Over the past two decades the use of wireless communication networks has grown at an unprecedented rate, and this growth is not likely to come to an end in the near future. The main barrier to the sustained growth is the fundamental limitation on increasing the date rate. In practical deployments scarce resources have to be shared among a multitude of users, each of which shows random behavior in terms of application usage and mobility. In the competitive markets of wireless communication services it is essential for network operators to deliver high-quality services at sharp prices. This raises the need for smart and differentiating methods to utilize, control and further optimize the scarce wireless network resources in a cost-efficient manner. Many geographical locations are covered by a multitude of overlapping wireless networks, which enables wireless users to access and use multiple networks simultaneously. Exploiting the concurrent access to multiple wireless networks, throughout referred to as Concurrent Access (CA), opens up the possibilities for increasing capacity, improving robustness, and enhancing Quality of Service (QoS). Despite the enormous potential for quality improvement, only little was known about how to fully exploit the possibilities offered by CA. In this thesis the main interest is in investigating the efficiency of different CA methods. As part of the more recent advances in communication systems that strive for increasing the data rate, transmission adaptation schemes have been introduced. These have caused some networks to provide a strongly fluctuating data rate, depending on the propagation environment. To this end, the last part of this thesis is devoted to traffic control methods. The first method is developed for making and maintaining a traffic contract to guarantee the QoS of applications to wireless users in networks where the available resources may greatly vary. The second method is used to subsequently enforce traffic contracts specifically for shared medium wireless networks. (Author/publisher)
Samenvatting