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."

Small Cells on the Train - A 2 hop solution

An Ericsson blog post some time back talked about the 2 hop solution for trains. Thinking about it, I quite like the idea. The post talks about 3 main challenges on high speed trains:

There are mainly three reasons communication services on high-speed trains is challenging:

First, large penetration loss via the shield of the train. This penetration loss is expected to be 20 to 30 dB.

Second, large numbers of handovers in very short time. This is due to hundreds or thousands of users needing handover from one site to another concurrently/sequentially. This phenomenon affects system stability and eats up capacity.

Third, high power consumption of user equipment (UE). This is because UE-s on the train need higher power to overcome the large penetration loss in uplink as well.

A common currently adopted solution for high speed trains is to densify the network along the railway to combat the large penetration loss. However, this will make the second issue more severe, as handover frequency is increased due to smaller site- to-site distance. Another way is to increase the transmission power of the base stations, which helps to solve the large penetration loss as well. However this cannot solve the third issue. And neither of these solutions are cost-effective.

Another solution I have discussed before is the Mobile Relay Node which was designed with avoiding multiple handovers when the vehicle moves between different macro cells. Not sure about its status in the standardisation process right now.

Anyway, coming back to the Ericsson post on Small cells on the train, while the Macro cells provide the TD-LTE backhaul outside, Radio Over Fiber (ROF) is used inside the tunnels to provide the same coverage.

Within the train Small cells (I guess multiple small cells will be needed in practical deployments, one for each carriage) can provide good coverage to the users and avoid the need for handovers.

Embedded is the video from Ericsson Taiwan that provides more details about this trial