3G still has a lot of life to give -- not just in existing networks but in future upgrades

With 4G dominating the attention of the industry, 3G seems to have fallen by the wayside. However, a sizable evolutionary path for both CDMA2000 and wideband CDMA still exists. Technologies such as evolved high-speed packet access and EV-DO Revision B have come out of the standards bodies, promising new capacity boosts and more efficient use of spectrum. But will operators actually deploy these technologies now that their sights are set on 4G?

On the UMTS side, high-speed downlink packet access (HSDPA) is quickly rising through its evolutionary iterations to top out at 14.4 Mb/s of downstream capacity per 5 MHz channel. Operators also have begun to deploy high-speed uplink packet access (HSUPA) to boost upstream speeds beyond 384 kb/s. Beyond even those technologies, the 3rd Generation Partnership Project 2 has approved new evolutionary steps in the UMTS line that enhance modulation from 16 quadrature amplitude modulation to 64 QAM. Known as HSPA Evolved or HSPA+, the technology also calls for the implementation of a flat IP architecture in the core and multiple input/multiple output (MIMO) smart antenna techniques — just like 4G systems. Those modifications to the standard could boost downlink speeds to 42 Mb/s and uplink speeds to 24 Mb/s, both over 5 MHz channels.

Things aren't quite so clear on the CDMA side. The 3GPP2 and the CDMA Development Group have promoted a standard for multicarrier 3G called EV-DO Revision B. The technology combines multiple Rev. A channels to create a mega-channel of sorts. Three 1.25 MHz Rev. A channels — each supporting 3.1?Mb/s of downlink capacity — would combine to form a single enhanced channel with a capacity of 14.7 Mb/s, matching HSDPA's top speeds over equivalent spectrum. But the 3GPP2 has not yet moved to enhance CDMA's modulation beyond 16 QAM or explore new antenna techniques.

Will carriers deploy these technologies? Vodafone announced plans at the Mobile World Congress to test Ericsson's and Huawei's HSPA+ equipment, but the global carrier also has committed to deploying long-term evolution (LTE), as has Verizon Wireless. Sprint Nextel already is looking past CDMA to its WiMAX network, which Ali Tabassi, vice president of technology development for Sprint, said would meet any future demands for bandwidth enhancements. “At this moment we don't plan to evolve to anything beyond Rev. A,” Tabassi said of the CDMA network.

Vendors ultimately follow their carriers — and the contracts those carriers award them. As Revision B's reception among CDMA operators has been lukewarm, vendors have been rather quiet about the technology lately. There's been more activity on the HSPA+ side, but many GSM/UMTS vendors are now focusing on getting LTE out the door behind WiMAX.

Arun Bhikshesvaran, vice president of strategy and chief technology officer for North America for Ericsson, said that the attention may be on 4G now, but that hasn't slowed down its development schedule for 3G. “If Verizon and Vodafone deploy LTE, we'll definitely be spending a little time on that technology, but development of HSPA won't stop,” he said. Not only will 4G players have massive 3G footprints to maintain, but only a handful of operators with new spectrum will be able to deploy new 4G networks.

4G won't displace 3G for years, if ever, so it makes sense that those networks will be maintained and expanded. Upgrading those networks will require a new generation of handsets, even if the infrastructure requires only new software. For example, adding MIMO to the networks will require dual antennas on the devices, a difficult conundrum when dealing with a handheld. And as with any new technology, the initial chipsets will be expensive until economies of scale are reached. That may mean that Revision B and HSPA+ deployments may come only in hotspot footprints, where laptops and other pricey, high-bandwidth-consuming devices can take best advantage of them.

Perry LaForge, executive director of the CDMA Development Group, said that asking how much more capacity the industry can get out of 3G may be the wrong question. The big potential in 3G is economic, not technological. The broadband speeds achieved by both HSPA and CDMA will support the vast majority of mobile data demands. In addition, the prices of 3G chipsets are falling, allowing 3G to be put into more inexpensive devices.

“I do believe we're at a sweet spot,” LaForge said. “Not just for EV-DO, but also with HSPA.”

UMTS EVOLUTION: 3GPP releases

5
High-speed downlink packet access

Expands maximum downstream capacity to 14.4?Mb/s. Already deployed in most major UMTS networks worldwide.

RELEASE

6
High-speed uplink packet access

Expands maximum upstream capacity to 5.76 Mb/s.

7
Evolved high-speed packet access

Better modulation, collapsed IP core, allows for MIMO.Downlink speeds increase to 21 Mb/s; uplink increases to 11 Mb/s (with MIMO, 42 Mb/s and 21 Mb/s, respectively).