The white space proposal is being promoted by the Wireless Innovation Alliance, an industry association funded by Google, Microsoft, Motorola, Dell, and others. Their public relations motto of "Free the Airwaves" can also be read as "Give us Free Airwaves". TV broadcasters and manufacturers of other wireless products that operate in those bands are claiming that white space devices would interfere with their products or services, and thus far, the interference tests that have been conducted seem to support that claim.
The white space decision is most interesting because it deals with two of the fundamental issues in regulation: how actively should the government be involved in shaping a competitive marketplace? And does the current policy of auctioning radio spectrum really foster the public good? However, what has been lost in the PR battle surrounding white space is the unique opportunity the FCC has to make a real long-term contribution to the development of wireless technologies.
What's "White Space?" While you might think you know what white space is, the definition has actually changed over time. The original white space idea was to send unlicensed transmissions on the guard bands between adjacent TV channels; guard bands are vacant slots of radio spectrum used to limit interference between channels. Along the way, the white space idea morphed into a plan to use whole TV channels that were not being used to carry broadcast programs. The Wireless Innovation Alliance claims that in many US markets, as much as 75% of the TV airwaves are unused.
The broadcast television band currently runs from 54 MHz to 806 MHz. The band is non-continuous, as other services like FM radio are interspersed among the TV channels. With the plan to migrate to digital over-the-air broadcast TV in February 2009, the portion from 698 to 806 MHz (channels 52 to 69) was auctioned off earlier this year, so the spectrum available to white space initiatives will be 54 MHz to 698 MHz (current TV channels 2 through 51). Those 700-MHz channels are greatly prized given their lower loss and excellent building penetration characteristics.
If we're talking about unused TV channels, a single channel 6 MHz wide could carry a simplex transmission rate of around 15 Mbps, though 5 Mbps to 10 Mbps would be more realistic. With 49 channels defined (channels 2 to 51), a 75% vacancy rate would leave as much as 216 MHz of available 700 MHz spectrum in those markets. To estimate the monetary value of that resource, the FCC's 700 MHz auction in March raised $19.6 billion and it covered roughly 60 MHz of spectrum.
The Two Parts of the White Space Debate The crazy thing about the press coverage of the white space debate is that it deals with only half of what's going on. "White space" is really about two separate applications: fixed-location wireless access and personal-portable white space devices. Fixed-location wireless access is the proposal to deploy WiMAX-like point-to-multipoint radio access systems based on unused TV channels using the developing IEEE 802.22 standard. These systems could use WiMAX technology, but the basic purpose is to provide broadband Internet service to underserved rural areas. What has escaped notice in the press is that the broadcasters seem to have no problem with this whatever.
The interference-avoidance solution proposed in 802.22 would use a database that identified TV broadcasters operating in each area. The base stations would be registered and all of the client devices would be slaved to a base station, so the interference issues can be effectively managed. According to Carl R. Stevenson, President of WK3C Wireless LLC and Chairman of the IEEE 802.22 Committee in a post to wireless blogger Steve Stroh, "I am happy to report that the broadcast community is supportive of what we're doing in 802.22 and they have, from the very beginning, been actively participating in the development of the standard in a most cooperative and constructive way."
The battle you've been reading about deals with the personal-portable devices where the technical issues are far more challenging. The plan to avoid interference from these devices was based on frequency sensing and avoidance. This turned out to be problematic as the system would have to be capable of sensing signals at very low levels given that the device might be operating indoors and need to detect a weak signal from a distant TV transmitter. In a series of FCC-sponsored tests, the prototype devices failed to detect legitimate signals effectively.
If you include a TV-band transmitter in personal-portable devices, there could be thousands of them scattered about. If any one of them failed, it would impact TV transmissions or possibly other TV band devices operating in that area. How are you going to locate and squelch the offending device, particularly if it is portable and operates on an unpredictable schedule? The proponents are now proposing a solution based on frequency sensing in combination with a database (akin to the 802.22 model, plus a requirement for other devices to transmit a beacon signal that would make them easier to detect.
Conclusion- The FCC's Opportunity of a Lifetime Despite the technical problems, white space represents an opportunity that's too good to pass up. However, the FCC should be looking at the strength of their bargaining position and what this could mean to the wireless industry as a whole. Non-interfering operation must be a sine qua non for white space devices, but new white space regulations will make a multi-billion dollar resource available to businesses at essentially no cost. The government should be looking for a lot more in return.
Here's my proposal. First, the fixed-location systems should continue, as those support the recognized public goal of improving broadband access. For personal-portable applications, the FCC should mandate that any product or service that is benefitting from this government-provided giveaway must include some new wireless technology that is not currently on the market. That's right, the price of admission to this game should be an R&D investment in wireless technology. There are plenty of great ideas floating around in the wireless space, this is our opportunity to work those into the mainstream.
Encouraging investment is an important role for government, and perpetual licenses and frequency auctions have left us with an entrenched, close-minded oligopoly in wireless. Correctly managed, white space gives us the opportunity to move the entire industry forward by providing the one element necessary for any wireless product or service: spectrum. Simply giving it away would be a travesty. The FCC should make white space the technology incubator for wireless. Anything less is simply cheating the public.
