1. A method for estimating IQ imbalance introduced on a receiver in a communication system, comprising the following steps: receiving a plurality of training signals comprising a preamble field with repeat training symbols during a frame time interval with N sampling intervals; calculating a ratio between each sampling point of the preamble field and a corresponding sampling point separated by N sampling intervals; deriving an equation for the calculated ratios assuming the calculated ratios are identical; and estimating parameters for IQ imbalance compensation according to the equation.