SK Telecom's In-building 5G NR Repeaters and 'Layer Splitter'

In-building coverage is the new battleground in South Korea. According to this report by Korea Times back in August

SK Telecom, KT and LG Uplus, which have been in cutthroat competition to improve the quality of their fifth-generation (5G) network services, are now in a race to boost 5G data speeds inside buildings.

Their move comes amid growing complaints over disappointing 5G network coverage since the next-generation mobile network services were launched in early April.

SK Telecom said Wednesday it has completed the development of the "5GX In-building Solution" that is capable of doubling the speed of 5G data transfer inside buildings and effectively dispersing data traffic to prevent overload on base stations in crowded areas such as shopping malls and subway stations.

The nation's top mobile carrier said the new technology will be applied to its commercial 5G networks after the third quarter of the year.

"We expect 80 percent of data traffic to be from inside buildings in the 5G era," said Park Jong-kwan, who heads 5GX Labs at SK Telecom. "We will continue to give efforts to provide users with seamless, high-quality 5G services inside buildings and in crowded areas."

The company said its new system features "Active Antenna" technology that allows 5G small cells, which refer to small indoor base stations, to be equipped with eight transmission and reception antennas.

This will double the speed of 5G data transfer as existing indoor base stations are capable of operating four transmission and reception antennas.

KT has also been working hard to expand 5G coverage inside buildings.

In May, the nation's largest broadband service provider and second-largest mobile carrier interlocked 5G repeaters with commercial 5G networks in cooperation with small and medium business partners.

Installed inside buildings where radio waves from base stations can hardly reach, the device helps improve the quality of 5G services.

KT is in charge of expanding 5G coverage in 95 large buildings out of 119 nationwide, such as airports and KTX stations, in a joint project by the three mobile carriers.

LG Uplus, the smallest player, also has been active in installing repeaters in small and medium buildings and underground parking lots to expand 5G coverage.

The company is planning to expand the application of beam-forming and multi-user MIMO (multiple-input and multiple-output) technologies to its 5G networks nationwide.

Back in May, SK Telecom won SCF Small Cell Awards 2019 in the category of “Commercial Small Cell Design and Technology” for commercializing the world’s first 5G NR RF repeater. According to the press release:

SK Telecom won this year’s SCF Small Cell Awards for developing and commercializing, for the first time in the world, two different types of 5G NR RF repeaters operating in the 3.5GHz band in 2018. 5G RF repeaters, which amplify 5G radio signals to allow them to travel greater distances, are used to enhance 5G service quality by improving coverage for in-building areas.

SK Telecom’s RF repeater is built with 5G NR standard-based Time Division Duplex (TDD) Synchronization detection technology, which enables a more efficient use of limited frequency resources. In addition, the 5G repeater provides wide bandwidth support and operational optimization features.

Going back to the Small Cells World back in May, SK Telecom presented their solution but the presentation was not shared. Here are some relevant pictures from their presentation:

SK Telecom: will use various inbuilding solutions to complete 5G network. e.g. A 3.5GHz RF repeater to extend home/small building coverage - running remote antennas from the repeater.

— TheMobileNetwork (@TMNmag) May 21, 2019

Source: Phil Kendall

As can be seen in the picture (click to enlarge), depending on the use case and location, the InBuilding solution would change from Small cells to AAU and Repeaters.

Source: Dean Bubley

As you can see in the picture above, the 3.5/28 GHz layer split solution improves capacity of the building by creating multiple layers to improve the capacity. There is a new press release on this topic, which is covered in the post later on.

Source: Dean Bubley

The Speed Repeater above and the RF Repeater below is backhauling on the existing macro, similar to the In-band backhauling (IBBH) I have described earlier or Sprint/Airspan MagicBox.

Source: Dean Bubley

In a recent press release, SK Telecom announced that they have expanded the 'Layer Splitter', a dedicated equipment for 5G inbuildings, to 1,000 buildings, starting with WeWork Seolleung Branch (Gangnam-gu, Seoul). SK Telecom customers will be able to use 5G services twice as fast as existing in-building equipment in major domestic buildings such as shopping malls and department stores.

'Layer Splitter' is the equipment based on '5GX In-building Solution' developed by SK Telecom in the world in August. If existing indoor equipment is equipped with two antennas for data transmission and reception, 'Layer Splitter' is a four-integrated antenna equipment that can process more data simultaneously in the same frequency band.

