AT&T is moving closer to realizing its vision of deploying virtualized and open radio access network (RAN) architecture more broadly in its 5G network. 

A recent vRAN test in New Jersey riding on Nokia’s cloud-based vRAN 2.0 system is a key enabler of its open RAN vision, Mazin Gilbert, VP of network analytics and automation at AT&T, told SDxCentral.

The operator and vendor said they successfully initiated an end-to-end layer 3 data call using a fully virtualized cloud RAN. The proof of concept test was operated on a virtualized distributed unit (vDU) and a virtualized centralized unit (vCU) across different data transfer scenarios, including web browsing, video playback, and network speed test measurements, according to AT&T and Nokia.

Gilbert said the trial bolsters AT&T’s open RAN outlook because “it facilitates decoupling of baseband hardware and software and allows AT&T to tap into an open, multi-vendor commodity hardware ecosystem for baseband compute and acceleration.”

Nokia, which provided multiple pieces of hardware and software for the effort, was the only vendor involved in this test, but “AT&T is always evaluating best-of-breed solutions and drives multi-vendor where we believe it drives value in performance, cost, or operational efficiency,” Gilbert explained.

The Finnish vendor provided its AirScale Cloud RAN vRAN 2.0 baseband with vDU and vCU running in the cloud, and a fronthaul gateway and packet switch that were converted to connect existing common public radio interface (CPRI) based radios to the Ethernet-based enhanced CPRI (eCPRI) 7-2x split that provides the basis for the interoperability specification adopted by the O-RAN Alliance. 

“AT&T is working towards more extensively testing the performance, power, and operational considerations of vRAN in a limited production setting on live traffic to develop a data-driven understanding of the impact of vRAN for a brownfield operator such as AT&T,” Gilbert said.

Nokia and AT&T are also collaborating on the development of a near-real time RAN Intelligent Controller (RIC) with the O-RAN Alliance to bring more programmability to the RAN and trial xApp-based RAN capabilities fused with machine learning.

Gilbert describes vRAN as a “generational opportunity to refactor legacy RAN software to a modern, cloud-native design” and believes “vRAN will drive the deployment of general purpose edge compute infrastructure that can also house open RAN based artificial intelligence (AI) and machine learning.”

Open architectures based on the RIC and service management and orchestration are “important because they will enable operators such as AT&T to use their wealth of RAN operational data and customer insights to customize their networks using data science and AI technologies to their particular customer base, geography, and spectrum position,” Gilbert explained. 

AT&T’s vRAN and open RAN trials are ongoing, so it’s too soon to tell when these architectures will be deployed commercially and more broadly on its network, he said. However, “one thing is very clear — full virtualization of the RAN including DU is real, not just hype,” Gilbert added.

He declined to share details about the performance AT&T and Nokia achieved during the trial and how that compares with AT&T’s requirements, but called the early results promising. “It is still early days, and there is a bit of work to do to catch up in feature parity with the legacy stacks that have undergone decades of development,” he said.

“Capacity and power are also evolving fast to the point where vRAN can approach and surpass custom-built solutions,” Gilbert claimed. “AT&T is closely monitoring and participating in these ecosystem developments and will make appropriate decisions to scale vRAN more broadly on its commercial 5G network as the technology matures.”