1. A method comprising: an apparatus non-coherently combining either results from correlating a received preamble sequence with root sequences in use in a cell or results from correlating a first instance of the received preamble sequence and a second instance of the received preamble sequence with root sequences in use in a cell, or results from correlating a first portion of the received preamble sequence and a second portion of the received preamble sequence, with the root sequences in a cell; the apparatus setting a first detection threshold based on the non-coherently combined results; the apparatus comparing correlation peaks from the correlating to the first detection threshold; the apparatus coherently combining either results from correlating the received preamble sequence with the root sequences, or results from correlating the first instance of the received preamble sequence and the second instance of the received preamble sequence with the root sequences; the apparatus setting a second detection threshold based on the coherently combined results; and the apparatus detecting the preamble sequence using the root sequences whose correlation peak exceeds either the first detection threshold or the second detection threshold.