Testing: Ensuring LTE Advanced Goes Without a Hitch

Tue, 12/10/2013 - 2:31pm
Andrew Berg

LTE Advanced may bring a number of new features to mobile networks. Carrier aggregation and Voice over LTE (VoLTE) are two aspects of the standard that have arguably created the biggest Mike Keeleyheadlines recently and for good reason. Carrier Aggregation promises more efficient use of disparate spectrum, while many see a carrier-grade VoLTE a possible way for operators to regain some of the revenue they’ve lost on the voice side their businesses. Still, these are features that come with some big challenges, which means testing will be key to moving forward with LTE Advanced. 

Mike Keeley, Director of Spirent Communications CDMA product segment, says features like carrier aggregation are a must for carriers seeking to make the most of their limited, and fragmented, spectrum allocations. 

“If they can’t seamlessly take advantage of this fragmented spectrum, they’re going to be in trouble,” Keeley said. “Carrier aggregation sounds like a nice way to solve that, but it comes with some pretty significant challenges.” 

Part of the problem with testing carrier aggregation is the sheer number of possible combinations. Keeley estimates there are already greater than 40 frequency bands designated for LTE. The last time Keeley checked, he says there were no less than 38 band combinations that were proposed for possible carrier aggregation scenarios. The complexities involved are pretty apparent. 

“I’m not a UE manufacturer, but if I was a UE manufacturer, steam would be coming out of my ears trying to figure out how to design a device that potentially will have to roam globally and end up using some number of those combinations over time,” Keeley quips. 

Right now, Spirent is attempting to create solutions that can test for this fragmented environment that will allow device manufacturers to ensure that one band isn’t interfering with the other band, at least from an RF perspective. Things get even more complex when you consider that each operator may need to test for multiple combinations. 

“In our U.S. ecosystem, the frequency is not consistent across an operator. So you may very well end up with different scenarios within an operator,” Keeley says. “So, in some cases, Band 17 may be your primary band and Band 4 is your secondary band, and then you go to another part of the country and that flip flops. So there’s just a staggering number of permutations that have to be addressed.”

When carrier aggregation was first introduced in Release 10 it brought with a finite number of carrier combinations that were defined. Those pairings didn’t include the combinations required by those carriers looking to use the technology, so Release 11 will bring with a number of new pairings. 

Another thing that complicates carrier aggregation is its newness and the fact that it hasn’t been proven out with any extensive deployments. South Korea has deployed the technology on a limited basis in smaller markets but other than that there’s very little real-world examples for operators to learn from. 

Keeley says that deployment was probably more to prove the technology than anything, and he says that regardless of the challenges ahead, operators in the United States don’t have a choice but to follow close on the heels of the South Koreans. 

“[The U.S. carriers] are already seeing issues with using up the spectrum they’ve got. They’re already at capacity…so I don’t see how they could not take advantage of carrier aggregation technology going forward,” Keeley said. 

On the VoLTE side of things, Spirent has been working closely with a number of operators to prove out a robust, carrier-grade IP-based voice product. He says he’s confident that VoLTE will produce a better quality of experience for end users than the traditional circuit-switched call. 

Keeley says that one of the biggest things that’s changing with the move to all IP networks is that the smarts of the call—routing, setup etc.—are being handled as much by the device as by the core network itself. 

“What we’ve seen…is that it’s created a whole host of new IOT [Interoperability] issues. So now it’s no longer sufficient to verify that the Device A can successfully interoperate with the network. Now, it’s essential that Device A be interoperable with Device B,” Keeley explains. “We’ve been involved in situations with VoLTE testing, where Device A could not set up a call with Device B because of IOT issues.” 

In the end, Keeley says that carrier aggregation and VoLTE are just two pieces of a whole and both need to be refined to provide users with a smooth-running network. He says that ensuring that things like carrrier aggregation are properly deployed is not just a matter spectrum efficiency, but of providing customers with a decent quality of experience.  

"What does carrier aggregation mean? Well, you’re now transmitting or receiving on two carriers simultaneously? That sounds like it has the potential to chew up more battery,” Keeley proposes.  

To that point, Keeley says Spirent was recently privy to a survey that queried smartphone user’s expectations for battery life, which revealed that at least 75 percent of respondents expected 24 hours of juice. He says that carrier aggregation needs to be implemented right or those users will be left with a less than satisfactory experience. 

“They’re already seeing a situation with battery life where actual experience is probably less than what 75 percent of the population expects, even before you add carrier aggregation.” 

Before you hit ‘Buy’ on that external battery case, Keeley says Spirent has a product that will monitor the relationship between carrier aggregation and battery drain before operators put the technology to use. 

“So we’ll be able to show what battery drain was before carrier aggregation, and then what the impact was after carrier aggregation,” Keeley says. 

As is the purpose of all testing, the endgame is to identify the problem and fix it before going to market with a new product. Hopefully that’s the case as operators consider employing the many useful new tools included in LTE Advanced.



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