【作者】 程国兵；

【导师】 李少谦；

【作者基本信息】 电子科技大学 ， 通信与信息系统， 2013， 博士

【摘要】 正交频分复用/偏移正交幅度调制（orthogonal frequency divisionmultiplexing/offset quadrature amplitude modulation, OFDM/OQAM）属于广义频分复用（generalized frequency division multiplexing, GFDM）的范畴。与传统OFDM相比，OFDM/OQAM具有抗符号间干扰和子载波间干扰能力强、无需循环前缀、带外辐射低等优点，并已成为IEEE802.22无线城域网、电力线通信和第三代陆地蜂窝移动通信系统长期演进技术的候选技术标准，具有很强的发展潜力。然而，OFDM/OQAM优势的取得是以放宽正交条件并引入具有优良时频聚焦特性的成形滤波器为代价的，从而导致系统运算复杂度的提高，并使传统OFDM系统的一些关键技术无法直接移植至OFDM/OQAM系统中。针对上述问题，本文在分析OFDM/OQAM系统特点的基础上重点研究了系统设计、信道估计、信道均衡和峰-平功率比抑制等关键技术，并提出了相应的解决途径和改进方法。首先，本文研究了OFDM/OQAM系统的实现方法和性能。通过对发送信号的直接离散化，推导得到了一种基于滤波器与离散傅里叶变换相结合的系统实现方法。同时，本文对OFDM/OQAM系统中几种常用的滤波器进行了研究，分析了它们的时频聚焦特性和抗干扰能力。此外，本文结合典型应用环境对OFDM/OQAM系统与OFDM系统的性能进行了分析比较，证明了OFDM/OQAM系统具有比较明显的优势。其次，本文研究了OFDM/OQAM系统的信道估计问题。分析了将传统多载波系统信道估计方法直接应用于OFDM/OQAM系统时存在的问题。在现有方法的基础上提出了一种基于迭代抵消的信道估计方法，使其能够利用更低的导频消耗获得更高的信道估计精度。同时，利用块状导频估计出的信道值之间存在较强相关性这一特点，提出了信道估计值加权处理的方法，有效克服了高斯白噪声的影响，具有很高的处理增益。同时本文还研究了信道与频率偏移的联合估计问题，并提出了一种有效的导频结构和相应的联合估计算法，该算法具有较高的频偏估计精度和信道估计精度，且对时间偏移具有较强的鲁棒性。第三，本文研究了OFDM/OQAM系统的信道均衡问题。针对迫零均衡存在性能平台的问题，提出了基于迭代抵消的干扰消除方法，并在单输入单输出和多输入多输出这两种系统中分别进行了研究。结果表明，通过迭代干扰抵消方法可以有效提高系统性能。另外，本文在证明了残余干扰服从高斯分布的基础上，提出将干扰看做背景噪声的一部分，然后利用最小均方误差准则进行信道均衡的方法。仿真结果表明，该方法可进一步提高系统性能。最后，本文研究了OFDM/OQAM系统的峰-平功率比抑制问题，主要研究了选择映射和限幅方法这两种常用方法。分析了将OFDM系统中的选择映射方法直接应用于OFDM/OQAM系统时存在的问题，并根据滤波器的特点提出了一种有效的选择映射改进方法，该方法既降低了计算复杂度又提高了峰-平功率比抑制性能。同时，本文研究了限幅噪声的消除问题，提出了一种有效的限幅噪声抑制方法。首先在接收端重现限幅噪声，然后将其从接收信号中去除，从而降低限幅噪声对系统性能的影响。以上研究成果从多个角度对OFDM/OQAM系统存在的主要问题给出了可行的解决途径和性能提升方法，可为在无线城域网、现代国际移动通信和未来移动通信等无线通信系统或标准中采用OFDM/OQAM技术提供支撑。更多还原

【Abstract】 Orthogonal frequency division multiplexing/offset quadrature amplitudemodulation (OFDM/OQAM) is a kind of generalized frequency division multiplexing(GFDM) technique. Compared to the traditional OFDM, OFDM/OQAM has someadvantages such as stronger immunity to inter-symbol interference (ISI) andinter-carrier interference (ICI), avoiding of cyclic prefix (CP) and lower out-of-bandradiation. OFDM/OQAM is a promising transmission technique and has been adoptedas an appropriate alternative for IEEE802.22wireless regional area network (WRAN),power line communication (PLC) and3rdgeneration partnership project long termevolution (3GPP LTE) technical standards. However, the advantages of OFDM/OQAMare acquired by relaxing of the orthogonality conditions from complex value to realvalue field. And pulse shapes with good time frequency localization (TFL)characteristics are introduced, leading to higher computational complexity and somekey techniques of traditional OFDM system can not be applied to OFDM/OQAMsystem directly. To solve these problems, based on the basic properties ofOFDM/OQAM system, this dissertation focuses on the key problems of systemrealization, channel estimation, channel equalization and peak to average power ratio(PAPR) reduction. And some novel solutions and improved methods are proposed forOFDM/OQAM system.Firstly, this dissertation researches on the system realization and performanceevaluation of OFDM/OQAM system. Through directly discretizing the transmittingsignal, a system realization method based on filters and discrete Fourier transform (DFT)is deduced. And then the popular filters used in OFDM/OQAM system are introducedand their time-frequency localization (TFL) characteristics are analyzed. Furthermore,this dissertation compares the performance between OFDM/OQAM system andtraditional OFDM system under the condition of typical application circumstances. Thesimulation results show that OFDM/OQAM system has some apparent advantages.Secondly, channel estimation of OFDM/OQAM system is addressed in thisdissertation. The problems of applicating the traditional channel estimation methoddirectly to the OFDM/OQAM system are presented. Based on the existing literatures, anovel channel estimation method based on iterative interference cancellation is proposed that it can acquire higher channel estimation precision while with lower pilotconsumption. At same time, since the estimated channel values among adjacentsubcarriers are correlative, a combining method is proposed to overcome the effect ofadditional white Gaussian noise (AWGN) channel and the channel estimation accuracyis improved. Besides, the joint estimation of carrier frequency offset (CFO) and channelis analysed. Furthermore, an effective preamble structure and a corresponding algorithmare proposed. The simulation results show that it can achieve high estimation accuracyand has strong robustness to time offset.Thirdly, this dissertation researches on the channel equalization of OFDM/OQAMsystem. Because of the performance floor when applicating simple zero forcing (ZF)equalization method for OFDM/OQAM system, an iterative interference cancellationmethod is proposed for both single-input single-output (SISO) and multi-inputmulti-output (MIMO) systems. Simulation results show that this method can improvethe system performance effectively. Furthermore, because the residual interference ofthe demodulated signal follows the Gaussian distribution, it can be treated as a part ofbackground noise for minimum mean square error (MMSE) equalization.Finally, this dissertation researches on the reduction of the peak-to-average powerratio (PAPR) in OFDM/OQAM system. According to the particularity ofOFDM/OQAM transmitting signal, an effective selective mapping (SLM) method isproposed with lower complexity. This dissertation also researches on the suppression ofclipping noise. The clipping noise is rebuilded in the receiver and then it is removedfrom the receiving signal to overcome its influence on system performance. Besides, theout-of-band radiation and the relation between clipping threshold and out-of-bandradiation are also addressed in this dissertation.The research achievements in this dissertation provide effective solutions andperformance improvements with respect to the primary problem of OFDM/OQAMsystem in different aspects. And these achievements can provide support for applicationof the OFDM/OQAM technique in popular system such as WRAN, advancedinternational mobile telecommunications (IMT-advanced) and future mobilecommunication systems.更多还原