自相关匹配方法降低多载波系统的PAPR

发布时间：2018-11-09 13:53

【摘要】：多载波系统因具有频谱效率高、灵活性强等多项优点而得到广泛应用。正交频分复用(Orthogonal Frequency Division Multiplexing,OFDM)因其高带宽效率和对抗多径衰落的鲁棒性而受到广泛关注。然而,OFDM和多输入多输出正交频分复用(Multiple Input Multiple Output Orthogonal Frequency Division Multiplexing,MIMO-OFDM)系统的高峰均功率比(Peak-to-average Power Ratio,PAPR)阻碍了它们在高速通信中的应用。高的PAPR要求功放(Power Amplifier,PA)和模数转换(Analog-to-Digital,A/D)器件、数模转换(Digital-to-Analog,D/A)器件等具有非常大的动态范围,发射超出线性范围的信号易引起信号的非线性畸变,使得系统的误码率(Bit Error Rate,BER)性能退化。因此,为推广应用OFDM技术,人们致力于降低包括OFDM在内的多载波系统的PAPR的研究。目前来说,降低OFDM系统PAPR的技术主要可以划分成3类:多信号替换和概率类技术,信号预畸变类技术,编码类技术。在第一类技术中,选择性映射(Selected Mapping,SLM)技术和部分传输序列(Partial Transmit Sequences,PTS)技术受到重视,主要因为其能有效降低信号的PAPR,不会引起信号失真,并且实现简单。因此本文选择SLM算法和PTS算法与自相关匹配的思想相结合并进行比较。传统SLM和PTS方法的一个显著缺陷是,为了在接收端正确地检测信号,必须额外传输一定的边带副信息。边带副信息的传输降低了系统的频谱利用效率。为了在接收端实现盲检测,本文提出了自相关匹配的基本算法,旨在根据信号本身的自相关性在接收端检测信号,而无需传输边带信息。本文的主要工作如下:(1)研究自相关匹配思想在时域的具体应用,提出时域自相关匹配算法降低OFDM系统的PAPR,并将此算法与传统SLM算法相比较。时域自相关匹配算法在获得与传统SLM算法基本相同的PAPR性能的同时,可以不需要边带副信息的传输,在接收端正确地恢复出原始信号;并且由于时域自相关匹配算法对信号的处理过程发生在时域,大大降低了快速傅里叶反变换(Inverse Fast Fourier Transform,IFFT)的运算次数,从而降低了计算复杂度。(2)研究自相关匹配思想在频域的具体应用,提出三种算法来降低OFDM系统的PAPR,分别是自相关匹配-SLM算法,自相关匹配-PTS算法和部分自相关-PTS算法。这三种算法能够在有效降低信号PAPR的同时,实现接收端信号的盲检测,提高了频谱利用效率。(3)研究自相关匹配方法降低MIMO-OFDM系统的PAPR在时域的具体应用。将时域自相关匹配算法与并行的SLM算法相结合,提出并行的时域自相关匹配算法。在获得与并行的SLM算法几乎相同的PAPR抑制性能的同时,并行的时域自相关匹配算法无需传输边带副信息即可实现信号恢复。
[Abstract]:Multicarrier systems are widely used because of their high spectral efficiency and flexibility. Orthogonal Frequency Division Multiplexing (Orthogonal Frequency Division Multiplexing,OFDM) has attracted much attention because of its high bandwidth efficiency and robustness against multipath fading. However, the peak-to-average power ratio (Peak-to-average Power Ratio,PAPR) of OFDM and multiple-input multiple-output orthogonal frequency division multiplexing (Multiple Input Multiple Output Orthogonal Frequency Division Multiplexing,MIMO-OFDM) systems hinders their applications in high-speed communications. High PAPR requires power amplifier (Power Amplifier,PA), analog-to-digital conversion (Analog-to-Digital,A/D) devices, digital-to-analog conversion (Digital-to-Analog,D/A) devices and so on to have a very large dynamic range. It is easy to cause nonlinear distortion of signals when transmitting signals beyond the linear range, which degrades the BER (Bit Error Rate,BER performance of the system. Therefore, in order to popularize the application of OFDM technology, people devote themselves to reducing the PAPR of multicarrier systems including OFDM. At present, the technology of reducing PAPR in OFDM system can be divided into three categories: multi-signal substitution and probabilistic technology, signal pre-distortion technology and coding technology. In the first category, selective mapping (Selected Mapping,SLM) and partial transmission sequence (Partial Transmit Sequences,PTS) techniques are paid more attention, mainly because they can effectively reduce the signal's PAPR, without causing signal distortion, and the implementation is simple. So this paper chooses SLM algorithm and PTS algorithm to combine with the idea of autocorrelation matching. A significant drawback of traditional SLM and PTS methods is that in order to detect signals correctly at the receiver, additional sideband sub-information must be transmitted. The transmission of sideband sub-information reduces the spectral efficiency of the system. In order to realize blind detection in the receiver, this paper proposes a basic algorithm of autocorrelation matching, which aims to detect the signal at the receiving end according to the autocorrelation of the signal itself, without transmitting sideband information. The main work of this paper is as follows: (1) the application of autocorrelation matching in time domain is studied. A time-domain autocorrelation matching algorithm is proposed to reduce the PAPR, of OFDM system and compare with the traditional SLM algorithm. The time-domain autocorrelation matching algorithm can obtain the same PAPR performance as the traditional SLM algorithm, and can recover the original signal correctly at the receiving end without the need of sideband sub-information transmission. And because the signal processing process of time domain autocorrelation matching algorithm occurs in time domain, it greatly reduces the operation times of Fast Fourier inverse transform (Inverse Fast Fourier Transform,IFFT). Therefore, the computational complexity is reduced. (2) the application of autocorrelation matching in frequency domain is studied, and three algorithms are proposed to reduce the PAPR, of OFDM system, which are autocorrelation matching and SLM algorithm, respectively. Autocorrelation matching-PTS algorithm and partial autocorrelation-PTS algorithm. These three algorithms can effectively reduce the signal PAPR and realize the blind detection of the signal at the receiving end. (3) the application of autocorrelation matching method to reduce the PAPR of MIMO-OFDM system in time domain is studied. Combining time domain autocorrelation matching algorithm with parallel SLM algorithm, a parallel time domain autocorrelation matching algorithm is proposed. At the same time, the parallel time-domain autocorrelation matching algorithm can achieve signal recovery without transmitting sideband side information while obtaining almost the same PAPR suppression performance as the parallel SLM algorithm.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN929.53

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