Enhanced DC estimation via sequence-specific frequency offset

A method for improving DC estimation over any particular training sequence is presented for use in direct conversion receivers. It is known that direct-conversion receivers suffer from a large DC-offset, which often cannot be adequately removed by a simple average of the received signal. To alleviate this problem, the DC offset can be jointly estimated with the channel over the training sequence in baseband. However, training sequences designed to facilitate channel estimation are not necessarily good for the estimation of DC offset. In the proposed method, an intentional frequency offset tailored to each training sequence is imposed at the radio front-end in order to improve the ability of estimating DC over that training sequence in digital baseband. We analyze the resulting DC estimation error and show analytically how the optimal frequency offset can be derived for each training sequence. Using the EDGE air interface, we demonstrate that significant gains can be achieved with this new method.