本文選題：認(rèn)知無線電 + 正交頻分復(fù)用　； 參考：《東北大學(xué)》2014年碩士論文

【摘要】：隨著無線通信技術(shù)的飛速發(fā)展,頻譜資源短缺、頻譜利用率低等缺陷越來越凸顯,Cognitive Radio OFDM(CR-OFDM)作為一種適用于離散頻譜環(huán)境的高效的頻譜調(diào)制技術(shù),不僅具備傳統(tǒng)OFDM的抗多徑衰落和高速傳輸?shù)膬?yōu)勢,在頻譜聚合、功率控制以及頻譜分配方面也具有很強(qiáng)的靈活性,因此,成為未來移動通信系統(tǒng)中最具競爭力的一個(gè)關(guān)鍵的傳輸技術(shù)。由于CR-OFDM系統(tǒng)可用頻譜的非連續(xù)和動態(tài)變化特性,隨之產(chǎn)生的關(guān)鍵技術(shù)和科學(xué)課題已成為相關(guān)領(lǐng)域的研究熱點(diǎn)。其中,導(dǎo)頻序列設(shè)計(jì)因其可以保證無線信道估計(jì)的準(zhǔn)確性以及通信系統(tǒng)的高性能品質(zhì)而成為研究的熱點(diǎn)。本文詳細(xì)介紹了CR-OFDM系統(tǒng)導(dǎo)頻序列設(shè)計(jì)的基礎(chǔ)理論,詳細(xì)地分析了最優(yōu)導(dǎo)頻序列設(shè)計(jì)的經(jīng)典算法,針對CR-OFDM系統(tǒng)下授權(quán)用戶和認(rèn)知用戶之間存在干擾的情況,提出了基于信道估計(jì)的最優(yōu)導(dǎo)頻序列設(shè)計(jì)算法,包括對導(dǎo)頻位置、導(dǎo)頻功率以及位置與功率的聯(lián)合優(yōu)化設(shè)計(jì),在保證系統(tǒng)性能的前提下,可有效提高信道估計(jì)精度�？紤]CR-OFDM系統(tǒng)子載波非連續(xù)且動態(tài)變化的特殊性質(zhì),傳統(tǒng)等功率、等間隔分布的導(dǎo)頻序列存在計(jì)算復(fù)雜度高、頻譜利用率低、處理時(shí)延大和干擾影響明顯等缺點(diǎn)。針對上述問題,首先,提出了基于交叉熵算法的導(dǎo)頻位置的優(yōu)化設(shè)計(jì)方法,該方法以最小化系統(tǒng)均方誤差為準(zhǔn)則,采用交叉熵優(yōu)化算法在所有可用子載波中求解目標(biāo)函數(shù)的最優(yōu)解,有效解決了窮舉搜索算法計(jì)算復(fù)雜度高等問題；其次,對導(dǎo)頻功率的設(shè)計(jì),以最大化系統(tǒng)容量為準(zhǔn)則,在認(rèn)知用戶與授權(quán)用戶之間的干擾溫度限制下,對優(yōu)化問題進(jìn)行建模,采用差分進(jìn)化搜索算法進(jìn)行目標(biāo)函數(shù)的求解,提高了頻譜利用率,解決了由于功率分配不合理造成的資源浪費(fèi)；最后,考慮等功率分配導(dǎo)頻會使信道估計(jì)不能有效地進(jìn)行,提出了一種對導(dǎo)頻功率和位置聯(lián)合優(yōu)化的設(shè)計(jì)算法,該算法以最小化系統(tǒng)均方誤差為準(zhǔn)則,對導(dǎo)頻功率進(jìn)行歸一化操作,并將交叉熵優(yōu)化算法應(yīng)用于對優(yōu)化問題的求解中。與傳統(tǒng)算法相比,所提算法提高了數(shù)據(jù)傳輸利用率,保證了信道的估計(jì)精度,降低了系統(tǒng)均方誤差(Mean Square Error, MSE)和誤碼率(Bit Error Rate, BER),從而從整體上提高了系統(tǒng)性能。
[Abstract]:With the rapid development of wireless communication technology, the shortage of spectrum resources and the low spectral efficiency are more and more obvious Cognitive Radio OFDM CR-OFDM) as an efficient spectrum modulation technology suitable for discrete spectrum environment. It not only has the advantages of anti-multipath fading and high-speed transmission of traditional OFDM, but also has strong flexibility in spectrum polymerization, power control and spectrum allocation. To become the most competitive mobile communication system in the future a key transmission technology. Due to the discontinuous and dynamic characteristics of available spectrum of CR-OFDM system, the key technologies and scientific topics have become the focus of research in related fields. Among them, pilot sequence design has become a hot research area because it can guarantee the accuracy of wireless channel estimation and the high performance of communication system. In this paper, the basic theory of pilot sequence design in CR-OFDM system is introduced in detail, and the classical algorithm of optimal pilot sequence design is analyzed in detail, aiming at the interference between authorized and cognitive users in CR-OFDM system. An optimal pilot sequence design algorithm based on channel estimation is proposed, including the joint optimization of pilot position, pilot power and position and power, which can effectively improve the accuracy of channel estimation on the premise of ensuring the system performance. Considering the special property of discontinuous and dynamic variation of subcarriers in CR-OFDM systems, the traditional equal-power and equal-interval pilot sequences have the disadvantages of high computational complexity, low spectral efficiency, large processing delay and obvious interference. In order to solve the above problems, a pilot position optimization method based on cross-entropy algorithm is proposed, which is based on minimizing the mean square error (MSE) of the system. The cross-entropy optimization algorithm is used to solve the optimal solution of the objective function in all available subcarriers, which effectively solves the problem of high computational complexity of exhaustive search algorithm. Secondly, the design of pilot power is based on maximization of system capacity. Under the restriction of interference temperature between cognitive user and authorized user, the optimization problem is modeled, and the objective function is solved by differential evolution search algorithm, which improves the spectrum efficiency. The waste of resources caused by unreasonable power allocation is solved. Finally, considering the pilot of equal power allocation, channel estimation can not be carried out effectively, and a joint design algorithm of pilot power and position is proposed. Based on the criterion of minimizing the mean square error of the system, the pilot power is normalized and the cross-entropy optimization algorithm is applied to solve the optimization problem. Compared with the traditional algorithm, the proposed algorithm improves the data transmission efficiency, ensures the channel estimation accuracy, reduces the mean square error (Mean Square Error, MSE) and bit Error rate (bit Error rate), and thus improves the performance of the system as a whole.
【學(xué)位授予單位】：東北大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：TN929.53

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