Iridium is a satellite system that is orginally designed to provide mobile phone service. The service is now extended to various other services like IoT. Probably Iridium would be the satellite mobile phone service that has been working for the longest time now.
As shown below, Iridium is orbiting in LEO. The constellation is made up of over 80 satellites at a height of approximately 781 kilometres (485 mi) and inclination of 86.4°.
The operating frequency of Iridium is 1,618.85 to 1,626.5 MHz band which belong to L-band.