Resource Allocation And Power Control In Cognitive Radio Networks And LTE Cellular Systems

With the quick development of wireless communication technology and sharp increase in its applications, Quality-of-Service (QoS) in wireless systems is becoming very important. QoS of each user in a multiple access network depends on bandwidth, transmission power, coding and modulation, channel quality, etc. How to assign these resources to each user to optimize the throughput or QoS of the whole network is a critical issue for future wireless networks. On the other hand, the battery technology is unable to catch up with the sharply increasing capacity requirement in mobile devices. Consequently, energy-efficient wireless networks, also known as Green Radio, is becoming a more and more popular and critical research area, as evidenced by many workshops in international conferences, special issues of journals, and research groups in the world. Reducing energy consumption in wireless communications is also beneficial to environments and good for sustaining development. Therefore, this paper will focus on resource allocation for energy-efficient and spectral-efficient wireless networks in this dissertation.To effectively improve spectral efficiency of wireless networks, cognitive radio (CR) has been proposed to use the licensed spectrum when the licensed users are not active spatially or temporally. In this dissertation, how a CR user senses available spectrum bands, selects the most appropriate one, and then optimizes transmission parameters will be studied. When determining transmission period and power, this dissertation also takes spectral efficiency, throughput, and interference limit to the licensed users into consideration. The dissertation proves that there is a closed-form solution for the duration of data transmission. A power allocation method for all the used channels is also proposed in the dissertation.Cooperative relay technique can improve throughput and mitigate interference in wireless networks, which is an ideal technique for CR. This dissertation will apply this technique in CR networks to increase throughput of cognitive users and avoid interference to the licensed users. Since both relay node selection and power allocation relate to the spectral efficiency of CR networks, this dissertation first develops a joint relay selection and power allocation approach that maximizes the throughput of a CR network with cooperative relay. The dissertation then proposes a simplified approach that significantly reduces the complexity with only minor performance degradation. The simplified approach performs almost as well as the optimal method, which can be seen from the simulation results.In cellular networks, inter-cell interference (ICI) significantly degrades performance, especially for a network with a unit frequency reuse factor. Long term evolution (LTE) is a standard for future cellular networks. In the LTE standard, many practical constraints are posted on frequency resource, coding and modulation, power allocation, etc. In the dissertation, a resource allocation and power assignment scheme for uplink transmission under the above practical constraints is developed. The dissertation also studies energy-efficient resource and power allocation for downlink transmission in LTE. Our research indicates that the energy-efficient design not only maintains reasonable high throughput but also effectively mitigates ICI by reducing transmission power.