This page describes decimation process with figures and example,mention matlab command for decimation.
Decimation is the process which decreases the sampling rate of the signal. Hence it is also called Down sampling. This is done by removing or dropping samples. We need to check here for any violation of sampling theorem.
Decimation exampleX (n) = [0 1 2 3 4 5 6 7 8], at Fs sample rate
D=2, sampling factor
Y (n) = [0 2 4 6 8], at Fs/D sample rate
MATLAB command for decimation>> resample
IQ_4 = resample (IQ_25, 4, 25)
Here IQ_25 is the IQ data at 25 MSPS
IQ_4 is the IQ data at 4 MSPS