| Summary: | In this thesis, we consider the more broad-based spectrum sharing where primary and secondary users transmit simultaneously in the same band. In the first part of thesis, we consider an overlay cognitive radio downlink network with non-causal primary message knowledge at cognitive base station. While conventional linear precoding techniques in cognitive radio networks aim to limit or completely cancel the interference to the primary users, we investigate new interference driven linear precoding techniques to improve the performances of primary and cognitive links by exploiting the use of interference energy when interference is constructive. In the second part of thesis, we investigate cooperative relaying in overlay cognitive radio network and analyze the outage performance of overlay cognitive radio network when cognitive nodes relay the causal primary message to the primary destination to improve the performance of the primary system. Further, assuming causal knowledge of the primary user's message at the cognitive transmitter, we investigate the problem of transmit power allocation and linear beamforming design in an overlay cognitive radio network in single-input-multiple-output (SI MO) and the rnultiple-input-sinqle- output (MISO) configurations. The third part of the thesis deals with the underlay spectrum sharing cognitive radio. We investigate the multiuser diversity introduced by opportunistic user selection in underlay cognitive radio network, Based on a simple cognitive user selection strategy aiming at maximizing the received signal-to- interference-plus-noise ratio (SINR) under interference constraints to the primary receiver, we study the statistics of the SINR at the cognitive receiver, and derive exact analytical expressions of its probability density function (PDF). We use it to analytically calculate the multiuser diversity gains introduced in the system due to the selection of one cognitive user amongst multiple cognitive users. We also analyze the asymptotic behaviour of multiuser diversity gains for different parameters.
|
|---|
