a computer implemented method of providing rstd data comprising receiving an uncertainty window centered around an expected rstd value , determining the pdp of each reference ofdm symbol within the uncertainty window , obtaining a main pdp by calculating a parameter indicative of signal quality for each determined pdp , the main pdp having the highest signal quality , obtaining a preceding pdp of the main pdp , obtaining a succeeding pdp of the main pdp , determining pdp metrics comprising , determining a channel metric for each of the main , preceding and succeeding pdps , determining a channel main tap for each of the main , preceding and succeeding pdps , determining a delay estimate for each of the main , preceding and succeeding pdps , wherein if the main pdp is a combined pdp , performing coherence testing on the pdp metrics to detect any ambiguity in the delay estimate of the main pdp , and correcting any ambiguity .