Youngwoo Kwak

Modular and High-Resolution Channel State Information and Beam Management for 5G New Radio

This article provides an overview of key features pertaining to CSI reporting and beam management for the 5G New Radio (NR) currently being standardized in 3GPP. For CSI reporting, the modular design framework and high-resolution spatial information feedback offer not only flexibility in a host of use cases and deployment scenarios, but also improved average user throughput over state-of-the-art 4G LTE. To accommodate cellular communications in the milimeter-wave regime where a combination of analog and digital beamforming is typically used at both a base station and user equipment, beam management procedures such as measurement, reporting, and recovery are introduced. The utility and joint usage of these two features are demonstrated along with some potential upgrades for the next phase of 5G NR. Introduction

Effect of 3-dimensional beamforming on full dimension MIMO in LTE-Advanced

Large-scale antenna system has attracted significant attention in the wireless industry and academia area in the past few years as a candidate technology for the next evolution towards beyond 4th generation cellular systems. It can utilize a large number of antennas placed in a two-dimensional (2-D) antenna array panel for realizing spatially separated transmission links to a large number of mobile stations (MSs). The arrangement of these antennas on a 2-dimensional active antenna array allows the extension of spatial separation to the vertical domain as well as the traditional horizontal domain with the user-specific 3-dimensional beamforming. Utilizing such spatial separation capability, a base station (BS) can realize spatial multiplexing to a large number of MSs under 3-dimensionally spread channel environment. In this paper, we study the effect of user-specifica beamforming using both veritcal and horizontal direction on the large-scale antenna evolution of LTE system: Full Dimension MIMO. Evaluation results with various antenna configurations show while FD-MIMO provides significant improvement over conventional LTE systems, the size and spacing of active array within 2-D antenna structure need to be carefully selected to maximize FD-MIMOs full potentials in different cell deployments.

3D beamforming for capacity boosting in LTE-advanced system

LTE-Advanced system has been deployed with 2 and 4 transmission antennas (Tx) while the specification supports up to 8Tx. Due to deployment space, antenna dimension and complexity, operators have not been interested in the deployment of 8Tx systems. Recently, three dimensional (3D) beamforming using 2D active antenna array has attracted significant attention in the wireless industry. By incorporating 2D active array into LTE-A systems, the system offers freedom in controlling radiation on elevation and horizontal dimension. In addition, 2D array antenna increases the number of antennas without exceeding form-factor where the conventional antennas are deployed. When the number of antennas increases in the form of 2D arrangement, spatial separation can be realized simultaneously in horizontal and elevation domain and vertical beam-steering can increase SINR of UEs in high floors. In this paper, we study the system operations and implementations for supporting 3D beamforming with 8Tx antennas. In our schemes, by reusing the conventional CSI feedback framework, the system can operate 2D active array without harming the backward compatibility. Evaluation results show that 3D beamforming provides capacity boosting over the conventional 2D beamforming systems while keeping same antenna structure.