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AT&T has submitted a proposal to the FCC asking for permission to use 2.3 GHz in the Wireless Communication Services (WCS) spectrum for 4G LTE service. AT&T already offers LTE service on the 700MHz band.

On Friday, AT&T and Sirius XM filed a joint proposal with the FCC (pdf) that is designed to bridge differences to reach an accommodation in the WCS band. AT&T and Sirius’s proposal would prohibit mobile use of the C&D blocks (next to satellite radio), while further liberalizing use of the A&B blocks.

Unfortunately, NextWave owns a lot of WCS spectrum, and nearly half its holdings are in the same blocks that AT&T wants to make off-limits.

The Satellite Digital Audio Radio Service (SDARS) is used by Sirius, which uses 12.5 MHz of the S band between 2320 and 2332.5 MHz and XM, which uses 12.5 MHz between 2332.5 to 2345.0 MHz. Presently, music is compressed to 44 kbps; voice, 20 kbps; and 16 kbps for low quality audio such as traffic and weather.

WCS is divided into four frequency blocks:

  • Block A: 2305-2310 MHz paired with 2350-2355 MHz
  • Block B: 2310-2315 MHz paired with 2355-2360 MHz
  • Block C: 2315-2320 MHz (adjacent to sat radio low-end)
  • Block D: 2345-2350 MHz (adjacent to sat radio high-end)

Blocks A & B are in 52 MEAs, while Blocks C & D are in 12 REAGs. LTE works most efficiently with at least 10 MHz channels. A combined A&B block might result in two symmetrical (FD-LTE) 10 MHz channels or two (unpaired), 10 MHz TD-LTE channels.

The proposal apparently offers a solution to allow 4G LTE service on the 2.3GHz band without interfering with satellite radio services. If the FCC approves the proposed usage changes for the WCS band, AT&T could use its 2.3GHz spectrum holdings to deploy LTE service to about 40 percent of the U.S.

The FCC adopted new rules governing the operation of Satellite Digital Audio Radio Service (SDARS) in 2010. SDARS can also use terrestrial repeaters. The FCC has a blanket licensing regime for repeaters operating up to 12 kilowatts (kW) of radiated power.

The FCC was concerned that SDARS repeaters could cause interference in the adjacent band and broadcasters claimed XM was taking advantage of repeaters to transmit local programming or advertising without a terrestrial license. Terrestrial broadcasters countered with digital HD radio. On July 29, 2008, Sirius formally completed its merger with former competitor XM Satellite Radio. The combined company began operating under the name Sirius XM Radio.

XM Satellite Radio and Sirius Satellite radio use different kinds of satellite coverage.

Sirius uses a highly elliptical orbit with three satellite, but only two of them broadcast at any given time. Because they can be seen at a higher angle on the horizon, the need for terrestrial repeaters is lessened.

XM has traditionally used geosynchronous satellites, which result in reception problems in canyons or cities. Consequently, XM developed satellite “repeaters” on rooftops in metropolitan areas, providing improved reception. But the satellite repeaters put out thousands of watts and would swamp nearby WCS basestations.

The agreement between Sirius/XM and AT&T would place a 5 MHz guardband between satellite radio and the 2.3 GHz broadband service.

If the proposal is approved, analysts estimate that it could take AT&T 3 to 5 years to make the WCS spectrum usable for LTE service, but the carrier has not publicly specified a timeline. AT&T did ask the FCC to extend the existing build-out requirements for WCS spectrum holders.

As it stands now, WCS license owners must provide service to 40 percent of the license area’s population within 42 months of obtaining the spectrum rights and 75 percent within 72 months.

Dish Network and Clearwire could be hurt by this move, says Guggenheim Partners analyst Paul Gallant. If AT&T can use 2.3MHz spectrum for LTE, it may not need to buy spectrum from Dish, and it may not need to partner with Clearwire. It may also indicate that a Dish and T-Mobile partnership could be strengthened.

Apple’s FaceTime, Google’s video chat, and Microsoft’s Skype need lots of wireless data and reduce the necessity for voice minutes. Whether content partners like Google, Microsoft, Amazon and Apple would be partners with a wholesale spectrum purchase is still just idle speculation. Dish (at 2.1 GHz) and Clear (at 2.6 GHz) have the most spectrum available for 4G.

Although it’s a bit crazy, perhaps combining WCS as an upstream path and Satellite Radio as a downstream path might be feasible. Merging XM and Sirius left duplicated satellites and frequencies. Perhaps one of the XM/Sirius satellite constellations could provide an alternative nation-wide delivery mechanism for ebooks and movies — multicasting to millions simultaneously.

Of the 300 operators who have TDD spectrum resources, 66% own 2.3GHz and 2.6GHz bands, according to ZTE.

The 2.3 GHz band is often used for 4G (LTE) service in other countries that are not using the band for satellite radio, such as China and India.

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