Abstract
In recent years, many wireless applications and services have been de-veloped to operate in unlicensed spectrum bands, resulting in a need of a new band for each of them. But most of the licensed spectrum bands are under-utilized, especially the TV bands and those used by the wireless mi-crophones (these users are known as Primary Users -PUs). So the Federal Communications Commission (FCC) has allowed to the unlicensed spectrum bands devices (known as Secondary Users -SUs) to use the licensed spectrum. But the main constraint is that SUs cannot cause any harmful interference with PUs. This is done using cognitive techniques, that lead SUs to stop any transmission on a spectrum chunk that is contemporaneously used by a PU, and to look for another one. In this environment there is not a static channel that can be used by all SUs in the same network to exchange control informa-tion (Control Channel Problem). The objective of the thesis is to solve the Control Channel Problem adapting to the time and space variability of the channels and avoiding any synchronization complexity. The idea on which this work is based, is the clustering: a network is partitioned in groups of devices called clusters. In any of them a different control channel is used. The work consists in a cluster formation protocol with whom SUs meet other SUs, decide to form a cluster and decide which SUs will be the cluster-head of that cluster. The protocol allows also to exchange control information between neighbor clusters. The referential environment is a wireless mesh network using the IEEE 802.11 wireless standard, in which nodes are wire-less mesh routers. Our protocol has been tested based on several metrics and compared to an existent algorithm that uses an a priori synchronization between SUs. Our work, although does not use a synchronization between
SUs, has performances similar to the comparison algorithm in most of cases, and in many others has better performances.
