How to get cell phone service underground?

Getting cell phone service to work underground is possible with the same cellular signal booster installation principle. Instead of typical in-building distributed antenna system (DAS) that uses a roof antenna to catch and inject signals into the building and then amplifying them with a signal amplifier, underground DAS uses above-ground donor antenna to inject mobile signals under ground. Those signals are then sent as deep below as needed using a thick coaxial cable. Upon reaching the depth necessary, they are connected to a signal booster which amplifies those signals exponentially. Those signals are then dispersed where needed below ground via network of underground antennas. This priciple works for all frequencies including consumer and commercial cellular or for public safety radio bands used by first responders such as police, firefighters, emergency medical service (EMS) ambulance personnel, etc.