Wireless cable and fixed wireless access
The wireless cable spectrum covers the 2500-2690 MHz band. Part of it was allocated for Instructional Television Fixed Service (ITFS), traditionally used by schools and colleges for broadcasting educational lectures. Part was allocated for Multichannel Multipoint Distribution Service (MMDS), traditionally used for pay television. MMDS operators have been allowed to lease channels from ITFS licensees and use that capacity for pay television as well. The band was channelized into 31 channels of 6 MHz each. In the old analog world, wireless cable operators soon ran out of capacity in trying to compete with 70-channel cable systems.
ITFS and MMDS systems were designed as multichannel TV stations, using high-power transmitters to broadcast video channels from a single tall antenna. In 1998, the FCC changed the technical rules for ITFS and MMDS, to allow the use of two-way digital transmissions. The new rules envisioned cellular re-use of frequencies using low-power transmitters, but prohibited the digital transmitters from causing interference into receivers that were still being used for lectures. The non-interference rules were complicated, and unworkable. It is impractical to have a high-power video channel, broadcasting to sites 30 miles away, adjacent to a channel with widely deployed low-power digital transmitters.
The new Broadband Radio Service will have, instead of 31 channels of 6 MHz each, seven 6 MHz channels in the center of the band, and eight channels of 16.5 MHz each, four at the top of the band, and four at the bottom. The 6 MHz channels can continue to be used for high-power video broadcasts, and the 16.5 MHz channels would be used for low-power transmitters carrying two-way data.
The term Fixed Wireless Access is used internationally for fixed point-to-multipoint service, but the FCC has always used different names for FWA-like services. In 1979, Xerox Corp. designed a digital document transmission service called "XTEN" and asked the FCC for spectrum around 10 GHz. In response, in the early 1980s, the FCC allocated spectrum around 10 GHz and 18 GHz for a service called Digital Electronic Message Service (DEMS), and later allocated spectrum at 24 GHz also. In the 1980s, zillions of companies applied for these area-wide DEMS licenses, and the FCC eventually used lotteries to grant them. Initially the DEMS licensees were companies like Tymnet, Telenet, DAMA Telecommunications, Contemporary Digital Services, VIA/NET and others that are long gone. For the most part, these companies returned their 10 GHz and 18 GHz licenses to the FCC, and the FCC reallocated the spectrum for individual point-to-point links. In the 1990s, Teligent acquired a number of DEMS licenses, and started to build out a network, but eventually went bankrupt when the dot-com bubble burst. DEMS was a failure.
Then there is the Wireless Communications Service, around 2.3 GHz. These frequencies were auctioned in 1997. Going into the auctions, the government expected to reap billions. But the total take for the U.S. Treasury was only $13 million. For example, Comcast paid $500,000 for a New York City license and $200,000 for Chicago. I haven't found any evidence that any of these frequencies are being used today.
Then there was the Local Multipoint Distribution Service (LMDS), using spectrum around 28 GHz. In 1998, the FCC auctioned off the LMDS frequencies. The big winner was Craig McCaw's NextLink, which morphed into XO Communications, which eventually morphed into bankruptcy. LMDS was a failure.
Also during the 1990s, Winstar and other companies acquired a large number of 39 GHz point-to-multipoint licenses. Winstar went into bankruptcy, emerged, and continues to operate, but recently announced it was shutting down most of its operations.
In Europe, frequencies around 3.5 GHz are being used for FWA. The U.S. Defense Department has successfully repelled efforts to allocate that band for FWA in the U.S., because the frequencies are used for military radars.
There are two additional points to make about the 2.6 GHz BRS. First, Craig McCaw is back in the race. According to press reports, he has acquired several companies that hold licenses in this band. Second, Intel has put its weight behind a technology approach called WiMax. The IEEE has just approved WiMax as a standard, IEEE 802.16d. Intel pretty much controls the market for the chipsets that go onto PC motherboards, and it may be planning to add WiMax capability to these chipsets. But that implies non-line-of sight transmission capability. Up until now, all point-to-multipoint FWA systems have relied on clear line-of-sight paths. Non-line-of-sight links may be possible at 2.6 GHz, but it introduces losses of 10 dB to 20 dB, which greatly decreases coverage area.
|Jeffrey Krauss, President of Telecommunications and Technology Policy|
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