Ji-Yun Seol

Bio: Ji-Yun Seol is an academic researcher from Samsung. The author has contributed to research in topics: Beamforming & Communications system. The author has an hindex of 26, co-authored 108 publications receiving 4413 citations. Previous affiliations of Ji-Yun Seol include Korea University.

Millimeter-wave beamforming as an enabling technology for 5G cellular communications: theoretical feasibility and prototype results

Abstract: The ever growing traffic explosion in mobile communications has recently drawn increased attention to the large amount of underutilized spectrum in the millimeter-wave frequency bands as a potentially viable solution for achieving tens to hundreds of times more capacity compared to current 4G cellular networks. Historically, mmWave bands were ruled out for cellular usage mainly due to concerns regarding short-range and non-line-of-sight coverage issues. In this article, we present recent results from channel measurement campaigns and the development of advanced algorithms and a prototype, which clearly demonstrate that the mmWave band may indeed be a worthy candidate for next generation (5G) cellular systems. The results of channel measurements carried out in both the United States and Korea are summarized along with the actual free space propagation measurements in an anechoic chamber. Then a novel hybrid beamforming scheme and its link- and system-level simulation results are presented. Finally, recent results from our mmWave prototyping efforts along with indoor and outdoor test results are described to assert the feasibility of mmWave bands for cellular usage.

Communication method and apparatus using analog and digital hybrid beamforming

Abstract: A communication method and apparatus using analog and digital hybrid beamforming are provided. The method includes receiving a first message including a measurement and selection condition for hybrid beamforming from a Base Station (BS), measuring channels of a plurality of BS transmission beams, selecting at least one BS transmission beam based on channel measurements, transmitting report information about the selected at least one BS transmission beam to the BS, receiving from the BS a second message, estimating an effective channel matrix for the selected final BS transmission beam according to the measurement and report condition, determining feedback information for digital beamforming of the BS based on the effective channel matrix, transmitting the determined feedback information to the BS, and receiving a data burst from the BS according to a Multiple Input Multiple Output (MIMO) mode and/or a configuration scheduled based on the feedback information.

Tens of Gbps support with mmWave beamforming systems for next generation communications

Abstract: The recent strong demands for higher data rate support to cope with the explosive mobile data crunch has initiated research on the next generation (5G) wireless mobile communication technologies that could provide with drastic capacity increase. One of the promising candidates is to use wide spectrum in the mmWave bands, where a breakthrough to overcome the unfavorable channel properties needs to be preceded. In this paper, we propose a novel hybrid beamforming scheme that jointly combines RF beamforming and baseband precoding as a key enabling technique to make efficient use of mmWave channel. The link level simulation results show that the proposed scheme can almost achieve the optimal performance with noticeably reduced implementation complexity. Furthermore, system level simulation results are provided pointing out the possibility of tens of Giga-bits/sec data rate support with the proposed scheme.

Multi-beam transmission diversity with hybrid beamforming for MIMO-OFDM systems

Abstract: The ever-increasing traffic crunch for the wireless communication has drawn attention to the large spectrum available in the millimeter-wave bands as a potential means to achieve several fold mobile data traffic increase. While the channel characteristics at the millimeter-wave bands are known to be unfavorable for the mobile wireless communication purpose, the high gain available from massive array antenna facilitated by the short wavelength makes it possible to overcome the large path-loss. In this paper, we propose a hybrid beamforming architecture that combines an analog beamforming with array antennas and a digital precoding with multiple RF chains. Furthermore, we propose a multi-beam transmission diversity scheme for single stream transmission for single user MIMO operation. It is shown through various simulation results that the proposed hybrid beamforming scheme leads to considerable performance improvements even with limited feedback.

Method and apparatus for beam allocation in wireless communication system

Abstract: A beam allocation method of a Base Station (BS) in a wireless communication system is provided. The method includes transmitting a reference signal to a Mobile Station (MS) using a plurality of downlink transmit (Tx) beams, receiving information of a plurality of candidate downlink Tx beams determined by the MS in response to the received reference signal, selecting at least one downlink Tx beam from the plurality of candidate downlink Tx beams according to a predefined rule, generating control information for burst transmission, comprising the selected at least one downlink Tx beam information, transmitting the control information to the MS using the selected at least one downlink Tx beam, and transmitting a data burst based on Tx beam information included in the control information.

What Will 5G Be

Abstract: What will 5G be? What it will not be is an incremental advance on 4G. The previous four generations of cellular technology have each been a major paradigm shift that has broken backward compatibility. Indeed, 5G will need to be a paradigm shift that includes very high carrier frequencies with massive bandwidths, extreme base station and device densities, and unprecedented numbers of antennas. However, unlike the previous four generations, it will also be highly integrative: tying any new 5G air interface and spectrum together with LTE and WiFi to provide universal high-rate coverage and a seamless user experience. To support this, the core network will also have to reach unprecedented levels of flexibility and intelligence, spectrum regulation will need to be rethought and improved, and energy and cost efficiencies will become even more critical considerations. This paper discusses all of these topics, identifying key challenges for future research and preliminary 5G standardization activities, while providing a comprehensive overview of the current literature, and in particular of the papers appearing in this special issue.

