AT&T Wants to Teach an Old Spectrum Band New 4G Tricks
Photograph by Tim Klein/Gallery Stock
A wireless band that the mobile industry has practically written off may get a new life as 4G spectrum if a new proposal from AT&T and Sirius XM gets regulatory approval. The two strange bedfellows have submitted a joint filing to the FCC requesting permission to use AT&T’s long dormant 2.3 GHz Wireless Communications Service (WCS) for an LTE network.
Deploying any kind of service on WCS has been a cluster-you-know-what for any operator that has made the attempt. ExtremeTech provides an excellent description of the problems of making WCS workable for mobile broadband:
WCS licenses were auctioned off by the FCC in 1997. The FCC hoped that it would be used rather quickly, but the restrictions that WCS imposed on licensees caused issues. For one, the power and emissions restrictions made it nearly impossible to deploy any sort of terrestrial network technology.
The other issue was that satellite radio (officially known as the Satellite Digital Audio Radio Service, or SDARS) lived in between two halves of the WCS frequency range. That meant that terrestrial network technologies would easily block out satellite radio signals from receivers. This alone has severely paralyzed efforts to make the WCS frequencies usable.
AT&T and BellSouth, which was eventually acquired by Ma Bell, experimented with the band for years, launching trial pre-standard WiMAX networks in several markets. (Oddly, one of those markets was Pahrump, Nev., the brothel capital of the U.S.) But neither company could make the technology work, and both were constantly running up against the protests of Sirius and XM, which themselves merged in 2008.
But apparently these old antagonists have come to an accord. From the FCC filing:
In order to resolve these issues, AT&T and Sirius XM met to discuss whether their differences could be bridged and have reached an accommodation with significant concessions on both sides. The accommodation, if accepted in its entirety, will enable the adoption of technical rules satisfactory to both interests and allow licenses in the 2.3 GHz band to exploit the most efficient new mobile broadband standards, including LTE, while limiting the potential interference to satellite radio reception to respectable levels.
The major concession appears to be on AT&T’s part. The carrier has agreed to carve out a 5 MHz guard band on either side of Sirius’s satellite spectrum, creating in essence a no-man’s zone where no transmissions can travel. That’s quite a big deal actually: As little as 10 MHz can support a full-fledged HSPA network and is equivalent to half the LTE capacity AT&T has deployed in most markets.
But AT&T figures it is better than not being able to use the spectrum at all—and risk losing it. In fact, AT&T has been trying to sell off the same WCS airwaves it now proposes to make guard bands.
If the FCC grants AT&T’s request, the company will be left with 10 to 20 MHz of remaining spectrum over which to launch LTE. That may seem like a win for all parties involved, but it won’t be an automatic approval for the FCC. AT&T is the largest spectrum holder in WCS, but other licensees could potentially get screwed by this proposal. As satellite broadband analyst Tim Farrar points out on his blog, NextWave owns a lot of WCS, and nearly half its holdings are in the same blocks that AT&T wants to make off-limits.
Also from GigaOM:
Why LTE in the iPhone Matters (subscription required)