Despite Some Changes, Additional Spectrum Will Still be the Way Most Capacity is Added to Mobile Networks

Historically, additional spectrum, smaller cells and more efficient radios or modulation techniques have been the principal ways mobile operators have gained more capacity. With some exceptions, that is likely to continue to be the case in the U.S market, even if new reliance on small cell architectures develops.

The reason is simply the huge absolute increases in spectrum that will come in the 5G era. Where total spectrum allocated for mobile service, for example, amounts to about 600 MHz, the Federal Communications Commission plans to release scores of gigaHertz--11 GHZ first, then possibly 18 GHz more new spectrum in the millimeter wave region, including seven GigaHertz of unlicensed spectrum.

In other words, two orders of magnitude more spectrum is coming. That is likely going to overwhelm gains from use of small cells (more intensive spectrum re-use) and better radios and modulation techniques.

There is something quite new, though. Millimeter wave spectrum will have propagation issues compared to the low band (600 MHz to 800 MHz) spectrum or mid-band (2 GHz) spectrum. By some estimates, “raw” spectrum will increase up to 400 percent between 2010 and perhaps 2022, at minimum, an older forecast had suggested.

That already is out of date as we consider millimeter wave allocations that will increase raw spectrum by an order of magnitude to two orders of magnitude.

Contributions of raw spectrum to U.S. mobile capacity growth
Year	Currently allocated spectrum (built-out MHz)	Baseline Spectrum Index	Additional built-out allocations (MHz)	Augmented spectrum quantity (MHz)	Upper bound Spectrum Index
2010	294.5	1.90
2011	334.5	2.16
2012	374.5	2.41
2013	426.6	2.75			2.75
2014	478.8	3.08	30	508.8	3.28
2015	513.4	3.31	30	573.4	3.69
2016	548.0	3.53	30	638.0	4.11
2017	548.0	3.53	30	668.0	4.30
2018	548.0	3.53	40	708.0	4.56
2019	548.0	3.53	40	748.0	4.82
2020	548.0	3.53	40	788.0	5.08
2021	548.0	3.53	30	818.0	5.27
2022	548.0	3.53	30	848.0	5.46

source: Science Direct

Spectrum reuse, which is the way small cells increase capacity, will grow at lower rates, perhaps 270 percent in an older forecast.

Contributions of additional spectrum reuse to mobile capacity
	Basic Reuse		Reuse with 4G+ Het-net lift
Year	Cell sites	Cell site Reuse Index	With currently allocated spectrum			With upper bound spectrum
			Reuse lift from 4G+ Het-nets	Number of effective sites	Baseline Reuse Index with Het-net lift	Reuse lift from 4G+ Het-nets	Number of effective sites	Upper Reuse Index with Het-net lift
2010	253,086	1.00		253,086	1.00
2011	283,385	1.12		283,385	1.12
2012	301,779	1.19		301,779	1.19
2013	325,921	1.29		325,921	1.29
2014	351,995	1.39		351,995	1.39		351,995	1.39
2015	380,155	1.50	1.0891	383,361	1.51	1.0882	383,025	1.51
2016	410,567	1.62	1.0967	420,424	1.66	1.0981	420,595	1.66
2017	443,412	1.75	1.0997	462,360	1.83	1.1034	464,079	1.83
2018	478,885	1.89	1.1055	511,154	2.02	1.1111	515,621	2.04
2019	517,196	2.04	1.1114	568,083	2.24	1.1174	576,166	2.28
2020	558,572	2.2 1	1.1194	635,913	2.51	1.1252	648,283	2.56
2021	603,258	2.38	1.1289	717,876	2.84	1.1323	734,060	2.90
2022	651,518	2.57	1.1383	817,173	3.23	1.1413	837,763	3.31
Basic site CAGR:  8.0%
4G+ Het-net effective site CAGR:  16.0%

source: Science Direct