MODELING RESOURCE SHARING DYNAMICS OF VOIP USERS OVER A WLAN USING A GAME-THEORETIC APPROACHINFOCOM 2008

Edson H. Watanabe, Daniel S. Menasch´e, Edmundo de Souza e Silva, Rosa M. M. Le˜ao

Systems Engineering and Computer Science Department

COPPE - Federal University of Rio de Janeiro, 21941-590 - Rio de Janeiro, RJ, Brazil

Presenter: Po-Jung Wang

OUTLINE Scenario Introduction Game-theoretic model Simulation Experiment Result Conclusion

SCENARIO – COFFEE SHOP

AIRPORT

USING VOIP THROUGH THE WIFI

NOW WE HAVE TWO QUESTIONS

What are the performance consequences of letting the users to freely choose their rates?

How to explain the adaptation process of the users?

MODELING

GAME THEORY EQUATION

SYMMETRIC STRATEGIC GAME

N is the number of users that share the access point. S is the discrete set of strategies available, that is, the set of joint codec plus FEC mechanisms that any application user can select from. U is the utility function.

WHAT IS MOS?

Mean opinion score (MOS)

MOS Quality Impairment

5 Excellent Imperceptible

4 Good Perceptible but not annoying

3 Fair Slightly annoying

2 Poor Annoying

1 Bad Very annoying

PERSPECTIVE FROM ONE USER

low, 20 kbps (Speex 6 kpbs, FEC 1:2::3:6);

medium, 33.6 kbps (Speex 14.2 kbps, FEC 1:2)

high, 47.5 kbps (Speex 14.2 kps, FEC 1:2::3:6).

SYSTEM SATURATION THROUGHPUT TESTING

EQUILIBRIUM STATES FOR THE MODEL AND THE EXPERIMENT

TRANSIENT PROBABILITY

PROBABILITY FORM ONE STATE TO ANOTHER

LETTING USER EXIT THE SYS IF MOS IS TO LOW

SUMMARY AND CONCLUSION Free users with local information can reach an

equilibrium which is close to optimal from the system perspective. However, the equilibrium can be unfair.

Using a game-theoretic model and propose a methodology to parameterize it.

Strength and weeknessDiscovery the phenomena of letting user to freely choose Need more scalable experiments