Resource allocation in OFDM-based relay and cognitive radio networks

Abstract

Resource allocation methods are highly system dependent and specic resource allocation methods should be tailored according to the respective system specications and requirements. This thesis investigates new resource allocation methods for OFDM-based relay and cognitive radio (CR) networks. Performance of the proposed methods is veried through computer simulations. Firstly, resource allocation in multi-relay assisted cooperative OFDM networks is considered. Resource allocation problem is mathematically formulated to maximize theinstantaneous capacity. As an alternative for more complex jointly optimal resource allocation methods, less-complex yet effective resource allocation methods are proposed. Secondly, power allocation in OFDM-based two-hop relay networks is studied in the presence of outdated channel knowledge. Two new power allocation methods are discussed to maximize the expected rate and the outage rate. Thirdly, relay selection and power allocation in OFDM-based CR relay networksis studied to maximize the instantaneous capacity of the CR transmission. Suboptimal resource allocation methods are presented for multi-relay assisted OFDM CR networks and their performance is compared with jointly optimal resource allocation method. Next, new resource allocation methods are presented to maximize the instantaneous capacity of CR relay networks when only the statistical channel information between the CR network and the legacy network is known. Optimal power allocation methods to maximize the instantaneous capacity of the CR transmission are derived and low complexity suboptimal power allocation algorithms are also proposed. Finally, a practical scenario of operating CR networks in TV white spaces is considered. An interference minimization based power allocation method is developed for OFDM-based single-hop CR transmission. Numerical results confirm that the proposed power allocation scheme produces less interference to TV receivers compared to other classical power allocation methods while guaranteeing an acceptable quality of service for secondary transmission.

Date of Award	2013
Original language	English