White space: the next leap for Wi-Fi

David Hughes's picture

The FCC is set to vote on final rules for ‘white space’ broadband, technology that uses unused frequencies between TV channels to considerably boost current Wi-Fi range without using extra power. Keeping in mind that the rules aren’t officially set, here’s how it will likely work.

Understanding ‘white space’ and what it means for wireless Internet access

White-space networks, as mentioned above, use the high frequency radio normally reserved for television broadcasts, transmitting in the space between TV channels. This untapped radio bandwidth is just sitting there, begging to be used—and it turns out to be quite useful for wireless data transfer. “White-Fi” compares to Wi-Fi as follows, according to figures provided by Microsoft: "4x range compared to 2.4 GHz (Wi-Fi) with same transmit power and receiver sensitivity."

That’s a rather large boost, especially for corporate campus networks like the one Microsoft has set up at its Richmond, Washington facility. It’s also been implemented by Google and Spectrum bridge in Claudville, a rural town in Virginia and as a semi-public city-wide network in Wilmington, North Carolina. So far, however, all of these are test beds helping both White-Fi backers and FCC regulators come up with a set of rules and regulations for the protocol’s wider adoption.

As it turns out, the range boost isn’t as free as it would seem on the surface. In many areas, there are a lot of unused television channels to use, but the devices have to know which channels to avoid. Unlike Wi-Fi, which permits interference at a cost for speed, the FCC won’t allow White-Fi to interfere with existing television broadcast channels (however faint the signal may be). This means that, before any such device begins transmitting, it has to ensure the frequency it is about to use is indeed free—and that the device set to receive also has that frequency free on its end.

To aid in those efforts, Microsoft, Google, and Spectrum Bridge have been developing a series of geo-location databases with TV transmission antennas, their channels, and apply a series of formulas to determine exactly which areas are covered by which channels. All proposed White-Fi devices will be required by the FCC to query a database of this kind before beginning transmission—and for the curious, Microsoft’s own database can be viewed here.

Implication #1: Standard residential Wi-Fi offers a limited set of channels and has become increasingly popular for use within homes. Especially in densely populated areas, extra frequency bandwidth for wireless data transfers will help compensate for increasing degradation in networks as the channels interfere with one another.

Implication #2: The significant range boost may bring back plans in many cities to offer free or low-cost public Wi-Fi access in many areas. With current technology, the sheer number of hotspots needed for adequate network coverage quickly becomes unwieldy. White-Fi alleviates this problem, but many people would say that reduced cost still wouldn’t justify the tax subsidy likely needed to support such planned networks.

All of this is dependent on the FCC’s final set of rules, of course, so developments can’t begin in earnest until the ruling comes down early this coming week.

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