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Selective fading is due to the time-dispersive medium. When an impulse (short pulse) is sent out from the base-station antenna, due to man-made structures the reflected waves travel in different paths and arrive at the mobile-unit antenna at different times. They form a signal e(t).
- What is selective fading?
- What is the difference between flat and selective fading?
- What is meant by fading in communication?
- What are the causes of fading?
- What causes time dispersion and frequency selective fading?
- Where does selective fading occur?
- What is large scale fading?
- What is coherence bandwidth and coherence time?
- What is fading in microwave?
- What is rician fading channel?
- What is frequency selective?
- What does fade in mean?
- What is coherence time in wireless communication?
- What do you mean by short term fading?
What is selective fading?
Selective fading or frequency selective fading is a radio propagation anomaly caused by partial cancellation of a radio signal by itself — the signal arrives at the receiver by two different paths, and at least one of the paths is changing (lengthening or shortening).
What is the difference between flat and selective fading?
"Flat fading, or nonselective fading, is that type of fading in which all frequency components of the received signal fluctuate in the same proportions simultaneously. Selective fading affects unequally the different spectral components of a radio signal."
What is meant by fading in communication?
In Wireless Communication, fading refers to the attenuation of the transmitted signal power due to various variables during wireless propagation. ... Fading can cause decline in performance in a wireless communication system because it results in the loss of signal power thus reducing the Signal to Noise Ratio (SNR).
What are the causes of fading?
What Causes Fading. Fading can be caused due to natural weather disturbances, such as rainfall, snow, fog, hail and extremely cold air over a warm earth. Fading can also be created by man made disturbances, such as irrigation, or from multiple transmission paths, irregular earth surfaces, and varying terrains.
What causes time dispersion and frequency selective fading?
Explanation: Multipath delay spread leads to time dispersion and frequency selective fading. Doppler spread leads to frequency dispersion and time selective fading. These two propagation mechanism are independent of each other.
Where does selective fading occur?
Frequency selective fading occurs when the symbol length is shorter than the delay spread, or equivalently when signal bandwidth is larger than the channel bandwidth.
What is large scale fading?
Large scale-fading represents the average signal-power attenuation or path loss due to motion over large areas and it is impacted by terrain configuration between the transmitter and receiver, and over a very long distance (several hundreds or thousands of meters), there is a steady decrease in power.
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 is fading in microwave?
The overall performance of fixed point to point microwave systems is limited by short-duration, large, received signal power variations called fading. ... Its effect is to produce a short-duration, broad, frequency-independent signal power depression near the operating frequency. This produces the well-known flat fade.
What is rician fading channel?
Rician fading or Ricean fading is a stochastic model for radio propagation anomaly caused by partial cancellation of a radio signal by itself — the signal arrives at the receiver by several different paths (hence exhibiting multipath interference), and at least one of the paths is changing (lengthening or shortening).
What is frequency selective?
A frequency-selective surface (FSS) is any thin, repetitive surface (such as the screen on a microwave oven) designed to reflect, transmit or absorb electromagnetic fields based on the frequency of the field.
What does fade in mean?
Definition of fade-in
: a gradual increase in a motion-picture or television image's visibility at the beginning of a sequence.
What is coherence time in wireless communication?
Coherence time is the time duration over which the channel impulse response is considered to be not varying. Such channel variation is much more significant in wireless communications systems, due to Doppler effects.
What do you mean by short term fading?
Fading- Fast (Short) Term. ➢ Describes the constant amplitude fluctuations in the received signal as the mobile moves. ➢ Caused by multipath reflection of transmitted signal by local scatters (houses, building etc.) ➢ Observed over distances = λ/2 ➢ Signal variation up to 30 dB. ➢ Is a frequency selective phenomenon.
