Monday, August 02, 2010

The AT&T 3G Microcell: YMMV

The AT&T 3G microcell is like a little personal cell tower that uses your internet connection to provide cell service in places where there is a weak signal, or none at all. Our new house sits in a cell dead zone, so I decided to try one. Six weeks, three trips to Fry's, two warranty replacement units, and I don't know how many hours on the phone with AT&T tech support later, I finally have a working unit. I thought I'd share the results of my experience in the hopes that it might save other people some time.

There are two fundamental problems with the microcell. The first is that it doesn't like to sit behind a firewall, but the documentation doesn't make this clear. It uses a proprietary protocol and some obscure IP port numbers which your router may or may not handle properly. It turns out this is pretty common knowledge on the microcell discussion forum but it's easy to waste a lot of time trying to figure this out. (AT&T does publish a troubleshooting guide that has this information, but it's hard to find. In fact, it's so hard to find that when I went to look for the link so I could put it in this post I couldn't find it.)

The situation is exacerbated by the second problem, which is much more serious: The microcell is not plug-and-play. In order to use the unit you first have to activate it. which requires you to register the physical address where the unit will be placed. AT&T says this is because of FCC requirements to provide cellular 9-1-1 emergency services, which makes a certain amount of sense I suppose. The problem is that AT&T doesn't just take your word for it that you've entered the correct address on their web site. The unit contains an internal GPS receiver, and before you can make any phone calls the GPS has to verify that the unit is in fact where you said it was. If it isn't, or if it can't lock onto its location, it won't work at all. (How it is supposed to be better in an emergency not to be able to make a call at all rather than make a call from a cell site whose location might not be known is not altogether clear to me.)

That is already bad enough, but get this: it can take up to ninety minutes for the GPS to lock onto its location. So if something isn't working properly you have to wait an hour and a half to find out. If after an hour and a half the unit hasn't activated, it gives you no indication as to what went wrong. Your only options are to power cycle or keep waiting. And waiting. And waiting.

My initial activation actually went fairly smoothly. The problems started a few days later. The unit can go off-line for any number of reasons (lost GPS lock, lost network connection, because it doesn't like your cologne) and when it does, the only way to get it running again is to power cycle it, which means going through the whole up-to-ninety-minute-long process of re-aquiring a GPS signal all over again. That is what happened to me, at first once or twice a day, then several times a day, and then it finally died altogether and refused to connect for five days straight. That's when I got my first warranty replacement unit.

Alas, the second unit was just as flaky as the first, which made me think that the apparently reliable operation I had experienced the first few days was a fluke (or maybe a hallucination). So I started experimenting. I relocated it onto a windowsill to provide better GPS satellite visibility. I added an external GPS antenna to help boost the signal. No joy. I was really discounting the possibility of a hardware failure because modern electronics tend to be pretty reliable, and the chance that I had somehow gotten two defective units seemed pretty remote. But one day I happened to plug in the external GPS antenna while it was working, and ten minutes later it went off-line. This behavior turned out to be repeatable, which seemed like pretty strong evidence that this unit was in fact defective. So I got a third unit, and this one seems to be working.

My verdict: the 3G Microcell is not quite ready for prime time. It has some serious design flaws and apparently some pretty bad quality control on the manufacturing side. I hope they fix these problems because when it works it's a very handy gadget.


Naum said...

Even if working properly, seems like you're paying to cannibalize your ISP bandwidth to extend carrier service…

…also, I ponder how much of the bandwidth channel allotted for cellular communication could grow, especially if others in the neighborhood hijacked the now solid 3G connection.

Ron said...

> seems like you're paying to cannibalize your ISP bandwidth to extend carrier service…

That's right, though I would call it "using" rather than "cannibalizing." The microcell is essentially a cellular to VOIP gateway.

> if others in the neighborhood hijacked the now solid 3G connection

I forgot to mention: only phones authorized by you can connect. So your connection can't be hijacked. Also, the range is not al that much. It barely covers an entire house, let alone a whole neighborhood.

But that actually raises in interesting possibility: the fact that it's possible to make what is essentially a cell tower in such a small form factor and sell it at (presumably) a profit for $150 means that it should be possible to build city-sized cell networks for very little money. That sounds like a business opportunity.

Anonymous said...

It's a business opportunity that's come and gone, really. The PHS system has been available for a couple of decades for anybody who wanted to use it.

I suspect that part of the issue may have been engineering costs; when you have lots and lots of small cells, you've probably got to spend a lot more effort securing locations and doing whatever RF analysis you do to properly site and set up an antenna.