Media-based Modulation关键技术研究

发布时间：2019-02-15 03:16

【摘要】：Media-based Modulation(MBM)是近年来提出的一种空间复用技术。其基本思想是在发射机通过廉价元器件改变发射天线周围的射频特性,从而改变发射机与接收机之间的信道状态,使发射机与接收机之间可以产生多种信道状态。发射机利用这些不同的信道状态承载信息,发送到接收机。MBM可以与传统的射频调制技术相结合,既可以发送信道状态信息,又可以发送射频调制信息。因此,MBM相对于传统的多天线技术在系统的频谱效率和能量效率上存在巨大的潜力。首先,本文研究了 MBM的实现原理。MBM有两种工作方式,即可以只发射信道状态信息,还可以发射信道状态信息和射频调制信息。通过研究MBM系统的符号映射规则,本文提出了一个等效系统模型。在此系统模型下,针对MBM系统不同的工作方式,推导并分析了其信道容量。结果表明MBM在信道容量上存在着巨大的优势。同时,研究了 MBM系统接收机的两种检测方式,即最大似然检测和球形解码,并提出了降低复杂度的球形解码算法。仿真结果表明,降低复杂度的球形解码算法的误码率性能与最大似然解码相同,而计算复杂度相比于最大似然解码和传统的球形解码都有很大程度的降低。然后,由于MBM系统的发射机能够产生丰富的信道状态,为了进一步提高系统的性能,本文研究了 MBM系统的信道状态选择算法。MBM系统可以通过采用一部分对系统增益较高的信道状态来承载和传输信息,进而降低系统的误码率。本文针对MBM两种不同的工作方式,提出了两个信道状态选择算法即CS-MBM和CS-MSBM。这两个算法的原理是最大化系统的最小欧式距离,大大的降低了选择过程的复杂度。仿真结果表明,当系统的星座图具有较高维度时,系统的误码率性能很好,当系统的星座图维度较低时,系统的误码率性能有少量损失。最后,由于MBM利用信道状态承载信息,精确的信道估计必不可少。然而实际的信道是时变的,尤其是在高速移动环境下。因此本文研究了 MBM系统在时间选择性信道下的误码率性能。为了能够提高接收机估计信道的准确性,本文推导了 MBM系统中基于最小均方误差准则和递归最小二乘准则的信道追踪算法。理论分析表明,这两个算法的复杂度在宏观上是相同的,但是具体的实现过程中递归最小二乘算法要复杂得多。仿真结果表明两个算法都能够在很大程度上提高系统的误码率性能,而且递归最小二乘算法相比最小均方误差算法性能更加优越。同时,导频长度也影响两个算法的性能,导频越长,两个算法的性能越好。
[Abstract]:Media-based Modulation (MBM) is a spatial reuse technology proposed in recent years. The basic idea is to change the radio frequency characteristics around the transmitter antenna through cheap components, thereby changing the channel state between the transmitter and the receiver, so that there can be a variety of channel states between the transmitter and the receiver. The transmitter uses these different channel state information to transmit to the receiver. MBM can be combined with the traditional radio frequency modulation technology to send both channel state information and radio frequency modulation information. Therefore, MBM has great potential in spectrum efficiency and energy efficiency compared with traditional multi-antenna technology. Firstly, this paper studies the implementation principle of MBM. MBM can transmit only channel state information, channel state information and radio frequency modulation information. By studying the symbolic mapping rules of MBM systems, an equivalent system model is proposed in this paper. Under this system model, the channel capacity of MBM system is deduced and analyzed according to the different working modes. The results show that MBM has great advantages in channel capacity. At the same time, two detection methods of MBM receiver, maximum likelihood detection and spherical decoding, are studied, and a spherical decoding algorithm is proposed to reduce the complexity. Simulation results show that the BER performance of the spherical decoding algorithm with reduced complexity is the same as that of the maximum likelihood decoding, while the computational complexity is much lower than that of the maximum likelihood decoding and the traditional spherical decoding. Then, because the transmitter of the MBM system can produce rich channel state, in order to further improve the performance of the system, In this paper, the channel state selection algorithm for MBM system is studied. The MBM system can carry and transmit information by adopting a part of channel state with high system gain, thus reducing the bit error rate of the system. In this paper, two channel state selection algorithms, CS-MBM and CS-MSBM., are proposed for two different working modes of MBM. The principle of these two algorithms is to maximize the minimum Euclidean distance of the system, which greatly reduces the complexity of the selection process. Simulation results show that the BER performance of the system is very good when the constellation diagram of the system has a higher dimension, and the BER performance of the system has a little loss when the constellation dimension of the system is low. Finally, because MBM uses channel state to carry information, accurate channel estimation is essential. However, the actual channel is time-varying, especially in high-speed mobile environment. Therefore, the BER performance of MBM system in time selective channel is studied in this paper. In order to improve the accuracy of receiver channel estimation, a channel tracking algorithm based on minimum mean square error criterion and recursive least square criterion in MBM system is derived in this paper. Theoretical analysis shows that the complexity of the two algorithms is the same in macroscopic, but the recursive least squares algorithm is much more complex in the process of implementation. Simulation results show that both algorithms can greatly improve the BER performance of the system, and the performance of the recursive least squares algorithm is better than the least mean square error algorithm. At the same time, the pilot length also affects the performance of the two algorithms, the longer the pilot frequency, the better the performance of the two algorithms.
【学位授予单位】：北京交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN929.5

【参考文献】