Why multi-path channel has linear phase within the coherence bandwidth?

1. Why is the linear phase important for a signal to be distortion less?
2. What is channel coherent bandwidth?
3. What is a multipath channel?
4. What is the coherence bandwidth for fading channels?

Why is the linear phase important for a signal to be distortion less?

So if the phase is linear then all the frequency components of the signal will undergo the same amount of delay in time-domain which results in shape preservation.

What is channel coherent bandwidth?

Coherence bandwidth is a statistical measurement of the range of frequencies over which the channel can be considered "flat", or in other words the approximate maximum bandwidth or frequency interval over which two frequencies of a signal are likely to experience comparable or correlated amplitude fading.

What is a multipath channel?

Multipath channel (MPC) allows you to code a single transmission group for host-to-host communication that uses multiple write-direction, read-direction subchannels, as illustrated in Figure 1.

What is the coherence bandwidth for fading channels?

The coherence bandwidth is proportional to the inverse of the RMS delay spread, or roughly to the reciprocal of the maximum excess delay [4, p. 960]. Narrow band signals, then, are susceptible to flat fading. Flat fading is countered by error correction coding and diversity reception.