Spectrum, as with any mobile wireless system, is critical to 5G. Frequencies, channel widths and licensing terms are very influential on technology development and therefore on end-user services. Spectrum will, in effect, shape 5G system design and the real-world deployment model.

To exploit advances in radio technology and unlock new capacity, 5G New Radio (NR), which is now under development in 3GPP, is widely expected to operate across very diverse spectrum, from low-band, to mid-band, to high-band (mmWave) frequencies. For mobile operators, exclusive licensed spectrum is preferred because it provides greater certainty of performance and reduced risk of interference. This will remain the case in 5G.

There are, however, tremendous opportunities for shared spectrum in 5G, as I argue in my new white paper, "Shared Spectrum for 5G New Radio."

Shared spectrum -- where more than one operator shares the band, either in time or space -- can be useful in several ways. For mobile network operators (MNOs) one option is to aggregate shared and exclusive-use licensed spectrum, to support extreme bandwidths and deliver "fiber-like" 5G services. There is precedent for this model in 4G with the use of unlicensed (i.e. shared) 5GHz spectrum to support LTE-License Assisted Access or LTE-LAA, and it is expected that 5G will extend this type of spectrum aggregation.

Perhaps even more disruptive is the potential for non-MNOs to use shared spectrum to take advantage of 5G NR technology. For these organizations, access to spectrum unlocks opportunities for innovative deployments -- for example, in public venues, workplaces, or industrial facilities. In this sense, shared spectrum can be a critical enabler of "permissionless innovation" in 5G. This will simultaneously extend the benefits of 5G NR to the wider networking ecosystem and drive demand (and all-important unit volume) from these new users.

Shared access can also make more efficient use of spectrum. For example, where spectrum is already allocated, but only lightly used by incumbents, offering it on a secondary basis to other users can radically increase utilization. This model is being adopted for Citizens Broadband Radio Service (CBRS) in the US, where incumbents, licensed priority secondary users and tertiary users without a paid license will all share 3.5GHz spectrum. The same general principles can be applied to other shared spectrum bands for 5G NR.

For shared spectrum to be most effective, it is vital to have effective and reliable mechanisms to optimize sharing. As discussed in the paper, tightly coordinated systems perform more efficiently under load than contention-based shared access. Co-ordination, however, requires information sharing between operators, which in turn requires some form of standardization. There are a number of ways to do this from the radio interface itself through to centralized database systems, or combinations of both. The challenge to the industry is to seize the opportunity in NR specification to realize the compelling economic benefits of shared spectrum.

— Gabriel Brown, Principal Analyst, Heavy Reading

This blog is sponsored by Qualcomm.