Free space path loss
L = fspl(R,lambda)
real-valued 1-by-M or M-by-1 vector
Propagation distance of signal. Units are in meters.
real-valued 1-by-N or N-by-1 vector
The wavelength is the speed of propagation divided by the signal frequency. Wavelength units are meters.
Calculate free space path loss in decibels incurred by a 10-gigahertz wave over a distance of 10 kilometers.
lambda = physconst('LightSpeed')/10e9; R = 10e3; L = fspl(R,lambda);
The free-space path loss, L, in decibels is:
This formula assumes that the target is in the far-field of the transmitting element or array. In the near-field, the free-space path loss formula is not valid and can result in a loss smaller than 0 dB, equivalent to a signal gain. For this reason, the loss is set to 0 dB for range values R ≤ λ/4π.
 Proakis, J. Digital Communications. New York: McGraw-Hill, 2001.