New methods to reduce intercarrier interference in OFDM systems

Performance of orthogonal frequency division multiplexing (OFDM) is heavily dependent on the intercarrier interference (ICI) caused by frequency offset. Recently, this ICI is shown to be mitigated by using the partial transmit sequence (PTS), in which the PTS weights minimizing the peak ICI noise-to-signal power ratio (MinMax search) are selected. The exhaustive search leads to exponential complexity in the number of PTS weights. Therefore, an algorithm using a modified sphere decoder to avoid exhaustive search is proposed. Furthermore, a new algorithm called MinSum is also introduced to minimize the total ICI power. Compared with exhaustive search, the MinMax and MinSum algorithms reduce complexity by IO and 170 times. Moreover, both algorithms are robust to mismatched optimization.