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What is coherence bandwidth and coherence time?
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 happens when transmission bandwidth greater than coherence bandwidth?
Therefore, a wideband signal which occupies frequency band greater than coherence bandwidth will experience frequency selective fading, so the knowledge of the coherence bandwidth of radio channels in the area covered by radio communication system service allows to decide whether the usage of equalizer unit in radio …
What is the cluster size for CDMA?
What is the cluster size for CDMA? Explanation: CDMA systems have a cluster size of N=1. Therefore, frequency reuse is not as difficult as for TDMA or first generation cellular systems.
Why is coherence bandwidth important in an OFDM system?
If training intervals are required, the training intervals need to happen faster than the coherence time would indicate. Likewise coherence bandwidth, for an OFDM system in particular, suggests that the frequency-domain equalizer coefficients over certain bandwidth spans will be similar.
So “coherence bandwidth” is related to the FT of the delay spread, and that delay spread is expected to stay correlated with itself over the length of the coherence time. Hope that helps a bit. Similarly, the doppler spread is the inverse of the coherence bandwidth, which means having a high coherence bandwidth will lead to small doppler spread!
How is coherence bandwidth related to frequency domain equalizers?
Likewise coherence bandwidth, for an OFDM system in particular, suggests that the frequency-domain equalizer coefficients over certain bandwidth spans will be similar. This is consistent with the definition you cited that the channel is essentially flat over the coherence bandwidth.
Time/Frequency Diversity Time Diversity ◦Transmit the same signal several times in different time-slots ◦In slow fading, it takes a long time to transmit another replica Frequency Diversity ◦Transmit a few replicas over different frequency band ◦With delay spread = 200ms, minimum frequency separation is 5KHz 40