Utility Thory Based Dynamic Spectrum Management Strategy

In recent years, with the rapid development of wireless mobile communication technologies and the extensive research & deployment of mobile communication systems, the demand for frequency spectrum increases vastly. The shortage of exiting fixed spectrum allocation method becomes more and more obvious.In the Fixed Spectrum Management (FSM) scheme, the government manages the spectrum through issuing spectrum licenses to different operators. FSM can effectively avoid sever interference between different Radio Access Networks (RANs), and the government can also manage the spectrum in a centralized way. However, because the demand for spectrum varies both in the time domain and the space domain, the fixed spectrum allocation method, in which the specific spectrum can only be used in the specific space or time, leads to underutilization of spectrum. According to the measurement reports on the spectrum utilization by the spectrum management agencies, e.g FCC (Federal Communication Commission), vast spectrum is not utilized most of the time, which means that the scarcity of spectrum is not because of the real "insufficiency", but because of the low utilization of spectrum. In order to efficiently exploit the spectrum utility, Dynamic Spectrum Management (DSM) strategy is proposed as a promising method to improve spectrum utilization and has attracted much attention in the past ten years.Generally speaking, DSM can be categorized as four parts:spectrum sensing, spectrum decision, spectrum access & sharing and spectrum mobility. Considering the high requirement for cell-edge performance in cellular network and the spectrum sharing problem in Femtocell network, according to the current research hotspots in DSM, the thesis mainly researches on intra-network cooperative spectrum access & sharing and spectrum handoff. The research contents are shown as follows:First, considering the requirements for mitigating interference and improving data rate in cell edge area, in order to improve spectrum utilization further more, a Dynamic Spectrum Access (DSA) scheme is proposed in the thesis. A joint power/channel allocation algorithm is also presented, which allows the cell-edge users to cooperate with each other to exchange information. The proposed DSA scheme improves cell-edge user experience, the network performance and the spectrum utilization.Second, considering the spectrum access and sharing problem in Femtocell network, a Dynamic Spectrum Sharing (DSS) scheme is firstly proposed in the thesis, in which a Dynamic Heuristic Clustering algorithm is presented to decrease the interference between Femtocells. A joint power/channel allocation algorithm similar to that in aforementioned DSA scheme is also used to improve the data rate of Femtocell users.Finally, in order to keep the communication continuity of cognitive users and improve the throughput, spectrum handoff is necessary when the specific portion of the spectrum in use is required by its owner. A cognitive radio based spectrum handoff mechanism and principle is proposed. Through designing reliable spectrum pre-evaluation method and flexible spectrum handoff mechanism, in which the relative thresholds can be adjusted, the communication continuity and QoS of applications can be guaranteed. It also improves system throughput.