| A goal of the cellular communication system operator is to maximize subscriber usage within a fixed channel allotment. However, co-channel interference degrades communication quality, further restricting cellular operators to provide reliable service with minimal channels. Currently conventional sectorized cellular systems restrict the reuse of frequency in clusters of 3, 4, or 7 cells. Each cell type is also allocated a disjoint set of frequency channels identical to the number of sectors in a cell. They have not taken full advantages of antenna directivities to enhance frequency reuse efficiency.; In this thesis, an innovative architecture design and frequency reuse scheme called Channel Alternation and Rotation (CAR) is proposed. By employing reuse clusters having multiple reuse distances and by allocating additional channel set(s) to each cell type for alternating and rotating frequency channels avoiding nearest front-lobe interferers, CAR allows deploying tighter and fractional reuse factors. As channels are alternated and rotated, the CAR approach also forms low interference regions enabling the deployment of inner-tiered cells that share the same frequencies. In a typical environment, for example, if a carrier to interference ratio (C/I) of 17 dB is required, CAR increases system capacity by up to 31 percent over a conventional sectorized system while CART further increasing system capacity to 75 percent, or up to 55 percent over a two-tiered counterpart. CAR and CART are simple and adaptable. Since no modification to the base stations is required, they introduce no additional costs.; With the growing demand in mobile services, the limited available radio spectrum, and the expensive infrastructure build-outs, cellular network designers must strive to achieve highest possible frequency reuse efficiency with minimal costs. An economical and simple approach, such as CAR or CART, is needed to maximally exploit the scarce radio spectrum and existing infrastructures. |
