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70-90% of AT&T Spectrum Capacity Unused
Written by Dave Burstein   
Tuesday, 22 March 2011 14:09
att_logo-no-textAT&T has enough spectrum today to deliver 150-200 megabits from most towers. Comparing that to the 10-12 because of backhaul. Some of the spectrum is also used for 2G voice, and can easy carry twice as much voice or loads of data when AT&T switches to voice over LTE/IP. Other spectrum is used 2G/3G data carrying a fraction of what the same spectrum carries with LTE.

Across the vast bulk of the country, T has plenty of spectrum not used at all right now. In a very limited number of places, there's little. Across the country, the figure is probably 20-60%, but that's a wild guess. Upgrade inefficient uses and put the fallow spectrum to use, and T can easily handle five times the current demand and probably ten to twenty times without adding spectrum. More spectrum is a good thing, but engineers at AT&T, Verizon, and almost all the other big carriers are confident they can handle anything likely for years without breaking the budget.

FCC sources tell me there's a massive efficiency improvement possible if more carriers shared spectrum but none were willing. AT&T Wireless & Cingular did a joint build in New York City that saved $100's of millions according to CFO Ron Dykes. AT&T and T-Mobile could do the same and get most of the spectrum advantage of the merger while staying independent.

Inside these figures

I'm reporting 70-90% of the capacity is unused, not 70-90% of the spectrum. Reflecting on the comments this article provoked, I suspect the act ratio of available bandwidth to potential capacity may be as low as 5%. Much of that spectrum is in use for 2G-3G voice and some for data, at a fraction of what the spectrum will handle when upgraded to LTE. I'm working from a comparison of what the spectrum could carry with current technology (LTE, HSUPA+) compared with the capacity in use.

AT&T has 80-110 MHz of spectrum, depending on whose figures you choose. You get 1.5-2.5 megabits/megahertz, depending on whether you're measuring average versus edge of cellsite, fixed antennae, etc. That's 120-260 megabits in most markets. Let's call it 200 megabits average.

Currently, the heavy majority of AT&T cellsites are still served by T-1's carrying a total of less than 12 megabits, often far less. It's typically used for "up to 7.2 megabit" data and lots of voice. Some percentage is completely unused - surprising high, but not 70-90% - is currently unused.(?20-60% on average as a wild guess, but that's unprovable without internal AT&T data.)

Much of the spectrum is currently used for voice, using older technologies that are far less efficient than today's. Glen Campbell of Merrill Lynch estimates that by refarming that spectrum and using it efficiently (if only for voice) you double the carrying capacity. Similar is true for all the spectrum being used for 2G and even 3G data. They only use 10-?50% of the capacity of the spectrum using today's technologies. .

Carriers around the world have begun this "re-farming" for more efficiency, including UK and Canada. Everyone has it in their plans because it's more efficient and hence cheaper. Sprint intends to do that with the Nextel spectrum and AT&T has discussed similar. It takes several years, because you have to change out all the handsets, but using existing spectrum more efficiently saves so much money the carriers are doing it almost universally.

Across the carriers, much spectrum lies purely fallow, about enough to carry us without upping capex about 5 years (FCC figure, badly calculated) or 10+ years (Ivan Seidenberg of Verizon and most technical people as opposed to lobbyists.) Most of the rest is used by older 2G and 3G tech (both voice and data) and has 2-10x the capacity with today's technology.

Hence, T (and almost every one else) is using only 10-30% of the capacity of their spectrum. They know this and are rapidly upgrading backhaul (2010-2011's primary problem) and radios. They are discussing plans to switch users from 2G voice - still what's in 3G and 4G handsets - to 4G voice over IP/LTE over the next few years.

AT&T's announced 2011 backhaul upgrades - from 20% GigE fiber or 100 meg microwave to 70% - that will yield 500% more capacity for data this year alone. http://fastnetnews.com/a-wireless-cloud/61-w/4073-lindner-atats-backhaul-500-in-2011 They are using it to go from 7.2 meg to 20 and 40 meg HSUPA+ and LTE.

A 300% improvement in bandwidth implies 75% of capacity was unused.
(Updated March 30th to suggest the usage of theoretical capacity may be as low as 5%)