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Study on Non-Linear Distortion Compensation Methods for OFDM Based Wireless Communications Systems
http://hdl.handle.net/10076/13564
http://hdl.handle.net/10076/1356483921d40-aefd-4a88-91f9-c5d7a86c3609
| 名前 / ファイル | ライセンス | アクション |
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2012D013.pdf (8.9 MB)
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| Item type | 学位論文 / Thesis or Dissertation(1) | |||||||
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| 公開日 | 2013-11-25 | |||||||
| タイトル | ||||||||
| タイトル | Study on Non-Linear Distortion Compensation Methods for OFDM Based Wireless Communications Systems | |||||||
| 言語 | en | |||||||
| 言語 | ||||||||
| 言語 | eng | |||||||
| 資源タイプ | ||||||||
| 資源タイプ識別子 | http://purl.org/coar/resource_type/c_46ec | |||||||
| 資源タイプ | thesis | |||||||
| 著者 |
Boonsrimuang, Pornpawit
× Boonsrimuang, Pornpawit
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| 抄録 | ||||||||
| 内容記述タイプ | Abstract | |||||||
| 内容記述 | The Orthogonal Frequency Division Multiplexing (OFDM) technique has been received lot of attentions especially in the field of wireless communications because of its efficient usage of frequency bandwidth and robustness to the multi-path fading. From these advantages, the OFDM technique has already been adopted as the standard transmission technique in the wireless LAN systems and the terrestrial digital broadcasting systems including the Digital Audio Broadcasting (DAB) and the Digital Video Broadcasting (DVB). The OFDM technique is also employed as the standard transmission technique in the next generation of mobile communications systems (LTE). One of the limitations of using OFDM technique is the larger Peak to Averaged Power Ratio (PAPR) of its time domain signal. The larger PAPR signal would cause the severe degradation of bit error rate (BER) performance and the undesirable frequency spectrum regrowth both due to the non-linear distortion occurring in the non-linear amplifier which is usually required at the transmitter in the wireless communications systems. The simple solution to overcome this problem is to operate the non-linear amplifier at the linear region with taking the enough larger input back-off (IBO). However, this approach leads the inefficient usage of non-linear power amplifier, and would lead a serious problem on battery consumption especially for the mobile handheld terminal and portable wireless LAN terminal. In order to maximize the usage of power efficiency, the non-linear amplifier is usually required to operate at the near its saturation region. However this approach will lead to the severe degradation of BER performance and undesirable frequency spectrum re-growth for the larger PAPR signal due to the occurring of inevitably higher non-linear distortion. Many PAPR reduction techniques for OFDM signal have been proposed to overcome the PAPR problem up to today. These techniques can be categorized into two major methods as the distortion and distortion-less methods. The distortion technique includes the clipping and filtering method. Although this method can improve the PAPR performance relatively, it leads the degradation of BER performance and undesirable spectrum re-growth to the adjacent channel due to the non-linear clipping distortion. The mitigation method of Non-Linear Distortion is required at the receiver side to improve the BER performance. On the other hand, the distortion-less techniques include the coding, tone reservation (TR), tone injection (TI), active constellation extension (ACE), and multiple signal representation techniques such as partial transmit sequence (PTS) and selected mapping (SLM) methods. These techniques can achieve better PAPR performance without degradation of BER performance and undesirable spectrum re-growth. However these methods improve the PAPR performance at the cost of data rate loss, higher computational complexity, larger memory size, and requirement of separate channel for informing the side information to the receiver. In this degree thesis, the following two types of methods are proposed to solve the above problems. 