Abstract
The static method of allocating fixed blocks of spectrum, over a considerable period of time is gradually giving way to a more flexible method of using the spectrum. Dynamic spectrum access offers a new promising method of addressing the inefficient use of the spectrum. However, three main barriers still need to be addressed to reap the full benefit. These include the technical, economic and regulatory barriers. This thesis focuses on the technical challenges that will enhance the opportunistic use of the spectrum between two operators in a dynamic manner. The aim is to optimise the use of the scarce spectrum resource. A coordinated network based approach for spectrum allocation between two wireless operators is investigated, using the Universal Mobile Telecommunication Service (UMTS) as a case study. This thesis proposes network centric algorithms to facilitate multi-operator spectrum sharing within the context of the cellular wireless network. The achievable gains in terms of the spectrum efficiency gain is compared with legacy Fixed Spectrum Allocation (FSA). The algorithms are investigated under uniform and non-uniform traffic conditions. The results show significant improvements in the spectrum efficiency gain of the network, up to thirty six percent for the non-pool algorithm (one primary earner and two secondary carriers) and ten percent for the pool based algorithm (two carriers). The gain is as a result of the improved statistical multiplexing of mobile users. The results also reveal that additional gains up to four percent could be achieved depending on the connection queuing times. Furthermore, the results show that the penalties associated with the proposed algorithms in the form of total call setup messages, can be minimised by sharing the radio resource management entity. Finally, the possible architectures to facilitate the improved spectrum sharing algorithm proposed in this thesis are also investigated.