同时同频全双工OFDM无线通信系统自干扰抑制研究

发布时间：2018-02-20 17:18

  本文关键词： 同时同频全双工 自干扰抑制 自干扰信道估计 模数转换 动态范围　出处：《哈尔滨工业大学》2016年硕士论文　论文类型：学位论文

【摘要】：随着近年来通信技术的不断发展,无线通信系统对频谱利用率以及通信效率等指标的要求越来越高,同时同频全双工通信系统在原有半双工通信方式的基础上可以在理论上提高一倍的传输效率。然而,来自本地发射机的强自干扰信号是全双工通信系统的最大障碍,关于自干扰抑制的研究是系统的研究重点之一。因此,本文将重点针对模拟域与数字域的自干扰抑制算法与模块的设计进行研究,并在此基础上进行系统有效性的验证。首先,对全双工通信基础以及系统模型进行研究分析。介绍了同时同频全双工通信系统及其收发机模型,研究了OFDM信号模型以及通信信道和自干扰信道模型。在同时同频全双工通信系统背景下,通信信道模型为瑞利衰落模型,自干扰信道模型为K莱斯因子较大的莱斯信道。第二,对模拟域自干扰抑制进行研究。采用信道估计重建模拟自干扰的方式对消抑制模拟自干扰,利用OFDM系统中的IFFT模块在频域利用乘积代替卷积的方式降低重建自干扰的复杂度,实验验证了在全双工高干噪比背景下,LS算法与MMSE算法进行信道估计的性能相近,在模拟自干扰抑制模块可以抑制32d B的自干扰。第三,对大动态范围模数转换算法的研究。分析了在信干噪比极低的背景下,提高模数转换动态范围研究的必要性,提出了一种基于模数转换量化误差信号补偿的级联形式大动态范围模数转换算法,验证了算法的有效性,并结合全双工通信系统实验背景分析了算法中所需采用的AD、DA转换器所满足的有效动态范围应不低于50d B和75d B,仿真验证了算法可在8位AD的基础上提高20d B左右的动态范围。最后,对数字域自干扰抑制进行研究。改进原有工作方式,在自干扰信道随时间变化不十分明显的前提下,采用在全双工工作之前以半双工的训练模式进行信道估计作为重建数字自干扰信号的依据并结合复杂度低的频域最小二乘算法进行信道估计,实验验证该估计方法可以比基于梳状导频的信道估计提高15d B的自干扰抑制量。在不同信干噪比的条件下结合模拟自干扰抑制研究了整个系统的自干扰抑制量,实验验证数字自干扰抑制模块可抑制36d B的自干扰,系统整体可抑制68d B自干扰。在不同信干噪比条件下比较系统的解调误码率与相同指标下半双工系统的误码率,验证了在不低于-55d B信干噪比条件下自干扰可以得到有效抑制的结论。综上所述,本文在同时同频全双工OFDM通信系统的背景下,对主动自干扰抑制进行了研究,提出了全双工通信背景下的大动态范围模数转换算法并验证其有效性。最终以自干扰抑制量为指标验证了自干扰抑制的有效性并以误码率为指标验证了通信系统的有效性。
[Abstract]:With the development of communication technology in recent years, the requirements of wireless communication system for spectrum efficiency and communication efficiency are becoming higher and higher. On the basis of the original half-duplex communication mode, the transmission efficiency can be doubled theoretically in the same frequency full-duplex communication system. However, the strong self-interference signal from the local transmitter is the biggest obstacle to the full-duplex communication system. The research of self-interference suppression is one of the key points of the system. Therefore, this paper will focus on the design of algorithms and modules for self-interference suppression in analog and digital domains, and then verify the effectiveness of the system. The basis and system model of full duplex communication are studied and analyzed, and the simultaneous frequency full duplex communication system and its transceiver model are introduced. The OFDM signal model, the communication channel and the self-interference channel model are studied. In the background of the simultaneous co-frequency full-duplex communication system, the communication channel model is Rayleigh fading model, and the self-interference channel model is the Rice channel with higher K rice factor. In this paper, self-interference suppression in analog domain is studied. Using channel estimation to reconstruct analog self-interference to suppress simulated self-interference, IFFT module in OFDM system is used to reduce the complexity of reconstruction self-interference by using product instead of convolution in frequency domain. The experimental results show that the channel estimation performance of the LS algorithm is similar to that of the MMSE algorithm under the background of full duplex and high error-noise ratio. In the analog self-interference suppression module, the self-interference of 32dB can be suppressed. Thirdly, This paper analyzes the necessity of improving the dynamic range of A / D conversion under the background of low signal-to-noise ratio. In this paper, a large dynamic range A / D conversion algorithm based on analog to digital conversion quantization error signal compensation is proposed, and the validity of the algorithm is verified. Combined with the experimental background of full-duplex communication system, the effective dynamic range of ADDA converter used in the algorithm should be no less than 50dB and 75dB, and the simulation results show that the algorithm can improve 20dB on the basis of 8-bit AD. Dynamic range. Finally, The self-interference suppression in digital domain is studied. The original mode of operation is improved, and the self-interference channel does not change obviously with time. Channel estimation based on half-duplex training mode before full-duplex operation is used as the basis for reconstruction of digital self-interference signal and channel estimation is carried out by using low-complexity frequency-domain least square algorithm. Experimental results show that the proposed method can increase the self-interference suppression by 15dB compared with the channel estimation based on comb pilot. The self-interference suppression of the whole system is studied in combination with simulated self-interference suppression under different signal-to-noise ratios. The experimental results show that the digital self-interference suppression module can suppress the self-interference of 36dB and the whole system can suppress the 68dB self-interference. The demodulation error rate of the system is compared with that of the half-duplex system under the same index under different signal-to-noise ratio. The conclusion that self-interference can be effectively suppressed under the condition of not less than -55dB signal-to-noise ratio is verified. In summary, active self-interference suppression is studied under the background of simultaneous full-duplex OFDM communication system. In this paper, a large dynamic range A / D conversion algorithm in full duplex communication is proposed and its validity is verified. Finally, the effectiveness of self interference suppression is verified by using self interference suppression as an indicator, and the effectiveness of the communication system is verified by using the bit error rate (BER) as the index.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TN929.53
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本文编号：1519546