FBMC系统中降低峰均比方法的研究

发布时间：2018-03-16 22:12

本文选题：滤波器多载波系统　切入点：正交幅度调制　出处：《东南大学》2017年硕士论文　论文类型：学位论文

【摘要】：随着技术的快速发展,正交频分复用技术应运而生,成为第四代移动通信的主流技术。但是在正交频分复用系统中为了抑制符号间干扰,需要插入循环前缀,这样就会降低数据传输效率。此外,正交频分复用系统旁瓣能量比较高,会降低频谱感知的准确度,很难判断信号是否是有用信号。针对OFDM系统存在的缺点,研究者们提出了基于滤波器多载波的正交幅度调制FBMC-OQAM技术。FBMC-OQAM系统相对于OFDM系统频谱泄露比较低,并且没有循环前缀。在多载波系统中,高峰均功率比PAPR问题一直是研究的重点问题之一,需要依据FBMC-OQAM系统自身的特点,在已有研究的基础上进一步提出新的降低峰均比的方法。在本文中分析了 FBMC系统的工作原理、信号结构特征以及峰均比定义,仿真验证了限幅滤波方法、选择映射方法和音频保留方法在降低信号峰均比方面的应用,并提出了改进的降低信号峰均比的方法。首先,理论分析验证了部分传输序列方法在FBMC-OQAM系统中的应用,但是因为部分传输序列方法需要传输边带信息用于接收端的信息解码,降低了频谱使用率。针对这一问题,文中提出星座映射方法和部分传输序列方法相结合降低信号峰均比的同时解决边带信息问题。星座映射的方法主要是在发送端将数据进行编码操作映射,并乘以相位旋转因子,在接收端通过信号判决规则进行信号的解码。最后通过仿真验证星座映射-部分传输序列方法在降低信号峰均比方面有较好的效果。然后,研究了通过导频的方式降低信号的峰均比。提出了将修正的干扰近似消除方法和OFDM系统中已经存在的部分传输序列方法相结合,充分利用两种方法的优点来降低FBMC-OQAM信号的峰均比。因为,传统的部分传输序列方法在降低峰均比方面有较好的性能,但是该方法需要传输边带信息,在一定程度上降低了频谱利用率,同时会增加接收端恢复数据的复杂度。所以提出了结合修正的干扰近似消除方法,利用信号中的导频进行信号解码,这样就可以实现在不需要传输边带消息的情况下恢复原始信号。此外,在此基础之上文中对修正的干扰近似消除方法进行了改进,通过仿真验证分析改变修正的干扰近似消除图案中导频的极性能够进一步降低信号的峰均比。通过理论分析和实验仿真,结果证明了部分传输序列-修正的干扰近似消除方法在降低信号峰均比方面的效果很好。最后,本文提出了新的基于导频方法降低信号峰均比的导频图案设计方法。新的导频图案是通过计算导频所受到的干扰,计算导频一阶范围内的保护值,降低导频在信号传输过程中所受到的干扰,有助于接收端准确的接收导频信息进行信号解码。相对于已有的修正的干扰近似消除导频图案,提出的新的导频图案的频谱利用率更高。通过仿真验证我们可以看到新的导频图谱方案在降低信号峰均比方面有较好的效果。
[Abstract]:With the rapid development of the technology, orthogonal Frequency Division Multiplexing (OFDM) has emerged as the main technology in 4th generation mobile communication. However, in order to suppress inter-symbol interference, cyclic prefix is inserted in orthogonal Frequency Division Multiplexing (OFDM) system. This will reduce the efficiency of data transmission. In addition, the orthogonal frequency division multiplexing system has a high side lobe energy, which will reduce the accuracy of spectrum sensing, and it is difficult to determine whether the signal is a useful signal. The researchers proposed a filter multicarrier based quadrature amplitude modulation (FBMC-OQAM) technique. The FBMC-OQAM system has a lower frequency leakage than the OFDM system and has no cyclic prefix. The peak-to-average power ratio (PAPR) problem has always been one of the key issues in the research. According to the characteristics of FBMC-OQAM system, a new method to reduce PAPR is proposed based on the existing research. In this paper, the working principle of FBMC system is analyzed. The characteristics of signal structure and the definition of peak to average ratio (PAPR) are defined. The amplitude limiting filtering method is simulated and the application of mapping method and audio retention method in reducing PAPR are selected. An improved PAPR reduction method is proposed. First of all, an improved PAPR reduction method is proposed. The theoretical analysis verifies the application of partial transmission sequence method in FBMC-OQAM system, but because the partial transmission sequence method needs to transmit sideband information to decode the information at the receiving end, it reduces the spectrum utilization rate. In this paper, the constellation mapping method and partial transmission sequence method are proposed to reduce the PAPR of signals and solve the problem of sideband information at the same time. The method of constellation mapping is mainly to encode the data at the sending end and multiply the data by the phase rotation factor. At the receiving end, the signal is decoded by the signal decision rule. Finally, the simulation results show that the constellation mapping-partial transmission sequence method can reduce the PAPR of the signal better. Then, In this paper, we study how to reduce the PAPR of the signal by pilot frequency, and combine the modified approximate cancellation method with the existing partial transmission sequence method in OFDM system. The PAPR of FBMC-OQAM signals is reduced by fully utilizing the advantages of the two methods, because the traditional partial transmission sequence method has better performance in reducing PAPR, but this method needs to transmit sideband information. The spectrum efficiency is reduced to a certain extent, and the complexity of recovering data at the receiving end is increased. Therefore, a modified interference approximate elimination method is proposed to decode the signal by using the pilot frequency in the signal. In this way, the original signal can be recovered without transmitting sideband messages. In addition, the modified approximate elimination method of interference is improved in this paper. It is proved by simulation that the PAPR of the signal can be further reduced by changing the modified interference and eliminating the polarity of the pilot in the pattern. Through theoretical analysis and experimental simulation, the PAPR of the signal can be further reduced. The results show that the partial transmission series-modified interference approximate elimination method is very effective in reducing the PAPR of the signal. Finally, In this paper, a new pilot pattern design method based on the pilot method to reduce the PAPR is proposed. The new pilot pattern is calculated by calculating the interference of the pilot and calculating the protection value in the first order of the pilot. To reduce the interference of pilot in the process of signal transmission, it is helpful for the receiver to receive the pilot information accurately and decode the signal. Compared with the existing modified interference, the pilot pattern is nearly eliminated. Through simulation, we can see that the new pilot spectrum scheme has better effect in reducing PAPR.
【学位授予单位】：东南大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN929.53

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