FOSTERING COLLABORATION IN EMERGING THREE-TIERED SPECTRUM MARKETS
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Ensuring optimum spectral efficiency is a critical requirement for current wireless networks to cope with the ever-growing flow of wireless data traffic, using limited spectral resources. As such, spectrum sharing, which allows different grades of users, as well as multiple networking standards to co-exist and utilize in the same frequency band, has become a topic of great intrigue. Due to the inherent advantages of these schemes, the US government has opened up vast amounts of federal spectrum that supports spectrum sharing. The Citizens Broadband Radio Service (CBRS) proposed by the Federal Communications Commission (FCC) is one of them. A tiered spectrum sharing approach, CBRS allows end commercial users to share the radio spectrum with federal incumbent users in the 3,550-3,700 MHz range. Employing a light leasing approach, the FCC aims to encourage the licensed providers of CBRS called the Priority Access License (PAL), to lease/share their licensed spectrum with unlicensed users named the General Authorized Access (GAA) for limited duration, which is essential for the maximum utilization of the CBRS bandwidth, but the current approach proves ineffective for that purpose. In this thesis, we propose a novel clustered framework to facilitate this sharing, where GAA users are grouped into multiple distinct geographical clusters and request access to licensed spectrum through the clusters in a collaborative manner rather than individually. Each cluster will nominate a central entity denoted as the GAA leader to communicate their requests to the PAL operators, as well as establish temporary connections with PAL access points once granted permission for licensed CBRS access, to be used by GAAs outside the operators coverage range. The leaders will also receive information from the PAL operators regarding the number of requests they are willing to accept and transmit that to the GAAs within the cluster. This process reduces the amount of information flow between the licensed and unlicensed entities, thereby providing a convenient platform for CBRS spectrum sharing. In order to determine the leader, the role of which can be assumed by any of the GAA users within the cluster, we formulate a distributed leader selection algorithm algorithm called the LSA, which takes into account the signal strength of the PAL access points available the GAA users, as well as the network density of each GAA node, to assign a score called the leader evaluation score (LES) to each GAA user and nominate the user with the highest score as the leader. To encourage PAL operators to frequently share their licensed spectrum, we incorporate a government reward model, where operators are incentivized by gaining access to additional spectrum for limited periods based on their level of sharing.