Please use this identifier to cite or link to this item: http://scholarbank.nus.edu.sg/handle/10635/17563
Title: On The Dynamic Spectrum Access For Next Generation Wireless Communication Systems
Authors: TANG PAK KAY
Keywords: Dynamic spectrum access; Spectrum Holes; Spectrum Admission Control; Grade-of-Service; Vertical Handoff; Heterogeneous Networks
Issue Date: 11-Feb-2009
Source: TANG PAK KAY (2009-02-11). On The Dynamic Spectrum Access For Next Generation Wireless Communication Systems. ScholarBank@NUS Repository.
Abstract: New spectrum management techniques with greater flexible spectrum usage rights have been called for to address the apparent spectrum scarcity problem. Dynamic spectrum access (DSA), which represents a paradigm shift away from the current static spectrum allocation approach, has been identified as a promising approach in the near future. In this thesis, the possible new spectrum access models are broadly classified into three categories, namely, the public commons model, the private commons model, and the coordinated access model. The public commons model refers to the coexistence of wireless networks in a given spectrum band where a typical example is given by the existing unlicensed bands. Opportunistic spectrum access (OSA) is an example of the private commons model, where secondary usage of spectrum aims to enhance the spectrum utilization efficiency in a licensed band. The coordinated access model involves sharing spectrum among multiple radio systems in either an agreed manner or through a spectrum agent. Complete spectrum sharing and virtual spectrum partitioning are two possible sharing schemes under this model. The OSA, complete spectrum sharing and virtual spectrum partitioning models are the main focus of this thesis. These models offer different levels of spectrum access flexibilities and impose new and unique design challenges. The main objective of this thesis is to develop analytical platforms for each of these spectrum access models so that the service capacity of the radio systems under prescribed Grade-of-Service (GoS) guarantees can be computed. From the results obtained, we design and propose appropriate spectrum admission control (SAC) policies and study the achievable improvement in the spectrum utilization efficiency.For OSA, we studied the impact of the PR activities on the SR transmission opportunity time. The theoretical probability density function (p.d.f.) of the opportunity time under a given PR traffic model is derived. In addition, the theoretical p.d.f. of the duration where SR transmission is not possible, due to PR transmission in all the frequency bins, is also derived. We next examined the virtual spectrum partitioning model whereby two proprietary radio systems with GoS guarantees can access each othersb excess spectrum to support additional traffic demands. The SAC problem can be formulated using four dimensional Markov chain models. FCFS, RES and random discard (RD) SAC policies were developed to study the service capacity and the incurred tradeoffs. The complete spectrum sharing model in which two radio systems completely share a spectrum band with their access being coordinated through a spectrum manager is also examined. We consider two possible scenarios under this model. In the first scenario, we analyze and compare the maximum service capacity of the radio systems while still satisfying their respective GoS requirements based on RES and RD SAC policies, as well as a policy developed based on constrained Markov decision process (CMDP). In the second scenario, we include the servicesb pricing in the utility function. The SAC problem is formulated as a CMDP and solved analytically to derive the optimal policy which results in maximum revenue for the spectrum manager.
URI: http://scholarbank.nus.edu.sg/handle/10635/17563
Appears in Collections:Ph.D Theses (Open)

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