Thursday, June 25, 2009

AT&T Gets Cheers for 850 MHz

While we feel many of the networks that utilize 1900 MHz (PCS) frequencies do an adequate job, many AT&T customers lament the overloads experienced presumably from so many iPhone users who are limited to 1900 MHz spectrum. So we have received more than just a few inquiries about the addition of AT&T's recently announced purchase of most of the divested Alltel network. While we feel the new spectrum and facilities will make a significant contribution to AT&T's rural footprint, it won't do much to improve the experience of those users who suffer from dropped connections in urban areas.

Fortunately, AT&T has admitted that most of their data is transferred at 1900 MHz and is now in the process of making it available on their 850 MHZ channels. One of our major complaints about AT&T was the limitation of using the 1900 MHz spectrum from their 850 Mhz cell sites during the rollout of GSM, and we are equally disappointed to find they are still doing that for data. Surprisingly, Verizon Wireless does the same thing where they have both 850 and 1900 MHz active...with few complaints. Are AT&T users more demanding of their network, or is the network not quite ready for prime time? We fear the latter. But AT&T has announced thousands of new cell sites on the drawing board.

You know what's funny? When Cingular and AT&T combined, it resulted in the largest US cellular network based on the number of cell sites, around 15,000, and still coverage suffers. Keep building, guys...it's still the network, ya know.

3 comments:

Ian said...

I think I have an easy explanation for iPhone overloads vs. Verizon's lack thereof:

1. EvDO on Verizon's network is sometimes deployed in the 850 band instead of 1900 if VZW doesn't have 1900 spectrum in a given area, or something like that. See http://evdotips.blogspot.com
2. AT&T 3G (WCDMA) is a voice and data technology, whereas EvDO is data-only.
3. WCDMA is not backward compatible with GSM, believe it or not.
4. Due to reasons 2 and 3, a 3G network has to have its own spectrum, etc. that's totally separate from GSM. Sound familiar? TDMA vs. GSM is the exact same way.
5. Thus if your phone is on 3G, no matter whether you're using voice or data, you're using up a channel on the UMTS system. When all the channels are gone (too many voice calls, too much data transferred or both) you drop calls, can't use the web, etc.
6. CDMA is actually more spectrally efficient for data than GSM, especially HSPA 3.6. CDMA uses a 1.25 MHz channel and crams either 3.1 Mbps of downlink or 1.8 Mbps of uplink bandwidth in there. HSUPA takes a full 5 MHz from what I've read to push that same 1.8 Mbps, and HSDPA takes 5 MHz for either 3.6 or 7.2 Mbps. So you need 10 MHz of spectrum just for data on a WCDMA 3G system, whereas the number is much lower for CDMA. This is the reason T-Mobile had to use AWS spectrum for its 3G system: no more room on PCS bands since they were all taken with GSM.

Now if AT&T killed their 2G network completely in 3G-covered areas (impossible, since they're still selling EDGE/GPRS-only phones) they probably wouldn't have any capacity issues. However since Verizon and Sprint aren't using two incompatible systems in one phone, they don't have the capacity problems, plain and simple.

Before you say "but Sprint uses WiMAX as their 4G technology and that's totally incompatible with CDMA" let me respond: Clear WiMAX is on the 2500MHz band, and there's PLENTY of spectrum to go around there. 80+ MHz to be exact. Sorta like Europe/etc., who use 2100MHz for their 3G spectrum.

Unfortunately this is a situation where better 3G quality will come at the expense of lower EDGE quality, which will certainly tick off Blackberry users, who until recently haven't had a 3G handset to pick. But c'est la vie for the company with more bars in more places. Too bad you can have a full five bars and still not make a call due to capacity problems; that's why Nextel has lost so many customers.

daveahl-clectcar said...

Is EvDO on Verizon's network deployed in the 850 band instead of 1900 in the state of North Dakota?
Folks with Verizon Aircards told me they had problems on Interstate 94 between Fargo and Bismarck?

Bill Radio said...

Verizon acquired 1900 MHz spectrum from Qwest Wireless in that area with the idea of using 1900 MHz for EVDO as they do in other markets. Whether they have actually started using that spectrum in such as rural area is unknown. A look at one of Verizon cell sites in the area for the smaller 1900 MHz antennas would answer that.