An important network technology that allows 5G service without a connection issue to be enjoyed even in indoors.
Electronics and Telecommunications Research Institute (ETRI, President Kim Myung-joon) announced on Thursday that the institute has developed the world’s first optical repeater technology that can receive millimeter wave-based (28 GHz) broadband 5G signals from base stations.
With this technology, people will be able to use 20 Gbps internet service, which is the fastest transmission speed of 5G, in indoor settings such as airports, stations, and large shopping malls. Compared to the current method, this new technology drastically improves transmission capacity, equipment size, and cost of construction.
“RoF (Radio over Fiber) optical transmission” and “5G base station interface” technologies are the key to the institute’s optical repeater technology. RoF optical transmission technology is able to convert 5G wireless signals into optical signals and send them without signal distortion within a section with 5 kilometers in diameter at the maximum. 5G base station interface technology connects indoor and outdoor 5G base stations and indoor distributed antenna system through wireless software (SW) update (Over-the-Air) method.
Because the optical repeater technology is able to send 5G signals by multiplexing them into 32 bands, its transmission capacity is very high. Cost of construction is also five times cheaper than installing base stations as only relatively simple functions need to be implemented.
Research team that developed the optical repeater technology was able to realize the RoF technology by developing a diary sized RoF optical transceiver and installing it in the indoor distributed antenna system host device and antennas. 5G base station interface technology was also developed as an independent module that is similar in size as a laptop.

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<Structure of 5G indoor distributed antenna system>

During 2018 Winter Olympics held in Pyeongchang, the ETRI became the first in the world to demonstrate a pilot 5G service by utilizing millimeter wave-based 5G indoor distributed antenna system technology. At that time, it was only able to multiplex 5G signals into only two bands.
The technology was recognized for its excellence by being selected as the best paper by the world’s most prestigious optical communication-related academic conference, published on excellent SCI journals, established as an international standard by International Telecommunication Union, and selected as the top 100 excellent R&D in the nation in 2020.
“As this technology guarantees quality service and eliminates radio shade areas, we hope that it creates various new convergent industries and recover South Korean industries related to optical repeater that have been stagnant.” said Kim Seon-mi who is the head of the ETRI Network Research division.
The research team is also conducting studies on next-generation communication infrastructure construction technologies and is working on development of next-generation 6G communication network technology based on ultra-wideband frequency bands.
Meanwhile, the optical repeater technology was developed along with Katy, Frtech, and HFR. The institute has applied for nine science citation index-level papers and 30 domestic and foreign patents and transferred the technology to optical module and system companies such as HFR, Literon, Lonetech, and JT.
Staff Reporter Kim, Youngjoon |