Hardware vs. software is one of the biggest questions wireless network architects face as they design networks that can handle not only today’s traffic but tomorrow’s as well. There is no shortage of purpose-built hardware for mobile networks, and there is also no shortage of vendors pushing virtualized solutions, software that runs on off-the-shelf hardware and aims to duplicate the performance of specialized hardware.
Nine use cases for virtualized networks have been defined by ETSI, the European Telecommunications Standards Institute. Two of these use cases are virtualization of the mobile core network and virtualization of the mobile base station, or radio access network.
“RAN virtualization is probably one of the hardest of the ETSI use cases to do, since the system has to respond in real time to the RF signal,” said Nick Marshall, research director at ABI Research. “Basically it’s about how much of the baseband you can virtualize in the cloud or in a data center and what physical elements you have to leave in the radio head. … The more of the real-time functions you can leave in the radio head, the better the performance will be.”
A typical wireless base station includes a baseband unit (BBU) in an equipment closet and a remote radio head, either at the base of the tower or at the top of the tower. Centralized RAN moves the BBU to a centralized location where it may share space with other baseband units. Cloud RAN, or virtualized RAN, takes that a step further by moving the baseband processor into a data center.
“It is typical to link the data center to the radio unit with fiber, for instance, but that’s expensive and so folks are looking at other ways of partitioning the baseband,” said Marshall. “There are multiple approaches. … The Small Cell Forum recently published its work on virtualization of the RAN and came up with multiple partitioning approaches for the baseband which would be suitable for small cells.”
Alcatel-Lucent demonstrated virtualized RAN this year at Mobile World Congress, and has said that its solution will be ready to launch commercially next year. Alcatel-Lucent’s software runs use off-the-shelf hardware and Intel processors to virtualize the baseband unit.
Dali Wireless is another V-RAN pioneer. The company is working on a remote radio head that it said could interface with equipment from multiple manufacturers.
“We will have the capability of using our DAS remote to function as both a multichannel DAS remote with multiple technologies as well as a remote radio head,” said Gary Spedaliere, VP of technology and market development at Dali.
“They have not only virtualized the RAN, but as I understand it they have packetized the RF signals so that it’s just like an Ethernet signal or packet; it’s got an address,” explained Marshall. “So this system that they have can take a signal from any source and route it to any antenna. That signal can be cellular, it can be Wi-Fi, it can be IP traffic or public safety.”
Marshall expects virtualized RAN solutions to be a key part of the evolution to 5G. In addition, he sees virtualized RAN as a way for operators to reduce network equipment expenditures.
“Once you get the ability to manage capacity and steer capacity to where demand is, then you no longer need to provision your system for maximum peak capacity,” he said. “You can move capacity to where it’s needed.”
