LTE's Next Step
LTE-Advanced offers advantages over its predecessor, but it might be a bit early to start thinking about “5G.”
The industry had barely begun rolling out LTE before it started talking about the next generation of the technology, LTE-Advanced. Sprint was the first to go public with its intentions, saying last fall that its then-unbuilt LTE network would be "LTE-Advanced-ready."
Clearwire soon followed suit, along with AT&T and Verizon Wireless. And this spring, T-Mobile USA said the LTE network it was building on spectrum gleaned from its failed merger with AT&T would employ "Release 10 compatible equipment," positioning itself for an eventual transition to the technology's next iteration.
So what's so special about LTE-Advanced?
“It’s an evolution from LTE, and with that comes a dramatic increase in peak, average and cell edge performance,” 4G Americas President Chris Pearson says. It allows operators to make better use of scarce spectrum resources without a major overhaul of their network – upgrading to LTE-Advanced is more akin to the transition from HSPA to HSPA+ than the move from 2G to 3G.
As Pearson explains it, operators can approach the standard as one would peruse a restaurant menu, picking and choosing only the items they want. “You don’t have to do everything that’s in there to get some great benefits,” he says.
Some features of the standard hold more near-term appeal than others, namely carrier aggregation, enhanced MIMO, new interference management techniques and methods to improve the performance of heterogeneous networks.
Carrier aggregation is probably the one you’ve heard the most about – when Sprint said its network would be LTE-Advanced-ready, it meant that it would be able to support carrier aggregation.
Carrier aggregation bonds together disparate swaths of spectrum into a single channel, allowing spectrum-starved operators to make their pipes fatter. In fact, the technique is critical to meeting the International Telecommunications Union standard for IMT-Advanced technologies offering "true" 4G speeds of 1 Gbps when the user is in a relatively stationary position.
“In North America especially, spectrum is at a premium and operators have a mixed bag, so the ability to bind those together is quite attractive,” says Andrew Green, vice president of marketing at Sierra Wireless.
For instance, Sprint’s LTE network starts off with a 5x5 deployment in the PCS band and then adds in some 800 MHz spectrum repurposed from its iDEN network, which is in the process of being phased out in favor of a CDMA-based push-to-talk network. Its ultimate goal, says Sprint network executive Bob Azzi, is to operate its LTE network as if it’s running on a 10x10 chunk of spectrum, which will require Sprint to bond its channels together through carrier aggregation.
“All the equipment we’re putting out there will accommodate the future capabilities of LTE-Advanced,” Azzi says. Sprint’s first flavor of LTE will use Release 9, but it’s planning on a quick transition to Release 10. “It’s ready for the next release.”
While Sprint has been the most public about its plans to use carrier aggregation, AT&T, Verizon Wireless and T-Mobile USA haven't said what features of LTE-Advanced they plan to implement. However, they all could potentially benefit from the technique.
For instance, AT&T told the FCC it plans to bond Qualcomm’s 700 MHz Flo TV spectrum with its 1900 MHz and 850 MHz holdings to supplement capacity on its LTE network, a feat that will necessitate the use of carrier aggregation. Why not pair the Flo spectrum with AT&T’s other 700 MHz holdings? “AT&T has no plans to bond the Qualcomm Spectrum with Lower 700 MHz B and C block spectrum due to self-interference concerns within a device,” Kris Rinne, AT&T’s senior vice president of architecture and planning, said in a letter to the FCC during its review of the Flo TV transaction.
Verizon, too, could make handy use of carrier aggregation. The company is in the process of trying to close a deal that would give it nationwide AWS spectrum, airwaves it says it plans to use for its LTE network, which currently runs on the 700 MHz band. Using carrier aggregation to bond its AWS and 700 MHz holdings could allow the separate swaths of spectrum into a single, larger channel.
Carrier aggregation is expected to be one of the earliest features of LTE-Advanced to be adopted by carriers, but it’s not the only one being eyed by the industry.
Another feature that could be beneficial to operators is enhanced MIMO, which juices up the performance of multiple-input, multiple-output antennas. Instead of the baseline 2x2 MIMO configurations in Release 9, LTE-Advanced supports higher-order antennas with up to 8x8 on the downlink and 4x4 on the uplink.
