DESIGN OF OPTIMAL INTERPOLATION FILTER FOR SYMBOL TIMING RECOVERY

We propose an optimal interpolation filter for symbol timing recovery in a digital receiver where the input analog-to-digital (A-D) conversi on sampling clock is not synchronized to the transmitter symbol clock, The optimal filter is designed by minimizing the mean-square error (M SE) at the output of the receiver, assuming that the correct timing di fference between the nonsynchronized input samples and the correct str obe synchronized to the symbol is given, The MSE minimization procedur e results in a system of linear equations which can easily be solved t o yield the optimal filter coefficients, We also analyze the symbol tr acking performance of a symbol synchronizer that employs the proposed optimal interpolation filter. Although the proposed optimal filter is designed assuming the availability of the correct timing difference, w e show that it minimizes the timing estimation error variance even whe n the computed timing difference values deviate from the ideal, We als o show that the timing estimation is virtually unbiased if the length of the interpolation filter is greater than or equal to 4. Simulation results are included to show the performance improvement realizable by employing the optimal interpolation filter.