Cognitive Radio Resource Management for Statistical QoS Guarantees in Multi-tier Networks

• Main Authors: Shao-Yu Lien, 連紹宇
• Other Authors: 陳光禎
• Format: Others
• Language: en_US
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/16816453611967609161

博士 === 國立臺灣大學 === 電信工程學研究所 === 99 === To satisfy the extreme high data rate requirement of the next generation cellular system, extending the available communications bandwidth and shortening the distance between the transmitter and the receiver have been regarded as effective means to further enhance the data rate in the cellular system. Such a requirement motives the developments of (i) the heterogeneous network architecture to deploy femto- cells and picocells overlaying the conventional Macrocell as a multi-tier network to shorten the distance between the transmitter and the receiver, (ii) the universal frequency reuse resource utilization scheme and (iii) the carrier aggregation technology to further extend the available bandwidth. However, without an effective radio resource management scheme, applying the universal frequency reuse to the heterogeneous network architecture may fail all communications due to severe inter-cell interference. Due to a potentially high computational complexity, it is infeasible to apply centralized resource managements to the next generation cellular system. In addition, providing quality-of-service (QoS) is the key for a successful wireless communications system. As a result, the most critical challenge lies in that inter-cell interference mitigation as well as QoS provisioning shall be autonomously achieved by each "cell" in the next generation cellular system. Inspired by the cognitive radio technology that enables a communication station to autonomously sense and adapt to the surrounding communications environment, in this dissertation, the cognitive radio resource management framework is proposed. By the proposed cognitive radio resource management framework, the second-tier network can sense the radio resource utilization of the first-tier network and adapt to the first-tier network, which provides the most important property of scalability for the next generation network. By applying the proposed cognitive radio resource management framework to femtocells, the most critical QoS guarantees provisioning is shown. Based on such a cognitive radio resource management framework, a game-theoretical radio resource management is further proposed with the facilitation of game theory for the intra-tier interference mitigation of the second-tier network. However, there is one critical assumption under such a framework that all the second-tier shall synchronize to the first-tier. A network synchronization algorithm is consequently proposed to achieve this critical synchronization in the multi-tier network. To further generalize the cognitive radio resource management framework to picocells with larger coverage areas as compared with that of femtocells, the spectrum map based radio resource management scheme is proposed with the facilitation of the compressed sensing theory. Consequently, cross-tier interference as well as intra-tier interference can be effectively mitigated autonomously by the proposed complete solution for the second-tier. To further extend the bandwidth of the first-tier by leveraging the ISM band, interference of the legacy system deployed on the ISM band (such as WiFi) shall be mitigated, which derives the development of the cognitive channel access for the first-tier to coexist with the legacy system. However, cognitive channel access results in severe variation on channel availability and poses a critical challenge to provide QoS guarantees. To alleviate end-to-end channel availability variation, a powerful means known as network multiple-input-multiple-output (MIMO) in cellular systems is particularly noted. To tackle two critical obstacles in the first-tier by leveraging network MIMO transmissions, (i) an effective packet transmissions coordination and (ii) an e±cient radio resources allocation, the statistical tra±c control scheme comprising packet transmission scheduling and admission control are consequently proposed to enable guaranteed QoS for the first-tier.