Samsung Electronics recently pulled off an impressive feat by demonstrating stable 5G Wi-Fi services in a subway train during high-speed transit.

The trial was performed on the Seoul subway system using Samsung’s 5G mmWave solution as a backhaul. It demonstrated how 5G mmWave can noticeably enhance the performance of legacy Wi-Fi systems—even in crowded public settings.

5G mmWave is a technology that delivers increased bandwidth, fast data speeds and low latency to users. This allows operators to significantly increase the capacity of their cellular networks. The technology allows for more powerful applications to be used, which gives subscribers fast and reliable connectivity. It’s particularly useful in applications for fixed wireless, enterprise operations, ultra–high-definition video, security, telemedicine and smart manufacturing.

5G mmWave is an economical way of increasing network capability and particularly beneficial in densely populated areas, such as campuses, stadiums, shopping malls and subways.

Samsung used a Galaxy S21 Ultra smartphone to reach downlink speeds of 1.8 gigabytes per second—25 times faster than the 71 megabytes per second commuters on Seoul’s subway currently enjoy with 4G devices. The trial covered a stretch of five stations in the Seoul Metro in major downtown areas.

Wi-Fi data speeds were enhanced with the company’s 5G Compact Macro, which leveraged the considerable capacity of the 5G mmWave spectrum. It was installed along the railways and used 800MHz in the 28GHz spectrum band. The Compact Macro device combined a baseband unit, radio and antenna in a single box. The device is compact and lightweight enough to be installed easily and unobtrusively on locations, such as the sides of buildings, stoplights and utility poles. It comes in two versions. The 4T4R is the workhorse meant for general coverage while the smaller 2T2R is used in high-traffic areas to boost signal capacity.

“We are pleased to deliver an enhanced mobile experience with faster download speeds and connections for subway passengers, leveraging our advanced 5G mmWave solution,” said Seungil Kim, Samsung Electronics vice president and head of Korea Business, Networks Business. “Our successful speed trial on public transportation proves the high potential of 5G mmWave, demonstrating its capability to complement existing wireless technologies and boosting the performance of legacy networks, all while providing a foundation for future telecommunication services.”

It’s impressive that Samsung was able to establish reliable 5G in the subway—an environment that’s traditionally unfriendly to a stable internet connection. Subway systems have unique challenges to overcome when installing Wi-Fi functionality.

The first and most obvious is being buried underground and encased in thick layers of concrete, making it difficult to get a decent signal. This means the electronic hardware needs to be installed underground in the subway network itself.

Temperatures in that system can fluctuate wildly, anywhere from below freezing to over 100 degrees. That means the hardware must be tough enough to withstand those temperatures and needs to be able to cope with rapid temperature fluctuations as the train moves between temperature-controlled stations and uninsulated tunnels. It’s a completely different scale than setting up a router in an office building.

And then there’s the problem of water. Not only puddles, leaks and rain runoff, but also the high-pressure hoses used to clean the stations themselves must be accounted for. Electronic equipment gets treated the same as the rest of the infrastructure and needs to be able to withstand the abuse.

Last of all is the dirt and grime. Brake dust is especially problematic. Fine particles of metal become airborne every time a train slows down to enter a station.

All this results in the need for seriously tough electronic equipment in an environment in which communications infrastructure is severely lacking—or nonexistent entirely. And Samsung seems to have pulled it off.