A novel approach for symbol timing estimation based on the extended zero-crossing property

Carrier- and data-blind recovery of the sym- bol timing is of paramount importance in digital receivers, i.e., detailed knowledge about carrier frequency and phase or any pilot sequences is not necessary for proper operation. In this context, feedforward algorithms are particularly useful in packet-oriented systems, where rapid and stable acquisition of the major transmission parameters is essen- tial for subsequent processing stages. In the current paper, we propose a novel approach for blind estimation of the symbol timing, which needs just one or two samples per symbol. The new method is characterized by introducing a second filter in parallel to the receiver matched filter. Un- der Nyquist conditions, this filter exhibits an impulse re- sponse satisfying the extended zero-crossing property, i.e., it vanishes for all integer multiples of the symbol period, including the origin! Using this idea for a suitably designed timing estimator, it is shown that the annoying jitter floor – typical for most timing estimators and caused by pattern noise – can be avoided.