Heterogenous networks, the combination of small cells, macro base stations and various connectivity standards known in industry shorthand as “hetnet,” also get a boost.
Hetnets create denser architecture with higher capacity than traditional macrocell deployments but raise a number of issues managing interference between the various picocells, femtocells and macrocells in the network. That’s where LTE-Advanced comes in.
The standard provides operators with new tools to manage interference, namely enhanced inter-cell resource and interference coordination (eICIC).
Another feature that is expected to be especially beneficial to inter-cell interference problems is coordinated multipoint, a complex technology that wasn’t included in Release 10 but is currently under consideration by the 3GPP for inclusion in Release 11.
Combining the jumbo-sized MIMO antennas and hetnets with better interference management technology could mean major improvements for peak data rates and efficiency gains, benefits multiplied by carrier aggregation.
“I expect carrier aggregation and eICIC to likely be the first LTE-Advanced features deployed and they will likely be deployed in very similar time frames,” says Jim Seymour, a senior director at Alcatel-Lucent’s wireless CTO organization.
The bottom line: Even implementing a few features from LTE-Advanced could boost speeds, increase capacity and make better use of spectrum.
This is all well and good, of course, but operators are looking for more than just ways to manage the veritable tsunami of data traffic coursing over their networks. They’re looking for ways to cash in on that data.
The Data/Revenue Discrepancy
Cisco's Visual Networking Index estimates global mobile data traffic more than doubled last year and forecasts an 18-fold increase by 2016.
Whether that forecast is high or low is a matter of debate, but one thing is certain: Operators aren't seeing revenue increase nearly as fast as they're seeing data traffic increase.
AT&T’s technology and network operations executive John Donovan said earlier this year that data traffic on its network has doubled every year since 2007, the year it got the iPhone. So has its data revenue doubled every year since 2007? Not by a long shot. Sprint, Verizon Wireless and pretty much every other carrier out there are fighting the same trend.
“It’s absolutely the biggest problem,” says In-Stat analyst Chris Kissel. “Data traffic globally is growing between 50 percent and 80 percent a year, but the revenues you’re going to be able to garner are in the upper single-digit range of growth.”
It’s unclear how far LTE-Advanced will go in addressing this discrepancy.
The technology could lower operators’ cost-per-bit, making it more profitable to keep up with customers’ insatiable demand for mobile data. But unless subscribers can be convinced to pay a premium for the extra services and speeds provided by LTE-Advanced – speeds that could vary considerably by provider – it’s unlikely to be a huge revenue generator.
“I don’t think of it in terms of revenue upside as much as enabling functionality,” says Serge Willenegger, vice president for product management at Qualcomm. “It provides carriers with some tools to try to differentiate their services and potentially increase revenue. But of course, the technology is just a technology.”
ABI Research analyst Phil Solis agrees. “LTE-Advanced addresses the issue, but is not enough by itself,” he says, explaining that operators will still need to be mindful of basics like Wi-Fi offload and using data caps to rein in usage.
Aside from the revenue conundrum, another big question is whether operators will be able to use LTE-Advanced to offer faster speeds, or whether the technology will merely allow them to keep pace with demand. The answer depends on which features of the standard operators deploy and how data-hungry their customers are.
Sprint, for one, says the extra capabilities will give it higher peak speeds, but it doesn’t necessarily intend to market its LTE network as being faster than the competition.
Azzi says the end goal is to ensure customer’s data rates hold steady even when the network is fully loaded. “Our objective is for a consistent customer experience,” he says. Using Clearwire’s TD-LTE network for offload and carrier aggregation will give Sprint’s LTE service “the same kind of performance characteristics as Verizon.”
Pearson isn’t so sure that early implementations of LTE-Advanced – such as only using a single feature like carrier aggregation – should be marketed to customers as performance improvements and is wary of marketing the service prematurely.
“I’m apprehensive when I hear people quoting ‘the standard is 1 Gbps on the downlink, 500 Mbps on the uplink. We shouldn’t be out there promising that kind of thing to users,” Pearson says. “But to talk about features and how they’re going to help operators and in the end help customers? I think that’s great. I just want to make sure we’re not overpromising to the end user.”
A word to the wise for marketing departments eager to jump to “5G”: It might be wise to back off for awhile.