ETRI develops the world’s first 5G indoor DAS(Distributed Antenna System) technology


Transmitting 5G signals based on 28GHz millimeter wave to indoor area; supporting 5G services at the speed of up to 20Gbps in indoor environments such as airports, stations, and shopping malls


Credit: Electronics and Telecommunications Research Institute(ETRI)

Researchers in Korea have developed a important network technology that allows users to enjoy 5G services seamlessly in indoor environment. It is expected to be of great help in expanding the 5G coverage area and further improving the domestic telecommunications infrastructure.

Electronics and Telecommunications Research Institute (ETRI) announced that it has successfully developed the world’s first 5G indoor DAS1) that can receive millimeter wave (28GHz) – based broadband 5G signals from base stations and transmit them into buildings.

About 80% of mobile data used in daily life is consumed indoors. This new technology allows accessing 5G technology at its peak speed of 20Gbps in indoor environments such as airports, stations, and large shopping malls. In particular, this new technology significantly improves transmission capacity, equipment size, deployment cost, etc. compared to the conventional one, so it is expected to have a diverse range of applications.

The core of the technology developed by the researchers includes RoF2) technology and 5G base station interface3) technology. The RoF technology that converts 5G wireless signals into optical signals and transmits them without distortion at the maximum distance of up to 5km. On the other hand, the 5G base station interface technology that connects a 5G base station located outdoors and an indoor distributed antenna system by using a OTA4) technique.

The 5G base station interface installed on the roof of the apartment receives 5G signals from nearby base stations, converts them into optical signals in the apartment basement with the help of RoF technology, and then transmits them to multiple antennas distributed in all areas of each floor of the building.

As this technology can deliver 5G signals by multiplexing them into 32 bands, its transmission capacity is very high. The cost of construction can be decreased by 5 times compared to previous DASas only relatively simple functions need to be implemented.

The researchers revealed that they developed RoF optical transceiver5) the size of a diary and installed it in the host unit6) and antenna unit constituting the indoor distributed antenna system. The 5G base station interface technology was also developed in the form of an independent module with the size of a laptop so that it can be easily linked with host unit.

According to the research team, the recent use of high-frequency bands and the rapid increase of large-capacity data have led to the employment of RoF technology, which has been studied since the 1990s, and they were able to achieve this feat based on accumulated original technology and know-how.

ETRI demonstrated the world’s first 5G pilot service using millimeter wavel-based on 5G indoor distributed antenna system technology at the PyeongChang Winter Olympics in February 2018. At that time, it was at the level of multiplexing 5G signals into two bands but has been upgraded to reach the current level.

The technology was widely recognized for its excellence by being selected as the best paper by the world’s most prestigious optical communication-related academic conference7) published on renowned SCI8) journals, established as an international standard by the International Telecommunication Union, and designated as one of the top 100 national R&D projects in 2020.

“We hope that this technology will contribute to the creation of an ecosystem of new convergent industries such as interactive entertainment and smart factory and the rejuvenation of the stagnant domestic industrial ecosystem related to repeaters for mobile communication, while ensuring quality of service and eliminating radio-eave shaded indoor areas,” said Sunmi Kim, head of ETRI’s Network Research Division.

The research team is also conducting studies on next-generation communication infrastructure construction technologies to provide 6G mobile networks beyond 5G in the future indoor environment. It plans to secure future intellectual property rights and lead the development of related domestic industries while developing next-generation 6G communication network technology based on ultra-wide frequency bands.

Meanwhile, the indoor DAS technology was developed as a part of the “The deveplopment of indoor DAS technology based on Analog IFoF9) for 5G mobile communication project” by the Ministry of Science and ICT and jointly by KT Corporation, FRTek, and HFR.

The research team has applied for 9 SCI-level papers and 30 domestic and foreign patents and completed a total of 5 technology transfers to optical module and system companies such as HFR, Lightron, Rontech, and JT Corporation.

Companies that have received technology from ETRI have now exported related products to Japan and the United States through active commercialization. As a result, ETRI’s technology is contributing to the construction of 5G infrastructure around the world.


About Electronics and Telecommunications Research Institute (ETRI)

ETRI is a non-profit government-funded research institute. Since its foundation in 1976, ETRI, a global ICT research institute, has been making its immense effort to provide Korea a remarkable growth in the field of ICT industry. ETRI delivers Korea as one of the top ICT nations in the World, by unceasingly developing world’s first and best technologies.

This demonstration technology was developed with the assistance of the Ministry of Science and ICT (MSIT). An article explaining the results of this research was designated as one of the top 100 national R&D projects in 2020.

Glossary description:

1) A technology that converts optical signals into electrical signals or vice versa and compensates for transmission loss to remove radio-wave shaded areas and expand the coverage of mobile communication services

2) Abbreviation for Radio over Fiber, a technology that optically transmits radio signals for mobile communication through fiber optic cables.

3) A technology that physically connects the base station and indoor DAS.

4) Over The Air: A method of exchanging information wirelessly.

5) A compound word of (optical) Transmitter and Receiver.

6) Network Host. Computers or other devices connected to the network.

7) OFC 2019. Optical Networking and Communication Conference & Exhibition

8) IEEE/OSA Journal of Lightwave Technology

9) Intermediate Frequency over Fiber: A technology that converts wireless signals converted into frequency into light and transmits it through optical fiber.

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Dr. Kil-ho Chong
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