BARCELONA -- Mobile World Congress --Of all the mobile carrier network technologies demanding particular attention from operators here this week, dual-carrier HSPA+ looks set to be high up carrier CxO lists.

There's good reason for that: Operators need to boost the capacity of their mobile broadband connections to meet the growing needs of smartphone and other 3G device users, and dual-carrier technology looks like the next best step to boost cellular data access links.

Dual-carrier (or dual-cell) is not new -- it was demonstrated at last year's event -- but is now coming into sharp focus as it becomes commercially available, the need for bandwidth-boosting techniques increases, and other approaches encounter some deployment issues.

The technique, in simple terms, involves bonding or aggregating two adjacent 5MHz channels to double the capacity of a data connection to an end user. So the technique doesn't add additional capacity to the cell, it multiplexes the existing capacity to cope with bursty data traffic -- it's a way of optimizing the use of existing capacity to meet subscriber bandwidth real-time needs.

Gabriel Brown, senior analyst at Heavy Reading and someone who lives and breathes mobile network developments (though he doesn't eat them), says "there's a lot of interest from carriers, because they're looking for evolved HSPA capabilities to deliver better mobile broadband speeds to their customers, and dual-carrier capabilities is one of the ways that can be achieved."

Brown notes that, "with HSPA, one way to boost the bandwidth is with better modulation. That's a relatively simple software upgrade for the base station that's already being rolled out, and which enables peak downstream speeds of 21 Mbit/s." (See Telefónica Picks Sierra Wireless, Rogers Rolls Out HSPA+, Teams With MTS, and DNA Preps HSPA+ Rollout, for example.)

That means, then, that adding dual-carrier HSPA+ capabilities to a network enhanced by better modulation would enable peak downstream speeds of 42 Mbit/s.

Brown continues: "The assumption was that, to take HSPA to the next level, MIMO [multiple-input and multiple-output] capabilities would be deployed. But MIMO has hit a few speed bumps, for various reasons, and the industry isn't moving to MIMO as quickly as previously anticipated. For MIMO, new antennas are needed at the cell site and in the end user devices. There are also concerns about interference, and these are proving hard to overcome."

As a result, says Brown, "currently, dual-carrier is in the ascendancy, and is the next technology option that's likely to be deployed next to help carriers achieve higher data rates."

The analyst notes that base stations can be upgraded with a new software release to enable them for dual-carrier, "so no new boards are needed," notes Brown. For the customer equipment, chip vendors such as Qualcomm Inc. (Nasdaq: QCOM) and ST-Ericsson have developed chips: Novatel Wireless Inc. (Nasdaq: NVTL), for example, is using Qualcomm chips in its dual-carrier HSPA+ devices. (See Novatel Touts Dual-Carrier HSPA+.)

Ultimately, dual-carrier is "a good solution for managing data traffic and for improving average user performance," says Brown. "It's better for the carriers and better for their customers, and, unlike MIMO, it doesn't involve the addition of new antennas or increase power requirements. So there's strong interest in dual-carrier capabilities from the carriers."

So who can deliver the network capabilities? The leading mobile network equipment vendors are (nearly) ready to oblige, and are battling to command thought and technical leadership in this evolutionary niche. And some are even taking the approach to the next level already by demonstrating quad-carrier capabilities.

Ericsson AB (Nasdaq: ERIC), for example, already has dual-carrier HSPA+ installed at Telstra Corp. Ltd. (ASX: TLS; NZK: TLS) in Australia and at 3 Group 's operations in Sweden and Denmark, while Vodafone Portugal is checking out the technology. (See 3 Pushes 3G Speed.)

The Swedish vendor is showing off its dual-carrier capabilities here in Barcelona (as it did last year), as well as its MIMO capabilities, and is even demonstrating quad-carrier capabilities with an LTE system. (See Ericsson Claims LTE Speed Record.)

Ericsson says its base stations are ready to deliver 84-Mbit/s peak data rates through the combination of dual-carrier HSPA+ and MIMO.

Nokia Networks says it will offer commercial dual-carrier HSPA+ upgrades during the first half of 2010, and says it's currently in trials with a number of operators, though it can't disclose their identities. Japan's SoftBank Mobile Corp. , though, has committed to deploying NSN's upgrade. (See Softbank Does HSPA+ With NSN.)

NSN is also demonstrating quad-carrier HSPA+ here in Barcelona. (See NSN Demos 112M HSPA+.)

Alcatel-Lucent (NYSE: ALU) says it has developed dual-carrier HSPA+ capabilities, and is working toward trials with carriers that will begin around mid-2010.

Huawei Technologies Co. Ltd. , meanwhile, has dual-carrier HSPA+ developed, and recently completed interoperability tests with Qualcomm. The Chinese vendor says its solution is now ready for "commercial deployment." (See Huawei, Qualcomm Push HSPA+ Speed.)

— Ray Le Maistre, International Managing Editor, Light Reading