階層式感知無線電使用多輸入多輸出正交分頻多工之最佳上傳模式設計

Abstract

感知無線電技術(Cognitive Radio)是一種能有效增加頻譜使用效率的方法，隨著頻譜資源的日益匱乏，階層式感知無線電網路被視為未來無線通訊系統的主要架構，此架構中非付費使用者和付費使用者同時使用相同頻段。在本論文中，我們採用最先進的多輸入多輸出天線(Multi-Input and Multi-Output Antenna, MIMO)且正交分頻多工(Orthogonal Frequency Division Multiplexing)系統，針對此系統提出一個波束權重設計與使用者排程的演算法以達到最大化系統上傳傳輸速率的目的。這篇論文的主要貢獻在於提出一個可行的演算法設計波束權重，確保上傳資料的非付費使用者可以達到最大傳輸速率，另外，我們提出一個使用者排程演算法以盡量減輕非付費使用者對付費使用者的干擾。模擬結果顯示和單一付費系統相比，加入非付費系統並使用本論文提出的方法可以提升系統的頻譜效率達65%，本論文提出的方法可以作為未來無線電網路設計的重要參考。

Hierarchical cognitive radio networks are discussed. As the cognitive radio (CR) technology becomes well-developed and the spectrum resource for wireless communication becomes more deficient, hierarchical CR networks is regarded as next generation networks. Concurrent transmissions for unlicensed (secondary) users and licensed (primary) users is allowed to enhance spectrum efficiency in CR networks. The challenge of hierarchical CR networks is to manage mutual interference between primary and secondary systems. In the thesis, we focus on the design of uplink transmission scheme. We present a scheduling algorithm to prevent primary systems from severe interference; afterwards, we use a beamforming approach to maximize the receive signal’s SINR of multiple users in the hierarchical CR network with multicarrier transmissions. The main contribution of this work is that we transform a SINR maximization beamforming problem into a quasi-convex form for the secondary network. After the transformation, The original beamforming problem becomes solvable and the optimal solution can be gotten by using bisection method and existing CVX [1] software toolbox. In addition, our scheduling algorithm for secondary system can mitigate the interference to the primary system effectively.