1)Non―linear distortion compensation method for OFDM signal 2)PAPR reduction methods for OFDM signal with lower computation complexity As for the first method, this thesis proposes the Improved DAR(IDAR) method, which can mitigate both the clipping noise and inter-modulation noise. In the proposed IDAR method, the characteristics of non―linear amplifiers are required to be known at the receiver for mitigating the inter― modulation noise. This thesis also proposes the estimation method for AM‐AM and AM―PM conversions characteristics of non―linear amplifiers by using low PAPR (Peak to Averaged Power Ratio) preamble symbols. This thesis demonstrates the effectiveness of proposed IDAR method when applying the satellite communication systems. From the computer simulation results, it is concluded that the proposed IDAR method can achieve the higher transmission data rate and higher efficient usage of non―linear power amplifier with keeping the better BER performance even in the non―linear satellite channel. As for the second method, this thesis proposes PAPR reduction methods based on PTS technique. The conventional PTS method requires the larger number of clusters and weighting factors to achieve the better PAPR performance which leads larger computation complexity. To reduce the computation complexity, DIF― PTS method is proposed which employs the intermediate signals within the IFFT and used radix-2, radix-4, Split―Radix and Extended Split―radix for decimation in the frequency domain (DIF) to obtain the PTS sub―blocks. Multiple IFFTs are then applied to the remaining stages. The PTS sub-blocking is performed in the middle stages of the N-point radix FFT DIF algorithm. The DIF―PTS method can reduce the computational complexity relatively while it shows almost the same PAPR reduction performance as that of the conventional PTS method. To improve the PAPR performance with low computation complexity, this thesis proposes a new weighting factor technique for the PTS method in conjunction with DIF-PTS sub―blocking based on radix-r, Split―Radix and‐Extended Split―Radix IFFT technique which can improve both the PAPR performance and computation complexity. The proposed method can achieve the better PAPR reduction performance than that for the DIF―PTS method without any increasing of size of side information. In this thesis, a new PTS method by using the permutation of data sequence in the frequency domain is also proposed to improve the computation complexity. The proposed method employs the dummy and parity subcarriers as the embedded side information in the data subcarriers, which is used for the demodulation of data information at the receiver. The proposed method includes two types of permutation methods Type l and Type II. Type l is to perform the permutation only for the first M/2 subcarriers, while Type II is to perform the permutation both for the first and the last part of M/2 subcarriers. Although the computation complexity for the Type II is larger than Type I, the improvement of PAPR performance for the Type II is better than Type I. The feature of proposed method is to detect the rotation number performed at the transmitter precisely at the receiver by using the very few dummy subcarriers which corresponds to the embedded side information. The propose method can achieve the higher transmission efficiency because the size of embedded side information in the proposed method is much smaller than that for the side information in the conventional PTS method. From the computer simulation results, this thesis confirmed that the proposed permutation of data sequence method can achieve the better PAPR performance and better BER performance in the non-linear channel with lower computation complexity. In this thesis, the numerous computer simulations are conducted to confirm the effectiveness of all proposed method. Form the simulation results, it is confirmed that the proposed methods show the better PAPR performance with lower computation complexity. As a conclusion of researches in this thesis, the proposed PAPR reduction methods and mitigation methods of non-linear distortion noise could provide various practical solutions for the next generation of multimedia wireless communications systems employing the OFDM technique. | |||||||
| 言語 | en | |||||||
| 内容記述 | ||||||||
| 内容記述タイプ | Other | |||||||
| 内容記述 | 三重大学大学院工学研究科博士後期課程システム工学専攻 | |||||||
| 内容記述 | ||||||||
| 内容記述タイプ | Other | |||||||
| 内容記述 | 120p | |||||||
| 書誌情報 |
発行日 2013-01-01 |
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| 内容記述タイプ | Other | |||||||
| 内容記述 | application/pdf | |||||||
| 著者版フラグ | ||||||||
| 出版タイプ | VoR | |||||||
| 出版タイプResource | http://purl.org/coar/version/c_970fb48d4fbd8a85 | |||||||
| 出版者 | ||||||||
| 出版者 | 三重大学 | |||||||
| 修士論文指導教員 | ||||||||
| 姓名 | 小林, 英雄 | |||||||
| 言語 | ja | |||||||
| 資源タイプ（三重大） | ||||||||
| Doctoral Dissertation / 博士論文 | ||||||||
