Research On Cognitive Access To Multiple Channels

As one of the most promising wireless communication technologies, cognitive radio (CR) can solve the conflict between the shortages of spectrum resource and underused licensed bands. The core technologies behind CR are spectrum sensing and adaptive communications. The secondary users (SUs) are required to sense and monitor the radio spectrum environment that are not occupied by primary users (PUs); A CR device can configure its transmission parameters to opportunistically make best use of the ever-changing available spectrum. In the dissertation, we attempt to exploit the two technologies of CR over the filter bank based multicarrier CR system.Beginning with the principle of multi-carrier communication technology, the mechanisms of OFDM, wavelet packet transform and filter bank multicarrier (FBMC) technologies have been analyzed systematically. FBMC has been suggested to uti-lize the white spaces in the spectrum, which provides the basis for the following analysis and processing.A transceiver framework based on cosine modulated filter banks (CMFB) for cognitive access is proposed. The aim is to bridge the gap between the claims made in multicarrier transmission and research into cognitive access to TV white spaces. An approach is proposed for designing prototype filters of CMFBs with nearly per-fect reconstruction. An objective function for optimization is introduced to control the trade-off between interference protection for PUs and spectral efficiency for SUs. An adaptive linear search optimization technique is employed for the minimization of a one-dimensional objective function. It is demonstrated that CMFB is capable of serving as another candidate for CR systems.A CMFB for multi-channel spectrum estimation and sensing is designed. Through the design of the prototype filter and composition of sub-filters, not only the spec-trum of non-uniform bandwidth can be estimated, but also the interference of ad- jacent passbands can be adjusted to a certain level. Moreover, the multi-channel detection framework for spectrum sensing with filter bank is introduced for sensing different bandwidth channels simultaneously. The multi-channel energy-detection performance in the AWGN and Rayleigh fading channels is investigated by theo-retical analysis and numerical simulation. Because CMFB is able to flexibly adjust the bandwidth and leakage of each channel, the proposed scheme can be used to detect the activities of PUs over channels with different bandwidths.The relationship between cooperation mechanisms and spatial-spectral diver--sity over multiple channels jointly sensing is investigated in the presence of an im-perfect reporting channel. The multiple channels are sensed at the receiver built on the filter bank-based multicarrier system. The multi-channel cooperative spectrum sensing (CSS) strategies are modeled by the introduced cooperative ratio to balance the requirements on sensing accuracy, efficiency and overhead, which is quantita-tively characterized by the energy consumption. The target of CSS is to maximize the aggregate opportunistic throughput of SUs by jointly considering constraints on sensing overhead and the aggregate interference to PUs. The optimization is di-vided into two sequential sub-optimization processes, which are solved with generic algorithms. This study has established a valuable cooperative model for the design of multi-channel CSS in CR.In summary, this dissertation focuses on spectrum utility and sensing, and systematically investigates key problems which fundamentally impact interference to PUs and spectral efficiency of SUs. Through theoretical and experimental analysis of the essential problems, reliable and efficient solutions can help SUs perform sensing and data transmission based on multicarrier transceiver framework.