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Minding the mid-band: Status update on C Band and CBRS

November 25, 2021

LitePoint’s Rex Chen is the author of this blog, which is based on his presentation at the RCR Wireless News Editorial Webinar titled Minding the mid-band: C Band and CBRS efforts.

Wireless spectrum has become one of the most important resources to stay connected because spectrum is the utility for all wireless communication. Mid-band spectrum, specifically in the 2 GHz – 4 GHz range, is playing an important role in 5G, both globally and in the U.S which include:

  • Citizens Broadband Radio Service (CBRS), 150 MHz of spectrum in the 3550 MHz to 3700 MHz band in the U.S. It previously was used by the U.S. government until the FCC identified it as spectrum that could be used for broadband services.
  • C band refers to frequencies between 4000 MHz and 8000 MHz that are now being used for satellite communications, RADAR systems and other unlicensed use case such as some Wi-Fi enabled devices.

In 2020, the U.S. C Band spectrum auction raised more than $81 billion, demonstrating the immense value and potential of mid-band spectrum for wireless communication. Each mobile network operator has a different mid-band strategy based on spectrum holdings – both in terms of how much spectrum they own and whether they need more low or high band frequencies.

Mid-band spectrum has the advantage of known transmission characteristics that is similar to existing 4G frequency bands. Mid-band frequencies are considered “goldilocks spectrum” because they have characteristics of good coverage (similar to low band frequencies), and fast data rates (similar to high-band frequencies). But there are challenges to these RF bands due to how the band has been divided for its incumbent users. MNOs then need to devise spectrum sharing and spectrum usage strategies.

Smartphone design using mid-band spectrum can support world phones that have global cellular coverage capabilities. In many instances, it has a contiguous spectrum, and the short wavelength allows innovations like MIMO between 8 and 16 spatial streams. This enables an ideal degree of spatial multiplexing, where operators can use beam forming techniques to target users spatially – increasing the capacity.

Why Mid-Band is so Valuable
Deployments for 5G mid-band is occurring across multiple countries including the U.S., Europe, Korea and China starting in the past year and a half. This trend will continue as MNOs start to work with higher frequency ranges of the spectrum.

Mid-band spectrum provides the opportunity for a contiguous spectrum with the potential for channels that are 200 to 400 MHz wide. This requirement presents new challenges for filters and other RF components and requirements that must be met by both mobile devices and base stations. LitePoint is seeing instance where in actual deployments, carriers aren’t using an entire capability because they’re still testing to make sure it works for across-the-board deployments.

Increase in remote work, video conferencing and other high bandwidth applications means that uplink capacity is becoming more important than ever. This in turn is leading carriers and chipset makers to re-think how they mix and match spectrum resources. There are inherently many use cases for 5G that may result in making deployment challenging – but the variety of device requirements has made mobile network carriers understand that mid-band is necessary as part of 5G growth moving forward.

To gain more insights on 5G mid-band status and wireless test challenges in this spectrum, as well as hear what other industry leaders have to say, watch this editorial webinar. You can access it on the LitePoint webinar page.