HSDPA: GSM's LONG ANSWER TO EV-DO

Like a professional athlete looking to lose a pound of fat or gain a pound of muscle in hopes that it will make him that much faster or stronger, the mobile industry keeps looking to the next best technology to make data networking faster and more efficient than the technology that came before it.

The bandwidth tug of war that started just a few years ago with CDMA 1X RTT and GSM/GPRS has escalated, with the chief instigators being competitive pride and a need to increase average revenue per data user by developing new, bandwidth-intensive applications.

Over the last year, GSM carriers around the world began upgrading their networks from GPRS to be more competitive with their CDMA counterparts. U.S.-based GSM carriers such as AT&T Wireless and Cingular Wireless have moved on to EDGE with eventual upgrades to UMTS planned in the future, while a few international GSM operators already have been looking toward UMTS.

However, just when these carriers might have thought they were getting ahead of the CDMA-based network operators using 1X RTT, the bar has been raised again. Verizon Wireless will start rolling out nationwide CDMA 1X EV-DO coverage this summer. With a peak data rate of around 2.4 Mb/s, EV-DO is somewhat better than UMTS' peak rate of at or near 2 Mb/s, but it's more devastating in comparison to EDGE — potentially 20 times faster.

Though UMTS is supposed to represent the 3G Promised Land for GSM carriers, they will need an answer to the challenge presented by EV-DO and, later, EV-DV. That answer could be an upgrade to high-speed downlink packet access (HSDPA). The technology has become a hot topic of discussion throughout the wireless industry since Verizon Wireless announced its national EV-DO strategy earlier this year.

“HSDPA is a natural evolution of the 3G UMTS standard,” said John Leonard, director of UMTS portfolio product management at Lucent Technologies. “If you're competing in a market and EV-DO is there, no other technology right now competes with it. The GSM guys are going to have to counter [Verizon Wireless' launch] with something more competitive.”

HSDPA was part of the 3GPP WCDMA/UMTS standard Release 5 approved back in 1999, when it seemed that investment in the technology could lie right around the corner, an expectation that eventually disappeared as carriers slowed their mobile data evolutions.

HSDPA can be implemented mostly as a software upgrade in UMTS networks, though some hardware might be required in other cases. “It impacts the channel card, base station and base station controller, so it depends on the UMTS platform the carrier has deployed,” Leonard said, adding that Lucent could upgrade its own UMTS equipment to HSDPA completely through software enhancements. The technology also requires HSDPA-enabled handsets.

The speed and the technology's inherent network efficiencies may be worth the investment. HSDPA is expected to have an average data rate of about 4 Mb/s to 8 Mb/s, making it at least twice the data rate of EV-DO.

The technology also could eventually reach peak data rates near 14 Mb/s, according to Leonard, though the standard calls for a peak speed of 10 Mb/s.

At the Wireless 2004 trade show in March, vendors were buzzing about HSDPA because they believe that competitive pressure will lend new urgency to long-delayed carrier investments in both UMTS and HSDPA.

“Verizon making its EV-DO announcement really changes the landscape for EDGE, UMTS and HSDPA,” said Dave Murashige, vice president of strategic marketing for wireless networks at Nortel Networks. “HSDPA is getting a strong push forward now, and UMTS with it.”

Mary Chan, vice president of research and development for mobility at Lucent, added, “HSDPA really enhances content as a quality service. Companies moving to HSDPA will be trying to get the video piece of their service offerings in place.”

Chan's team at Bell Labs recently developed a “turbo” decoding chipset that will help future handset designs take full advantage of the newly enriched services. Qualcomm and Nokia also are working on HSDPA chipsets for handsets.

However, greater bandwidth for richer applications is not the only benefit of HSDPA. It also provides operational advantages that increase in value as more and more mobile customers adopt some form of data services.

In western Europe, for example, there is a lack of competitive pressure from CDMA-based networks as there is in the U.S., but carriers can realize more efficient use of existing data network facilities with HSDPA.

“If you don't have the competitive threat, your reason for deploying it could be that with HSDPA, you can cram more bits and more users of data into the same amount of spectrum,” Leonard said. “You can get more users on the network without spending more capital on hardware.”

HSDPA also offers improved latency over UMTS and other technologies, providing better support for new services. “With HSDPA, you can start thinking more seriously about a wireline replacement strategy,” Leonard said.

As the name suggests, HSDPA is all about enhancing the downlink portion of mobile data transmissions, such as accessing the Internet and downloading content. Having those same improvements upstream isn't as important in today's mobile data market, but that will eventually change with the arrival of voice over IP, push-to-talk related applications and peer-to-peer data uploading.

For that upstream evolution, there also is an uplink upgrade solution for UMTS on the horizon. HSDPA's sister, enhanced uplink data channel (EUDCH) technology, might help combat the perception that mobile data networks can't support consistent quality of service for packet-based voice applications.

An EUDCH standard will be approved by the end of this year, according to the UMTS world trade organization.

For now, HSDPA is in carrier labs going through early testing. Most network operators generally won't say right now what their plans are for HSDPA. Bill Clift, chief technology officer at Cingular, acknowledged that the carrier is “looking” at HSDPA, but remains focused on its current EDGE deployment and developing plans for UMTS trials to follow. However, some industry watchers believe that Cingular's pending acquisition of AT&T Wireless could change or accelerate Cingular's evolution to UMTS and other technologies.

Lucent's Leonard said the combined entity would be in a better spectrum position to deploy HSDPA. “If there's a bottleneck for HSDPA, it might be that some carriers don't think they have the spectrum for an upgrade,” he said. “A Cingular/AT&T Wireless merger would relieve that concern for those two companies.”

Following the lab testing stage, the mobile industry is likely to see carrier field trials of HSDPA later this year, with commercial deployments and handset availability happening in late 2005. Japan's NTT DoCoMo is so far the only carrier that has committed to eventually deploy HSDPA, a project that probably will begin next year.

As is typical in the mobile industry, Asian carriers that already have started deploying UMTS probably will be among the first to adopt HSDPA. Surprisingly, however, U.S. GSM carriers could be next, with European carriers making the transition later, Leonard said. “In the U.S., with the NextWave spectrum becoming available and market consolidation, this could be easier to do,” he said.

The U.K.-based ARC Group market has predicted there could be a $3 billion worldwide market for HSDPA by 2007, though the agency lumps HSDPA in with 3.5G solutions such as integrated cellular/Wi-Fi in making that forecast. However, Leonard didn't want to over-hype HSDPA as something above 3G. “We have to be careful here,” he said. “Trying to look three years out just tends to give everybody headaches.”