Given the background design criteria; many rural users are scattered in a large area, we need to reduce cost of building and maintaining wired communications. In this project, we choose to use radio communications between remote nodes and use a controller to upload the motoring data to a remote web server. We can then monitor the electricity usage and send commands to control the meters. In this way, we could build up a cheap and fast way for electricity control in rural and remote areas.
One key factor in reducing the distribution costs is to use wireless protocol rather than the wired connection. To handle this problem, we choose to use LoRa radio to transfer data between each meter node. LoRaWAN™ is a Low Power Wide Area Network (LPWAN)[7] specification intended for wireless battery operated Things in a network. LoRaWAN targets key requirements of Internet of Things such as secure bi-directional communication. We plan to add additional encryption below the radio transmission but the LoRa protocol provides security in our initial prototypes. The LoRaWAN specification attempts to provide seamless interoperability among smart Things without the need of complex local installations. The Figure above is the structure of a classic LoRa application. LoRa can transmit over 1.2mi/2Km line-of-sight with wire quarter-wave antennas and over 20Km with tweaking and directional antennas. This exceeds our demand to send and receive data in rural area. We are currently using a 6.5 inch quarter wave whip wire antenna.
The other main design consideration is cost. Since Arduino is an open source platform, it is relatively cheap for deployment. The Arduino community provides libraries to help in the prototyping phase. With further development we could use an M4 ARM processor with built in Ethernet capabilities for even more economy.