Mark Twain once said, “Buy land. They’re not making it anymore.” Such is the case with electromagnetic frequency spectrum. They’re scarce, coveted, and very expensive. Furthermore, they’re subject to regulation both nationally and internationally.
The general consensus is that most of the good spectrum are already allocated. But the opposing view is that lots of existing unused or underutilized spectrum could be used (see “A Technology Solution To Spectrum Limitations”). Both views are correct up to a point. The recent transition from analog to digital TV has freed up some great spectrum in the U.S., and the Federal Communications Commission (FCC) is attempting is to make more efficient use of it.
The frequency spectrum is a continuously changing landscape. The best way to keep up with changes is to monitor the two U.S. agencies that control it: the FCC and the National Telecommunications and Information Administration (NTIA).
The FCC deals with personal and commercial spectrum, while the NTIA handles government and military spectrum assignments. Their Web sites offer a mass of information for those who need to follow regulatory actions. And while the U.S. spectrum is relatively settled, two recent events have opened an unusually large segment previously tied up by TV broadcasters.
First, the broadcasters abandoned their assignments from channels 52 to 69 (698 to 806 MHz) as part of the FCC-mandated digital TV switchover. This is the so-called 700-MHz spectrum. It was auctioned off last year in Auction 73. A total of 101 bidders won 1090 licenses for a net income to the U.S. Treasury of $19,592,420,000.
AT&T and Verizon won most of this spectrum for cellular expansion, but other licenses will support mobile TV, wireless broadband, and a mix of other services. Little or none of the spectrum is in use so far, but it will be soon because of the final digital TV switchover on June 12.
Second, in another action related to the DTV transition, most TV stations were assigned new operating frequencies in the remaining spectrum from channels 2 through 51 (54 to 698 MHz). These new assignments don’t use all of the available spectrum. Many gaps exist, and they vary in frequency depending on the local TV station’s frequency assignments. These gaps of unused spectrum are called “white spaces.”
The FCC recently declared that these unused frequencies may be applied to new wireless services. These new services will be unlicensed, and they will come under the FCC’s CFR 47 Part 15 as recently amended. This spectrum still retains its 6-MHz channel assignments, though, and the available bands vary from locale to locale.
The spectrum assignments in the U.S. are a nightmarish tangle of regulations and recordkeeping. Changes occur daily, so keeping track of it all is difficult. While who owns and uses which spectrum is generally known, some forgotten assignments and recent changes slip through the cracks. This lack of exact knowledge of the spectrum assignments recently led to the Radio Spectrum Inventory Act, a bill sponsored by U.S. Senators John Kerry (D) of Massachusetts and Olympia Snowe (R) of Maine.
The bill directs the FCC and the NTIA to perform a U.S. spectrum audit and report on the use of all spectrum from 300 MHz to 3.5 GHz. The outcome of this bill should more clearly define spectrum usage. It will determine if the spectrum is overcrowded as well as if unused segments could be put to good use (see “What’s So Special About The White Space And 700-MHz Bands?”).
Also, it should help ensure that our available spectrum is fully used for the benefit of U.S citizens, increasing services for consumers and profit for businesses, especially in the broadband service sector. Never before has so much good spectrum opened up at the same time. It no doubt presents many new products and services possibilities.
WHAT TO DO WITH 108 MHz OF BANDWIDTH?
That’s the total amount of available spectrum in the 700-MHz block. Spectrum blocks don’t always follow the original 6-MHz channel assignments. The gray C and D blocks in Figure 1 in the lower 700-MHz band and the gray A and B blocks in the upper 700-MHz band were auctioned off before Auction 73 last year. The remaining blocks were sold off in Auction 73, except for the D block in the upper 700-MHz segment.
So, how will these bands be used? Most of the spectrum will go to cellular service expansion. Cellular service continues to grow as more new subscribers come aboard, including those dropping their wired telephone service in favor of wireless only. Consequently, there’s always a demand for more spectrum among carriers and operators.
Another factor is the increased use of data services—specifically messaging, e-mail, and Internet access. And much of that Internet access involves video. Data services require more bandwidth to push data speeds to a level that’s satisfactory for subscribers expecting data rates comparable to their home broadband services. Most carriers are seeing steady growth in 3G data services.
Also, new 4G cellular technologies like Long-Term Evolution (LTE) will be implemented in 2010 and beyond. LTE will bring even faster data services (Fig. 2). Yet this orthogonal frequencydivision multiple-access (OFDMA) technology, which uses multiple- input multiple-output (MIMO), needs more bandwidth.
Some of the spectrum has already been allocated to mobile TV. MediaFLO is transmitting on old TV channel 55 to cell phones with built-in receivers. Additional spectrum was assigned to mobile TV. AT&T recently announced the beginning of its Mobile TV effort in 20 new markets nationwide. It includes CBS, Comedy Central, and MTV. Both LG and Samsung offer phones with mobile TV capability for this new service (Fig. 3).
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