Posts tagged AT&T

AT&T 4G LTE in Tucson, AZ – Coming Before End of 2012

It has been what seems like an eternity since I wrote a bit about Verizon 4G LTE coming to Tucson, AZ. Since then, the network has been deployed and working just fine, and made it into my mental take-it-for-granted state. Since then, Cricket has lit up their own LTE network on AWS (1700/2100 MHz), and next up is AT&T who just recently announced details about their LTE deployment for a bunch of markets before the end of this calendar year. I wrote about the AT&T LTE news at a high level at AnandTech, and the announcement comes a not-so-coincidentally timed week before the next iPhone announcement in an attempt to prevent lots and lots of LTE related churn.

I’m burying the lead a bit, but before the end of 2012 AT&T will have LTE finally lit up in my part of the world. There’s a relevant press release here which is relatively light on detail – there’s no outline for what parts of town will get LTE, whether it will include surrounding areas, or any further detail. I guess we can only hope that they mean the greater metro area. I’ve asked a few of my sources for a better timeline, but can only say that before December LTE should be lit up.

I hope it goes without saying, but LTE (3GPP Long Term Evolution) is completely different from the earlier announcements AT&T made about “4G” coming to Tucson in May 2011. That was really just deployment of HSPA+ with up to 16QAM on the downlink (HSDPA 14.4) and some additional WCDMA carriers for capacity reasons. I’m pretty pleased with the state of AT&T WCDMA in town, I see around 2-3 carriers on PCS (1900 MHz) around town and what I consider very good peak speeds.

AT&T Spectrum Holdings in Pima County (As of Sept. 7 2012)

Since AT&T LTE doesn’t use the same channel bandwidth everywhere, it’s worth noting that in this particular market (Pima County), AT&T can run 10 MHz FDD-LTE on Band 17, (Lower 700 MHz B+C blocks) and 5 MHz FDD-LTE on AWS (1700/2100) when the time arises. I haven’t seen AT&T enable any LTE on AWS quite yet, this is likely coming at some future date after the rollout is closer to completion or as a way to mitigate loading in the future.

AT&T 3G MicroCell Review

In case you missed it early, early this morning, my AT&T 3G MicroCell review is up and live at AnandTech here.

I played around with the product all last week and finally think I know all there is to be gleaned about it - undoubtedly in time the handover performance (which is pretty abysmal) will improve. It’s something that I talk about a lot in the article itself, but exists across all the major femtocells, and T-Mobile’s implementation of UMA. From a technical standpoint, the problem seems to be that the phone almost treats the femtocell like a roaming tower – implicitly disabling soft handovers to the public network. It’s handled this way most likely for a billing segmentation reason, but that’s unclear.

I learned in the comments that there are enterprise picocells, although I’m not sure what kind of carrier interaction is required for installation. I’d really like to investigate those for something future. Whatever the case, if you’re interested definitely give it a read!

AT&T 3G in Las Vegas

While I was in Las Vegas for MIX10, I couldn’t suppress my inexplicable urge to run as many speedtests as I could muster. Of course, I was packing the usual iPhone 3GS with AT&T. Sadly, nearly the entire visit speeds were barely 250 kilobits/s down, 220 kilobits/s up, if I could even get the speedtest.net application to run. Take a look at the following:

(kilobits/s) Average Min Max
Downstream 251.8 14.0 552.0
Upstream 220.8 0.0 357.0

This data is from 13 tests taken during my 3 day stay. They’re from over 3G UMTS when it did work, and GSM EDGE when it didn’t, and that was virtually the entire time. 3G was either slow, or didn’t work at all; switching to EDGE was the only way to do anything.

How is this possible?

Now, it’s fair to say that some of this is sampling bias and the fact that I was at a conference, but even then, there’s no excuse. This is a city used to a huge flux of visitors in a short time for trade conferences. Frankly, I can only begin to imagine how overloaded networks are during major conferences like E3.

Take a look at the following plot of the average speeds for each day:

Average Downstream Speed

Can you spot which three days are the ones I’m talking about? Note that on the 16th, I couldn’t even get a test to run to completion; it just didn’t work. There’s nothing more to really say about the issue than simply how bad this is. If this is the kind of performance AT&T users see and complain so vocally about in the San Fransisco Bay Area and Manhattan, I can completely understand. Frankly, I can see no other reason for that kind of performance degradation other than congestion.

AT&T Observations and Bandwidth

Bandwidth and Latency Data

I’ve always kind of been obsessed with bandwidth. I find myself constantly testing latency, bandwidth, and connection quality (mostly, in fact, through smokeping). Needless to say, that same obsession applies to my mobile habit, and especially given the often-congested perception of AT&T.

