1. A method of performing coherent detection for differentially encoded orthogonal-frequency-division-multiplexing (OFDM) systems, said method comprising: providing a series of consecutive OFDM data symbols in a digital multimedia broadcasting (DMB) frame of a signal received by a receiver; storing a channel phase value of a first OFDM data symbol in said series of consecutive OFDM data symbols; calculating a primary estimate of a channel phase difference by hard thresholding said first OFDM data symbol; combining said channel phase value of said first OFDM data symbol with said primary estimate of said channel phase difference; generating a secondary estimate of a said channel phase difference of a second OFDM data symbol based on the combined channel phase value of said first OFDM data symbol and said primary estimate of said channel phase difference, wherein the first and second OFDM data symbols are consecutive OFDM data symbols in said DMB frame; correcting decisions of which OFDM data symbols to encode based on said secondary estimate of said channel phase difference; sending the corrected decisions to a Viterbi decoder in said receiver for decoding of said OFDM data symbols; plotting said series of consecutive OFDM data symbols in a graphical format; connecting the plotted OFDM data symbols with a line; and determining a region of the plotted series of consecutive OFDM data symbols where said primary estimate of said channel phase difference is likely to be correct, wherein said region is determined by: corresponding a frequency to each OFDM data symbol; for each said frequency, calculating an average phase difference of a number of neighboring frequencies of a particular frequency of interest; calculating a variance of said neighboring frequencies to said particular frequency of interest; and calculating a mean value of said variance over an entire OFDM data symbol, wherein said region is defined as frequencies over which a value of said variance is below said mean value of said variance.