From Delay Spread to Coherence Bandwidth?

1. What is the relationship between RMS delay spread and coherence bandwidth?
2. How do you calculate channel coherence bandwidth?
3. What is the effect of delay spread?
4. What happens when transmission bandwidth is greater than coherence bandwidth?

What is the relationship between RMS delay spread and coherence bandwidth?

Coherence bandwidth is related to the inverse of the delay spread. The shorter the delay spread, the larger is the coherence bandwidth.

How do you calculate channel coherence bandwidth?

Bandwidth (range of frequencies) over which channel is constant is called coherence Bandwidth. The better way to calculate coherence bandwidth is using RMS Delay Spread, as different channel will experience different signal intensity over different delay span with same delay spread.

What is the effect of delay spread?

Frequency-selective fading caused by multipath time delay spread degrades digital communication channels by causing intersymbol interference, thus resulting in an irreducible BER and imposing a upper limit on the data symbol rate.

What happens when transmission bandwidth is greater than coherence bandwidth?

If MDM signals occupy a bandwidth much greater than the coherence bandwidth of the capacity, statistical averaging over frequency should cause the outage channel capacity to approach the average channel capacity. Figure 11.18 shows the outage capacity as a function of SNR, for signals occupying different bandwidths.