8. introduction to small scale fading
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Small scale fading, also known as fading, describes the rapid fluctuations of signal amplitude and phase over short periods of time. It is caused by interference between multiple versions of a transmitted signal that take different paths to the receiver. This can result in changes to amplitude, phase, and time of arrival depending on factors like multipath propagation, Doppler shifts from mobile speed, movement of surrounding objects, and the signal bandwidth.
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8. introduction to small scale fading
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- 3. • Definition: • SmallScale fading or simply fading , is used to describe the rapid fluctuations of the amplitude and phase over a short period of time or distance. • Causes: • Fading is caused by interference between two or more versions of the transmitted signals which arrives at the receiver at slightly different times. These waves are called the multipath waves that are combined at the receiver end. • Effects: • As the result of signal combining, there will be a change in amplitude and phase depending on • Distribution of intensity • Relative propagation time • Bandwidth of propagated signal
- 4. • Multipath Propagation: •Presence of reflecting objects and scatters in the channel creates a constantly changing environment that affects the signal in terms of amplitude, phase and time. • This leads to a situation that the receiver could receive multiple copies of transmitted waves that have difference phase and time of arrival and creates Signal smearing. • Speed of Mobile: • The relative motion between the base station and the mobile station results in random frequency modulation due to different Doppler shifts on each of the multipath component.
- 6. • Speed ofsurrounding objects: • If the objects in the radio channel are in motion, they include time varying Doppler shift on multipath components. Movement of surrounding > Mobile User Fading Movement of surrounding < Mobile User Ignored • Transmission Bandwidth of the signal: Bandwidth of the Signal > Bandwidth of the Channel Signal is affected rapidly and smearing will also be high. Bandwidth of the Signal < Bandwidth of the Channel Fading is not significant
- 7. Definition of SmallScale Fading Causes of Small Scale Fading Effects of Small Scale Fading Factors Influencing the Small Scale Fading Multipath Propagation Speed of the Mobile Gives Raise to Doppler Shifts Speed of Surrounding Transmission Bandwidth of the signal