著者

Eiji Okamoto

出版者

The Institute of Electronics, Information and Communication Engineers

雑誌

Nonlinear Theory and Its Applications, IEICE (ISSN:21854106)

巻号頁・発行日

vol.12, no.3, pp.257-274, 2021 (Released:2021-07-01)

参考文献数

35

被引用文献数

2

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In recent years, there have been several advances in wireless communication systems, including the increase in transmission rate, and as a result, they are playing an increasingly significant role in our lives. To meet the widespread application scope, the commercialization of the fifth-generation mobile communications system (5G) has been initialized. This paper gives an overview of the 5G system and discusses the nonlinear signal processing technologies that support its performance improvement. Here, the term “nonlinear signal processing” is defined as an algorithm for transmitting and receiving data in communications that uses a nonlinear mechanism. Because there is a significant shortage of frequency bands in wireless communications, advanced technologies are being integrated to maximize frequency utilization. In addition, unlike in the 4G era, there are additional use cases that require performance guarantees for quality, delay, and the number of multiple connections in the 5G system, and the performance requirements for wireless systems are becoming more stringent. Nonlinear signal processing is key to improving the performance of these systems, and this paper outlines the nonlinear technology used in 5G wireless access. We will introduce multiple-input multiple-output transmission and non-orthogonal multiple access (NOMA), which will help improve the performance of wireless systems. In addition, we introduce a radio wave-encrypted NOMA with a physical layer security that is proposed by the authors. Furthermore, the technical trend of 6G is briefly introduced.

著者

Ryo Kato Mamoru Okumura Eiji Okamoto

出版者

The Institute of Electronics, Information and Communication Engineers

雑誌

IEICE Communications Express (ISSN:21870136)

巻号頁・発行日

vol.11, no.5, pp.189-194, 2022-05-01 (Released:2022-05-01)

参考文献数

6

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In 5G vehicular communications, beamforming technologies for vehicles, which compensate for large propagation losses at high carrier frequencies, are being considered. However, because the deflected beamforming loss degrades the communication quality, an accurate beam tracking system that follows the movement of the vehicle is required. In conventional schemes using a periodic codebook, the main lobe often deviates from the direction of the base station owing to fast movement. Therefore, in this study, a scheme for adaptively generating beam candidates using beam selection logs and the steering angle of the vehicle is proposed. Numerical results show that the scheme has high accuracy.