AT&T doubling 3G capacity

AT&T is in the process of doubling the capacity of its 3G networks, using software enhancements to squeeze one last boost in bandwidth from its current generation networks before it begins its migration to evolved 3G and eventually 4G.

AT&T is increasing the downlink capacity on its high-speed packet access (HSPA) from 3.6 megabits per second to 7.2 Mb/s through software upgrades at the base station, said Scott McElroy, AT&T Mobility vice president of technology realization. AT&T currently has the enhanced networks running in two test markets but plans to extend those capabilities to its entire network. Later this year, AT&T plans to start migrating its 3G networks to evolved-HSPA (or HSPA+), which would triple peak speeds.

Theoretically HSPA can support up 14.4 Mb/s of capacity over a 5-MHz downlink, but when the technology was first introduced, commercial equipment wasn't able to meet HSPA's full potential. The results have been a series of iterations in the HSPA standard that operators have been implementing as vendors release both the upgrade modules needed at the base station and the enhanced device chipsets required to support the increased capacities. AT&T, then Cingular, launched its network in 2005, supporting 1.8 Mb/s, but boosted that capacity to 3.6 Mb/s by 2008. Most of the laptop cards and smartphones AT&T sells, including the iPhone, have the silicon necessary to access that additional capacity. AT&T is now in the process of field certifying 7.2-Mb/s devices on its two test networks, McElroy said.

The next obvious step would be for AT&T to further upgrade its 3G networks and devices to its full 14.4-Mb/s potential, but McElroy said AT&T will most likely skip the final HSPA iteration for two reasons: There have been technical difficulties implementing the final step, and HSPA+ is now ready for prime time. There's little point in migrating to 14.4 Mb/s if AT&T can go straight to 21 Mb/s, McElroy said. HSPA+ actually encompasses a bevy of upgrades, including evolving to a flat IP core and the introduction of smart antenna technology, but AT&T is focusing on upgrades to the baseband, which will dramatically increase capacity without having to fiddle with the elements on the tower or in the core.

AT&T isn't just adding capacity through upgrades; it's also adding HSPA carriers at many cellsites. "It's being done on a market-by-market basis," McElroy said. "We're adding second and even third carriers according to demand. We're also in the early phases of an 850-MHz overlay." Though the initial 3G network was built over AT&T's PCS spectrum, AT&T has started using its cellular band for expansion, giving its 3G network far more range and the ability to reach into buildings.

McElroy added that AT&T is upgrading its backhaul network, where possible, to handle the increased data traffic resulting from its network upgrades, though McElroy said he could not reveal the exact extent of those efforts. In cases where the AT&T mothership has built fiber to cell sites, AT&T Mobility is taking advantage of its high-bandwidth transport. AT&T is also using microwave backhaul in some cases, and in some areas has moved sites entirely over to carrier Ethernet transport.

AT&T PURSUING NEW DATA DEVICES

As AT&T beefs up its network capacity, it's seeking out new categories of data devices beyond smartphones and PC cards. At CTIA Wireless earlier this month, AT&T's president of emerging devices highlighted new data-only gadgets, ranging from digital cameras to e-book readers AT&T was testing and certifying for launching. The first of these new devices were announced at the show: netbooks from Acer, Dell and LG embedded with HSPA and WiFi chips that would connect to both AT&T's 3G and hotspot networks.