Mobile connectivity is becoming a necessity and this is compelling mobile operators to provide coverage in very hard to reach areas within cities. One such example is in subways and metros where connectivity enhances the overall quality of life for commuters, improves safety and efficiency, and supports the growth of smart, connected urban environments. There are several other advantages like emergency communications, being able to communicate with friends/family/colleagues as and when required, and much more that I an not going to expand here. Some years back we made an explainer on how connectivity is provided in case of metro/subway here . While there were limited examples available then, we have seen a boom in underground connectivity since then. Recently O2 Telefónica in Germany announced (in German, translated via Google translate): It was now possible for all passengers of the Berliner Verkehrsbetriebe (BVG) to access high speed connectivity. The Berlin subway, the backbone of
2G, 3G, 4G, 5G, 6G, Wi-Fi, IoT, Bluetooth, LoRaWAN, Sigfox, Satellites