News Analysis: The FCC has to create a band plan, usage rules and protection policies for digital data channels to make broadcast spectrum "white space" usable for Internet traffic.
The announcement that the Federal Communications Commission
was prepared to approve unlicensed digital operations in slices of frequency
spectrum occupied by television guard bands is being greeted eagerly by many, including
Google and Microsoft
Ultimately it will probably be a good idea, but it's by
no means clear that it will be the panacea to a national broadband solution
that some hope it will be. In fact, there's every possibility that the whole "White
Space" excitement is badly overhyped and in the long run will likely to
lead to more disappointment than broadband growth.
First, it helps to know exactly
what this "white space"
that everyone's talking about really is.
No doubt you have some idea that a television channel is a set of frequencies used
by broadcasting stations for transmitting their signals. In the past, the FCC
has always allocated a slice of spectrum between TV channels as a guard band.
These were frequencies where nothing was allowed to operate so that television
could be protected from interference from another broadcast station operating
on an adjacent frequency.
The reason the stations needed this guard band was
because television signals really consisted of two radio transmissions, one for
the audio and one for the video. One signal was transmitted in analog using AM
and the other using FM. The result was that these signals used a lot of
bandwidth, and the amount of bandwidth could vary slightly depending on the
nature of the signal. The guard bands kept things separate, and given the
fairly primitive technology used by television receivers when these were set
up, the television sets needed that space as much as the broadcasters
Since then, things have changed. Television in the United
States is almost entirely digital, except
for some low-power community stations. Television receivers have vastly
improved technology with far greater precision, so guard bands are less
necessary. The idea is to use those formerly empty bands for digital
transmission that includes (but isn't restricted to) high-speed broadband. This
all sounds good, right?
The problem is that television broadcasters don't want
their signals interfered with any more than they ever did. While televisions
stations produce an effective radiated power in the hundreds of thousands of
watts in some cases, it's not the transmitted signal they're worried about.
Because radio waves diminish greatly with distance, and because every white
space data device includes its own little transmitter, the broadcasters are
worried that somebody's broadband Internet will interfere with their
programming at sites where their signals are relatively weak.