Mobile Capacity Demands (All Other Things Equal) Will Require Millimeter, TeraHertz Frequencies

Claude Shannon’s information theory is the reason we are moving to millimeter and teraHertz frequencies in the mobility business. Shannon defined the maximum data capacity over a communications channel in the presence of noise.

source: CableLabs 

Basically, capacity requirements are a linear function of the bandwidth available. Shannon’s model shows that as the available bandwidth in the frequency range increases, so does the capacity of the channel. All else being equal, a doubling in frequency can double the channel capacity.

Basically, as frequency increases, wavelength decreases. As wavelength decreases, there are more opportunities to code symbols per second.

Basically, if a mobile signal in the 800 MHz to 2 GHz range has a wavelength between one meter and 10 centimeters, a radio signal in the 6-GHz to 30-GHz range has a wavelength in the 5 cm to 1 cm range. 

source: Researchgate 

That shapes potential bandwidth because there is a direct relationship between frequency and capacity. All other things being equal, signals in the above-6-GHZ range can carry 10 times the information of signals in the less-than-2-GHZ range. 

Since end user bandwidth consumption in the wireless space grows over time, as does consumption over fixed networks, there is a continual need to add spectrum (capacity) over time. 

Aside from the fact that lower-frequency bands already are occupied by other users, 10-times increases in capacity (again, all other things being equal) can be gotten only by adding new frequencies higher in the spectrum. 

This is relatively easy to visualize. This chart shows the traditional mobile communications spectrum in light blue, compared to other bands used for point-to-point (non-mobile communications). The orange bar supports Wi-Fi and some other uses. 

source: Researchgate 

The point is that above 38 GHz, most of the spectrum is commercially unused. So as bandwidth demand increases, we will make more extensive use of the sub-40-GHz spectrum, and then begin adding frequencies higher than that. 

So Claude Shannon’s information theory explains why we will move into millimeter and teraHertz radio frequency ranges to support future mobile network generations. Since there is no way to reassign most of the lower-frequency assets to mobility, unused bands must be sought. 

And most of those resources are in the millimeter and teraHertz regions. 

Or, if you like, uncertainty plus information volume is the driver of the move upwards in frequency.  It is the combination of the minimum number of bits required  to represent any bit of information and the amount of information to be coded that fuels the move to millimeter and teraHertz frequencies, as challenging as that might be, in terms of building commercial wireless networks.