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Frontiers of Information Technology & Electronic Engineering
ISSN 2095-9184 (print), ISSN 2095-9230 (online)
2021 Vol.22 No.4 P.527-547
Modeling and performance analysis of OAM-GSM millimeter-wave wireless communication systems
Abstract: In recent years, the conventional degrees of freedom in frequency and time have been fully used. It is difficult to further improve the performance of communication systems with such degrees of freedom. Orbital angular momentum (OAM), which provides a new degree of freedom for millimeter-wave (mmWave) wireless communication systems, has been recognized as a key enabling technique for future mobile communication networks. By combining OAM beams that have theoretically infinite and mutually orthogonal states with the generalized spatial modulation (GSM) strategy, a new OAM-GSM mmWave wireless communication system is designed in this paper. A bit error rate (BER) model of the OAM-GSM system is established based on channel flip precoding. The channel capacity, energy efficiency, and BER of the proposed OAM-GSM mmWave wireless communication system are simulated. Numerical results show that, compared with traditional GSM systems, the OAM-GSM system has more complex transmission and reception mechanisms but the channel capacity and maximum achievable energy efficiency are increased by 80% and 54%, respectively, and the BER drops by 91.5%.
Key words: Orbital angular momentum (OAM), Generalized spatial modulation (GSM), Millimeter-wave communication, Channel capacity, Energy efficiency, Bit error rate (BER)
华中科技大学电子信息与通信学院，中国武汉市，430074
概要：随着5G与物联网快速发展，海量移动设备涌入网络，产生巨大的数据交互需求，对未来网络发展提出严峻挑战。如何进一步提高通信网络容量、支持更大规模的网络接入，成为亟待解决的关键问题。在传统无线通信系统如MIMO中，空间调制、广义空间调制等调制策略被提出，以提升毫米波通信系统的传输速率，同时频率、时间等传统自由度也已被充分利用。因此，基于以上自由度很难进一步提高通信系统性能。由于轨道角动量（Orbital Angular Momentum, OAM）波在理论上具有无限个状态，并且不同状态之间存在自然正交性，OAM技术可以为无线通信系统提供新的自由度。随着无线通信系统中使用的电磁波频率逐渐升高，OAM技术也受到广泛关注。受OAM状态对信号进行编解码的思想启发，本文设计了OAM-GSM毫米波无线通信系统。与传统的广义空间调制（GSM）系统相比，OAM-GSM毫米波无线通信系统能够带来显著的性能提升，可作为未来移动网络的候选解决方案。
OAM-GSM系统发射端采用由M个OAM发射天线阵元组成的均匀线性阵列（Uniform Linear Array, ULA）。系统接收端由M组接收天线对组成，每组接收天线对包含两个接收天线，均安置在对应发射天线发射的OAM波的环形区域内。在OAM-GSM系统中，我们通过利用不同的OAM状态进行编码调制。信源的二进制比特流中的部分比特可以映射到不同的OAM状态，从而通过选择发射不同的OAM波实现信息传输。此外，在OAM-GSM系统中，信源的二进制比特流中还有一部分比特用于天线选择，一部分比特用于星座符号选择。
文中使用分离检测法检测传统调制符号、激活天线矩阵和OAM状态。在判断OAM电磁波的OAM状态时，可根据接收端两个接收天线分别检测出的所在位置OAM波的相位，利用相位梯度法确定。在OAM-GSM系统中，发射天线数量的增加使系统的误比特率（Bit Error Rate, BER）增大。为降低大发射天线数下的BER值，文中提出OAM-GSM系统预编码解决方案。
数值结果表明，与传统GSM通信系统相比，OAM-GSM毫米波系统虽然具有更复杂的收发机制，但其信道容量和最大能量效率分别提高80%、54%。同时，与传统GSM系统相比，通过采用提出的信道预编码算法，OAM-GSM毫米波系统的误码率下降91.5%。综上所述，文中设计的OAM-GSM毫米波无线通信系统具有良好性能，可作为未来移动网络的候选解决方案。
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DOI:
10.1631/FITEE.2000444
CLC number:
TN928
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On-line Access:
2021-04-15
Received:
2020-08-31
Revision Accepted:
2021-02-06
Crosschecked:
2021-03-15