As network operators furtively roll out 5G services, the cellular communications industry is learning about 5G on the fly, finding one unexpected challenge after another. It’s more difficult than they had anticipated, and in response they’re incurring greater startup costs than they’d originally budgeted for.

One ray of sunshine: millimeter wave (mmWave) signals are more robust than many had feared. So far it seems the worries about rain fade and soft obstructions, such as foliage, were overblown.

A critical element of 5G is virtualizing the network, with the goal of making communications networks endlessly configurable to suit the various and changing needs of network users. On-demand network reconfigurability creates a need to make sure that each new configuration is delivering what was ordered. By definition, testing in advance is not possible.

5G has qualities new to cellular communications, including network configurability and lower latency that presage innumerable potential new uses, but the first impression most people are going to have of 5G is going to be with familiar telephony and broadband services. It would be bad for carriers if phone and internet on 5G networks aren’t appreciably better than they are on 4G. Services on 5G had better not be worse.

Carriers are consequently calling on their T&M partners to extend their test capabilities from the lab into the network itself, to a) make sure the technology works when installed and b) new services perform as advertised when they’re spun up.

They’re worried that “the radio technology might not deliver on day one,” noted Steve Douglas, the head of Spirent’s 5G practice. Consequently, carriers find themselves having to invest more heavily in network operations, incurring startup costs they hadn’t anticipated, he explained.

“Our customers, especially the large service providers, were asking us if we can help them with the operation of the network,” he said. “Not just test, but how to launch, and how to operationally assure they’re delivering, whether its quality, performance, or meeting SLAs.”

Some T&M companies have responded by virtualizing their test capabilities so that they can be instantiated anywhere within a network.

Spirent has virtualized much of its test functionality, and has also set up cloud access to some of its test resources, Douglas explained.

“We’re seeing this complexity of the network being a bigger headache than a lot of our customers thought,” Douglas said. “They knew using the new frequency ranges was going to be difficult enough, but the technology of the radios is a lot more complex than they anticipated.”

He noted that many of challenges with handsets that have been revealed in recent months persist. In 4G, there might be a 4G antenna, one for GPS, one for Wi-Fi, and one for Bluetooth. 5G handsets need all of those along with multiple antennas for 5G.

The problems all those antennas cause start with a simple shortage of real estate. Handset manufacturers are having a difficult time cramming all those antennas in. Douglas said Spirent is working with some of those manufacturers to lay out and miniaturize handset electronics.

“We’re also starting to see the impact of multi-antenna interference, because suddenly we have to have additional cellular antennas,” Douglas said. “They utilize the multi-MIMO architecture that 5G brings. Because there’s so many of them, and they’re so compact, we see them interfering, for example with GPS. Some of the early prototype smartphones we’re working with, we see cellular degrading the performance of the GPS signal. It’s very detrimental at the moment, so we’re working with those guys on that.”

On the network system side, Douglas said, “there’s an arms race,” and manufacturers feel they need to start shipping commercial equipment fast – so fast some are cutting the length of their ordinary production cycles in half. The result is that the equipment coming available isn’t as robust as it could be, he said.

Some of Spirent’s Tier 1 customers in the US are in the process of deploying their first base stations, and Spirent is helping them figure out optimal configurations to ensure 5G performance. If carriers are going to be charging more for 5G, they have to ensure “new data speeds are visibly different from 4G,” Douglas said.

When it comes to the various slices of spectrum that can be used, Douglas said that mmWave bands do in fact experience some signal degradation, but it’s not as bad as feared. Carriers had backed off the notion of using mmWave spectrum for fixed wireless broadband, but given the encouraging results of mmWave tests so far, Douglas said some of Spirent’s customers are reconsidering.

Nonetheless, mmWaves don’t propagate as far and carriers who rely on mmWave bands will have to install more base stations. Cocktail napkin math says it might be anywhere from 4× to 9× more, but Douglas said a model of Vancouver, BC suggested the number might be as high as 30×.

The factor might be lower in more densely populated areas and more frequently trafficked environments, which would do little to undermine the practicality of 5G, but there’s a question if installing that many more base stations will be justifiable in suburban and rural areas, where the utilization rates of the equipment are guaranteed to be lower.

Douglas said there’s a couple possibilities that are being considered. One would be virtualizing parts of the radio. He said it might be possible to take as much as 50 percent of the processing off the base station and move it into the cloud. The potential downside is whether that will slow network traffic too much. He said several Spirent customers are investigating the arrangement.

The other is mesh networking, an architectural option for 5G networks that will be defined in the next round of 3GPP 5G standards. The idea is to have three or four base station nodes that connect to each other wirelessly-only, all relaying to a central base station that would be the only one in each base station cluster that would connect to the fiber network. Again, the approach would have to be tested to verify that network performance can be maintained.

Another entirely unanticipated issue, Douglas said, was that MIMO antennas are physically big and much heavier than 4G antennas – so heavy that the additional weight can exceed what rooftops and other mounting sites can bear. “It actually breaks some of the planning rules. Sometimes they have to reinforce roofs; an interesting thing a lot of us probably never thought about.”

EDN editor-in-chief Brian Santo has been writing about science and technology for over 30 years, covering cable networks, broadband, wireless, the Internet of things, T&M, semiconductors, consumer electronics, and more. 

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