Hierarchical structure of wireless systems - an analytical performance study

The use of hierarchical structures for providing excellent wireless connections for customers has attained growing attention. Models to investigate the QoS requirements rather quickly become complicated and hard to analyze. In the paper a first rough analytical approach for the answer is given. As the users devote more and more time to be connected through wireless connections, and at the same time becomes more and more mobile the traditional systems does not work. Our model is based on a hierarchical structure where different, already existing, wireless systems interact to maintain coverage for moving customers outdoors as well as indoors. The QoS requirements are based on the type of service used and the mobility pattern. The system should be able to configure the connection to make the optimal choice among those networks present at the location of the customer. Further, the mobile terminals must be able to handle the different networks. In a general case, systems with broader coverage and usually lower bandwidth will act as backup systems for higher quality systems. Our analytical tool shows the benefits and drawbacks of such a system. The transition duration times between usage of different systems are analyzed together with their variance and squared coefficient of variation. Each handover is a source for failure. By changing the parameter setting it is possible to get at better understanding of how to configure hierarchical wireless systems for best performance. With the presented formulas this could be achieved in a fast and thorough way.