Forget Rakuten. NTT DoCoMo, the Japanese upstart's local rival, has built the most extensive open RAN anywhere on the planet. Using the fronthaul specification nailed down by the O-RAN Alliance, it today boasts a footprint of more than 10,000 5G basestations where radios and baseband products come from different suppliers. And rather like Rakuten – whose 4G network is not O-RAN-compatible and whose 5G network comprises only about 4,000 sites – the elder statesman of Japanese telecom is now marketing its open RAN expertise to operators in other parts of the world.

Its basic pitch to the international community? It has been doing this for a long time – since the days of 4G, in fact, when it first reckoned that buying radios and baseband gear separately would allow it to choose the best in each category. With O-RAN specifications still immature (or incomplete), it has already done the hard work on integration. A squad of 13 vendors can be quickly deployed in one of several formations. From the end of February, other telcos have been able to use NTT DoCoMo's custom lab as a kind of open RAN changing room and gym, where they can try on kit and work out.

The 13 vendors in what NTT DoCoMo calls OREC (its open RAN ecosystem) are Dell, Fujitsu, HPE, Intel, Mavenir, NEC, NTT Data (a sibling), Nvidia, Qualcomm, Red Hat, VMware, Windriver and Xilinx, each of which brings its own specialism. Mavenir, for instance, supplies baseband software in one configuration where the virtualization platform comes from VMware, the processors from Intel and the servers from Dell.

Figure 1: Fujitsu figures prominently in NTT DoCoMo's open RAN plans.
(Photo by Fiona Graham)

"We just opened the lab, and we are talking to multiple operators explaining the capability, but one thing we've announced is Korea Telecom," said Sadayuki Abeta, the general manager of NTT DoCoMo's RAN development department, on a call with reporters earlier. "They decided to do open RAN tests with our support, so we announced a contract in January."

It sounds like a far less comprehensive offering than Rakuten Symphony, the part of Rakuten pitching various cloud and software technologies to other telcos. Nor is there any indication yet of the revenue opportunity. "There are so many options we need to consider on how to make a business," said an NTT DoCoMo spokesperson. "One is a consulting model, helping operators to introduce open RAN technology to their networks."

Testing and integration should, in principle, require less effort as O-RAN specifications are finalized and hardened, allowing operators to combine vendors more easily. Until then, NTT DoCoMo can effectively lend support. "If we can share the interoperability testing results among operators, then we do one test and share results and reduce costs and save time," said Abeta. "Some interfaces are not completed yet, so we are working with partners to submit our experience to the O-RAN Alliance to complete specifications. In future, we can theorize that plug and play will reduce costs."

Slashing the bill

This all speaks to a broader objective of cutting open RAN expenses, partly by encouraging other telcos to use NTT DoCoMo's preferred ecosystem of suppliers and generate economies of scale. What's notable is that NTT DoCoMo still has a long way to go on 5G rollout. It expects to have 20,000 open RAN basestations deployed "in a short time," said Abeta, but its 5G network will not cover 90% of the population until March 2024, according to company forecasts he shared today.

Nor is the NTT DoCoMo network a virtual one. "Our network is not virtualized yet," said Abeta. "It is open, and we use different vendor equipment through the X2 interface and the O-RAN interface. The core is virtualized, but the RAN is traditional and purpose-built at this moment."

X2, a 3GPP interface, supports handover between cells when the equipment comes from different suppliers. Quizzed on the various players it uses, Abeta revealed that Fujitsu and NEC are supplying both baseband products and radios in different parts of the country, with Samsung and "smaller Japanese vendors" also lining up on the radio side. The identity of another "European" baseband provider has not been disclosed, although Light Reading has learned this is Nokia.

But the operator still has numerous concerns about RAN virtualization that broader international adoption might help to address. "Just using COTS [common off-the-shelf servers], power consumption is not so good," said Abeta. "But using accelerators such as GPUs or FPGAs or ASICs, we can offload some calculations to the accelerators, and we estimated similar performance we can achieve compared to traditional or purpose-built hardware. We are trying to show this performance with OREC."

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That ecosystem, critically, features several chip vendors that have been working on these accelerators for improved RAN performance, including Intel, Nvidia, Qualcomm and Xilinx. As improvements are made, NTT DoCoMo is weighing its virtualization next steps. "Thanks to open interfaces, we can introduce the vRAN according to different scenarios, because we can connect existing RUs [radio units] through that interface," said Abeta.

An important goal is driving down the cost of COTS equipment. NTT DoCoMo can do this in future partly by bulk-purchasing servers for both the RAN rollout and its data centers, but a wave of international enthusiasm for RAN virtualization would obviously make a difference. Abeta says he is encouraged by pricing trends. "The price is decreasing every year," he said, indicating the cost of purpose-built hardware is not falling as quickly.

Even so, open and virtualized network products may need global scale for long-term commercial viability, explaining NTT DoCoMo's promotion of OREC. These economies may be harder to realize in a market divided among numerous players, and yet many operators are backing open RAN mainly as a spur to competition. "It is hard to say how many vendors we will have in the future," said Abeta. But he will obviously hope the OREC squad figures prominently.

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— Iain Morris, International Editor, Light Reading