Feature Article

June 22, 2012

AT&T and Sirius Get Serious Over Spectrum - Enabling Nationwide FDD LTE Deployment

Yes, it is technical, but that does not mean it is trivial. About a week ago AT&T and Sirius XM filed a joint proposal with the Federal Communications Commission (FCC) that has major ramifications and obviously not just for the two parties involved.

A Solomon-like proposal on 2.3GHz  

For technology enthusiasts below are some highlights from the filing, however, first some history.

AT& T in 1997 bought at auction vast swaths of what is known as the Wireless Communications Services (WCS) spectrum in what is still all these years later an unused decent chunk of the 2.3GHz band. The problem has been that the spectrum is actually divided in half by the Satellite Digital Audio Radio (SDARS) spectrum used by Sirius XM for its radio service. It literally stands as a kind of “river runs through it,” barrier. On each side of the SDARs are the WCS A and B blocks and C and D blocks respectively.

SDARS use restrictions on power and emissions have kept the WCS spectrum in the AT&T inventory rather than being developed. However, time is running out on the licenses in terms of conditions for actually using it for a service. So let’s just say AT&T, facing a spectrum shortage for deploying LTE because of its failed T-Mobile deal and not likely the possibility of having to lease spectrum in other frequencies from the likes of Dish and LTE wholesaler Clearwire, was highly motivated to reach an accommodation with Sirius.

So what’s the deal?

  • 10MHz of spectrum will be permanently blocked of as a pair of 5MHz bands on either side of the SDARS spectrum to insure Sirius does not get blown off the air.
  • A power limiter (to 50mW per MHz) is proposed to heavily concentrate a signal at the edges of the frequencies when deployed on the A and B block. Sirius believes this would not be necessary if transmission on C and D blocks were forbidden and the technology deployed on WCS does not concentrate too much at the edge of the A and B block. This means it may not be required for an LTE deployment, which is what AT&T wishes to use it for, and thus the power limit would be 250mW per MHz.
  • The proposal also addresses a bone of contention. AT&T wants to deploy FDD technology on the lower WCS blocks. Right now that is not allowed, and FDD can only be used on the upper WCS spectrum but there are many restrictions. AT&T and Sirius XM agree to have this restriction to be removed because other safeguards in the proposal will prevent interference.

There are also agreements on flat ground power and a relaxation of rules for outdoor antennas for fixed wireless, and most importantly AT&T is asking the FCC to extend the build out deadlines on WCS.

 For all of you non-technical mobile industry enthusiasts, put simply this proposal if accepted will provide AT&T the spectrum it needs, with a national footprint, for LTE which would put it in total control of its LTE destiny. It may take up to five years for AT&T to be able to build out the spectrum using FDD LTE assuming a fast-tracking of the proposal, but from their perspective this would be time and money well-spent. 

There is no denying AT&T is facing a spectrum shortage as it is running out of capacity on its Advance Wireless Services (AWS) licenses —actually two segment ( 1710 to 1755 MHz for uplink, and from 2110 to 2155 MHz for downlinks) originally allocated for the failed MMDS (Wireless Cable) services years ago. Staying in the lower frequencies is highly desirable for coverage and quality reasons. This is what made the MMDS spectrum attractive in the first place and is why most smartphones include AWS radios and why WCS is so attractive as an alternative once the interference with SDARS has been resolved.

Moving forward

There is no telling how long the FCC will take to review and act on the proposal. However, the proposal has already shaken things up a bit. In fact, for those who may have counted AT&T out of the LTE race when the T-Mobile deal blew up and have been delighting in their deployment advantage, the news from AT&T is a cautionary warning. This may turn out to be an instance where competitors should be careful what they wished for. This is a potentially large change in the landscape. The vitality of a number of players in the satellite and terrestrial businesses can’t help but impacted. We shall see how all of this evolves. 

AT&T is a sponsor of ITEXPO West 2012. To be held Oct. 2-5 at the Austin Convention Center in Austin, TX, ITEXPO is the world’s premier IP communications event. For more information on IEXPO West 2012 click here.




Edited by Brooke Neuman


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