| The surest way to increase the capacity of a wireless system is by getting the transmitters and receivers closer to each other, which creates the dual benefits of higher quality links and more spatial reuse. In a network with nomadic users, this inevitably involves deploying more infrastructure, typically in the form of microcells, hotspots, distributed antennas, or relays. Compared to these deployments, a less expensive alternative for cellular operators is the recent concept of femtocells---also called home base-stations---which are end consumer installed data access points in the desire to get better indoor voice and data coverage. A two-tier network consisting of a conventional macrocell overlaid with shorter range wireless hotspots offers potential capacity benefits with low upfront costs to cellular operators. This dissertation addresses the key technical challenges inherent to a femtocell-aided cellular network, specifically managing radio interference and providing reliable coverage at either tier, for different physical layer technologies. Specific contributions include (1) an uplink capacity analysis and interference avoidance in two-tier networks employing Code Division Multiple Access (CDMA), (2) a decentralized power control scheme in two-tier networks with universal frequency reuse, (3) a coverage analysis of multi-antenna two-tier networks, and (4) spectrum allocation in two-tier networks employing Orthogonal Frequency Division Multiple Access (OFDMA). The goal of this research is to inspire and motivate the use of decentralized interference management techniques requiring minimal network overhead in ongoing and future deployments of tiered cellular architectures. |
