Testing Vendors Adapt to LTE, Interoperability
Here’s a key takeaway from the exhibits in the testing solutions pavilion: As a standard, LTE has a simpler architecture and is more efficient than legacy technologies. But that doesn’t mean testing it is a cakewalk.
"There's a tremendous amount of complexity around testing these air interface techniques on which the performance of LTE is very dependent," says Spirent Vice President of Product Marketing Nigel Wright, referring to MIMO configurations that use multiple antennas on both base stations and devices.
And on top of LTE's air interface intricacies, "there are all kinds of potential for interoperability issues" between legacy technologies and new IMS-enabled services like VoLTE, the standards for which "still leaves us with an awful lot of room for interpretation," Wright says.
As operators work to ensure the quality of these new services, “there’s kind of an exponential increase in the complexity of the average interaction between the device and the network, and all the services running over them,” he says.
Take MIMO, for instance. It’s a key feature of LTE that uses multiple-input, multiple-output antennas to increase network performance.
Vendors have made MIMO-specific adaptations to their solutions and equipment to support the technology. For example, Anritsu’s MD8430A signaling tester has four RFs to support 2x2 MIMO and companies like Azimuth Systems and EB Elektrobit are stepping up with channel emulation technology designed to test whether MIMO is performing as expected.
“LTE depends on MIMO performance, and MIMO is even more dependent on the correlation of multiple spacial channels than a 2G or a 3G protocol,” says Erik Org, who heads up marketing at Azimuth.
Then there’s the sheer volume of information that can be gleaned from LTE.
“The amount of data that we get for LTE is far more voluminous than we get for 3G technologies,” says Goodman Networks engineering executive Manmohan Chima.
Instead of limited tidbits of data at the beginning and end of each session, LTE provides vendors with a veritable gold mine of information about network and device performance, what kind of mobile content is traversing their infrastructure and the kind of experience their customers are having.
With older generations of cellular technology, the data sources were “single tine – at the beginning or end of a call, but not a particularly rich data set. With LTE we can work the information on a real-time basis and get a much richer data source during the course of an entire event,” says Warren Dumanski, vice president of sales and marketing at Newfield Wireless.
Handling all this information required Newfield to overhaul the architecture of its TrueCall platform. “The architecture is fundamentally different than for legacy technologies because of the volume, the richness and the capability to recreate the entire call event from start to finish,” Dumanski says.
LTE-related overhauls don’t stop with the vendors – it extends into lab testing as well.
Gwyn McNew, engineering manager of wireless at third-party testing lab Intertek, says the company uses four different platforms for LTE because testing technology just isn’t mature yet.
For perspective, Intertek uses just a single platform from Spirent for CDMA testing. Spirent has long dominated the CDMA test market.
"It's par for the course considering the relative time frame that LTE was introduced versus CDMA – we had a decade to work out the kinks in CDMA. There was such an emphasis to launch LTE, the timeframe was maybe a fifth of that," McNew says. "There are going to be maturity issues that are going to have to be dealt with."
Intertek has invested "millions" in the four platforms it currently uses for LTE because each has their own area of specialization and may not be fully mature, only covering a portion of what needs to be tested. It is considering adding additional platforms to its roster.
Spirent agreed with McNew’s characterization. Because conformance testing for LTE is still “relatively immature,” getting the widest coverage may require multiple platforms to get best-of-breed for each test area, Wright says.
LTE is still pretty fresh on the scene, and the testing community is working to harden its solutions even as operators go full-bore ahead with their deployments.
So is this a bad thing? Not at all, says Wright: “I dare say the industry will figure it all out in the end – it's all really good news from a test vendor perspective.