Although stakeholders characterize it as still early days, Verizon’s 5G specs for fixed wireless are not exactly matching up with the standards being developed by 3GPP, which could pose onerous problems for the carrier and infrastructure suppliers down the line.
Michael Thelander, president and founder of research firm Signals Research Group -- who has been involved in the 3GPP standardization process since the initial work on the 5G standard -- said that based on his research, there’s not an obvious migration path between the Verizon platform and what’s being developed by the industry standards body 3GPP.
“I believe what they’re [Verizon] doing is not hardware-upgradeable to the real specification,” he told FierceWirelessTech. “It’s great to be trialing, even if you define your own spec, just to kind of get out there and play around with things. That’s great and wonderful and hats off to them. But when you oversell it and call it 5G and talk about commercial services … it’s not 5G. It’s really their own spec that has nothing to do with Release 16, which is still three years away. Just because you have something that operates in millimeter wave spectrum and uses Massive MIMO and OFDM, that doesn’t make it a 5G solution.”
Specifically, Verizon’s specs denote a sub-carrier spacing of 75 kHz, something Verizon unsuccessfully argued for inclusion in the standards during an August 3GPP RAN1 meeting, according to Thelander. But it’s not included in the 3GPP’s current specs, which call for subcarrier spacing for 5G New Radio (NR) to be 15 kHz, 30 kHz, 60 kHz, 120 kHz, etc., said Thelander, who’s been tracking the standardization process, including the 75 kHz issue, in his firm’s Signals Ahead publication.
The compatibility question is a big one because of costs associated with ripping out non-standards-compliant gear in order to match the standards -- or risk not being interoperable with other operators’ gear and essentially deploying non-standard, proprietary infrastructure. Operators typically gain economies of scale when they deploy standards-based infrastructure, not to mention being interoperable with other operators around the world, which would seem a desirable prerequisite for 5G.
Verizon notes that there is still time for closer alignment. “3GPP is still in a study phase until March 2017,” Sanyogita Shamsunder, director, Network Infrastructure Planning at Verizon, told FierceWirelessTech in a statement. “Verizon continues to tweak the specifications based on trial learnings. Early commercial equipment will be closely aligned with both standards and software upgradeable as needed.”
Verizon did not directly address the 75 kHz sub-carrier spacing question, but a source at a leading infrastructure vendor corroborates Thelander’s 75 kHz assertion. The source, who requested anonymity, told FierceWirelessTech that 3GPP has a “15 KHz*N (squared) (narrow band physical uplink channel on single-tone) option, so 75 kHz is not possible.”
This source also said that the Verizon specs are likely to be presented into 3GPP as proposals. However, as 3GPP is a larger voting bloc, it is unlikely all aspects will be adopted – some will, some won’t. Ideally, hardware replacements will be avoided, but time will tell how practical that will be after the outcome of 3GPP in year-end 2017. Until then, they have to plan along these lines.
Thelander asserts, however, that with respect to the 75 kHz option, “the 3GPP train has left the station.” In some cases, 3GPP reaches consensus by including optional features which some companies advocate but others oppose. “In this case, the technical complexity of supporting an option that doesn’t adhere to the 15x2^N numerology makes it highly unlikely that 3GPP will later include it and it all but guarantees that no vendor will support it in a solution that is also compatible with the 3GPP specification,” Thelander said.
One of Verizon’s key collaborators, historically and currently, is Qualcomm. During its 4G/5G Summit in Hong Kong earlier this month, Qualcomm unveiled the Snapdragon X50 5G modem, making Qualcomm the first company to announce a commercial 5G modem chipset solution. The Snapdragon X50 5G modem is designed to initially support early 5G deployments based on the Verizon 5G Technical Forum (VZ-5GTF) spec and on the KT 5G-SIG specification in Korea.
The Snapdragon X50 5G modem features initial support for the 28 GHz mmWave band, MIMO antenna arrays with beamforming and beamtracking, and low-density parity-check (LDPC) codes. “These features are also proposed to be included in the 5G NR 3GPP standard,” Sherif Hanna, product marketing staff manager at Qualcomm Technologies, said in an emailed statement. “The X50 modem will give us real-world experience into commercializing mmWave technology in challenging mobile scenario with early 5G deployments. It is QTI’s intent to use these insights to accelerate the 5G-NR standard, Snapdragon chipsets and ecosystem development. We believe that NR acceleration will be possible because of the lessons learned from developing the Snapdragon X50 5G modem.”
Asked if the X50 5G modem is will be software-upgradeable to what the 3GPP ratifies for 5G, he said: “At the moment, we are only announcing that the Snapdragon X50 5G will initially support the Verizon and KT specifications in 28 GHz.”
So, while these stakeholders hope to contribute their experiences to the broader 5G community, there’s no guarantee how the rest of the 5G ecosystem will respond. Verizon’s biggest U.S. rival, AT&T, isn’t sitting idle when it comes to 5G tests and trials, but it’s been a stickler about waiting to tout real 5G until the standards community decides what it is and ratifies the final specs rather than trying to create its own brand of 5G. Perhaps it all goes to show that even as the industry strives to collaborate, there’s no easy -- or fast -- going when it comes to standards.