Next Generation 5G Wireless Networks: A Comprehensive Survey

Abstract: The vision of next generation 5G wireless communications lies in providing very high data rates (typically of Gbps order), extremely low latency, manifold increase in base station capacity, and significant improvement in users’ perceived quality of service (QoS), compared to current 4G LTE networks. Ever increasing proliferation of smart devices, introduction of new emerging multimedia applications, together with an exponential rise in wireless data (multimedia) demand and usage is already creating a significant burden on existing cellular networks. 5G wireless systems, with improved data rates, capacity, latency, and QoS are expected to be the panacea of most of the current cellular networks’ problems. In this survey, we make an exhaustive review of wireless evolution toward 5G networks. We first discuss the new architectural changes associated with the radio access network (RAN) design, including air interfaces, smart antennas, cloud and heterogeneous RAN. Subsequently, we make an in-depth survey of underlying novel mm-wave physical layer technologies, encompassing new channel model estimation, directional antenna design, beamforming algorithms, and massive MIMO technologies. Next, the details of MAC layer protocols and multiplexing schemes needed to efficiently support this new physical layer are discussed. We also look into the killer applications, considered as the major driving force behind 5G. In order to understand the improved user experience, we provide highlights of new QoS, QoE, and SON features associated with the 5G evolution. For alleviating the increased network energy consumption and operating expenditure, we make a detail review on energy awareness and cost efficiency. As understanding the current status of 5G implementation is important for its eventual commercialization, we also discuss relevant field trials, drive tests, and simulation experiments. Finally, we point out major existing research issues and identify possible future research directions.

Millimeter-wave beamforming as an enabling technology for 5G cellular communications: theoretical feasibility and prototype results

Abstract: The ever growing traffic explosion in mobile communications has recently drawn increased attention to the large amount of underutilized spectrum in the millimeter-wave frequency bands as a potentially viable solution for achieving tens to hundreds of times more capacity compared to current 4G cellular networks. Historically, mmWave bands were ruled out for cellular usage mainly due to concerns regarding short-range and non-line-of-sight coverage issues. In this article, we present recent results from channel measurement campaigns and the development of advanced algorithms and a prototype, which clearly demonstrate that the mmWave band may indeed be a worthy candidate for next generation (5G) cellular systems. The results of channel measurements carried out in both the United States and Korea are summarized along with the actual free space propagation measurements in an anechoic chamber. Then a novel hybrid beamforming scheme and its link- and system-level simulation results are presented. Finally, recent results from our mmWave prototyping efforts along with indoor and outdoor test results are described to assert the feasibility of mmWave bands for cellular usage.

An Overview of Signal Processing Techniques for Millimeter Wave MIMO Systems

Abstract: Communication at millimeter wave (mmWave) frequencies is defining a new era of wireless communication. The mmWave band offers higher bandwidth communication channels versus those presently used in commercial wireless systems. The applications of mmWave are immense: wireless local and personal area networks in the unlicensed band, 5G cellular systems, not to mention vehicular area networks, ad hoc networks, and wearables. Signal processing is critical for enabling the next generation of mmWave communication. Due to the use of large antenna arrays at the transmitter and receiver, combined with radio frequency and mixed signal power constraints, new multiple-input multiple-output (MIMO) communication signal processing techniques are needed. Because of the wide bandwidths, low complexity transceiver algorithms become important. There are opportunities to exploit techniques like compressed sensing for channel estimation and beamforming. This article provides an overview of signal processing challenges in mmWave wireless systems, with an emphasis on those faced by using MIMO communication at higher carrier frequencies.

A Survey of 5G Network: Architecture and Emerging Technologies

Abstract: In the near future, i.e., beyond 4G, some of the prime objectives or demands that need to be addressed are increased capacity, improved data rate, decreased latency, and better quality of service. To meet these demands, drastic improvements need to be made in cellular network architecture. This paper presents the results of a detailed survey on the fifth generation (5G) cellular network architecture and some of the key emerging technologies that are helpful in improving the architecture and meeting the demands of users. In this detailed survey, the prime focus is on the 5G cellular network architecture, massive multiple input multiple output technology, and device-to-device communication (D2D). Along with this, some of the emerging technologies that are addressed in this paper include interference management, spectrum sharing with cognitive radio, ultra-dense networks, multi-radio access technology association, full duplex radios, millimeter wave solutions for 5G cellular networks, and cloud technologies for 5G radio access networks and software defined networks. In this paper, a general probable 5G cellular network architecture is proposed, which shows that D2D, small cell access points, network cloud, and the Internet of Things can be a part of 5G cellular network architecture. A detailed survey is included regarding current research projects being conducted in different countries by research groups and institutions that are working on 5G technologies.