The wireless channel is usually unreliable, and it mainly suffers from time-varying fading due to multi-path propagation.

The problems mainly exhibit to be multi-path propagation in the wireless fading channel, signal fading caused by the scattering and Inter-Symbol Interference caused by the long multi-path time delay.

A typical model to simulate the multi path effects up to three different propagation paths was introduced, more paths 'simulation can be implemented by increasing the number of same units.