【正文】 摘要 I 摘 要 現(xiàn)如今無線通信的技術發(fā)展的越來越火熱，但同時也會面臨這樣的問題：頻譜的資源變得也來越少。 以前處于靜態(tài)的無線頻譜管理的方式會讓一些頻譜常常處于一種空閑的狀態(tài)。 這些常常處于空閑的狀態(tài)會限制頻譜利用率。如果長時間這樣，則會影響頻譜的利用率，造成頻譜 資源的浪費。 主要的目的是 為了提高頻譜的利用率，人們于是提出認知無線電的思想。 在基于認知無線電的基礎上發(fā)展正交頻分復用可以降低總的發(fā)送功率，由串行的高功率變成多個并行的子載波低功率發(fā)送。 首先，這篇文章介紹了認知無線電產生的背景和兩個對認知無線電的概念的解釋，認知無線電特點當中的認知能力 更夠感應外部環(huán)境的檢測，分析頻譜和對頻譜的判定。其次，就 OFDM 的認知無線電 頻譜感知做出了一些研究，通過搭建感知的系統(tǒng)模型，研究其功能等特點。 對于認知無線電 OFDM 系統(tǒng)資源分配算法，本節(jié) 通過 簡單的介紹了 Wong 算法、最小容量最大化算法、 RA 算法、迭代注水算法等，需要找一種多用戶資源分配算法當中的最優(yōu) 算法。本章節(jié)仿真采用的是典型的迭代注水算法， 得出的結論是 這個算法的主要是能夠實現(xiàn)使功率最小或者速率的最大化。 關鍵詞 ：認知無線電 ； OFDM； 多用戶 ； 注水算法Abstract II Abstract Now the technology of wireless munication is developing more and more hot, but at the same time, it also will face the problem: the resources of the spectrum bee more and less. Before the static wireless spectrum management approach will let some spectrum is often in an idle state. These are often idle and limit the spectrum utilization. If this is long, it will affect the utilization of the spectrum, resulting in the waste of spectrum resources. The main purpose is to improve the utilization of the spectrum, people then put forward the idea of cognitive radio. The development of the orthogonal frequency division multiplexing based on the cognitive radio can reduce the total transmission power, and transmit the high power from serial to multiple parallel sub carriers with low power. First, this article introduced explained the background of cognitive radio and two of cognitive radio concept, cognitive radio characteristics of cognitive capacity enough induction of the external environment detection, analysis of spectrum and the spectrum determination. Secondly, some research is made on the cognitive radio spectrum of OFDM, and the features of the cognitive radio spectrum sensing system are studied. For cognitive radio OFDM resource allocation algorithm, in this section, through simple introduced Wong algorithm, minimum capacity maximization algorithm, RA algorithm, iterative water filling algorithm and need to find a multiuser resource allocation algorithm for the optimal algorithm. This chapter uses a typical iterative water injection algorithm, and the conclusion is that the algorithm can achieve the maximum of the minimum power or rate. Keywords: cognitive radio。 OFDM。 multiuser。 water flooding algorithm 目錄 目錄 摘 要 .........................................................................................................................................I ABSTRACT ............................................................................................................................. II 1 緒論 ...................................................................................................................................... 1 認知無線電的提出 ........................................................................................................... 1 認知無線電產生的背景 ............................................................................................ 1 認知無線電的相關專業(yè)術語 ................................................................................... 1 認知無線電 ....................................................................................................................... 2 認知無線電定義 ....................................................................................................... 2 認知無線電的特點 .................................................................................................... 2 認知無線電的使用領域和關鍵技術 ............................................................................... 3 認知無線電的技術應用 ............................................................................................ 3 認知無線電的關鍵技術介紹 ................................................................................... 4 本章小結 .......................................................................................................................... 6 2 OFDM 系統(tǒng)的研究 ............................................................................................................. 8 OFDM 的簡介 ................................................................................................................ 8 OFDM 的產生背景 .................................................................................................... 8 OFDM 的概念 ......................................................................................................... 8 OFDM 系統(tǒng)原理 ..................................................................................................... 8 OFDM 的系統(tǒng)設計 ........................................................................................................ 9 串 /并變換 ................................................................................................................... 9 OFDM 系統(tǒng)中 DFT 的實現(xiàn) ................................................................................. 10 保護間隔和循環(huán)前綴的技術 ................................................................................. 10 RF 調制 ................................................................................................................. 12 OFDM 系統(tǒng)的優(yōu)缺點 .................................................................................................. 13 OFDM 系統(tǒng)的關鍵技術 .............................................................................................. 14 OFDM 系統(tǒng)用 戶資源分配算法的研究 ...................................................................... 15 單用戶比特分配算法 .............................................................................................. 15 目錄 多用戶子載波和比特分配法 .................................................................................. 16 本章小結 ........................................................................................................................ 19 3 認知無線電 OFDM 系統(tǒng)多用戶資源分配算法的研究 .................................................... 21 OFDM 系統(tǒng)中多用戶自適應分配問題模型 ......................