Fixed wireless broadband and the 28 GHz spectrum band are driving initial 5G moves, though technology and propagation challenge the business model.
Momentum is definitely on the side of “5G” technology, with most large mobile telecom operators either having already announced plans to begin trials of what they expect to be a technology standard or in the planning stages for such trials.
Among the early domestic movers, two trends have emerged in terms of plans for commercial trials: fixed wireless broadband will be the service, and the 28 GHz spectrum band will be the wavelength of choice. AT&T, Verizon Wireless, T-Mobile US, U.S. Cellular and C Spire have all announced plans to trial 5G services using the nonconventional spectrum band.
However, despite the broad support, the business case for such moves remains in limbo.
Research firm Mobile Experts recently released a case study on broadband-based 5G services focused on return on investment for deployments, noting current technology tied to the limited propagation characteristics of the 28 GHz band come up short in terms of supporting a business case.
The firm said it calculated the potential ROI for operators investing in a pre-5G network using the 28 GHz band compared with LTE costs and “the potential costs for a sub-6 GHz network using 5G technology,” and found at “historical prices, 5G will not be successful.” To reach the necessary ROI, Mobile Experts said the market would need inexpensive access to large spectrum blocks.
“The business case for 5G fixed broadband is not a slam dunk,” said Joe Madden, principal analyst at Mobile Experts. “We expect pre-5G deployment to be a very targeted investment by mobile operators, addressing very specific neighborhoods instead of nationwide deployment.”
Madden noted millimeter wave links at 50 meters created a “challenge to the business case, because the number of customers served by each radio will be too small.” The firm noted links of at least 200 meters would be required to reach enough users to support sufficient ROI.
“Link distance is a key factor in the pre-5G business case at 28 GHz,” Madden explained. “We’ve conducted some in-depth link budget calculations and compared our results to trial results reported by Samsung, Ericsson, Intel and others. Based on this deep technical work, we have some concerns about the power, linearity and heat dissipation in pre-5G infrastructure. The laws of physics will limit these pre-5G networks.”
Mobile Experts noted the 28 GHz band and fixed wireless broadband services will be a starting point, “but a combination of low-band and high-band spectrum will be important to reach mobile gigabit performance.”
The 28 GHz band is one of many being proposed by the Federal Communications Commission as part of its Spectrum Frontiers proceedings in support of 5G deployments. Those efforts include 3.85 gigahertz of spectrum for licensed use in the 28 GHz, 37 GHz and 39 GHz bands, and 7 gigahertz for unlicensed use across the 64 GHz to 71 GHz bands.
Some operators are also looking at network trials using the 15 GHz band, which could improve on the propagation characteristics and improve the business case behind initial 5G deployments. In announcing its trial plans using the 28 GHz and 15 GHz band, U.S. Cellular EVP and CTO Michael Irizarry said the carrier plans to do a lot of work on propagation characteristics, with a strong focus on understanding what services work best on which bands.
While there has been considerable attention placed on the use of millimeter wave spectrum bands to provide the capacity needed for next-generation networks, carriers are still trying to work through just how exactly they will implement networks using bands that have historically been considered outside the range of use for commercial wireless services.
Thomas Keathley, SVP of wireless network architecture and design at AT&T, noted potential performance degradation issues connected with using the millimeter wave spectrum bands expected to be central to 5G networks.
“If you put a hand in front of a transmitter you will see degradation of performance,” the AT&T exec explained during a panel discussion at the recent CTIA Super Mobility event. “It’s going to be a very different implementation than traditional cellular networks.”
Adam Koeppe, VP of access technology planning at Verizon Communications, noted that indeed propagation characteristics of high-band spectrum will be a challenge, but those “issues are not anything news.” Instead he noted what is different is the use of beamforming and beamtracking technology that allows the use of those bands in access-type deployments.
“Our trials have been to take those out of the lab and into real world scenarios,” Koeppe said of the carrier’s 5G network trials.
The FCC is currently conducting an especially complex 600 MHz incentive auction process, which the government agency and some analysts have noted could provide the needed low-band spectrum support for 5G services.
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