【文章內(nèi)容簡介】 ............................................................................................24 Selection of RadioFrequency Module..........................................................................28 Brief Summary ..............................................................................................................28 3 Design and Implementation of the Software Framework in CR Terminals .........................29 Algorithm Flow in CR Terminals ..................................................................................29 Dispatch of Base Band Algorithms ...............................................................................29 Algorithm Flow in DSP .................................................................................................32 Design of Multitask Software Frameword Based On DSP/BIOS................................34 Brief Introduction of Realtime Multitask Operating System and DSP/BIOS .....34 Design method of software Based on DSP/BIOS ..................................................36 Software Frameword in Transmitting DSP ............................................................36 Software Frameword in Receiving DSP.................................................................39 Brief Summary ..............................................................................................................42 4 Reasearch of Algorithm Reducing the PAPR in CR Experimental System .........................43 Brief Introduction of PAPR Problem of OFDM Signal ................................................43 Definition of PAPR.................................................................................................43 Statistical Properties of PAPR of OFDM Signal ....................................................44 Impact to CR Experimental System Caused by High PAPR .........................................45 Common Algorithms Reducing the PAPR of OFDM signal .........................................47 Signal Distortion Techniques..................................................................................47 Coding Techniques .................................................................................................48 Probability Techniques ...........................................................................................48 Improved Clipping Algorithm Reducing PAPR of OFDM signal.................................49 Basic Idea of Clipping Algorithm...........................................................................49 西安交通大學碩士學位論文 VIII Improved Clipping Algorithm ................................................................................50 Selection of Parameters in Improved Clipping Algorithm .....................................52 Simulation Result of Improved Clipping Algorithm ..............................................53 Implementation of the Improved Clipping Algorithm in CR Experimental System.....54 Brief Summary ..............................................................................................................56 5 Testing and Debugging of Hardware and Software Framework in CR Terminals ...............57 Debugging of Hardware in CR Terminals .....................................................................57 Debugging of Power Module .................................................................................57 Debugging of Clock Module ..................................................................................59 Signal Integrity Testing of High Speed Digital Signals .........................................61 Debugging of Software Framework in CR Terminals ...................................................62 Configurating the Underlying Hardware ................................................................62 Interface of All Algorithm modules........................................................................63 Timing and Realtime Properties of All Algorithm Tasks ......................................64 Brief Summary ..............................................................................................................64 6 Conclusions and Suggestions ...............................................................................................65 Conclusions ...................................................................................................................65 Suggestions ....................................................................................................................65 Acknowledgements .................................................................................................................66 References ...............................................................................................................................67 Appendice ................................................................................................................................69 Achievements ..........................................................................................................................70 Declaration Equation Chapter 1 Section 1 1 緒論 1 1 緒論 無線通信從出現(xiàn)到現(xiàn)在短短幾十年 時間 ，歷經(jīng)幾代變革，到現(xiàn)在呈現(xiàn)多種無線通信系統(tǒng)共同發(fā)展的態(tài)勢。目前各個無線通信系統(tǒng)在 政府有關部門 的 授權 下使用各自的通信頻段和帶寬 。這種靜態(tài)的無線頻譜管理方式，雖然可以簡單有效地避免不同無線通信系統(tǒng)間的相互干擾，但常常導致 頻譜利用率非常低 [1]。 并且對于日益增長的無線通信帶寬需求和新出現(xiàn)的通信系統(tǒng)沒有很好的支持，成為無線通信技術發(fā)展的瓶頸。 在此背景下 ，認知無線電 技術被提出用于提高頻譜利用率， 解決 不斷增長的頻譜資源需求與當前效率低下的頻譜管理方式之間的矛盾 。 認知無線電研究現(xiàn)狀 1999 年 Joseph Mitola 在軟件定義無線電 (Software Defined Radio, SDR)基礎上 提出認知無線電 (Cognitive Radio, CR)[2]。 其 基本思想是認知無線電系統(tǒng) 能夠 感知 周圍的 無線通信環(huán)境 ， 動態(tài)檢測和有效利用 已 被 分配但暫時未使用或者 未 完全使用的 頻譜 ， 根據(jù)一定的學習和決策算法 ， 實時自適應地改變系統(tǒng)工作參數(shù) ， 在時間、頻率以及空間上進行多維的頻譜復用 ，從而提高頻譜利用率 [3]。 在 Mitola 之后， Fatih Capar 提出 一種比較簡單，容易實現(xiàn)的認知無線電定義 [4]，將 認知無線電 定義為 一種智能化、動態(tài)頻譜資源管理使用方式，授權用戶擁有最高的頻譜使用優(yōu)先級，它可以和若干具有低優(yōu)先級的認知用戶分享頻譜資源，以提高頻譜資源利用率 。 目前國際上開展的 CR 研究大多采用類似的 簡化 定義