Unlicensed Operations in the Lower Spectrum Bands: Why is No One Using the TV White Space and What Does That Mean for the FCC’s Order on the 600 MHz Guard Bands?
23 Pages Posted: 1 Apr 2015
Date Written: March 30, 2015
In 2008, the FCC authorized unlicensed use of vacant channels in the TV bands (TV white space) following the digital TV transition. Supporters of the FCC action asserted that giving unlicensed devices access to the lower bands would forestall congestion at 2.4 GHz and 5 GHz, provide mobile broadband coverage to underserved areas, and power a new wave of innovation (Google’s CEO famously said TV white space would bring about “Wi-Fi on steroids”). We were among a small minority who countered that the TV white space could not support effective unlicensed operations both because the limited bandwidth would make it inferior to 2.4 GHz and 5 GHz for Wi-Fi-type applications, and because the necessarily stringent power limits and lack of interference protection would preclude most long-range applications. We also argued that the TV white space could be used for licensed services, generating billions of dollars in auction revenue. In this paper we analyze a) the impact to date of the FCC’s TV white space policy and b) the implications of this for the FCC’s 2014 proposal to allow unlicensed operations in 600 MHz guard bands following the incentive auction, which is an extension of the TV white space policy.
The FCC’s TV white space policy to date has been a flop, as evidenced by the anemic market response. The FCC has approved only nine products for operation in the TV white space, and none of the major manufacturers of Wi-Fi routers or Wi-Fi chips fields a product that can be used there. Nor does any major smartphone or tablet vendor offer a product with the capability to use TV white space. As another indicator, users in this country have registered fewer than 600 individual devices (registrations are a proxy for sales), in contrast to the tens of millions predicted.
Although regulatory uncertainty may be a factor, the market’s anemic response to the TV white space has far more to do with fundamentals, in particular the predictably slow data rates for short-range, Wi-Fi-type applications. The maximum data rates for TV white space devices range from 3.25-16 megabits per second (Mbps), which is below the FCC’s new threshold for what constitutes broadband, compared to 600 Mbps to 1.7 gigabits per second for unlicensed devices that operate at 2.4 GHz and 5 GHz. For long-range applications, TV white space faces other challenges (key are the 4 watt power limit and the risk of interference from short-range devices), making licensed spectrum a superior choice.
The FCC’s decision to allow unlicensed operations in the (post-auction) 600 MHz guard bands is likely to meet the same fate. For short-range applications, because of limitations on bandwidth (six megahertz) and transmit power (40 milliwatts), unlicensed devices operating in the 600 MHz guard bands will have a data rate that is one-tenth to one-hundredth that of a Wi-Fi device operating at 2.4 GHz and 5 GHz. That handicap will trump almost any propagation advantages that the 600 MHz band may offer. For long-range voice and data communications, unlicensed operations in the 600 MHz guard bands will have even less to offer. With a power limit of 40 milliwatts, unlicensed guard band devices will simply not be capable of providing rural broadband access and other long-range communication services on any meaningful scale.
Keywords: Unlicensed Spectrum
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