Entwicklung und Leistungsbewertung von Koexistenz und Zusammenarbeit fördernden Verfahren in IEEE 802.11e zur Untersuchung im Spektrum konkurrierender Funknetze
The upcoming IEEE 802.11e is an extension of the 802.11 WLAN standard for provisioning of QoS. This diploma thesis evaluates the problem of QoS support in 802.11e in coexistence scenarios. As long as a set of 802.11e-stations operates without any other competing stations in the area, QoS can be guaranteed by a central coordinator, using polling techniques. However, in the situation of overlapping sets of 802.11e-stations (OQBSS), all stations support priorities between different data streams, but cannot guarantee any QoS, because of the uncoordinated access to the common radio channel. An approach to model such a competition scenario is the stage-based game model evaluated through a Cournot analysis. The Cournot elements are the gained utility of the provided QoS the price a player has to pay for its utilization of the radio channel and a resulting payoff. Each player, representing a QBSS, maximizes its individual payoff. The extension of the Single Stage Game to multiple stages covers the dynamic effects of the competition. The model's intention is the definition of an etiquette, i.e. a framework for the player's interaction. The aim is to establish adequate stable states in the Multi Stage Game , such as cooperation, under which adaptive QoS support is achieved. The Matlab simulator YouShi was developed to model this game theoretical approach. Within YouShi the basic 802.11e mechanisms were implemented together with the game intelligence of the players. The gained results are evaluated and summed up to a conclusion: QoS in an unlicensed band can be guaranteed in coexistence scenarios of OQBSSs with help of intelligent strategies. Directly related is the question of social behavior respectively fairness in the case of a at the Multi Stage Game participating low priority player.
