Coverage Extension of Indoor 5G Network Using RoF-Based Distributed Antenna System

Eon-Sang Kim,Joon Ki Lee,Joonyoung Kim,Jong Hyun Lee,Seung-Hyun Cho,Minkyu Sung

doi:10.1109/access.2020.3033592

Abstract

We propose and demonstrate a cascaded distributed antenna system (DAS) for efficiently extending the coverage of the mmWave-based 5G indoor network. For this, we exploit the radio-over-fiber (RoF) system based on the intermediate-frequency-over-fiber (IFoF) transmission technique that is enabled to add/drop the specific wavelength to the designated remote antenna unit (RAU) with using optical splitters and coarse wavelength division multiplexing (CWDM) filters. Moreover, the IFoF transceivers (TRx) perform the subcarrier multiplexing (SCM) in order to transmit 2 × 8 frequency allocation (FA) 5G signals per a single optical carrier, where each FA has 100 MHz bandwidth, leading each RAU to support 2 × 2 MIMO operation. Consequently, the cascaded structure allows for the adaptive and flexible configuration of the order of MIMO in accordance of the required data throughput at the specific indoor area. We introduce the cascaded IFoF link structure that can support up-to 13.5 dB optical power budget with following errorvector-magnitude (EVM) performance characterizations. And then we experimentally demonstrate the RoFbased cascaded DAS network, showing that more than 1 Gb/s total throughput can be achieved per a single antenna. Furthermore, we examine the use of avalanche photodiode (APD) to further increase the optical power budget (i.e., the coverage) based on experiment as well as simulation.

Highlights

In mobile telecommunications, the millimeter wave is drawing increasing attention as it provides abundant spectrum to enable the emergence of diverse next-generation applications
The 5G network is evolving from the mid-bands (i.e., 1-6 GHz) to the mmWave (i.e. 24-60 GHz)-based services that will be delivering multi-gigabit speeds to end-users, allowing for the realization of the ultimate 5G scenarios such as enhanced mobile broadband as well as ultra-reliable and low-latency communications (URLLC) and massive internet of things [1], [2]
The active distributed antenna system (DAS) captures and digitizes the mobile signal based in the standard protocols such as Common Public Radio Interface (CPRI) [8], [9]

Summary

INTRODUCTION

The millimeter wave (abbreviated mmWave) is drawing increasing attention as it provides abundant spectrum to enable the emergence of diverse next-generation applications. The active DAS captures and digitizes the mobile signal based in the standard protocols such as Common Public Radio Interface (CPRI) [8], [9] This solution solved many RF cabling-induced problems of the passive DAS network, it was at the expense of the system cost and complexity. In the IFoF, on the other hand, the mobile signal is downconverted to IF-band (e.g., 2 GHz) prior to the fiber-optic transmission It prevents the 5G signal from the dispersion-induced quality degradation with no use of extra optical devices such as reference lasers and optical frequency comb. We investigate the use of avalanche photodiode (APD) in the RoF link for further extension of the coverage based on simulation in conjunction with the actual experiment

CASCADED DISTRIBUTED ANTENNA SYSTEM

FURTHER IMPROVEMENT USING APD

CNRThm

Findings

CONCLUSION