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
Performance - Data
I noted a few times that I tried the device at two different residences, both for completeness sake and because they're completely different coverage-wise. Location one is relatively urban and already had excellent signal and performance; I regularly see speedtests over HSPA of nearly 5 Mbps. The internet connection here is a 20 Mbps downstream, 4 Mbps upstream DOCSIS 3.0 Cox Cable connection shared using a WRT54G-TM running Tomato. I sat in the same room as where the AT&T MicroCell was installed, my office. There's some irony in using T-Mobile's branded router (as it's sold expressly for UMA), however I use it because it has double the RAM and ROM of the WRT54GL.
Location two is more rural and doesn't have good performance or signal coverage; there are more than a few dead zones throughout the house, and I chose what I perceived to be the worst one. Internet here is Comcast Cable with 6.6 Mbps downstream, 1.1 Mbps upstream shared using a m0n0wall router running on a WRAP PC Platforms board.
I installed the microcell at both locations and let it sit for an hour. I assigned a static DHCP IP address, and then set that IP to maximum QoS priority for both upstream and downstream. For testing, I used four iPhone 3GSes, including my daily device, which is jailbroken so I can report RSSI. This is the relative signal strength reported by the baseband in arbitrary units, though still in dB. If you're rusty, remember that every factor of two change in power corresponds to 3 dB - if we go down 3 dB, we're at almost exactly half the signal. If we go up 3 dB, we're at double the power. In this case, RSSI is not dBm. As an aside, this is a much better way to gauge signal at a glance than the vague signal bar visualization; the iPhone seems to show a very optimistic moving average in its bar metric.
On the iPhone, -113 dB is effectively zero to one "bars." In fact, this seems to be the bare minimum in practice before the radio disconnects. Similarly, -51 is absolute maximum. If you put the phone next to the microcell, you'll see this, or if you're standing within line of sight very close to a macrocell. Thus in the following plot, closer to 0 is better.
For testing bandwidth, I ran tests using speedtest.net on the iPhone over 3G with and without the microcell, and over WiFi for a comparison point of my network bandwidth. Of course, we're limited to 802.11b (11 Mbps) rates on the iPhone over WiFi.
One thing that stands out doing lots of tests is that upstream performance is arbitrarily capped at exactly 58-60 kilobits/s on the MicroCell. Remember that 256 kilobits/s requirement earlier? It's obvious now where they derived that 60 kilobit/s cap from: 60 * 4 is roughly 240 kilobits/s. Add in some overhead fudge factor, and you've got 256 kilobits/s. So in the worst case, where there was previously almost no signal at all, we can now get a pretty speedy 3G data connection over the microcell. However, in the best case, at location 1, we're actually slower than before.
Remember again that AT&T's MicroCell currently only supports HSDPA speeds of up to 3.6 Mbps - at location 1 it's obvious that AT&T is running HSDPA at 7.2 Mbps, as I regularly see results like these:
Oh yeah, I'm always up that late doing bandwidth tests
Location 2 Before and After
But performance is still a function of signal strength even with the MicroCell. As you move away, you'll see speeds go from being ideal for HSDPA 3.6 Mbps all the way down to a respectable but less than ideal 1.2 Mbps.
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A beautiful mind - Thursday, April 1, 2010 - link
My Nokia N900 already uses the home/office wifi connection to access the internet, with the possibility to receive/make calls from/to skype.There is absolutely no extra functionality that is provided by the femtocell approach.
softdrinkviking - Thursday, April 1, 2010 - link
For you and me, this is true.But not for everyone.
That's the really sad thing about this device. It's designed as a way to nickel and dime poor souls whose homes are in a dead zone and absolutely have to answer their phone for business.
nafhan - Thursday, April 1, 2010 - link
Great article, and you did an excellent job of diving into the tech behind the femtocell.An interesting follow up to this article might be to see what kind of results you get from purchasing an antenna and repeater. I've seen antenna/repeater setups online in the $350 and up range, and wondered how they would do. If they work OK, it might be a viable alternative, especially for people without good internet connections.
gwolfman - Thursday, April 1, 2010 - link
Where is the print article feature on the new site?Maroon - Thursday, April 1, 2010 - link
They've been sneaking these things in Apple stores. No wonder the iPhone feelgood only lasts untill you get out of the store and have to rely on the "standard" AT&T network. LOL.soccerharms - Thursday, April 1, 2010 - link
Are you kiddin' me? I am going to approach this from two angles. The first being that this article is completely fake. ITS APRIL 1st people! The tech community should have an uproar for such a device. We buy internet and it is usually our responsibility to distribute it around the house with a router for wireless and whatnot. HOWEVER, we do not buy a wireless......phone plan with the intention on increasing a carriers crappy signal in our own house out of our pocket. That's ludacris! There is another much cheaper solution...........its called a LAN line with a cordless phone HA!The only company that could profit from a device like this would be Apple. But they would have to make it a little more shiney and put that quarter eaten logo on the side :)
Let the battles begin....
Jaybus - Thursday, April 1, 2010 - link
This is like buying an airline ticket only to find there is no flight. Since they don't have a flight, the airline offers to sell you your own airplane. You have to provide your own pilot, fuel, and maintenance, but you still have to pay them the full price for a ticket whenever you fly your own airplane. So my idea is to start a car rental business that has no cars. Anyone willing to pay AT&T for a microcell that uses their own Internet connection would surely be willing to pay me a rental fee for driving their own car.HotFoot - Thursday, April 1, 2010 - link
Eh... much of this market is iPhone users - people already willing to accept the concept of ecosystem lock-in. By a similar analogy to your car rental company, they're already willing to buy a car from a company that requires that they drive only on roads built or approved by that company, buy gas only at that company's stations, and buy car insurance from that company.Why not charge them for the roadside delivery of a jerry can of gas when the customer finds out the station filled their tank with water instead of fuel?
yacoub - Thursday, April 1, 2010 - link
I give it a year or two before the first cancer danger report comes out. ;)loydcase - Thursday, April 1, 2010 - link
AT&T cell reception at my house is weak in spots. OTOH, if a femtocell allows me to rip out my landlines, it might be worth it. So I'd like to know if a femtocell would be viable for that purpose.