Synchronization for all digital receivers

When data are transmitted from one location to another, the receiver must reconstruct the time base of the transmitter in order to convert the continuous time received signal into a sequence of data symbols. Synchronization is the process of reconstructing this time base. There are two synchronization problems encountered in passband communication systems: Symbol timing recovery and Carrier recovery.; Implementation of the receiver by digital techniques implies sampling of the input signal. In many circumstances the sampling cannot be synchronized to the correct symbol timing of the incoming signal. Digital processing of frequency multiplexed signals is an example. As it is not possible to alter the sampling clock, symbol timing recovery must be performed by interpolation. Conventional interpolation filters to achieve this are based on continuous time functions such as the sinc function. These filters are not optimal and can therefore degrade the SNR.; An interpolation filter optimal in a particular sense is proposed for symbol timing recovery in a digital receiver where the input analog-to-digital conversion sampling clock is not synchronized to the transmitter symbol clock. The optimized filter is designed by minimizing the mean square error (MSE) at the output of the receiver. The MSE minimization procedure results in a system of linear equation which can easily be solved to yield the filter coefficients. The tracking performance of the synchronization system employing this interpolation filter is also analyzed. Simulation results are included to show the performance improvement realizable by employing the optimized interpolation filter.; All digital symbol timing recovery using a filter bank and interpolators is computationally more efficient than an oversampling technique in a multichannel FDM receiver. This is demonstrated by performing a detailed analysis of the two schemes for the headend demodulator in the upstream direction in a coaxial cable system.; A new algorithm is proposed for estimating the carrier frequency offset from a block of PSK symbols. Its computational complexity is comparable to existing methods, but it attains the Cramer-Rao bound down to lower input SNR values for somewhat smaller values of frequency offset.