Data-aided symbol timing estimation for linear modulation

Timing phase estimation (TPE) plays the key role in feedforward (FF) symbol timing. For reasons of performance often data-aided (DA) methods are preferred. But frequently, they turn out to be critical with respect to the implementation and the spectrum efficiency (due to the required overhead). This paper presents three DA TPE methods for quadrature pulse amplitude modulation (PAM). In spite of their very low complexity, these methods closely approach the theoretical limit for timing estimation with respect to the estimation variance, even at low SNR. This enables power efficient transmission. Further, they employ a CAZAC (constant amplitude, zero auto-correlation) sequence as training-sequence (TS), or a sequence with similar correlation properties. Since such sequences are suited for almost all DA receiver tasks, a high spectrum efficiency can be obtained by the use of a single TS. A generalization of the proposed methods for DA TPE with respect to the choice of the TS is also shown. The presented methods can be applied to noncoherent receivers. They are suited for high data-rate applications, since they can work with an oversampling factor of 2.