Iterative symbol synchronization using variable IIR and FIR fractional-delay filters with arbitrary oversampling ratios

Software radio systems employ direct conversion receivers with asynchronous sampling such that the actual sampling instants are not synchronized with the incoming symbols. In this paper, an iterative low-complexity symbol synchronization algorithm is proposed. In our proposal, the timing estimate is obtained using two iteration rounds. Qn the first iteration round, we find a rough estimate of the timing error and on the second iteration round, we obtain our final improved timing error estimate. The technique is illustrated with example implementations using both FIR and IIR FD filters showing improved estimation accuracy with comparisons to previously published results. Furthermore, the proposed iterative symbol synchronization algorithm is also shown to reduce the overall implementation complexity.