This article originally appeared in the May 2012 issue of INTERNET TELEPHONY magazine.

LTE (News - Alert) gets the lion’s share of the mobile broadband coverage these days, but it’s HSPA that is the most widely deployed mobile broadband technology.

Indeed, HSPA is used in more than 400 commercial networks in some 150 countries today.  And it’s forecast to be in use by more than 3.5 billion subscribers by the end of 2016. In North America, HSPA passed the 100 million connections mark by the end of 2011, Informa (News - Alert) Telecoms & Media recently reported.

AT&T is employing HSPA as part of its LTE mobile strategy here in the U.S. The company has deployed HSPA+ to virtually 100 percent of its network, an AT&T (News - Alert) spokeswoman tells INTERNET TELEPHONY.

“It’s important to us that our customers have a consistently fast mobile Internet experience,” says AT&T’s Jackie Janus. “Customers of competitors who went straight to 4G LTE without upgrading the speeds on their existing network will see a steep drop-off in speeds when they leave 4G LTE coverage areas. Our customers will have a more consistent speed experience as they move between 4G LTE and HSPA+ coverage areas.

“For example, LTE delivers speeds up to 10 times faster than 3G, and HSPA+ is up to four times faster,” she adds. “AT&T customers moving between the two will have a more consistent mobile Internet experience. Compare that to customers of competitors who haven’t made the speed upgrades we’ve made in recent years, and they are falling from LTE to EVDO.”

Many service providers abroad also are enjoying the benefits of HSPA. For example, 3 Italia recently upgraded its 3G mobile broadband access, core and transport network to 42mbps HSPA. (A 3 Italia commercial launch of 100mbps LTE is planned for later this year.)

Chris Pearson (News - Alert), president of 4G Americas, tells INTERNET TELEPHONY that LTE is deployed when a service provider gets additional spectrum, but that HSPA and HSPA+ are a great migration path that UMTS operators can jump on right now to lower their incremental costs and make more efficient use of their spectrum.

And that’s just what they’re doing. All UMTS and HSDPA networks are expected to be upgraded to HSPA, according to 4G Americas, an industry trade association focused on GSM- and LTE-related carriers, issues and technologies in North, Central and South America.

In case you’re not already familiar with HSPA, it’s a 3GPP technology that stands for high-speed packet access. It’s backward compatible with UMTS, EDGE and GPRS, which means that HSPA-enabled devices can default to these networks where HSPA is not available.

HSPA can deliver up to three times the capacity of UMTS networks, meaning carriers can add new services and customers without investing in new spectrum or an entirely new network. From a user perspective, HSPA typically provides downstream rates of 1 to 4mbps and upstream rates in the 500kbps to 2mbps range.

(Although, in late February, Ericsson (News - Alert) announced that it has developed a solution that triples uplink capacity in HSPA networks. The company has demonstrated that over-the-air uplink throughput for simultaneously active devices in a cell was increased from around 4mbps to more than 12mbps with the technology. “The demonstrated capacity is an unprecedented figure for a 5mHz WCDMA carrier,” according to an Ericsson press release, which explained these results were achievable through the combination of its commercially available receiver technology, Ericsson Interference Suppression, with 4-antenna radio base stations. "We have proven that Ericsson's unique Interference Suppression is a giant leap forward and it will be the new reference for WCDMA uplink performance for years to come,” says Nils Viklund, director of WCDMA RAN at Ericsson. “This can even be further enhanced by combining it with multi-receive antenna technologies. Because these technologies work with existing devices, operators that implement them will instantly benefit from the attractive gain.")

It gets even better with HSPA+, also known as high-speed packet access plus or HSPA Evolution. HSPA+ also brings a variety of new features to the table, including interactive services like push-to-talk, picture and video sharing, MIMO-enabled IP video and voice, and more.

The initial iteration of HSPA+, which employs 64 QAM, provides peak theoretical downlink throughput rates of 21.6mbps in 2X5mHz of spectrum. Typical user speeds for this are on the order of 1.9mbps to 8.8mbps on the downstream and 1 to 4mbps on the upstream. HSPA+ enhancements like dual-carrier operation can double that. And the next release (11) from the 3GPP on this promises peak theoretical speeds up to 336mbps.

4G Americas says that 43 percent of HSPA operators have upgraded to HSPA+, and nearly all are expected to go this route eventually.

Not only has HSPA technology enabled wireless broadband operators to address capacity needs in the age of the mobile boom and what say is a spectrum crunch, some also credit this technology as moving the industry forward at a point in which things were stalled.

A January 2012 item on Ericsson’s website reads as follows: “The development and early rollouts of HSPA marked the first lights of recovery in the darkness that enveloped mobile broadband in the early 2000s. Just how bright that mobile broadband light was to become surprised many as subscribers embraced the technology, especially through the arrival of the smartphone era.”

As of January 2012, there were 423 commercial HSPA networks in 160 countries worldwide; 184 commercial HSPA+ networks in 94 countries worldwide; 31 commercial HSPA+ networks in 19 countries in Latin America; and expectations of 2 billion UMTS-HSPA subscriptions worldwide as of mid-year 2014.