AT&T Roars Back in PCWorld’s Second 3G Wireless Performance Test

Upgrading the Cell Sites

When wireless carriers upgrade their networks in a particular market, what do they actually do? Usually the improvement isn't a matter of erecting more cell towers, a process that can be expensive and fraught with bureaucratic hassles with local government.

Often, wireless carriers focus on upgrading the software at their cell sites to increase speed and capacity. This is what AT&T did when it recently upgraded its cell sites from HSPA 3.6 technology to HSPA 7.2 technology.

The wireless carrier may also add capacity to an existing cell site by adding a new frequency band to the wireless spectrum already available for its subscribers to use in that cell zone.

When Sprint and Verizon added a new frequency band added to their cell sites, the sites theoretically gained 9.3 mbps in download speed and 5.4 mbps in uploadspeed. (After an upgrade, the actual speed that a wireless device can achieve depends on its distance from the cell tower, the number of other wireless subscribers using the cell, and the complex wireless protocols baked into the device itself--which determine its maximum connection speed.)

The same procedure is used by AT&T and T-Mobile engineers when they add a new frequency to cell sites in their GSM networks. These networks add three GSM radios to transmit and receive on the newly allocated slice of wireless spectrum. For the newest variation of the GSM data standard--HSPA 7.2--this upgrade adds 21.6 mbps of maximum download capacity and about 17 mbps of maximum upload capacity to the cell.

There is, however, one big difference in the way new bandwidth is added to CDMA and GSM towers, respectively. On Sprint and Verizon CDMA radios, voice and data services occupy separate frequency bands. Because the radio can communicate on only one band at a time, CDMA subscribers can?t carry on a voice call while surfing the Web.

In AT&T's and T-Mobile?s GSM networks, voice and data service run on the same frequency band, so the caller can talk on the phone and surf the Web simultaneously.

4G Is Coming Fast

Consumers are getting used to the idea of a mobile, connected, on-demand world. As consumer expectations of wireless networks rise, carriers are in a position to make a lot of money at a high profit margin. All four of the Big Four carriers are feeling the pressure to increase the speed and capacity of their wireless networks to accommodate the bold new world that consumers want.

On key component of the emerging mix is a new generation of wireless network called 4G, and mobile operators are scrambling to start building such networks.

For Sprint, 4G means providing WiMax service via the Clearwire network, which now reaches 27 U.S. cities and is spreading to new cities rapidly. This development puts Sprint well ahead of the other U.S. mobile operators in the move toward 4G. Sprint plans to release a number of dual-mode 3G/4G devices, including phones (the first of them this year), that will connect at superfast 4G speed when possible, and will fall back to a 3G connection when not.

For Verizon Wireless, 4G means adding an overlay network using LTE (Long Term Evolution) technology. New hybrid modems and phones will use the 4G LTE network for high-performance applications, but will continue using the existing 3G CDMA network for voice and in situations where 4G is unavailable. Verizon says that it will launch its new LTE network in 25 to 30 markets in 2010, and it hopes to have 4G coverage for almost all of its current nationwide 3G footprint by the end of 2013.

T-Mobile is moving toward 4G by converting its network from HSPA (High Speed Packet Access) to HSPA+, which T-Mobile says can pump out maximum download speeds of 21 mbps. T-Mobile has deployed HSPA+ in Philadelphia, where some users have reported obtaining download speeds of up to 19 mbps. The carrier says that it will continue to build out its HSPA+ network this year, achieving a ?broad national deployment? during 2010.

AT&T says that it will use its new HSPA 7.2 technology to bridge its current GSM/UMTS mobile platform to its LTE future. AT&T plans to commence field trials of its LTE technology later this year, and then begin switching on commercially available LTE networks in 2011. If the speed of AT&T?s recent upgrades is any guide, however, the company?s LTE launch may happen sooner than expected.

For comprehensive coverage of the Android ecosystem, visit Greenbot.com.

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