In detecting low altitude targets, the presence of reflections from sea or ground surface can cause multipath propagation
. In some literatures, the implicit assumption is that only one reflection path exists .
However, also terrestrial signals experience multipath propagation
. Multipath propagation
biases range estimates if standard correlator based methods are used.
Reference  proposes the following distributions for different fading types: Gaussian distribution with mean equal to the RSS mean for flat fading; Log-normal distribution for slow fading due to shadowing effects; Rayleigh or Ricean distribution for fast fading due to multipath propagation
The experiment - long-term GNSS measurements to monitor changes in multipath propagation
errors GNSS signal - was implemented at the field laboratory of the Research Institute of Geodesy, Topography and Cartography, v.v.i.
The coherence will be low when there are more number of multipath propagation
in the medium.
For CS based channel estimation methods, an important assumption of sparse multipath channel, where a multipath propagation
channel can be separated into a few strong paths and many uncountable weak paths whose transmission energy is approximate to zero, should stand in practical application.
To make the system robust to multipath propagation
, a cyclic prefix is added.
In SS communications, the ZCZ property can make spreading codes more robust to the effects of multipath propagation
. In fact, a delay spread Tmax within the ZCZ interval may be tolerated, assuming that each ith user's signal, affected by a relative path delay Ti, satisfies the condition:
Small scale fading is caused by multipath propagation
and Doppler spread.
Other topics include chaos in optical communications, channel equalization for chaotic communications systems, using coupled maps to improve synchronization performance, blind source separation in the context of deterministic signals, isochronal synchronization and digital chaos-based communication, and the robustness of chaos to multipath propagation
For studying multipath propagation
in this channel, we consider ray theory model  as a mathematical model.