Factors Influencing Small-Scale Fading
There are several physical factors that influence Small scale fading. The main factors which influence small-scale fading are the following:
- In the channel due to the presence of reflecting objects and scattersa constantly changing environmentcreates that dissipates the signal energy in amplitude, phase, and time.
- These effects result in multiple versions of the transmitted signal that arrive at the receiving antenna,.
- The random phase and amplitudes of the different multipath components cause fluctuations in signal strength, thereby inducing small-scale fading, signal distortion, or both.
- Multipath propagation often lengthens the time required for the baseband portion of the signal to reach the receiver which can cause signal smearing due to intersymbol interference.
Speed of the mobile:
- The relative motion between the base station and the mobile results in random frequency modulation due to different Doppler shifts on each of the multipath components.
- Doppler shift will be positive or negative depending on whether the mobile receiver is moving toward or away from the base station.
Speed of surrounding objects:
- If objects in the radio channel are in motion, they induce a time varying Doppler shift on multipath components resulting in fading.
- If the surrounding objects move at a greater rate than the mobile, then this effect dominates the small-scale fading.
The transmission bandwidth of the signal:
- If the transmitted radiosignal bandwidth is greater than the "bandwidth" of the multipath channel,the received signal will be distorted, but the received signal strength will notfade much over a local area (i.e., the small-scale signal fading will not be significant).