Question

For fast fading channel, the coherence time of the channel is smaller than _______ of transmitted signal.

(a) Doppler spread

(b) Bandwidth

(c) Symbol period

(d) Coherence bandwidth

I have been asked this question in exam.

Question is taken from Types of Small- Scale Fading topic in section Mobile Radio Propagation: Small – Scale Fading and Multipath of Wireless/Mobile

Answer 1

The correct choice is (c) Symbol period

The explanation: In fast fading channel, the channel impulse response changes rapidly within the symbol duration. Thus, the coherence time of the channel is much smaller than the symbol period of the transmitted signal.