KT announced on the 12th that it successfully demonstrated 5G NTN (Non-Terrestrial Network) communication technology, overcoming the disadvantages of delayed transmission in satellite communication environments. This achievement was made possible through collaboration with Rohde & Schwarz Korea and Viavi Solutions Korea.
5G NTN is a standard technology that uses satellites instead of ground-based base stations to dramatically expand the coverage of 5G services. In existing terrestrial network (TN) environments, such as urban areas, wireless signals encounter various obstacles leading to scattering, diffraction, and reflection, which result in multipath fading phenomena as they reach the receiver. This may temporarily reduce the strength of the received signal, and to overcome this, a retransmission technique known as HARQ (Hybrid Automatic Repeat request) is used.
Since NTN involves communication between satellites and terminals, unlike terrestrial networks, phenomena such as scattering, diffraction, and reflection of signals are minimal. Consequently, the effectiveness of retransmission techniques is low, and if the distance between the satellite and terminal exceeds a certain range, it may lead to low transmission efficiency due to the limitations of the retransmission technique (restrictions on the number of HARQ processes).
In this test, KT applied a method that accurately calculates the path loss between the satellite and the terminal according to their varying distance over time, without using retransmission techniques (HARQ-less), taking into account the free-space propagation environment.
Through this, communication at a distance of approximately 35,800 km between geostationary satellites and terminals achieved a transmission efficiency of about 10 Mbps, and utilizing this increased transmission efficiency, full HD video transmission was successful. KT plans to showcase the results of this test at the MWC 2025 event in March.
The 5G NTN technology is defined in 3GPP (3rd Generation Partnership Project) Releases 17, which signifies the 17th mobile communication standard developed by 3GPP, and was completed in 2022. KT successfully conducted the world's first interoperability experiment applying the 5G NTN standard to the Mugunghwa satellite 6 in September, and continuous follow-up research led to the acquisition of this 5G NTN communication technology. During the testing process, it was found that when the distance between the ground terminal and the satellite exceeded a certain range, the transmission efficiency (throughput) dropped sharply.
KT aims to expand its communication coverage beyond supporting 100% of the national territory into three-dimensional aerial domains. The company is committed to continuously securing NTN technology compatible with various non-terrestrial communication platforms, such as low Earth orbit (LEO) satellites and high-altitude communication platforms (HAPS), supported by the 3GPP NTN standard.
Kim Tae-hoon, CEO of Rohde & Schwarz Korea, noted that "Rohde & Schwarz has been diligently working to overcome various technical limitations in satellite communication environments. This collaborative research with KT has satisfied the rigorous requirements of mobile communication technologies such as 5G and NTN, and was carried out using R&S's CMX500 platform, which allows for flexible utilization, enabling us to acquire the latest technology and validate its advanced implementation."
Seo Beom-seok, president of Viavi Solutions Korea, stated, "We achieved communication over long distances in satellite communication of more than 10 Mbps using HARQ-less technology. By utilizing this technology, we can expand applications beyond emergency situations like disaster broadcasting to similar application services."
Lee Jong-sik, director of KT's Future Network Research Institute, remarked, "NTN is an essential technology for ubiquitous connectivity in the 6G era, and KT will continue to expand communication coverage beyond terrestrial limitations into three-dimensional aerial domains, leading the way into the 6G era."