CTIA: Ericsson pushes UMTS to its limits

Vendors says it will demo 42 Mb/s over Evolved HSPA

Though the industry’s attention may be caught up in 4G, Ericsson isn’t prepared to give up the 3G spotlight just yet. The vendor is highlighting its Evolved High-Speed Packet Access (HSPA) gear at CTIA Wireless this year and promises to demonstrate the maximum capacity that can be squeezed out of a 3G network.

Ericsson said it would demonstrate downlink speeds of 42 Mb/s over a 5 MHz channel, using HSPA evolved gear enhanced with technologies defined in 3GPP’s UMTS release 7 standard. Release 7 ups the modulation scheme from 16 Quadrature Amplitude Modulation to 64 QAM, allowing the radio to deliver an additional 7 Mb/s over High-Speed Downlink Packet Access’ (HSDPA’s) theoretical threshold of 14.4 Mb/s. The addition of Multiple Input/Multiple Output (MIMO) dual antennas doubles that speed to 42 Mb/s.

The higher-order modulation architecture will be commercially available in 2008, and it can be added to Ericsson’s later-generation UMTS base station with a software upgrade. Ericsson is likely targeting the demo at its two largest customers in the US, AT&T and T-Mobile, both of whom have deployed Ericsson’s HSDPA solution. AT&T has said it plans to upgrade its current 3G network to Evolved HSPA--also known as HSPA+--while T-Mobile hasn’t yet commercially launched 3G.

How far Evolved HSPA will make it into the existing networks is still a matter of debate, though. While the upgrade will be commercially available before the Long Term Evolution networks rollout, operators may be hesitant to invest in another technology if 4G is only a year or two away. While the base station upgrade might be relatively painless, operators will need to seed their customer base with new devices embedded with Evolved HSPA chips to take advantage of the capacity increases.

MIMO, which produces Evolved’s biggest capacity boost, is particularly problematic because it requires multiple antennas on the device, not just on the tower. While spacing apart two antennas on a laptop or other large portable device isn’t difficult, doing so on something as small as handset is. For that reason, Evolved HSPA may be deployed in hotspot footprints, focusing on areas of high traffic where people commonly use laptops to access the 3G network.

Arun Bhikshesvaran, Ericsson's vice president of strategy and chief technology officer for North America, pointed out that not all operators have 4G spectrum. Those that don’t will be much more in favor of getting as much life out of their 3G networks as possible as well as needing to match the speeds of their 4G competitors.

“There is a trigger point for 4G,” Bhikshesvaran said. “The deployment of any new technology depends on having the spectrum to use it in.” If an operator has 10 MHz of contiguous spectrum, then LTE is an obvious choice, but if an operator has 5 MHz up and down in different frequencies, it makes much more sense to stick with the existing 3G architecture, Bhikshesvaran said.

Both AT&T and Verizon Wireless have picked up 700 MHz spectrum, which they will almost certainly use to launch their LTE networks. T-Mobile, on the other hand, didn’t participate in the 700 MHz auction, and it’s using the licenses it acquired in the Advanced Wireless Spectrum (AWS) band to build its 3G network. If T-Mobile doesn’t acquire new spectrum and opts not to pursue 4G, it could become a prime candidate for a large-scale Evolved HSPA rollout.