A method for processing input data for use in a time-deinterleaver of a receiver is provided. Input data is first received, wherein the input data is data inputted to the time-deinterleaver and includes a plurality of symbols and each symbol includes a plurality of samples and each sample includes a signal quality (SQ) data corresponding thereto. A down sampling ratio is then determined according to a channel condition. The input data is down-sampled in the time and/or the frequency domain with the down sampling ratio according to whether a modulation mode is a single carrier mode or a multi-carrier mode and outputting the down-sampled data. Thereafter, the outputted down-sampled data is stored in a data buffer of the time-deinterleaver for further signal processing.