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Research on Simulations and Applications of PAPR Reduction in OFDM Communications

Author: GaoZhi
Tutor: YuJianGuo
School: WRI
Course: Communication and Information System
Keywords: Orthogonal frequency division multiplexing PAPR Clipping Companding transform Selective mapping
CLC: TN919.3
Type: Master's thesis
Year: 2009
Downloads: 49
Quote: 0
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Abstract


As mobile communications become the main way people communicate more and more spectrum resources become increasingly scarce, the traditional single-carrier transmission can no longer meet the needs of the user, and orthogonal frequency division multiplexing (OFDM) is a species using a plurality of subcarriers for transmission, and it is an efficient access technologies. OFDM wireless communication technology as a novel technology, it has outstanding advantages, one of the main features is its ability to overcome multipath effects and frequency selective fading. The same time, we have an orthogonal frequency division multiplexing as a parallel technology, is a high-speed data block packet into a number of low-speed data blocks, then each data block for sub-carrier modulation, and so on can achieve high-speed data transfer rate. Is well known that due to the relatively low rate of the subcarriers of each of the low-speed data block, so that the OFDM symbol period is relatively long, and thus the delay spread of the multipath effects caused by strong resistance at the same time, since the front of each OFDM symbol plus a guard interval, also known as cyclic prefix (CP), and this can significantly reduce inter-symbol interference, ISI. OFDM there is a significant advantage is that portion of the spectrum of the plurality of subcarriers overlap each other, and each sub-carrier orthogonal to each other, precisely because of this, it is easily separated from the mixing subcarrier superimposed on the original data, and thus the spectrum utilization is high, and thus its mobile communications spectrum scarcity of resources is a practical transmission technology. OFDM technology a lot of attention due to its outstanding advantages, but it also has a serious drawback, if they do not, it will affect the promotion and application of its main disadvantage for the following two aspects: (1) higher peak wave-average power ratio of PAPR problem is a difficult problem of OFDM technology, if they do not, it will hinder the application of OFDM technology in reality. Because the OFDM symbol is not a constant envelope, i.e. not linear and nonlinear signal into the amplifier would result in a multi-order intermodulation components, which will seriously affect the quality of the signal and the system bit error rate performance. Therefore, in order to improve the system of BER performance and the transmission efficiency of the system, in the system of emission electrode must separate envelope peak and mean factor taken into account. If the maximum amplitude of the input signal of the RF power amplifier can not be controlled within the linear region, the power amplifier can not output power, which would seriously affect the signal transmission; (2) more sensitive to the frequency offset and noise. Reduce noise and reduce the frequency offset of the orthogonal frequency division multiplexing is very important, if technically can not reach, it will destroy the orthogonality between the OFDM sub-carriers, each sub-carrier so that it will inevitably cause between carrier-to-interference and signal interference; paper first chapter presented the research background and the current status of the OFDM technology, pointed out that the goal of this study and innovation and structural arrangements, was chosen because of its superior performance and next-generation generation mobile communication mainstream technology; second chapter introduces the basic principles of OFDM technology. First analyzes the traditional single-carrier transmission multipath effect, which leads to the OFDM technology, and then analyze the advantages and disadvantages of the orthogonal principle of OFDM technology and OFDM, and finally for the shortcomings of OFDM its high PAPR problem discussed its definition and impact on the system, and the common solution; Chapter III discusses the distortion technology and coding techniques to reduce the PAPR of OFDM system and an improved clipping method and a block encoding method; chapter discusses non-distortion technology to reduce the PAPR of OFDM the selective mapping technology and Partial Transmit Sequence technology, and proposes an improved method and apparatus, and finally the possibility of realization of fusion method has been studied and proposed a species the OFDMA system applicable to multi-antenna fusion method. The fifth chapter of the full text of a summary and future research are discussed.

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