5G Raises Spectrum Concerns

The launch of fifth-generation (5G) cellular networks brings to mind the seemingly distant past—the rollout of fourth-generation (4G) Long Term Evolution (LTE) networks. LTE was the last major leap in cellular evolution, enabling much higher data rate applications like social media and video streaming. 5G promises to support a slew of applications that will revolutionize how we live, ranging from autonomous vehicles to augmented reality. Despite the excitement around its rollout, however, we should remember that issues remain unresolved regarding sharing and clearing spectrum for 5G.

With spectrum sharing, you can have multiple services occupying the same frequency band. For example, much of 5G will deploy in bands previously used for military systems like the Ka-band for radar and satellite services. To ensure optimal 5G performance, the industry will look to clear some spectrum—moving some services to other bands. Interference often results from such efforts, however, as some users do not comply with the deadline.

In the early days of 4G, for instance, some LTE frequencies were already allocated for wireless microphones in the US. Users of those 700 MHz microphones were instructed to leave those channels and move to a different set of frequencies. Not all organizations complied, such as churches and lecture halls. After LTE started deploying, some of these locations started to have major interference problems because the microphones were transmitting on the same frequency as LTE. In addition to the noise suffered by the people inside the buildings, those driving by them would experience some loss of service to their LTE device.

Many existing services will operate alongside 5G. For example, 5G sub-6-GHz bands sit right on top of the C-band for satellite, so that spectrum already is used for satellite services. Regulators therefore must ensure that turning on 5G services will not knock out C-band satellite services, giving the industry an early interference concern that could affect both satellite and 5G communications.

C-band very small aperture terminals (VSATs) also operate in a similar or very close adjacent band. These frequencies are right around 3.5 GHz. If you have a 5G base station located in the azimuth beam of a VSAT terminal, which is blasting in an adjacent band, it could bleed over. It might raise the effective or ambient noise for that C-band terminal, potentially causing harmful interference.

The Coexistence Puzzle

As the regulatory authorities allocate frequencies for 5G in the FR1 sub-6-GHz bands, they must be very careful about the C-band satellite services already existing in an urban environment. Those can be fairly important services—for example, providing government communications. To prevent issues, the regulatory authority also must be very selective in choosing where they allow network operators to place base stations. With spectrum sharing, the low-power nature of today’s devices can have an impact. Interference can stem from a fairly low-power emitter.

Across the world, countries and regulatory authorities are working to allocate frequencies for the carriers to move in with their 5G services. Band-clearing activity is ongoing to ensure that we do not again see the problems we witnessed with LTE. Yet problems may still arise due to the lack of compliance regarding spectrum clearing and issues with coexistence. Spectrum monitoring is evolving to better detect and locate interferers in cellular and satellite communications while reinforcing key optimization tactics like spectrum sharing and clearing. In doing so, it provides better assurance that communications services will operate as planned.

For information on detecting interference and other spectrum monitoring issues, visit our sites on Signal Monitoring and Spectrum Monitoring.