Telecom Italia has turned away from Ericsson and teamed up with four smaller companies on the development of a new mobile network technology it hopes may dramatically reduce the cost of building a 5G network after Italy's recent spectrum auction left it with a €2.4 billion ($2.8 billion) bill. (See Italy's $7.6B 5G bonanza puts telcos on the rack.)

The new technology is only at trial stage but would allow Telecom Italia (TIM) to "virtualize" its radio access network, separating the software functions from the underlying hardware. That move would allow the Italian phone incumbent to process signals on commodity rather than dedicated equipment, and host this at data centers or other aggregation points to benefit from cost savings.

The trials include a radio specialist called Baicells, a software startup known as Phluido and a more established software player in the shape of Radisys Corp. (Nasdaq: RSYS), which was acquired by India's Reliance Industries Ltd. (RIL) in June. Indian IT systems integrator Tech Mahindra Ltd. is also involved. Telecom Italia is due to begin lab testing in November.

While the operator has already worked on so-called "vRAN" technology with Ericsson AB (Nasdaq: ERIC) in Turin, that trial does not appear to have delivered sufficient benefits. "We are looking to a deeper virtualization that will increase the cost attention we are looking for," said Lucy Lombardi, the senior vice president of technology ecosystem innovation for Telecom Italia, during a conference in London this week.

One challenge with vRAN is the connection between the signal-processing "baseband" equipment and an actual radio unit when they are no longer both at the mobile site. Historically, the industry has relied on a technology called CPRI (common public radio interface) to support this connection, but CPRI has lacked the performance requirements to work effectively over anything bar optical fiber. (See Is vRAN Still Too Hot to Handle?)

Consequently, the "deeper" virtualization that Lombardi wants would put enormous pressure on this "fronthaul" part of the operator's network.

Critics say traditional vendors like Ericsson have little incentive to adapt CPRI. Implemented in "closed" ways, the interface usually forces an operator to buy radio gear from its baseband supplier, locking service providers into one vendor's radio system.

Efforts are underway to create a more open radio access network. Some of the world's biggest service providers have clubbed together in a group called the Open RAN Alliance (ORAN Alliance), which has come up with specifications for an alternative to CPRI. (It's worth noting that Ericsson is currently flirting with the ORAN Alliance -- see Ericsson Weighs ORAN Alliance Membership.)

In the meantime, the Facebook-led Telecom Infra Project (TIP), which hosted the conference where Lombardi made her remarks, has set up a "vRAN fronthaul" project group to address the issue.

Phluido, which is involved with that group, plays a key role here. Founded in 2014, the company has developed a fronthaul technology that compresses data and allows it to be carried over transport links other than fiber, including Ethernet and WiFi connections. "There are very tight latency controls between the radio and the front end of the distribution unit, and Phluido is doing clever innovation in that space to enable the latency restrictions to be loosened," says David Hall, the European vice president of technology solutions for software company Mavenir. (See Facebook's TIP Seizes vRAN Initiative From 3GPP.)

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"The scope is to test fronthaul in existing networks, including microwave and fiber, as well as interoperability between different vendors" says Lombardi. "We are in the process of integrating Radisys and Phluido on one side and producing a radio resource unit with Baicells."

Unlike some other mobile operators, Telecom Italia already owns an extensive fiber network, but Lombardi is keen to ensure fronthaul expenses do not escalate with the rollout of 5G technology.

Noting that Italian operators spent heavily on 5G spectrum, Lombardi said Telecom Italia now faced a "big wave" of investment in 5G networks. "We are looking at revenues and they are stabilizing in the industry so cost attention is a priority for telcos, and especially on the radio side because most of the costs are there," she said.

The UK's BT Group plc (NYSE: BT; London: BTA) is another European incumbent that has been involved with the TIP-led trials of vRAN. Howard Watson, BT's technology boss, spelled out the attractions at this week's conference.

"The challenge is that if you take 20MHz of spectrum and get 150 Mbit/s with LTE usable bitrate over that, you need a CPRI capability in that fronthaul bandwidth over fiber of 2.5 Gbit/s to convey that," he said. "What we've achieved through this project with the same demand on the radio network is the ability to do that with 180 Mbit/s. That's more than a tenfold increase in the efficiency of how you use the network bandwidth to connect the radio unit and the baseband unit together."

Watson said trials had demonstrated the feasibility of using new vRAN fronthaul technology on Gfast connections with a copper drop of up to 350 meters. Gfast is a technology used to boost the performance of last-mile copper networks, most frequently for residential broadband access services.

— Iain Morris, International Editor, Light Reading