A receiver that receives a reference symbol comprising a sequence of a plurality of synchronization repetition patterns, wherein each repetition pattern contains a predetermined number of samples. The reference symbol is part of a digital signal modulated by using OFDM modulation. An end synchronization repetition pattern in the reference symbol is phase-shifted by 180°, and the phase-shifted synchronization repetition pattern is positioned after the sequence of the number of synchronization repetition patterns. The receiver detects a timing of a correlation peak at the end of said reference symbol by performing a cross-correlation of the synchronization repetition patterns.