Forty-Five Mile Wireless Tech For the Smart Grid 77
holy_calamity writes "San Diego startup On-Ramp Wireless has put together a proprietary protocol that sends data over 2.4GHz (like WiFi) but over distances of up to forty-five miles. Links using the technology are slow, 50bps at most, but could reduce the cost of smartgrid deployments. Connecting up home energy meters today requires using cell networks or unlicensed spectrum with much shorter reach."
Bandwidth and Time vs. Range trade-off (Score:5, Informative)
The application for this is reading power meters and other continuous but low-bandwidth data. These generally operate in a mesh network. The devices used are generally low-cost and low-power, often in the "Part 15" section of the FCC rules for low-power devices that aren't allowed to interfere with licensed services. The problem is that some homes are too far from any other to link into the mesh, and the expense of reading those meters goes up significantly.
Signal processing theory allows you to trade bandwidth and time for range, such that a signal with a wider bandwidth or longer duration can be received over a greater distance. Hams have been doing this for decades using ultra-low-speed morse, PSK31 [bi.ehu.es], and other digital modes.
The achievement isn't really getting a long-range link, you can get 45 miles between mountaintops with wifi and parabolic antennas on a clear day. The achievement would be doing this for a very low installed parts cost and in unlicensed spectrum (which also reduces cost) while avoiding interference from wifi etc.
Re:Color me unimpressed (Score:4, Informative)
in fact TFA said that it could actually still communicate if the signal-to-noise ratio was less than 1.
Yes. Sharp-cutoff bandpass filters, Autocorrelation and chopper-stabilized amplifiers can make it possible to pull signal that is way below the noise level. This is done in certain low-signal-level sensor applications and deep-space communications all the time.
The trick is, it used to call for massively-expensive discrete operational amplifiers. Now, such op-amps can be had for pennies.