ATT Microcell in Austin, TX

Since people on here like to talk about the generatorn run time on cell towers, I thought y’all might like to see an ATT microcell in downtown Austin, TX. No apparent generator or battery on it.


Looks to me like a mostly shared-fate design with the traffic signal it appears
to be attached to. All depends on what ATT risk management thinks in that
situation. They may have decided that sticking a 10-minute battery in the base
of that thing is good enough.

This is a small cell. They are very common across all of the carriers.

It is NOT intended to provide primary coverage for the area.

It IS intended to provide additional capacity to the immediate area.

Think of the large cell towers as providing blanket coverage, while small cells provide hot spots of increased capacity.

Most small cells have no battery backup or generator at all, as it’s not feasible given the real estate available.

It will be interesting to see how this plays out as reliance on these small cells for capacity grows. I’d imagine demand for cellular bandwidth goes up during a power outage and not down.

Is it reasonable to think that there could be a situation where cell capacity is not available during a time of need because these sites will simply go down and significantly reduce coverage/quality in dense metropolitan areas?



You’re correct that if most of these small cells goes offline during a power outage, the remaining macro cells would not be able to handle the load well.

Data would be nearly useless and phone/texts may be sporadic.

I believe that when this happens, they should proactively block or limit video and file download/upload traffic as much as possible to make sure communications like calls and texts can go through with the highest success rate possible. Netflix and YouTube should never hinder more important communications in my opinion. Maybe it’s as simple as putting a rate limit for each cellphone connected to these now overloaded sectors so no one can hog the cell capacity.

It would be pretty sweet though if small cells all had a linked power source following the same fiber paths that all hook back into a large battery backup or generator somewhere. Maybe 30-40 small cells can have backup power from one macro cell generator. I’m not sure if they’re installed that way or not but it would ideal. Otherwise, you’re losing 10 to 100x of the capacity of a cell network during power outages if the small cells go down.

Net neutrality!*

*Except if someone drives through a power pole.

The feasibility of back hauling power from a central location is almost zero. Conduit can be direct buried and then fiber shot through it, this would be almost impossible with DC power cables.

Keep in mind that WPS already provides priority to “priority” traffic.


Most of the small or micro cells are there to add data capacity not necessary device count, which are two different things.

However, where they are added to augment device count we will have problems if they are not backed up.

As the tech shrinks and battery tech improves this will become solvable, but we are a ways out still.


There is power backup and then there is power backup.

The former is a small power pack (batteries, supercapacitors, whatever) that will allow the microcell to weather a short blackout or brownout. We are talking seconds, to bridge switching transits. To be useful in a deployment, such a holdover battery needs to be very low maintenance. (Think about cars that use supercapacitors as a battery replacement -- good for short needs like a single engine start.)

The latter is longer-life power to keep the microcell going for days or weeks. It's debatable whether this is mandatory.

I can tell you that most carriers have neither type, at least in the US.


Most towers can survive a brown/blackout lasting a few minutes
(usually enough to last the safety system cycling and the fuses blowing
on a grounded leg).

  Major towers tend to have 8-12h of battery, with sometimes 24h.

  Most utility outages are restored in that time with the exception
being major storms.

  In michigan we can get a credit for lack of restoration in 16 hours:

-- snip --
A customer is eligible for a credit under normal
conditions if the utility fails to restore service
within 16 hours after an outage resulting from
conditions other than catastrophic conditions.
-- snip --

  this lines up with the planning strategy of the utilities.

  - Jared

Agreed, specifically talking about small/micro cells.


This is very easy to do, thanks for the widespread adoption and use of HTTP, which lets you easily filter these sorts of things in times of need and to suit the requirements.

Or, what, we no longer use HTTP, because it’s not “secure”?

Nevermind, folks. Don’t forget to update your certs and thank IETF, Mozilla, Cloudflare and Google Chrome for your lack of connectivity. But at least you’re secure, as no bad traffic can reach you now!


This is already how much of the cable networks operate.

Power goes out and the pole mounted nodes go out eventually.

Where "eventually" seems to vary a LOT. I've observed hold up times as long as 8+ hours all the way down to "well, I guess there was a minor power glitch at the nearest power injection point because it dropped everything for 30 seconds while stuff came back up". Lots of factors seem to play in this both in terms of design and maintenance. For a while, some MSOs took their job seriously as they were offering relatively popular business-oriented voice products. MSOs targeting only consumer service and still in the mindset of linear TV (or having not touched their plant since that was the major use case) often have no battery at all.

The same seems true of many FTTN deployments. Hold-up time on nodes varies a lot. The older the deployment, the more design hold-up time it seems to have, but of course maintenance varies a lot. Newer deployments, especially fiber-to-the-curb often have essentially no hold-up at the local node unless it's back powered from the customer prem (in which case the customer can keep it up themselves).