Sampling rate conversion and symbol timing for OFDM software receiver

Sampling rate conversion combined with symbol timing loop for orthogonal frequency division multiplexing (OFDM) software receiver is investigated. Generally, symbol timing and sampling frequency tracking for the OFDM receiver can be achieved by adjusting the ADC´s sampling frequency and phase with a voltage controlled oscillator (VCO). On a software radio platform, the intermediate frequency (IF) OFDM waveform is digitized with a free running clock. So, the symbol timing method of the OFDM receiver for software radio is a little different from the generally implemented one. To implement such an OFDM receiver, an interpolation loop is investigated to realize sampling rate to symbol rate conversion. Also, the residual symbol timing offset and sampling frequency error can be compensated by the NCO controlled loop. According to the proposed structure and the symbol synchronization methods, the symbol timing and sampling error tracking loop is constructed via computer simulation and the results prove that it is effective.