ENERGY DETECTION OF UNKNOWN SIGNALS OVER FADING CHANNELS

Abstract

There are differences in characteristics between fast and slow fading .These differences have great importance for the mathematical modeling of fading channel and performances evaluation of operating channel. The coherence time Tc of the channel concern with the motion. The coherence time has a relation with the channel Doppler spread fd and is given as If the coherence time Tc is greater than the symbol time duration Ts then fading channel is said to be slow, otherwise it is considered as fast fading. In slow fading, many successive symbol will be affected by certain fade level and results burst errors. In fast fading the symbol to symbol fading is de-correlated. It becomes necessary to observe the changes of the fading channel from one symbol duration to the next. This should be done through a range of correlation models depends on communications scenario and the propagation environment