OFDM峰均功率比抑制算法的研究
文献类型：学位论文
| 作者 | 彭翔 |
| 学位类别 | 博士 |
| 答辩日期 | 2007-06-05 |
| 授予单位 | 中国科学院声学研究所 |
| 授予地点 | 声学研究所 |
| 关键词 | 正交频分复用 峰均功率比 削波 噪声消除 自适应技巧 |
| 其他题名 | New technique for Peak-to-Average-Power Ratio Reduction in OFDM Systems |
| 学位专业 | 信号与信息处理 |
| 中文摘要 | OFDM能够有效克服符号间干扰和信道频率选择性衰落，目前已在无线局域网、数字音视频广播（DAB/DVB-T）、x-DSL等领域得到了应用，并被公认为第四代移动通讯的核心技术。 相比单载波系统，OFDM信号具有很高的峰均功率比（PAPR）。这对发射机内高功率放大器（HPA）的线性动态范围提出了很高的要求。如果高功率放大器的动态范围不能满足信号的变化，则会给信号带来畸变，从而导致各个子信道信号之间的正交性遭到破坏，产生相互干扰，使得系统性能恶化。因此降低信号的PAPR是 OFDM技术走向商用的关键。 本文的研究目标是如何有效降低OFDM信号的PAPR，其主要内容包括如下： 提出了一种新的OFDM PAPR抑制算法（误差削波算法），新算法继承了传统削波算法计算简单，对调制方式和载波数的适应性强，传输效率高的优点。同时又克服了传统削波算法会带来较大频谱扩展的缺点。即误差削波算法能够在降低信号PAPR的同时做到零频谱增益。文中对误差削波算法中滤波器的设计、削波前后信号的频谱、CCDF、EVM、功率损失、相位轨迹等特性作了详细的讨论，同时给出了和传统削波算法的对比。 提出了两种误差削波噪声消除算法。误差削波是以牺牲信号EVM为代价换来了零频谱增益，这意味着误差削波会带来更大的带内干扰噪声。由于误差削波噪声的产生过程已知，故可以在接收端通过噪声消除算法减少噪声对系统性能的影响。研究了误差削波噪声产生模型，算法1）根据误差削波噪声产生模型，通过在接收端重现削波噪声来达到噪声消除的目的。算法2）采用迭代重建信号的技巧消除削波噪声。讨论了算法1）和2）的数值关系。仿真表明，两种算法在加性白噪声信道和多径衰落信道下都能有效得消除误差削波噪声，使得削波后信号的误码性能接近理想未削波信号的误码性能。文中同时研究了误差削波噪声对信道估计算法的影响，并提出了相应的改进办法。 提出了一种自适应误差削波算法。该算法的优化准则是在保证系统获得指定的误码性能的前提下，尽量的降低信号的PAPR，提高功率放大器的工作效率，降低系统的发射功率。研究表明，误差削波算法中的削波门限值参数在不同信噪比和不同调制方式下对系统的误比特率的影响程度不一样。自适应误差削波算法根据不同的信噪比，自适应的选择不同的削波门限值和调制方式，可以在满足指定系统误比特率的情况下，最大限度的降低系统的PAPR，提高功率放大器的工作效率，从而达到降低系统的发射功率的目的。 |
| 英文摘要 | Orthogonal Frequency Division Multiplexing (OFDM) has recently gained relevance among modulation schemes thanks to its intrinsic robustness in frequency selective fading channels. This is one of the reasons that made OFDM a popular technique for systems such as Digital Audio and Video Broadcasting (DAB and DVB-T), Digital Subscriber Lines (x-DSL), and Wireless LAN. OFDM has become a candidate for 4G system. One of the major drawbacks of OFDM system, which is often an obstacle to its use, is the fact that the signal has a high Peak-to-Average-Power Ratio (PAPR). This prevents from the use of high-efficiency amplification devices (High Power Amplifiers, HPA), which exhibit deep non-linearities that give rise to intermodulation products; the latter cause in-band distortion and increase Out-Of-Band Radiation (OOBR), which results in a disturbing Adjacent Channel Interference (ACI) and a Bit-Error-Rate (BER) increase. Objective of this research work is the study of techniques for reducing the PAPR of the original OFDM signal. The major jobs include: A new clipping method (error clipping) for reducing PAPR is proposed. New method inherits some advantages of traditional clipping, such as simple, undepending on carrier numble and modulation type, high efficency etc. At the same times, it can avoid out-of-band radiation which is the major drawback of traditional clipping. That means error clipping can reduce PAPR without out-of-band radiation. In this letter, we discuss the filter design of error clipping and some properties of the OFDM signal after error clipping, such as frequency, CCDF, EVM, phase tracy, power losing etc. Two clipping noise cancellation approches have been investigated. Error clipping will cause bigger in-band noise. In order to recover the signal from error clipping noise, clipping noise cancellation is necessary before demodulation. Error clipping noise model has been studied. Algorithm1) reconstructs the error cliiping nosie based on the noise model. Algorithm2) removes clipping noise by using iterative reconstructing singal technique. The performance under the AGWN and mutipath channel has been studied. The result of simulation shows that the system BER can be restored to the ideal unclipped signal BER level with only moderate complexity. In this letter, we also study the clipping noise effection on channel estimation. Adaptive error clipping technique for OFDM PAPR reduction has been proposed. Simulations shows that the system BER not noly depends on SNR, but also depends on clipping threshold and modulation type. Adaptive error clipping uses different clipping threshold and modulation type according to different SNR. This technique can effectively reduce PAPR and enhance HPA efficiency under target BER. |
| 语种 | 中文 |
| 公开日期 | 2011-05-07 |
| 页码 | 137 |
| 源URL | [http://159.226.59.140/handle/311008/202]  |
| 专题 | 声学研究所_声学所博硕士学位论文_1981-2009博硕士学位论文 |
| 推荐引用方式 GB/T 7714 | 彭翔. OFDM峰均功率比抑制算法的研究[D]. 声学研究所. 中国科学院声学研究所. 2007. |
入库方式： OAI收割
来源：声学研究所
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