A world first for 5G: Rakuten Mobile & NEC deploy groundbreaking radios for new 5G network

This article is part of a series highlighting the collaboration between Rakuten Mobile and its partners to build the world’s first end-to-end fully virtualized cloud-native mobile network. In this edition, we speak with Nozomu Watanabe, senior vice president, NEC Corporation.

Working together, Rakuten Mobile and NEC Corporation have achieved a world first – they have built the world’s first 5G mobile network radios based on an open and fully virtualized architecture. These high performance radio units, which can be used with network equipment from many different partners, will be front and center when Rakuten switches on its 5G services in summer 2020, initially in the Tokyo area.

Production of the groundbreaking radio units is now underway at NEC’s Fukushima plant and Rakuten Mobile has taken delivery of the first shipments. By deploying a fully virtualized network with an open architecture, Rakuten Mobile is aiming to reduce the capital cost of its mobile infrastructure by approx. 40% compared to legacy mobile operators, while also enabling it to tap a strong and diverse vendor ecosystem. In virtualized networks, the software is decoupled from the hardware, increasing flexibility and lowering costs. NEC is working closely with Massachusetts-based Altiostar, which is supplying the software for Rakuten Mobile’s virtualized radio access network (vRAN).

“As a leader in integrating network and IT technologies, NEC is playing an invaluable role in realizing Rakuten Mobile’s vision of creating the world’s first fully virtualized, end-to-end cloud-native mobile network,” explains Tareq Amin, chief technology officer of Rakuten Mobile. “NEC’s 5G radio units are now being installed in our first 5G base stations, paving the way for our subscribers to enjoy very cost effective, highly secure and high quality 5G connectivity that will enable an array of exciting new services for businesses and consumers alike,” he adds.

Nozomu Watanabe, senior vice president, NEC Corporation on stage at Rakuten Optimism Conference 2019 in Japan.
Nozomu Watanabe, senior vice president, NEC Corporation speaking at the 2019 Rakuten Optimism event in Yokohama, Japan.

As Rakuten Mobile has already tackled the “many challenges” associated with vRAN in its 4G network, it can now use that expertise to build a 5G Open RAN system, explains Nozomu Watanabe, senior vice president, NEC Corporation.

Despite the disruption resulting from COVID-19, the rollout of Rakuten’s mobile network is running ahead of schedule – the operator is on course to deploy 4,400 outdoor base stations in Japan at the end of March 2020, ahead of its original target of 3,432 for its initial launch. Rakuten Mobile’s 5G service is scheduled to be launched later this summer.

The world will be watching

Mobile operators across the world are watching the rollout of Rakuten Mobile’s network closely to see if they can also harness the benefits of an open and virtualized radio network. “There are many operators interested in introducing a virtualized RAN architecture,” says Watanabe. “But they want to see the Rakuten Mobile network working before they introduce it.”

NEC hopes to be able to export the expertise it has gained by working with Rakuten Mobile to operators outside Japan. “We are in a very important moment to show potential customers that a virtualized network is going to work,” says Watanabe. “We are expecting other opportunities outside of Japan after we show that the Rakuten Mobile network is working.” 

The new multi-vendor virtualized open architecture could also help inject more competition and dynamism into the network infrastructure market, which has been dominated by a small number of players. “It will enable the market to have an alternative network to that which other vendors can provide,” Watanabe adds. “There are high expectations.”

NEC, which has been working on 5G technologies, such as massive MIMO and beamforming, for several years, initially conducted multiple field-tests as part of a project in conjunction with the Japanese government. It then took NEC a year to develop a commercial radio unit for Rakuten Mobile.

A diverse and vibrant ecosystem

As it builds out its mobile network, Rakuten Mobile is nurturing an open ecosystem that encompasses a wide variety of suppliers from around the world. The new operator is working closely with these partners to build the Rakuten Mobile Platform, which it will offer to other operators seeking to deploy an Open RAN solution within their 5G networks.

The 5G mobile network radios based on an open and fully virtualized architecture will be front and center when Rakuten switches on its 5G services.
The 5G mobile network radios based on an open and fully virtualized architecture will be front and center when Rakuten switches on its 5G services.

NEC’s new 5G radio units build on the work Rakuten Mobile has already done in building an open architecture into its 4G network. In October 2019, Rakuten Mobile implemented the world’s first architecture based on the Open-RAN (O-RAN) specification. “The O-RAN interface with Altiostar had already been defined and that has helped us,” says Watanabe. “Although O-RAN has an open interface, there are still some options we need to choose to make it work in combination with other vendors’ equipment. But it is good enough to use as a strong base line and we can prove it works in combination with Altiostar.”

The new 5G radio units are equipped with a massive MIMO (multiple input multiple output) antenna operating in the 3.7GHz frequency band, yet have a small footprint, are lightweight and are frugal with power. NEC has focused on keeping the cost of these units low, while keeping the quality high. “We have very compact equipment, offering high quality performance, which matched with what Rakuten Mobile wanted for their commercial system,” says Watanabe. “We have had a joint activity with Rakuten Mobile to reduce the bill of materials cost. With the automation of the manufacturing system, we have also minimized the labor fees…and we have minimized the complexity of the mechanical system to make the assembly as easy as possible.”

As new spectrum frequencies are assigned and more bandwidth becomes available, NEC and Rakuten Mobile plan to upgrade and expand the 5G radio units. “The base technology will be similar, but there will be more things to work on in terms of performance, which is largely governed by the hardware,” explains Watanabe.

As it doesn’t have a legacy network, Rakuten Mobile has been able to rip up the telecoms infrastructure rulebook and start again. Although existing operators can’t necessarily be quite so radical, NEC believes most will end up employing a similar architecture to Rakuten Mobile as 5G matures.

“Going forward, NEC aims to drive the global expansion of virtualized network architecture with Rakuten Mobile,” said Atsuo Kawamura, executive vice president and president of the Network Services Business Unit at NEC. “By expanding the open 5G ecosystem, NEC will contribute to the creation of new mobile services around the world.”

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