ATIS: Carriers mapping different routes toward LTE

DALLAS—Speaking at a Long Term Evolution summit this week, AT&T Mobility and T-Mobile USA executives stressed the importance of LTE in their network evolution plans, but both also said that LTE isn’t their next step. Both plan to tap into evolved high-speed packet access (HSPA) technologies that would allow them to upgrade the capacity and capabilities of their 3G network long before they need to take the ultimate step of investing in a brand new 4G network.

While AT&T has identified both new spectrum (700 MHz) and a timeline (initial deployments in 2010 and commercial launch in 2011) for LTE, T-Mobile, T-Mobile plans to repurpose its PCS spectrum at 1900 MHz for LTE as it moves voice calls from the GSM network to its new 3G network on the Advanced Wireless Services band. T-Mobile senior vice president of engineering of operations Neville Ray said the operator’s brand spanking new HSPA network gives T-Mobile plenty of breathing room to make that transition, while also allowing a final LTE standard to emerge and vendor equipment to prove itself in the market. “Sometimes you want to pioneer, sometimes you don’t. We can wait.”

T-Mobile rolled out the bulk of its HSPA network in 2007 and 2008, commercially launching the network last summer and fall when it released its first consumer 3G device, HTC’s G1 smartphone powered by Google’s new Android operating system. The network now is live 130 cities, including 27 major markets, and its total footprint covers 100 million people. Though T-Mobile was far behind the other U.S. operators in launching 3G, being the last to market has certain advantages. Ray pointed out that its 15,000 Ericsson and Nokia Siemens networks base stations are all of the latest advanced design, each easily software upgradable to the next evolutionary step of UMTS, HSPA+. Operators with older UMTS equipment in their networks won’t necessarily be able to make the transition so easily. Ray said T-Mobile plans to begin its upgrades to HSPA+ in the late 2009 or early 2010.

AT&T is planning to begin its HSPA+ upgrades this year, but it won’t necessarily adopt every aspect of the standard said Hank Kafka, vice president of network architecture for AT&T. HSPA+ isn’t so much an upgrade to HSPA, but a series of upgrades to the radio network, antenna structure and packet core, which operators can embrace as a whole or in part. Upgrading the base station software to support a higher order of modulation gives a sufficient boost in the downstream capacity of HSPA channel, from 14.4 Mb/s to 21 Mb/s, but adding multiple input-multiple output (MIMO) smart antenna technologies--which could theoretical double the speeds of the network--would require significantly more work and resources. In light of the fact that AT&T’s LTE network will start going up in 2010, AT&T will have to weigh the benefits of investing in each upgrade, Kafka said.