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What You Need to Know About Your Network

How does a mobile phone work?
Mobile devices are two-way radio devices that let you make a call, send short messages and connect to the Internet wirelessly. The devices communicate with the network by a wireless signal between the mobile phone and a nearby cell site. That cell site is connected to the wired network, and from there it either routes your call to another person, a messaging gateway or connects the user to the Internet.

What is a cellular network and how does it work?
A cellular network is a radio network made up of cell sites. Each of the sites is connected to the wired network via "backhaul." To help maintain your connection as you move from location to location, the signals for your mobile device are "handed over" to another nearby cell site in order to provide the best coverage.

How are the signals transmitted to the cell site?
The mobile device "communicates" with a nearby cell site via wireless signal over a frequency dedicated for use by AT&T. The use of these airwaves (spectrum) is similar to tuning into a radio station — each has a particular frequency dedicated for their use to help avoid interference. We currently use frequencies in the 1900 MHz and 850 MHz ranges, although we have licenses to operate in other ranges.

What does a cell site typically look like?
They come in all shapes and sizes, but the most common is a tower that consists of a tower structure with three sets of rectangular antennae at the top. Some cell sites are located atop buildings.

What type of technology does AT&T use in their mobile network?
We use technology based on the 3GPP family of standards. Currently our wireless networks consist of GSM/EDGE and UMTS/HSPA and we have announced plans to begin to deploy LTE in 2011. The 3GPP family of standards are the most broadly-deployed worldwide, and allow for our customers to use their mobile devices on networks around the world. The standard determines how the digital wireless signal is transmitted between the mobile device and the cell tower and also manages the limited amount of frequency available in a given location.

What about data speeds?
That depends on the network technology. Our mobile broadband network utilizes HSPA, which is part of the 3GPP family of technology standards, and covers nearly 80 percent of the U.S. population. With mobile broadband, customers can not only surf the Web and download files faster than ever, but they can also experience the very latest interactive mobile applications.

We also provide data service via our EDGE network, which is based on the GSM standard and is available throughout our network footprint.

Will my mobile device work on other companies' networks?
In most cases around the world, yes. That's because we use the 3GPP family of technology standards, which includes GSM and UMTS/HSPA, the most widely-deployed standard around the world. There are two major things to consider in compatibility for your mobile device: technology (i.e. GSM/UMTS) and frequency. Some of our competitors in the United States use a different network technology, so your handset won't necessarily work on their network.

Okay, so what about dropped calls? Why does that happen?
Dropped calls can occur for several reasons — capacity limitations (congestion) and traveling out of the range of the network (coverage) are the more common issues. Sometimes it can be attributed to the "handoff" of the wireless signal between cell sites. To address these issues, AT&T is constantly monitoring and optimizing our network to minimize them as much as possible. But we also encourage you to let us know if there's an area in which you've noticed problems.

What is the difference between 850 MHz and 1900 MHz?
Much like an FM radio signal and an AM signal have different advantages, so do the 850 MHz and 1900 MHz frequencies. 850 MHz offers better in-building coverage because the signal can better penetrate walls than signals at other frequencies, while 1900 MHz is best for protection against interference with nearby sites.

I'm not happy with the coverage in my area, what can you do to improve it?
There are actually quite a few things that we can do to provide better coverage, but it can depend on several factors — some of which may be out of our control. While we're constantly monitoring and optimizing the network to ensure the best coverage possible, sometimes we need to obtain permits to install new cell sites or even upgrade existing locations. Earlier this we year began a major initiative to expand mobile broadband capacity throughout the country, which will help to relieve congestion. We are also trialing a new technology called Femto cells which will improve mobile broadband coverage in consumer dwellings.

Why can't I get coverage in my basement, inside a building, etc.?
Like all wireless technologies, things like buildings and other large, immobile objects (trees, walls, concrete foundations, etc.) interfere with wireless signals. While some frequencies can better penetrate walls, sometimes it will not matter if the obstruction is big enough. It's just like a TV signal — you'll tend to get better reception closer to the window than you would in your basement, for the most part.