The xRAN Forum released its first specification dedicated to virtualizing the fronthaul portion of the network. Fronthaul is the interface that delivers traffic from the baseband units (BBUs) and the remote radio heads.
The specification will drive interoperability between baseband units and the remote radio heads, even if they are from different vendors. According to Sachin Katti, a professor at Stanford University who heads up the xRAN Forum and is in charge of the technical steering committee, the group’s operator members wanted to be able to use different radio heads from different vendors and have them work with existing BBUs. “They wanted a spec that could provide true interoperability because interoperability is not possible today,” Katti said.
The spec also provides guidelines for efficient bandwidth scaling as a function of user throughput and spatial layers. Katti said that this was needed as operators face growing bandwidth demands and also to support deployment of massive multiple-input multiple-output (MIMO) beamforming antennas.
And while this spec will be critical for upcoming 5G deployments, it also can be applied to 4G networks today. “Operators are trying to test these massive MIMO systems that are out there,” Katti explained.
Interestingly, Verizon chaired the fronthaul working group that developed the spec. Katti said that the operator was pushing hard for this specification and was instrumental in getting the fronthaul specification started because initially the xRAN Forum didn’t have a fronthaul working group. “They were instrumental in getting this off the ground,” Katti said, adding that other operators were very involved in the process including AT&T and NTT DoCoMo.
But Verizon is also pushing ahead with its own virtual RAN initiative. In February, the company announced it was teaming with Intel and Nokia to develop a vRAN architecture that will be based upon Verizon’s vRAN 1.0 that it used in a trial in Oklahoma City. For that trial, Nokia built a cloud RAN (C-RAN) software platform for Verizon’s commercial cloud infrastructure using COTS hardware. A Verizon spokesman said that the two efforts are complimentary. “The press release on xRAN is a step towards supporting broad ecosystem enablement of Open RAN across the industry, leveraging key operators and partners, to ensure the way in which the industry virtualizes moves towards a standard approach.”
The xRAN Forum was formed in 2016, and this is the first specification the group has released. Interestingly, in February the group announced it was merging with the C-RAN Alliance to form the ORAN Alliance. According to a xRAN Forum spokesperson, that name change and merger is still happening but probably won’t be finalized until June.
Noticeably absent from the vendor membership is Ericsson, a key partner for many of the operator members. At Mobile World Congress 2018, Ericsson CEO Borje Ekholm deflected questions about Ericsson’s efforts to virtualize the RAN by only saying that this was something Ericsson would have to take a look at.