Mobile tech explained: The Future of Radio Access Networks

This article is part of a series breaking down the complex systems and technologies that make up the Rakuten Mobile network and Rakuten Communications Platform. In this edition, we speak with Sushil Rawat, director of vRAN access product development at Rakuten Mobile, Inc.

Changing mobile user behavior, new mobile devices and new demands for mobile networks are driving the need for mobile operators to re-examine how they deploy next generation networks. Growing data consumption and high costs for deploying 5G are forcing operators to re-evaluate their capital expense (CAPEX) and operating expense (OPEX) plans while turning them to look to technology options capable of delivering accelerated innovation. Because the Radio Access Network (RAN) can account for more than half of a network’s total cost of ownership (TCO), innovation and cost savings within the RAN is critical.

“We have disaggregated the hardware and software so that the actual brain behind the cell site is sitting in a data center, where we have a pool of hardware that gives us the freedom to scale up and scale down in real time.”

Sushil Rawat, director of vRAN access product development at Rakuten Mobile, Inc.

Traditionally the RAN is built with custom hardware provided by a few select vendors, and their technology works perfectly fine. However, technology development and innovation has been in the hands of just a few suppliers, which has restricted the vision and strategy for the future of network deployments. At the same time, the telecom industry is experiencing unprecedented growth in data use. Customer data consumption patterns are becoming unpredictable. Service providers are forced to explore highly scalable, modular and intelligent network deployment strategies. This is only possible with a diverse supply chain and radical technology transformation using web scale technologies.

Redefining radio

Rakuten Mobile and its partners have redefined what it means to build and maintain the RAN that interacts wirelessly with mobile devices. By using advanced IT technologies, such as the cloud, virtualization and containerization, it is now feasible to strip a base station back to the bare essentials – a tower or pole, the antenna that transmits the signal and a power source. The computing power required to filter and interpret the radio signals can now be located in a data center, where it is easier to manage and maintain.

By streamlining a base station in this way, Rakuten Mobile has reduced the footprint of a typical cell site by 30%, which translates into lower capital and operating costs. That’s a big deal given Rakuten Mobile plans to deploy about 44,000 base stations across Japan for its 4G network. Virtualization and commoditization of RAN computer hardware has enabled Rakuten Mobile to speed up simultaneous 4G and 5G network deployment.

Bringing virtual machines to bear

What’s more, Rakuten Mobile’s RAN uses generic off-the-shelf computer servers, rather than the dedicated hardware employed in traditional mobile networks. This is made possible by virtualization – tools that can create a virtual computing platform on generic hardware that allocates the necessary processing, memory, storage, and network capacity to run the software required to perform a specific task. Each virtual machine can run independently while sharing hardware resources.

“Because it’s virtual, you essentially have unlimited capacity to scale and deploy infrastructure anywhere,” notes Sushil Rawat, director of vRAN access product development at Rakuten Mobile. “We have disaggregated the hardware and software so that the actual brain behind the cell site is sitting in a data center, where we have a pool of hardware that gives us the freedom to scale up and scale down in real time.”

Responding to traffic surges

This kind of flexibility can help a mobile operator cope with the dramatic changes in usage patterns that might take place during live events. For example, most of the time a sports stadium lies empty. But on match day, it fills with thousands of people and their handsets, which suddenly generate a vast amount of signaling traffic for the network. During the game, the spectators will be absorbed in the action – they aren’t using much mobile data. But when it ends, many of them might take a selfie and upload it to social media – now the network has to cope with a surge in traffic in the uplink. Rakuten’s disaggregated RAN is much better placed to cope with such scenarios than a traditional cellular network because with a software approach, you can immediately scale capacity up or down based on demand.

“The beauty is that, because you are using APIs, you can spin up a micro-service somewhere else and, if you need to, you can stretch it up, make it better, make it taller, make it bigger, while the rest of the application can still remain the same size.”

Sushil Rawat, director of vRAN access product development at Rakuten Mobile, Inc.

Small and beautifully formed

But the disaggregation doesn’t stop there. Rakuten and its partners are now packaging the RAN software into so-called containers that have the configuration files, libraries and dependencies the application needs to run in an efficient and reliable way. Containerization allows an application to be much smaller, meaning it can be developed and deployed faster. It also allows for the application to be broken down into modules, known as micro-services, which communicate with each other via application programming interfaces (APIs). This architecture offers greater flexibility and resilience: a failing or flawed micro-service can be quickly isolated and replaced with another one. “The beauty is that, because you are using APIs, you can spin up a micro-service somewhere else and, if you need to, you can stretch it up, make it better, make it taller, make it bigger, while the rest of the application can still remain the same size,” adds Rawat.

In contrast to the traditional telco industry approach, all the major internet platforms, including Rakuten, rely on a combination of the cloud, virtualization and containerization to make their online services flexible, resilient, scalable and cost-effective.

Growing global momentum

Although the well-established equipment vendors tend to favor a more traditional RAN architecture, a new breed of vendor is supporting the rollout of open RAN technology, which enables operators to mix and match systems from different vendors. As these systems all use the same open architecture, they can be managed in the same way – the operator doesn’t need to employ engineers that are expert in how a specific proprietary system works. Similarly, with an open approach, network automation systems will be compatible with equipment from multiple vendors, rather than only working with kit from a single vendor. “In our network, the same person can actually manage every single network element, which brings operational efficiency,” says Rawat.

Rakuten Mobile is working with Altiostar, Robin.io, Airspan, QCT, NEC and other challengers of the status quo to deploy a low-cost 5G network using its own virtualization layer. It is even engaging with contract manufacturers directly. “We started getting into the hardware, we started getting into the components, we actually opened up the boxes,” says Rawat. This enables significant reductions in hardware costs for 5G compared to the traditional model.