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8 October 2019

Cell site gateways lead the charge towards open, virtualized networks

For the vast majority of operators, deploying a fully open and virtualized RAN remains a distant prospect because the technologies are so immature and the specifications scarcely agreed. But a few frontrunners are starting to make significant breakthroughs which could inject confidence into the wider market.

Many of the early efforts focus not on the virtualized base station itself but on the cell site gateway, which sits at the base station site to enable functions such as backhaul and timing/synchronization. While the Linux Foundation’s ORAN Alliance is driving common interfaces for the disaggregated RAN – as deployed pre-commercially by Japan’s NTT Docomo in Tokyo – the other most significant open network initiative, Telecom Infra Project (TIP), is leading the charge in cell site gateways.

The Facebook-backed group, which aims to slash the cost of telecoms equipment by driving common, open platforms through the supply chain, has defined specifications for a Disaggregated Cell Site Gateway (DCSG) solution.

And two vendors, Aviat and Metaswitch, have cooperated to develop a product based on these specs. The gateway uses Aviat’s network operating system, AOS, and a routing stack and network operating system toolkit from Metaswitch, an early pioneer in virtualized networks including the core. The combination of software runs on hardware which conforms with the TIP specs.

Two other partners, Volta Networks and Edgecore Networks, are also working on an open, virtualized cell site gateway. Volta’s cloud-native virtual routing software, the Elastic Virtual Routing Engine (VEVRE), has now been implemented on Edgecore’s AS7316-26XB open cell site gateway switch.

A year ago, TIP announced its cell site gateway working group, and gained early support from ADVA, which has been building a commercial product based on DCSG specs, which will be offered as a white box gateway, with the vendor adding value with installation, commissioning and monitoring services.

ADVA has also been working with Edgecore Networks on a product to conform to the DCSG specifications, called Odyssey-DCSG. This promises to support open operations and management (O&M) approaches in order to allow MNOs greater freedom to select different technologies for each layer of the stack. Edgecore contributed the hardware design of the cell site gateway to TIP and it will be part of ADVA’s integrated solution. The gateway should be available later this year.

“What we’re developing with the team at ADVA has the potential to dramatically change the whole nature of cell site gateways,” said Facebook’s Luis Martin Garcia, co-chair of the DCSG project group. “By moving away from a closed proprietary system to an open, disaggregated and vendor-neutral infrastructure, mobile network operators have a genuine opportunity to increase network efficiencies.”

DCSG is a project within the CANDI (converged architecture for network disaggregation and integration) working group. CANDI is led by one of TIP’s most active operators, Telefónica, plus Japan’s NTT. This is, in turn, a sub-group within the existing, and highly active, Open Optical Packet Transport (OOPT) initiative. That was established near the start of the TIP adventure, and has already increased its potential impact by collaborating with another high profile open effort in the same area, the Open Networking Foundation’s (ONF’s) ODTN (Open Disaggregated Transport Network), which is also led by Telefónica and NTT, plus China Unicom, Comcast and TIM.

The OOPT and the ODTN are focused on disaggregation of hardware and software, and on white box platforms, for the transport networks, focusing on technologies such as

open transponders, disaggregated cell site gateways, software abstraction interfaces and routers. The founding product in the OOPT was the Facebook-designed Voyager, a DWDM optical transponder whose reference design has been adopted by several companies such as ADVA.

Other leading operators in the DCSG sub-group include Vodafone, Orange and TIM Brasil, which plan to announce a joint Request for Information (RFI) to assess what the vendors, new and old, can offer in compliance with the new specs.