Joint channel and DC offset estimation and synchronization with reduced computational complexity for an EDGE receiver

EDGE (Enhanced Data rates for GSM Evolution) is a set of improvements to the GSM, aiming at providing higher data rate transmission per radio timeslot and increasing spectral efficiency. Such high data rates put new requirements on the receiver design. On the other hand, the receiver design needs to be efficient from a cost, size and power consumption point of view in order to allow high volume production. A receiver architecture that fulfills such mobile terminal requirements is e.g. the direct conversion receiver. Such a receiver, however, suffers from some problems. One of the problems is that the DC offset can not be eliminated completely in the RF part of the receiver and has to be taken care of in the baseband signal processing. Lindoff (2000) proposed to use a least square (LS) algorithm to jointly estimate the channel parameters and the DC offset by a standard correlation algorithm for synchronization. In an environment which generates a high delay spread to the signal, this algorithm can be applied directly only with very high computational complexity, for the LS estimation has to be repeated several times. In order to reduce the complexity we propose to introduce a fine-synchronization step before the LS estimation. This step, usually used for channel estimation and synchronization in the absence of DC offset, can reduce the computational complexity by a factor 5 or 6.