本文選題：動(dòng)態(tài)頻譜接入　切入點(diǎn)：正交頻分復(fù)用　出處：《電子科技大學(xué)》2014年碩士論文

【摘要】：隨著信息的爆發(fā)式增長(zhǎng),無線通信開始扮演越來越重要的角色,然而屬于空中資源的無線頻譜卻日漸緊張,于是出現(xiàn)了一種基于OFDM技術(shù)的動(dòng)態(tài)頻譜接入(DSA)方案,這種技術(shù)旨在提高對(duì)目前已被分配的頻譜的利用率。由于OFDM信號(hào)存在帶外功率過大這一缺點(diǎn),導(dǎo)致其無法直接與DSA相結(jié)合,于是如何降低OFDM信號(hào)的帶外功率輻射便成為了研究DSA應(yīng)用的關(guān)鍵之一。本文首先介紹了動(dòng)態(tài)頻譜接入技術(shù)及其分類,并分析了OFDM技術(shù)的基本原理,在此基礎(chǔ)之上分析了造成OFDM帶外功率過大的兩個(gè)原因:OFDM時(shí)域隱性加窗所造成的旁瓣過大以及信號(hào)的峰值功率過高致使功率放大器產(chǎn)生非線性失真的概率增大,針對(duì)Rapp功率放大器的非線性失真對(duì)信號(hào)功率譜密度的影響進(jìn)行了進(jìn)一步的分析和仿真。然后,分析和總結(jié)了常用的旁瓣和峰均功率比抑制算法,對(duì)比了這些方法的優(yōu)缺點(diǎn)。由于這些方法存在諸多的問題,人們開始研究多選擇序列(MCS)和選擇性映射(SLM)。這兩種技術(shù)以其無失真和計(jì)算復(fù)雜度相對(duì)較低等優(yōu)點(diǎn)得到了廣泛關(guān)注。在本論文中分析了影響他們性能的各項(xiàng)因素。對(duì)基于不同轉(zhuǎn)換矩陣的低復(fù)雜度SLM改進(jìn)方案進(jìn)行了分析和比較。通過大量的仿真,得到的低相關(guān)性轉(zhuǎn)換矩陣方法與傳統(tǒng)的SLM相比在擴(kuò)展因子同樣為16的情況下僅有0.1dB左右的性能損失,而計(jì)算復(fù)雜度卻得到了非常顯著的降低。最后,對(duì)基于改進(jìn)的轉(zhuǎn)換矩陣的低復(fù)雜度SLM建立了定點(diǎn)仿真模型,將定點(diǎn)模型與浮點(diǎn)仿真的性能損失限制在0.3dB以內(nèi)。在此模型基礎(chǔ)上進(jìn)行電路設(shè)計(jì),并介紹了各子模塊的接口、核心電路以及Modelsim仿真結(jié)果。最后,在Terasic公司DE4開發(fā)板之上對(duì)所設(shè)計(jì)電路進(jìn)行板級(jí)測(cè)試。經(jīng)驗(yàn)證,總資源占有率為4%,電路的最高時(shí)鐘頻率能夠達(dá)到250MHz。
[Abstract]:With the explosion of information, wireless communication begins to play a more and more important role. However, the wireless spectrum which belongs to air resources is becoming increasingly tight, so a dynamic spectrum access scheme based on OFDM technology has emerged.The technology is designed to improve the efficiency of the spectrum currently allocated.Because the outband power of OFDM signal is too large, it can not be directly combined with DSA, so how to reduce the out-of-band power radiation of OFDM signal has become one of the key issues in the study of DSA applications.This paper first introduces the dynamic spectrum access technology and its classification, and analyzes the basic principle of OFDM technology.On the basis of this, the paper analyzes two reasons causing the excessive out-of-band power of OFDM: OFDM, which is caused by the excessive sidelobe caused by the implicit window addition in time domain and the high peak power of the signal, which increases the probability of the nonlinear distortion of the power amplifier.The influence of nonlinear distortion of Rapp power amplifier on signal power spectral density is analyzed and simulated.Then, the common sidelobe and peak-to-average power ratio (PAPR) suppression algorithms are analyzed and summarized, and the advantages and disadvantages of these methods are compared.Due to the many problems in these methods, people begin to study multi-selection sequences (MCSs) and selective mapping (SLM).These two techniques have attracted wide attention due to their advantages of distortion-free and relatively low computational complexity.In this paper, the factors affecting their performance are analyzed.The improvement scheme of low complexity SLM based on different transformation matrix is analyzed and compared.Through a large number of simulations, compared with the traditional SLM, the low correlation transformation matrix method has only about 0.1dB performance loss under the same expansion factor of 16, but the computational complexity is significantly reduced.Finally, a fixed-point simulation model for low-complexity SLM based on improved transformation matrix is established, which limits the performance loss of fixed-point model and floating-point simulation to 0.3dB.On the basis of this model, the circuit is designed, and the interface of each sub-module, the core circuit and the simulation results of Modelsim are introduced.Finally, the designed circuit is tested on the DE4 development board of Terasic Company.It is verified that the total resource share is 4 and the highest clock frequency of the circuit can reach 250 MHz.
【學(xué)位授予單位】：電子科技大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：TN929.53

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