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Forty-Five Mile Wireless Tech For the Smart Grid
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."
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, 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.
Bruce Perens.
Isn't the record for WiFi over 100 miles with amplifiers?
Isn't the record for WiFi about the same as this without amplifiers, just using bigass dishes?
Is there any actual need to have quite this much range for this particular application? Wouldn't it make more sense to just use mesh networking? Wires don't tend to run 45 miles into nowhere to serve a single customer.
"You're right," Fisheye says. "I should have set it on 'whip' or 'chop.'"
Typical wifi ranges with a clear line of sight are, what, 300 feet or so? 5280 * 45 / 300 = 792 times normal wifi range. With signal strengths dropping off proportional to distance squared, that's an attenuation ~630k times greater. And you're complaining about 1/100,000th the bitrate?
Furthermore smartgrids don't need high bitrate. It's irrelevant to them. So what's the point? What they need is a widely deployable, low cost solution.
"This wallpaper is killing me. One of us has got to go." -- Oscar Wilde on his deathbed
if only we could find a way of connecting to all of these electricity meters with wires somehow...
Nullius in verba
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.
RTFA:
"There's no technology available for devices that just need a trickle of connectivity over long distance," says On-Ramp's chief technology officer, Ted Myers, who says that with a clear line of sight, On-Ramp's technology can send a signal 45 miles.
That's because the idiots chose the 2.4 GHz ISM band for their carrier frequency. If they had chosen something down closer to the AM broadcast band (but using something more robust than AM, like Spread Spectrum FM), they wouldn't have had line-of-sight requirements. But they WOULD have had FCC Licensing requirements that they obviously wanted to avoid.
It really depends on the antenna required. I've run 50 mile links with 802.11g/2.4ghz that ran at full speed -- it's not difficult. If this product does it without requiring 4 foot antennas 250-300' in the air on both ends.. great.
Just because you disagree doesn't make it offtopic or flamebait.