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PATH LOSS:
Basic transmission loss, or path loss (PL), is the signal attenuation between transmit (TX) and
receive (RX) antennas due to the TX to RX separation and multipath (scattering). Basic transmission loss
determines the range of a wireless link. Basic transmission loss is given by
where Pt is the transmitted power, Pr is the received power,
Gt is the transmit antenna gain, and Gr is the receive antenna gain.
An ideal free space (FS) path (no ground reflection, no multipath) has a path loss which is proportional
to the square (n = 2) of the separation d
where l is the wavelength. This typically represents the minimum path loss
and serves as a lower limit. Values of n on the order of 4 are more representative of realistic, cluttered
environments. The figure below shows an example of measured path loss measured in a suburban environment
(near to the ITS Boulder Labs location). The free space is shown for reference. Also shown is a least
squares fit which yields an attenuation exponent of 4.9.
Measured path loss in a suburban environment.
(CLICK image to enlarge.)
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