I am doing spectral shaping in OFDM , so I am applying a raised cosine filter to the signal at the end of the transmiiter chain after the IFFt and the guard interval insertion ,right before the Digital to Anlog converter and sending it over my link(in my case optical fiber).
I have my System in c++ and the output before the spectral shaping is a block of complex samples(every 256 represent one ofdm symbol) and i want to multiply that with my RC filter which is function in time ,
w(t) = 0.5 + 0.5*cos(pi +pi*t/(ß*T)) for 0<t>ß*T
w(t)= 0.5 + 0.5*cos((t-T)*pi/(ß*T)) for T<t<(1+ß)T
`w(t)=1; for the middle part
ß is the roll off factor
How can i apply that fiter on my discretized series of complex values , i dont have it as a function in time
convert the filter function into its spectrum and apply it to the ofdm symbols in your ofdm transmitter