A detect decision is made by non-coherently combining results from correlating a preamble (CAZAC) sequence with base/root sequences used in the cell and setting a detection threshold based on those combined results. Another threshold can be set based on coherently combining results from correlating the preamble sequence, in which case the detect decision is based on satisfying either one of the thresholds. Where the sequence repeats in the same preamble, the results that are combined are from correlating the first instance of the CAZAC sequence and from correlating the second instance of the CAZAC sequence. Where the sequence does not repeat, different segments of the CAZAC sequence, each less than the whole and not necessarily of the same length, are correlated for a partial correlation on each segment, then the segments are combined and used to set the detection threshold. Detection may be done in stages, adjusting the threshold after the first stage based on comparing the results of non-coherent and coherent combining.