Sorry, I had to add some information. The topic is about frequency
domain equalization in broadband communication. It is an alternative to
OFDM to deal with frequency selective fading channel.

Hi,
For a single carrier system, rooted raised cosine pulse shaping filter
is generally used in both transmitting and receiving. I have read a
paper which said the FFT bin outside of signal plus excessive bandwidth
were set to zero to suppress aliasing signal component. I find that in
frequency selective fading channels, suppress aliasing signal component
does give better performance for ZF or MMSE equalizer than that without
suppressing. In AWGN channel, this will worsen the performance in
contrast. I think this is because suppress aliasing component will
distort signal. The above facts are right?

My second thought is that simply suppress some frequency component
without using windowing will generate Gibbson effect. I want to know if
there are some better method in simulation, or in field implementation?
In simulation, it is necessary to use low pass filter to suppress
aliasing component? Or, simply to chose a high order RRC filter? For
me, RC (or RRC) looks like a special low pass filter.

Thanks in advance