Small cells are meant to boost mobile network coverage and capacity, but they can actually hurt network performance if they cause interference. Test equipment makers say that small cells make network testing more important than ever. The testing process is changing in at least three ways:
1. Self-organizing network technology is critical.
Paul Denisowski, senior applications engineer at test equipment maker Rohde & Schwarz, said that while most tower sites are deployed with an awareness of other tower locations, this is not always true for small cells.
“Towers have neighbor lists, sites are configured in such a way that they understand that there are other sites in this area, other sectors, whereas with small cells you can kind of set them up anywhere,” Denisowski said. “We all tend to think of small cells from a user point of view as something good … you fill in the coverage holes, get more throughput, etcetera, but it is to a certain extent a planning nightmare because now you have all these little cells. How do manage that? How do you make sure they’re not interfering with each other? How do you make sure they’re optimized to provide coverage and give you a net plus in terms of performance?”
Denisowski said that when operators discover signal disruptions in the network, a “rogue small cell” has to be considered as one of the possible causes. He said that even though operators have a good understanding of how to plan networks up front, testing them is an iterative process.
“It’s really important that we deploy small cells in such a way as to improve coverage, bearing in mind that they absolutely have the potential to impact coverage, and I think the network operators understand this,” he said. “I’m not sure there’s a clear understanding of how to deal with this issue other than by trial and error at this point.”
The solution lies in self-organizing networks, Denisowski said. He said right now SON technology is well understood at the macro level, and next the technology needs to be built into small cell networks.
2. Interoperability testing is more important.
Small cells are often deployed in a multi-vendor environment, increasing the need for interoperability testing.
“Interoperability is a significant concern,” said Accedian Networks’ Scott Sumner, VP of solutions development and marketing. He added that there are three main areas of concern. “One is radio and rate compatibility (3G, LTE, LTE-A, frequencies, etc.) between small cells and macro-cells, as well as between indoor/outdoor,” he said. “Two is SON capabilities – to date, no standards have been finalized, and each vendor has their own approach. This limits the ability for operators to roll out multi-vendor solutions in a uniform way. Three is performance visibility – wide range of support, degree of implementation of standards-based test protocols and technologies, makes managing multi-vendor networks a challenge.”
3. Fiber testing is more important.
Fiber connects many outdoor small cells and distributed antennas to a headend or remote baseband unit. Network testers who are comfortable testing cable are now learning how to perform line sweeps with fiber.
“We’re basically characterizing the fiber system, looking for maximum throughput through the fiber, so an improperly spliced connector or poorly fusion-spliced cable in the system, or other losses that might be additive such as multiple connection points – those can be very detrimental to oDAS,” said Dennis Burt, lead DAS trainer for Anritsu. “So it does take somebody who’s really qualified and knows what they’re doing to make sure that fiber system is installed such that it meets or exceeds vendor and customer expectations.”
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