Radio communication

2006-09-15

in Geek stuff, Internet matters, Science

I have long found it surprising, and a bit unsettling, to think how many different overlapping radio signals there are surrounding and traversing us at all times. There are all the AM and FM radio stations, cell phones on different frequencies, communications from satellites, broadcast television, military and police radio frequencies, and miscellanous other signals such as aircraft transponders.

Most of that bandwidth is very inefficiently allocated, as with analog phones. Because frequencies have dedicated purposes that are not always being employed, there is a lot of bandwidth that is allocated but unused at any one time. The clever thing about more advanced systems like Code Division Multiple Access (CDMA) cellular phones is that they can use dynamically allocated frequency, and thus scale bandwidth according to need.

If we could do the same with some the the excellent bandwidth given over to television or military purposes, large scale wireless internet could come about rather more quickly and easily. Wireless internet, such as it exists now (the 802.1x standards) are located in a really undesirable part of the radio spectrum – hence problems with range and interference. As in so many other cases, the stumbling block is more regulatory than technological.

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{ 4 comments… read them below or add one }

Anon September 15, 2006 at 9:07 pm

Feeling guilty about not writing any substantive posts lately?

You probably shouldn’t – you are on vacation.

Milan September 16, 2006 at 10:39 am

Indeed I was – top quality blogs cannot simply be personal narration of a life as mundane as mine can be.

Anon April 8, 2007 at 2:50 pm

An interesting post on open v. closed 802.11x networks.

. October 1, 2010 at 10:58 am

“In a little-noticed meeting on May 9, 1985, the Federal Communications Commission adopted a rule that changed the tech world forever. Until that point, the FCC’s main role had been to define specific uses for the public radio waves. If you picture all of the country’s available radio spectrum as a pie, the FCC was the waiter who sliced it up and handed it out to the nation’s most well-connected institutions: the radio and TV networks, telecom companies, and the military. The 1985 rule changed that. At the prodding of Michael Marcus, an engineer who joined the FCC under the Carter administration and stayed on during the Reagan era, the agency set aside a few distinct radio bands for “unlicensed” use. The rule allowed tech companies and customers to run devices on these bands for free, for any purpose, and without seeking government permission. In other words, the FCC was reserving a slice of the pie for the rest of us.

It wasn’t a very pretty slice. The frequencies that the FCC gave away—the 900 MHz, 2.4 GHz and 5.8 GHz bands—were known as “garbage bands,” because they were generally considered too prone to interference to be of much use (microwave ovens, for instance, emit radiation on the 2.4 GHz band). But as a result of a clever broadcasting technique known as “spread spectrum”—in which a device can communicate along a range of radio frequencies, making it less susceptible to interference—tech companies managed to make good use of the garbage bands. Thanks to the 1985 rule, the public has enjoyed a bonanza of wireless technologies—today, nearly every wireless device you use, from your cordless home phone to your Wi-Fi router to your Bluetooth headset, operates on the unlicensed band. None of these technologies would have been possible under any other regulatory regime.

Still, there is a downside to the unlicensed radio spectrum. Because the frequencies reserved for public use were never envisioned for widespread communication, they’re prone to failure—they don’t easily penetrate through walls or cover vast distances. That’s why your Wi-Fi router doesn’t reach your basement, and why your Internet connection conks out every time you microwave a burrito.

In a long-anticipated ruling last week, the FCC adopted a regulation (PDF) that could dramatically improve our wireless devices. The rule offered a brand new and much-improved slice of the radio space for unlicensed use. The new frequencies are known as “white spaces”—the waves that were freed up when TV channels switched from analog to digital transmission last year—and unlike the garbage band, they’re considered prime real estate. Radio waves on white-space frequencies can travel for miles, they’re much better at penetrating walls and buildings, and they’re capable of carrying lots of data. “

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