PhDFemtocell is an effective approach to increase system capacity in cellular networks.
Since traditional Femtocells use the same frequency band as the cellular network,
cross-tier and co-tier interference exist in such Femtocell networks and have a major
impact on deteriorating the system throughput. In order to tackle these challenges,
interference mitigation has drawn attentions from both academia and industry. TV
White Space (TVWS) is a newly opened portion of spectrum, which comes from the
spare spectrum created by the transition from analogue TV to digital TV. It can be
utilized by using cognitive radio technology according to the policies from
telecommunications regulators. This thesis considers using locally available TVWS to
reduce the interference in Femtocell networks. The objective of this research is to
mitigate the downlink cross-tier and co-tier interference in different Femtocell
deployment scenarios, and increase the throughput of the overall system.
A Geo-location database model to obtain locally available TVWS information in UK
is developed in this research. The database is designed using power control method
to calculate available TVWS channels and maximum allowable transmit power based
on digital TV transmitter information in UK and regulations on unlicensed use of
TVWS. The proposed database model is firstly combined with a grid-based resource
allocation scheme and investigated in a simplified Femtocell network to demonstrate
the gains of using TVWS in Femtocell networks.
Furthermore, two Femtocell deployment scenarios are studied in this research. In the
suburban Femtocell deployment scenario, a novel system architecture that consists of
the Geo-location database and a resource allocation scheme using TVWS is proposed
to mitigate cross-tier interference between Macrocell and Femtocells. In the dense
Femtocell deployment scenario, a power efficient resource allocation scheme is
proposed to maximize the throughput of Femtocells while limiting the co-tier
interference among Femtocells. The optimization problem in the power efficient
scheme is solved by using sequential quadratic programming method. The
simulation results show that the proposed schemes can effectively mitigate the
interference in Femtocell networks in practical deployment scenarios
