Hi Sindhu,
According to your last question about the difference between Gaussian and rectangular filters, I agree with the explanation given by Sam Sung. I just want to add from me that, according to a theory, your final filter choice will depend on shape of pulses that you have in your system. Here I mean that the “Matched filters” should be used for best filtration: the shape of your pulses should always match the shape of your filter’s impulse response!