Editing Communication channel (section)

===Analog channel models===
In an analog channel model, the transmitted message is modeled as an [[analog signal]]. The model can be a [[linear]] or [[non-linear]], [[Discrete time and continuous time|time-continuous or time-discrete (sampled)]], [[memoryless]] or dynamic (resulting in [[burst error]]s), [[time-invariant]] or [[time-variant]] (also resulting in burst errors), [[baseband]], [[passband]] (RF signal model), [[Real number|real-valued]] or [[complex-valued]] signal model. The model may reflect the following channel impairments:
* [[Electronic noise|Noise]] model, for example
** [[Additive white Gaussian noise]] (AWGN) channel, a linear continuous memoryless model
** [[Phase noise]] model
* [[Interference (communication)|Interference]] model, for example [[crosstalk]] ([[co-channel interference]]) and [[intersymbol interference]] (ISI)
* [[Distortion]] model, for example a non-linear channel model causing [[intermodulation distortion]] (IMD)
* [[Frequency response]] model, including [[attenuation]] and [[phase-shift]]
* [[Group delay]] model
* Modelling of underlying [[physical layer]] [[Transmission (telecommunications)|transmission]] techniques, for example a complex-valued [[equivalent baseband model]] of [[modulation]] and [[frequency response]]
* [[Radio frequency propagation model]], for example
** [[Log-distance path loss model]]
** [[Fading]] model, for example [[Rayleigh fading]], [[Ricean fading]], log-normal shadow fading and frequency selective (dispersive) fading
** [[Doppler shift]] model, which combined with fading results in a [[time-variant system]]
** [[Ray tracing (physics)|Ray tracing]] models, which attempt to model the signal propagation and distortions for specified transmitter-receiver geometries, terrain types, and antennas
** [[Propagation graph]], models signal dispersion by representing the radio propagation environment by a graph. 
** [[Mobility model]]s, which also causes a [[time-variant system]]