Coherence Time

Coherence time is the time duration over which the channel impulse response is considered to be not varying

$T_c=\frac{c}{v}\times \frac{1}{f}$

• $c$ is the velocity of the signal,
• $v$ is the velocity of the receiver (e.g., moving car or train), and 
• $f$ is the frequency of the carrier signal that is being modulated