Hot in 2020: 5G mobile fronthaul, backhaul choices

Jan. 22, 2020
Last year saw the first roll outs of true 5G networks; this year should see more of the same. But that doesn’t mean every service provider has a 5G deployment strategy in place.

Lightwave recently conducted interviews with technology experts on the major trends that will drive optical communications technology deployment and development in 2020. The result will be a series of articles on some of these trends, beginning with the subject top of mind among many if not most communications services providers: how to roll out 5G infrastructure.

Last year saw the first roll outs of true 5G networks; this year should see more of the same. But that doesn’t mean every service provider has a 5G deployment strategy in place – or has determined how to deal with the ramifications of 5G traffic demands on the rest of the network.

This uncertainty is certainly present in the minds of many customers of Tejas Networks, a communications technology provider headquartered in India whose customer base extends throughout Southeast Asia, Africa, and in parts of Latin America. “Some of our customers whom I've talked to as late as like three or four months ago, they don't know what their 5G deployment will be, which version of eCPRI and so on,” says Dr. Kumar N. Sivarajan, CTO of Tejas Networks, in regards to fronthaul strategies. “So they're broadly preparing for having to fronthaul Ethernet with a very tight timing constraint.”

These network operators are thinking along two lines, according to Dr. Sivarajan. “If you make the packet size small then you don't have to do time-sensitive networking. So that gets a lot of discussion,” he reports. “But the more popular option for somebody who wants to deploy in 2020 is just OTN. OTN in the fronthaul will meet the timing, the jitter constraints, and so on. And so multiplexing that can carry eCPRI or OTN – it is really Ethernet over OTN, ODUflex, or something – will meet the requirements. But I think initial deployments of fronthaul may happen on OTN until the time-sensitive networking gets more established.”

The same packet versus OTN discussion will occur for 5G backhaul as well, Dr. Sivarajan predicts. (“I don’t think there’ll be a midhaul,” he states.) The decision of where to use one versus the other will be influenced by how high transmission rates climb. Dr. Sivarajan says his customers are looking at both 25G and 100G networking. “Of course, OTN makes sense at 100G. I would say in the backhaul there are more takers for packet than OTN, but OTN is an interesting option,” he says.

Meanwhile, members of the PON community have suggested 10G PON technology could play a role in 5G mobile network roll outs. Dr. Sivarajan says that XGS-PON should have the horsepower to at least be considered for fronthaul applications. However, “I have not found it exciting so far for many customers,” he reports.

Change ripples toward the back

But prepping for 5G requires changes in other parts of the service provider infrastructure beyond radio access networks. “5G is a combination of a lot more traffic, a lot more radios, lower latency, and with the increased bandwidth that 5G provides, content continuing to move closer and closer to the user. And so that becomes a forcing function that drives network architecture changes for the operator,” comments Glenn Laxdal, senior vice president of disaggregated, edge, and access solutions at Infinera (NASDAQ:INFN). “Commensurate with that or consistent with that is the whole shift to mobility. All data is being consumed by mobile devices and so the data patterns, the traffic patterns, are becoming much more non-deterministic and variable. And so I've got to lay in bandwidth now in a much more distributed away than we've had to in the past.”

Stephen Alexander, senior vice president and CTO at Ciena Corp. (NYSE: CIEN), says that the need to meet the demands of mobile content consumers combines with carriers’ desire to support cloud-based service provision to move computing resources closer to the edge. Latency requirements now range from 30 to 100 msec, he reports, but he foresees network operators architecting their metro networks to 10-msec latency levels. Network architectures will have to support the latency demands of a variety of applications, depending on the service involved, according to Alexander.

Laxdal also foresees operators moving data center resources closer to the edge. “Operators need to do this both to reduce the cost of delivering the applications and content to the end user, but to improve the performance and reduce the latency of delivering the content to the end user,” he explains.

Alexander and Laxdal see operators embracing network automation to help their infrastructures keep pace with requirements; Alexander points to virtualization in the 5G core as an example. The move toward virtualization and software-defined networking (SDN) – the separation of the control plane from the data plane and software from hardware – also is changing the way some operators buy and specify 5G-related systems, Laxdal points out. He cites Telefónica’s adoption of the Telecom Infra Project’s Disaggregated Cell Site Gateway as an example of this trend (see “Telefónica rolls out Telecom Infra Project’s Disaggregated Cell Site Gateway”; AT&T has taken a similar approach via the Open Compute Project – see “AT&T shows off Ufi Space white box cell site gateway router based on OCP specifications”).

However, Alexander doesn’t believe more than a handful of very large operators will decide to become their own systems integrators and developers of 5G-related technology. But he foresees more operators asking their technology suppliers to deliver similar “data center style” systems and software flexibility.

For related articles, visit the 5G Mobile Topic Center.

For more information on high-speed transmission systems and suppliers, visit the Lightwave Buyer’s Guide.

To stay abreast of fiber network deployments, subscribe to Lightwave’s Service Providers and Datacom/Data Center newsletters.

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