Coherence Bandwidth
Coherence bandwidth is a concept in wireless communication and signal processing that relates to the frequency range over which a wireless channel remains approximately constant in terms of its characteristics.
coherence bandwidth is The inverse of Doppler spread delay time, or any spread delay time due to fading in general. The coherence bandwidth is related to the delay spread of the channel, which is a measure of the time it takes for signals to traverse the channel. The two are related by the following formulae:
Coherence bandwidth = 1/(2*pi*delay spread time)
(Coherence bandwidth in Hertz)
For instance, the coherence bandwidth is 2 MHz when the delay spread is 80 ns in a household indoor environment.
Coherence bandwidth is a measure of the frequency spread over which a wireless communication channel behaves approximately like a flat fading channel. In other words, it's the bandwidth over which the channel's frequency response remains relatively constant. Coherence bandwidth is a crucial parameter in the design of wireless communication systems, particularly for systems that employ frequency-selective fading channel models.
Coherence Time
MATLAB Code1 to find Coherence Time and Coherence Bandwidth
Output
Coherence Bandwidth: 498867.5012 Hz
Coherence Time: 2.0045e-06 seconds
Relationship between Coherence Time and Delay Spread
The coherence time of a wireless channel is related to its delay spread. Delay spread refers to the time difference between the arrival of the first and last significant multipath components of a signal. Coherence time represents the time over which the channel's impulse response remains relatively constant, and it's inversely proportional to the delay spread.
The relationship between coherence time (Tc) and delay spread (Td) can be approximated using the formula:
Tc≈1/β⋅Td
where β is a factor depending on the specific characteristics of the wireless environment, typically ranging from 2 to 4.
MATLAB Code to find Relationship between Coherence Time and delay Spread