Though the 5G standards do not specify frequency as strictly as did earlier mobile next-generation networks, 5G has leaned on mid-band spectrum for a few obvious reasons. In most countries, mid-band spectrum is available to use, even if other assets in the low-band and millimeter wave regions (high band) also are being authorized.
The big capacity gains are to be found in mid-band and high-band frequency ranges, however. Low-band spectrum’s greatest value is coverage, though. Latency performance is partly a result of cell architecture and partly a result of the actual design standards.
Over time, spectrum used to support legacy mobile networks eventually is decommissioned as the legacy networks are shut off. So, over time, all spectrum assets are repurposed to support the next-generation networks as well.
Over time, this has implications for device design, as radios must be capable of supporting literally all the frequencies the newer networks use. All that affects device cost as well.
There are some obvious reasons why mid-band spectrum will be the core of 5G access efforts. It provides coverage that can be as much as 90 percent the same as existing mid-band networks supporting 4G. That means less capital investment than new millimeter wave small cell networks.
So ABI Research forecasts that approximately 90 percent of 5G cell sites in emerging markets will use a combination of sub-6 GHz bands by 2026. Mostly, that means the mid-band frequencies that already underpin 5G in countries that have launched 5G service commercially.
The choice of mid-band spectrum is partly borne of necessity and partly borne of availability. The necessity is that every next-generation mobile network requires additional spectrum resources.
The availability is that spectrum in the 3 GHz to 4 GHz range is relatively less encumbered in many markets. So it is available to assign for support of 5G. Also, since frequency is positively correlated with capacity, while negative correlated to signal propagation, mid-band spectrum provides a balance of coverage and capacity.
Looking only at the potential 5G capacity, it is clear that, eventually, millimeter spectrum will be the source of most of the coming capacity gains.
In a spectrum survey of 32 emerging markets conducted by ABI Research, at least half of countries will have allocated the low band (less than 1 GHz) spectrum for 5G. Some 87 percent of countries will use spectrum in the 1 GHz to 6 GHz regions by 2023.
Spectrum in the 26 GHz and 28 GHz regions will be used by 34 percent and 12 percent of respectively by 2023.
Mid-band is the anchor region of spectrum for 5G, as important as millimeter wave capacity is to supply capacity.
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