This invention discloses a method and an apparatus for reducing false alarm rate in preamble detection due to discontinuities between successive symbols in a received signal. The invention is usable in, e.g., a LTE compliant system. In one embodiment, the apparatus includes a filter for filtering the received signal to yield a filtered signal, and a correlator for correlating the filtered signal with a predetermined preamble. The apparatus further comprises a first multiplier for modifying the received signal before it is filtered, or a second multiplier for modifying the filtered signal before it is correlated, or both. The first multiplier multiplies the received signal with a first time-domain window function configured to substantially smooth discontinuities at symbol boundaries in the received signal. The second multiplier multiplies the filtered signal with a second time-domain window function configured to substantially suppress spikes present in the filtered signal around the symbol boundaries.