Atot	The total electromagnetic wave attenuation in soils for Fresnel model
CRIM	Complex refractive index model
d	The distance between the wireless transmitter and receiver
D	The largest physical linear dimension of antenna
df	Far field distance of the antenna
EM	Electromagnetic
f	Operation frequency of EM waves
GPR	Ground penetration radar
K′	The real part of relative soil complex dielectric constant
IoT	the Internet of things
K″	The imaginary part of relative soil complex dielectric constant
K*	The relative soil complex dielectric constant
Lm	Additional path loss induced by EM waves transmission from air into soils
L m1	Path loss induced by the wavelength change in soils
Lp	Path loss of wireless signals
Lα	Path loss induced by attenuation
R 2	Coefficient of Determination
Rc	Reflected energy loss
RF	Radio frequency
RMSE	Root mean squared error
RSS	Received signal strength
RSSI	Received signal strength index (in dBm)
TDR	Time domain reflectometry
VWC	Volumetric water content
WSNs	Wireless sensor networks
WUSNs	Wireless underground sensor networks
α	Soil attenuation factor
αc	Attenuation constant for the Fresnel model
α 0	Attenuation constant for the Friis model
β 0	Phase shift constant for the Friis model
ε	Relative soil dielectric permittivity
ε′	Real part of relative soil dielectric permittivity
ε″	Imaginary part of relative soil dielectric permittivity
ε 0	Dielectric permittivity of free space
λ	The wavelength of EM waves
μ 0	Free space permeability
μ	The magnetic permeability of soil
σb	Bulk electric conductivity of soils