I have been breaking my head for a long time. Please help with this..any input would be helpful!
I am trying to implement a OFDM system using SDR (USRPN210 for Transmitter and USRP2 for receiver) using Simulink and my laptop (core i5).
Baseband specifications: OFDM signal sample rate = 25.6MS/s No. of samples in one frame = 10880 duration of one ofdm frame = 425e-6s signal bandwidth = 25.6MHz Used bandwidth is 22.4MHz
USRP specs: DAC Master clock rate (fixed)= 100MHz Interpolation factor = ??
As far as I have understood, I have to design a multirate system which converts 25.6MS/s to a sample rate which is a factor of the master clock rate i.e. 100MHz. And give the factor as the Interpolation factor.
For example, convert 25.6MS/s to 25MS/s and give interpolation factor as 4, so it matches with the 100MHz(25*4). However this causes Underrun. So I need to increase the interpolation factor and decrease the input baseband sample rate.
My problem is how to design a downsampler which will reduce the 25.6MS/s to a lower sample rate without loss of data.?