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Published in Lal Chand Godara, Handbook of Antennas in Wireless Communications, 2018
A universal relationship between coherence bandwidth and delay spread that would be useful for all applications does not exist. An approximation can be derived from signal analysis (usually using Fourier transform techniques) of actual signal dispersion measurements in particular channels. Several approximate relationships have been developed. If coherence bandwidth is defined as the frequency interval over which the channel complex frequency transfer function has a correlation of at least 0.9, the coherence bandwidth is approximately [16] () f0≈150στ
Wireless Transmission Mediums
Published in Mário Marques da Silva, Cable and Wireless Networks, 2018
The coherence bandwidth is defined as the bandwidth above which the signal starts presenting a frequency selective fading. In other words, a signal with a bandwidth higher than the coherence bandwidth presents different attenuations and nonlinear phase shifts* at different frequencies. This effect is known as distortion. As exposed in Chapter 3, in the case of digital transmission, the distortion is viewed in the time domain as interference.
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Published in Jerry D. Gibson, The Communications Handbook, 2018
coherence bandwidth represents a frequency range over which frequency components have a strong potential for amplitude correlation. That is, a signal's spectral components in that range are affected by the channel in a similar manner, as for example, exhibiting fading or no fading. Note that f0 and Tm are reciprocally related (within a multiplicative constant). As an approximation, it is possible to say that
Curve Fitting Optimization based Improved Channel Estimation for VANET
Published in International Journal of Electronics, 2022
Devesh Shukla, Arun Prakash, Rajeev Tripathi
The vehicular channel consists of special features such as high mobility and severe signal propagation environment due to the multiple reasons such as motion of transmitter, receiver, and stationary surroundings. These give rise to short channel coherence time while distance scatterers lead to long multipath components, resulting in narrow coherence bandwidth (Fernandez et al., 2011). Also, in vehicular communications maximum Doppler frequency is four times as compared to cellular scenarios with same speed (Mecklenbrauker et al., 2011). Thus time-varying characteristic of vehicular ad-hoc network (VANET) scenario is significant which makes the extraction of information and data tougher. Channel estimation plays a major role in providing a reliable communication in mobile environments. The precise estimation enhances the accomplishment of functions such as equalisation and demodulation.