Japan’s NTT DoCoMo touted multi-vendor interoperability using 4G LTE and 5G base station equipment compatible with the Open Radio Access Network (O-RAN) Alliance. The carrier will use that equipment as part of its “pre-commercial” 5G service it’s launching this week.

The test included equipment from Fujitsu, NEC, and Nokia. DoCoMo said it showed what it believes is the first interoperability of signal transmission and reception between equipment from different vendors. The carrier said this is key for operators as they look to deploy network equipment from a variety of sources.

“The ability to deploy and interconnect base station equipment from different vendors will make it possible to select the equipment most suitable for deployment in any given environment, such as base stations offering broad coverage in rural areas or small base stations that can be deployed in urban areas where space is limited,” the carrier explained in a statement.

DoCoMo is using the O-RAN fronthaul specifications for the connection between centralized units hosting baseband processing and remote units hosting radio processing in 5G remote-installed base stations. This allows for the pooling of resources by aggregating hardware, minimizes equipment footprint for reduced operational costs, and allows for a smaller remote radio unit that is easier to locate in size-constrained environments.

It’s also using the O-RAN X2 profile specification to establish the connection between 4G LTE base stations and 5G base station centralized units. That specification supports interoperability between 5G non-standalone (NSA) equipment that also relies on core components from a 4G LTE network.

AT&T cited similar interoperability benefits from using the O-RAN architecture.

“O-RAN will help drive greater interoperability between RAN equipment vendors,” Andre Fuetsch, president of AT&T Labs and CTO at AT&T, told SDxCentral earlier this year. “I think it’s fair to say that all the O-RAN operators are highly motivated to drive more innovation and interoperability, and thus competition into their radio access networks.”

The O-RAN Alliance was initially formed last year by the merger of the xRAN Forum and C-RAN Alliance. It counts some of the world’s largest telecom operators, including AT&T, Deutsche Telekom, China Mobile, Verizon, DoCoMo, and Orange.

It has since established seven working groups that look at use cases and architecture; radio intelligent controller; fronthaul; stack reference design; cloudification and orchestration; resource information and control; and white-box hardware. The group late last year released its inaugural white paper outlining its architecture and vision. This included developing key open interfaces, white-box base station hardware, and creating NFV infrastructure (NFVI) and virtual infrastructure management (VIM) specifications.

The O-RAN Alliance is also working with the Linux Foundation to establish an open source software community and to create open source RAN software that supports O-RAN architecture and interfaces.

DoCoMo’s most pressing domestic rivals SoftBank and KDDI are also part of the O-RAN Alliance and are expected to also use components to help construct their 5G networks.

According to a report earlier this year from Japan’s Nikkei news service, Japan’s four operators – including soon-to-launch Rakuten – are planning to invest a combined $14.4 billion in their networks during the next five years. DoCoMo will lead the way with $7.1 billion in investments, followed by KDDI’s pledge of $4.16 billion in investments, SoftBank’s $1.84 billion in investments, and Rakuten’s planned $1.73 billion in spending.

Those operators have all committed to build nationwide 5G networks by 2022, but initial services are slated to go live beginning next year.