It also integrates several signal conversion devices * that go through for communications services. The integrated device is half the size of the device as before, and data transfer rates are faster with fewer signal conversion steps. In addition, the integrated device is placed forward in the base station and only the antenna is installed inside the building, enabling quick action in the event of a problem without visiting the building.

※ Previously, it had to go through four-step signal conversion (digital signal → optical signal → base signal (IF) → optical signal → wireless signal (RF)), but 'layer splitter' Combined 'matcher' and 'donor', a device that converts the base signal (IF) into an optical signal

SK Telecom plans to expand in-building coverage centered on 'layer splitters' in buildings with a large number of floating populations such as large shopping malls and department stores. 

Wework, the first construction site, is a shared office where several ICT-related companies collaborate and expect various business models based on Korea's best 5G infrastructure. In particular, SK Telecom and Wework have been working together since last year's strategic partnership, including building 5G infrastructure.

Chang-Kwon Chung, head of infrastructure engineering group at SK Telecom, said, SKT customers can experience differentiated communication quality with the only equipment dedicated to 5G in-building. “In-building will be able to efficiently accommodate in-building traffic that will continue to increase in the 5G era. "We will continue to advance our proprietary solutions."

Hopefully we will learn more about this solution in near future.


Related Posts:

• SK Telecom's 5G Strategy and Services
• 5G+ Strategy of the Republic of Korea 

ETRI working on Small Cell Base Station in a Backpack and 5G Indoor Femtocells

Came across this slightly old news in March issue of ETRI Webzine:

Following the development of the LTE small-cell base station SW in 2016, ETRI announced on February 7 that it successfully developed a SW supporting LTE-TDD dual connectivity.

These technologies are evaluated as core technologies for future 5G communication through upgrading of conventional SW technologies, since they may be applied to buildings, stadiums, and homes.

The technologies are suitable for the locations where the traffic is rapidly increased, such as stadiums, department stores, disaster-stricken areas, and military camps. The small cells may be attached, like a wireless LAN AP, to walls inside and outside buildings, utility poles, and communication antennas, or may be carried in the form of a backpack. The research team explained that the size of the small-cell was minimized as the size of a wireless LAN AP for indoor purposes and as the size of a shoe box for outdoor purposes. The small-cell backpack weighs about 10 kg.

These accomplishments will remove the communication shadows and blind spots between cells, and will help to develop independent technologies by replacing the conventional products from other countries.

In a more recent news on this topic (September 2018):

Following the successful localization of software for LTE Small Cell, which is used in the same manner as wireless access points operating within tens of meters to 1 km, while serving as a small base station, ETRI researchers began research to localize small cell equipment essential to establishing 5G infrastructure going forward. The focus of the research is on the development of technology capable of increasing the maximum transmission speed (eMBB), which is one of the most critical criteria for 5G technology, and especially the perceived transmission speed on the user side.

According to Yonhap News (translated by Google translate):

SK Telecom will be participating in 'Intelligent 5G Small Cell Technology Development Task' together with Korea Electronics and Telecommunications Research Institute (ETRI), domestic wireless communication equipment company Teltel and U Cast. The project is sponsored by the Ministry of Science, Technology and Information and is organized by ETRI.

In this project, SK Telecom sets up requirements for small cell system development. In addition, ETRI and equipment companies provide a test environment for small cell equipment verification. ETRI develops software, and Contela and Yu Cast develop hardware.

SK Telecom and other collaborative research groups plan to open API (application programming interface) to small cell. This reduces the burden of SMEs and start-ups to develop their own interfaces.

SK Telecom and ETRI are planning to develop international standard technology and secure original patents in the small cell field based on research results.

SK Telecom announced on February 23 that it will participate in 'Intelligent 5G Small Cell Technology Development Task' together with Korea Electronics and Telecommunications Research Institute (ETRI), Kontela and U Cast of domestic wireless communication equipment. A joint research team is taking a commemorative photo in front of the first workshop at Daejeon ETRI fusion technology research and production center. 2018.8.23

SK Telecom Park Jong-kwan, director of Network Technology, said, "In the 5G era, 80% of total traffic will occur indoors." "We will take the lead in 5G technology development so that customers can fully enjoy virtual reality and hologram services."

SK Telecom: Commercial deployment of LTE Femto cell

SK Telecom does not fail to impress with their aggressive roll-outs and impressive solutions to challenging problems. One such presentation from the Small Cells World Summit 2013 in London is embedded as follows: