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 bene¯ts 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 o®ers poten- tial capacity bene¯ts with low upfront costs to cellular operators. This dissertation addresses the key technical challenges inherent to a femtocell-aided cellular network, speci¯cally managing radio interference and providing reliable coverage at either tier, for di®erent physical layer technologies. Speci¯c contributions include 1) an uplink capacity analysis and interference avoidance in two-tier networks employing Code Di- vision 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 requir- ing minimal network overhead in ongoing and future deployments of tiered cellular architectures. / text