Multipath fading occurs when there is more than one transmission path t the MS or 4 BTS, and therefore more than one signal is arriving at the receiver. This may be due t buildings or mountains, either close to or far from the receiving device.
Time Dispersion
Time dispersion is another problem relating to multiple paths to Rx antenna either an MS or BTS. However in contrast to Rayleigh fading the reflected signal comes from an object faraway from the Rx antenna.
Time dispersion causes Inter-Symbol Interference (ISI) where consecutive symbols (bits) interfere with each other making it difficult for the receiver to determine which symbol is the correct one. An example of this is shown in the figure below where the sequence 1,0 is sent from the BTS.
If the reflected signal arrives one bit time after the direct signal, then the receive detects a 1 from the reflected wave at the same time it detects 0 from the direct wave the symbol 1 interferes with the symbol 0 and the MS does not know which is correct.
Time Dispersion
Time dispersion is another problem relating to multiple paths to Rx antenna either an MS or BTS. However in contrast to Rayleigh fading the reflected signal comes from an object faraway from the Rx antenna.
Time dispersion causes Inter-Symbol Interference (ISI) where consecutive symbols (bits) interfere with each other making it difficult for the receiver to determine which symbol is the correct one. An example of this is shown in the figure below where the sequence 1,0 is sent from the BTS.
If the reflected signal arrives one bit time after the direct signal, then the receive detects a 1 from the reflected wave at the same time it detects 0 from the direct wave the symbol 1 interferes with the symbol 0 and the MS does not know which is correct.
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