All engineering and communications network design involves trade offs. That can be seen clearly in the properties and value of 5G spectrum of various types. Low-band is best for coverage, indoors and outside, but does not supply capacity so sell.
Mid-band provides a balance of coverage and capacity. High-band (millimeter wave) is best for capacity, but at the expense of coverage. To the extent that T-Mobile expects to increase capacity of its U.S. network by as much as 14 times over the next few years, primarily by deploying new mid-band spectrum.
Low-band 5G spectrum comes from a mix of refarmed spectrum from early mobile generations (1G, 2G) and previously unused bands.
Mid-band spectrum covers the 1-GHz to 6-GHz bands. Millimeter runs between 30 GHz and 300 GHz, though capacity in the 24-GHz range is classified as “millimeter” capacity for purposes of mobile communications.
The mid-band is of primary importance for 5G globally because it offers a balance of capacity increases and coverage not so different from low-band spectrum. That helps the business case as use of mid-band spectrum obviates the need for many small cells.
U.S. mobile operators and regulators have had to work around the fact that much of the 5G mid-band spectrum already was allocated to other users. So spectrum sharing and reallocation of the C-band formerly used by satellite service providers have been key mechanisms for making mid-band spectrum available.
Though the 3.55-GHz to 3.7-GHz Citizens Broadband Radio Service (CBRS) added 80 MHz of shared and 70 MHz of licensed spectrum for mobile use, th
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