AT&T 3G MicroCell: A Comprehensive Exploration
by Brian Klug on April 1, 2010 1:55 AM EST- Posted in
- Smartphones
- AT&T
- Microcell Review
- Mobile
Femtocell handovers don't quite work..
So back to the AT&T MicroCell - handovers just didn't work for me. I didn't keep perfect track, partly out of frustration, partly because doing all this walking in and out and in and out of the house was physically exhausting, but to say 20% of calls handed over would be optimistic.
For this test, I called the local Automated Surface Observing System (ASOS) lines for several airports and simply walked a common path outside. The ASOS stations are for pilots to get the current weather conditions at airports quickly, but I use them as simple repeatable test calls. They terminate automatically after a few minutes to prevent misuse.
The most common mode of failure I saw was what's in the following video. The call starts fine, continues until the edge of microcell coverage, noticeably breaks up, and simply drops. All four of the iPhones I tested behaved the same way. Please forgive how shaky these are, it's challenging to walk rapidly, hold one phone, and take video with the other.
Of course, there were a few times where the handover went successfully. In these two videos, I unfortunately left WiFi enabled, but the handovers are hard and vertical and you can see "3G" disappear right after the transition. Listen carefully for how noticeable the audio change is; the phone has switched from UMTS to GSM to continue the call. Virtually all of the successful handovers at both location 1 and 2 were of this variety. After the call completed, I was clearly on 2G EDGE for some time.
But the most disturbing mode of failure happened on my daily device. During the vertical handover, there's loud audio corruption and distortion. Most of the time the call would then fail, a few times it successfully handed over.
This is something you should never, ever see on a modern cellular network. In fact, I was so shocked that I had my SIM replaced, rebooted multiple times, and did everything I could think of. Audio corruption still sporadically happened at locations 1 and 2, inexplicably. It's reasonably rare, but very alarming.
Call handover just doesn't work well. Even in location 1, where I could move freely about without dropping calls, migration from the MicroCell to the public 3G network would fail. That was an important test, because there are ample macrocells for the call to be migrated to; something just doesn't happen.
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leexgx - Friday, April 2, 2010 - link
the UMA thing looks good idea, seems Way more piratical then these base stations ( http://en.wikipedia.org/wiki/Generic_Access_Networ... ) only ever seen it on blackberry phones thought, only issue i could see with them is if it doe snot work with the wireless router correctly or intermittently out of range of routerjulioromano - Friday, April 2, 2010 - link
Very nice and geeky review.Thanks for all the infos!
Simozene - Friday, April 2, 2010 - link
1. These units need to be very cheap or free for consumers.2. Any minutes or data usage that is routed over this instead of AT&Ts regular network should not be counted towards the limits on your data plan. It's not their network so you should not have to pay for using it.
If those two conditions are met I can see how this could be a very useful product.
sxr7171 - Friday, April 2, 2010 - link
But it's not. It can't even hand off properly.Chrisg331 - Friday, April 2, 2010 - link
1st off, great article. Good methodology as well. Will you be able to test different handsets (Primarily different chipsets/antenna designs to eliminate bias on the dropped calls), possibly test a repeater (as mentioned before) and possibly test data usage pattern(s) for those that may be bandwidth capped on their broadband? Great job. Could really be useful to those looking to ditch landlines.GregHH - Friday, April 2, 2010 - link
In your haste to slam AT&T you neglect to notice that the other cell carriers offer the same type of device. That implies their coverage must not be perfect and all encompassing. Everyone seems to think cell coverage should be ubiquitous whether in a metro area or in the wilderness. I feel good that my area finally got 3G coverage in December of 2010.JKflipflop98 - Saturday, April 3, 2010 - link
So, we're in the future looking back on the past then? Or we're in the past looking towards the current? Oh God, my head's going to explode.ivwshane - Friday, April 2, 2010 - link
There is no required monthly cost. Buy just the microcell and use your existing minutes and data plan. Buy a microcell with a $20 feature and you can have unlimited minutes while using it and you also get a $100 rebate.No one is forcing anyone to buy these, at&t is simply giving it's users a choice, if you want to improve your in home coverage then buy one, otherwise don't.
mikeshady - Saturday, April 3, 2010 - link
So if I understand it correctly the price,$20/month unlimited calling$10/month with AT&T DSL
$0 with AT&T landline.
Will i be able to use it for the unlimited free since i have att landline
mrSHEiK124 - Tuesday, April 6, 2010 - link
Those failed handover videos; that happens ALL OF THE TIME on at&t in the Tampa, FL area. If you're on a highway or main-road and venture off into the boonies, as you get booted off 3G all you can hear is distortion (the handover is successful and the call doesn't drop, but good luck continuing the phone call...) and weird audio artifacts. at&t...more bars in more places.