Browsing by Subject "Code Division Multiple Access"
Now showing 1 - 2 of 2
Results Per Page
Sort Options
Item Coexistence in femtocell-aided cellular architectures(2009-05) Chandrasekhar, Vikram; Andrews, Jeffrey G.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.Item Handoff issues in a transmit diversity system(Texas A&M University, 2005-02-17) Jaswal, KavitaThis thesis addresses hando? issues in a WCDMA system with space-time block coded transmit antenna diversity. Soft hando? has traditionally been used in CDMA systems because of its ability to provide an improved link performance due to the inherent macro diversity. Next generation systems will incorporate transmit diversity schemes employing several transmit antennas at the base station. These schemes have been shown to improve downlink transmission performance especially capacity and quality. This research investigates the possibility that the diversity obtained through soft hando? can be compensated for by the diversity obtained in a transmit diversity system with hard hando?. We analyze the system for two performance measures, namely, the probability of bit error and the outage probability, in order to determine whether the improvement in link performance, as a result of transmit diversity in a system with hard hando?s obviates the need for soft hando?s.