It sounds weird, but the two most-run applications on my iPhone are Speedtest.net Speed Test and Xtreme Labs SpeedTest. The Xtreme labs test used to be my favorite, largely because of its superior accuracy and stability. As great as Speedtest.net’s website is for testing, the iPhone app continually fell short. Tests ended before throughput stabilized, often the test would start, then the data would start being calculated a second later (skewing the average), or it’d just crash entirely. I could go on and on about the myriad problems I saw which no doubt contributed negatively to perception of network performance.

A few months ago, I wrote a big review and threw it up on the App Store. In the review, I noted that being able to export data would be an amazing feature. At the time, I had emailed Xtreme Labs and asked whether I could get a sample of my speed test results for analysis (I have yet to hear back). On Feb. 2nd, Ookla finally got around to releasing an update to the Speedtest.net app; it included the ability to export data as CSV.

Since then, I’ve been using it exclusively. I’ve gathered a bit of data, and thought it relevant to finally go over some of it. This is all from my iPhone 3GS in the Tucson, AZ market, largely in the central area. I’ve gathered a relatively modest 76 data points. Stats follow:

Gathered Statistics

Downstream (kbps)
Upstream (kbps)
Latency (ms)
Average 1880.3 263.3 1029.2
St. Dev. 1179.6 101.6 1140.2
Max 4279.0 356.0 6011.0
Min 82.0 18.0 366.0

These stats really mirror my perceptions. Speeds on UMTS/HSPA vary from extremely fast (over 4.2 megabits/s!) to as slow as 82 kilobits/s, but generally hang out around 1.2 megabits/s. On the whole, this is much faster than the average 600 kilobits/s I used to see when I was on Sprint across 3 different HTC phones.

Next, I became curious whether there was any correlation between time of day and down/up speeds. Given the sensitivity of cellular data networks to user congestion (through cell breathing, strain on backhaul, and of course the air link itself), I expected to see a strong correlation. I decided to plot my data per hour, and got the following:

Downstream and Upstream Bandwidth

Some interesting trends appear…

  1. I apparently sample at roughly the same time each day (given the large vertical lines that are evident if you squint hard enough). Makes sense because I habitually test after class, while walking to the next.
  2. There is a relatively large variation per day for those regular samples, sometimes upwards of a megabit.
  3. There does appear to be a rough correlation between time of day and bandwidth, but the fact that I’m moving around from cell to cell during the day makes it difficult to gauge.
  4. Upstream bandwidth is extremely regular, and relatively fast at that.

I’m still mentally processing what to make of the whole dataset. Obviously, I’m going to continue testing and gathering more data, and hopefully more trends will emerge. You can grab the data here in excel form. I’ve redacted my latitude and longitude, just because my daily trends would be pretty easily extracted from those points, and that’s just creepy.

3G Bands – Where is the 850?

Lately I’ve been getting an interesting number of hits regarding the 850/1900 MHz coverage of AT&T here in Tucson.

To be honest, I’ve read a number of different things; everything from certainty that our market has migrated HSPA (3G) to 850 MHz, to that AT&T doesn’t even have a license for that band in Arizona. For those of you that don’t know, migrating 3G to the 850 MHz bands is favorable because lower frequencies propagate better through walls and buildings compared to the 1900 MHz bands. In general, there’s an industry wide trend to move 3G to lower frequencies for just that reason.

I’ve been personally interested in this myself for some time, and finally decided to take the time to look it up.

Maps, maps, maps…

The data I’ve found is conflicting. Cellularmaps.com shows the following on this page:

AT&T 1900 MHz

AT&T 850 MHz

Note that the entire state of Arizona doesn’t have 850 MHz coverage/licensing.

However, the GSM authority over at GSM World shows three very different maps:

HSPA 3G Coverage (yellow)

AT&T 850 MHz coverage

AT&T 1900 MHz coverage

Note that the 3G data coverage map is labeled ambiguously; HSPA coverage exists, but it could be on either 1900 or 850. However, what we do glean is that (at least according to GSM world) there is equal 850 and 1900 MHz coverage in Tucson and the surrounding area. This contradicts the earlier map.

Then you have maps like these, which are relatively difficult to decipher but supposedly show regions of 800-band coverage from Cingular and AT&T before the merger:

Cingular 800, AT&T 850

Finally, you have websites such as these that claim Arizona is only 1900 MHz.

So what’s the reality? Uncertain at this point.

The map given by cellularmaps.com is sourced from 2008, whereas the GSM world maps are undated, and ostensibly current. The other maps are also undated, but the majority consensus is that AT&T isn’t licensed to use 800 MHz in this market.

If anyone knows about some better resources or information, I’d love to see it.

Update – 3/24/2010

I finally spoke with someone at AT&T, and it turns out that my initial suspicions were correct – Arizona does not have the 850 MHz UMTS Band 5. It’s as simple as that.

Oh well, at least we know now!