SKT insisted on active use of low and mid-band 6G frequencies used in existing mobile networks.

SKT published the '6G White Paper' on the 10th, presenting key requirements for 6G standardization and future network evolution direction. The white paper discusses the main candidate frequencies for the 6G era and introduces SKT's exploration status.

In 5G, the IMT spectrum has been expanded into two FR1 and 2 to meet various usage scenarios. The allocated frequency bands linked to each country's frequency policy have enabled expanded services than the existing 3G and LTE. Korea has been allocated a 3.5GHz band in RF1 and a 28GHz band in FR2.

However, the Ministry of Science and ICT made the final decision to cancel the allocation of the 28GHz 5G frequency band to SKT in May, following KT and LG Uplus last year. SKT said, “The use of high-frequency spectrum has not been activated due to the insufficient market environment and difficulty in monetization.”

Additional candidate frequencies for 6G include mid-band (1–24 GHz), high-band (24–92 GHz), and sub-terahertz (92–300 GHz) bands. In addition, the importance of the upper-mid band (7-24 GHz) that can satisfy both capacity and coverage has recently been drawing attention.

The upper mid-band is an upper mid-band among the 6G candidate frequency bands that can secure base station coverage and capacity in a balanced manner, and has relatively better radio characteristics. Compared to the perceived speed of about 100 Mbps and the maximum speed of 3.6 Gbps of the 5G Sub-6 band, the perceived speed of the upper mid-band is expected to be about 1 Gbps and the maximum speed is expected to be 200 Gbps.

However, SKT said, “In the upper mid-band above 7GHz, other services such as satellite, ultra-wideband (UWB), and NATO already exist across multiple bands, and it is also true that it is difficult to discover new IMT bands due to differences in interests in the three regions distinguished by the ITU-R for international radio frequency management.”

He also argued that “learning from the sluggish activation of the 28GHz 5G frequency band, we should consider the constraints on the availability of RF technology and base stations to compensate for the poor propagation characteristics of high frequency bands,” and “we should actively review the utilization of low-band and lower-mid-bands currently used in existing mobile communication networks.”

■ 3G·LTE frequencies used for 5G SKT said it is reviewing the 4-10GHz band as a new candidate frequency for 6G. He also said, "Although the band has the characteristics of being able to build efficient coverage and secure base station capacity, it is already being used by multiple services, so we are researching ways to coexist and redeploy with existing services."

Global major mobile carriers are also focusing on technology research to utilize 3G and LTE frequencies for 5G. They are efficiently and quickly building 5G networks through mid-band and millimeter bands and CA and DC by utilizing the same-band frequency sharing technology (Spectrum Sharing).

SKT added, “We must actively conduct preemptive research to identify the characteristics of 6G candidate frequency bands and establish early-stage requirements.”

Meanwhile, although the Ministry of Science and ICT announced in July that it would allocate the 28GHz band to the fourth mobile carrier, there are concerns that if the business model and response to unprofitable high-frequency bands are inadequate, the situation experienced by the three existing mobile carriers will be repeated.

'Mirae Mobile', which has thrown down the gauntlet to become the 4th mobile carrier, revealed in a previous interview that it plans to build a nationwide 5G network using the 2.3GHz band. The goal is to continue investing in 28GHz by generating revenue by providing competitive nationwide 5G services along with 28GHz.

“It will be difficult to make a profit with only the 28GHz frequency when first entering the market,” said Lee Gyeong-su, senior advisor at Mirae Mobile. “The 2.3GHz frequency, which was used for WiBro in the past but is now an idle frequency resource, has a longer frequency than the frequency bands of the three mobile carriers, so it requires less investment, making it advantageous in recovering investment costs.”

The 6G candidate frequency bands are expected to be put on the agenda at the World Radiocommunication Conference (WRC-23) to be held in November 2023 and confirmed at the World Radiocommunication Conference (WRC-27) in 2027.

Currently, the International Telecommunication Union (ITU)-R is in the early stages of discussions for the establishment of the next-generation mobile communications 6G standard. This is actually based on the 6G standard specifications that satisfy the IMT-2030 technical performance requirements presented by the ITU-R, a standardization organization, written by the 3GPP. After the 3GPP completes the actual implementable specifications, equipment and terminal manufacturers will develop commercial products, and it is expected that 6G will be commercialized around 2030.

Our country will also define performance, standards, and evaluation methods for about three years from 2024 to 2026. We have a goal of demonstrating Pre-6G system technology in 2026, with a target period of 2028-2030.