The present disclosure is described in the exemplary context of a Long Term Evolution (LTE) cellular network and is directed to a method and apparatus for estimating a gain and phase imbalance between an in-phase path and a quadrature path of a receiver operating in such a network. The method and apparatus specifically exploit channel coherence in time and frequency, and the properties of the Primary Synchronization Signal (PSS), and/or the Secondary Synchronization Signal (SSS), and/or information in the Physical Broadcast Channel (PBCH), all of which are defined by the LTE standard, to estimate the gain and phase imbalance of the receiver while it remains connected to a base station to receive data.