douros