Low Power Wide Area Networks
LoRa and SigFox are the two leading communication technologies for Low Power Wide Area Networks (LPWAN) on free-licensed ISM bands (433MHz and 868MHz in Europe, 915 MHz in US/CA/MX, ...). LoRa and Sigfox enable communication over several kilometers (Line of Sight and Non Line of Sight) with low-power consumptions and long battery lifetime (several years with 2 AAA batteries). Therefore, the typical network topology is the star topology : all endpoints transmit data to (resp. receive data from) one or several gateways. Ten gateways are enough to cover a city of 1 million inhabitants. Moreover, LoRa can leverage private networks.
LoRa gateways manage up to 49 LoRA channels and cost 500 - 1000 € /per unit. However, LoRa allows to build DIY Pico-gateways with ESP8266 or Raspberry Pi for instance starting at 40 € (including antenna and enclosure). Pico-gateways manage only one channel, but that's would be enough for a small private LPWAN.