PAR reduction in OFDM via active constellation extension

The high peak-to-average power ratio (PAR) in orthogonal frequency division multiplexing (OFDM) modulation systems can significantly limit performance. Methods exist which alter or introduce new signal constellations to combat large signal peaks. We present an improved PAR-reduction method that dynamically extends outer constellation points in active (data-carrying) channels, within margin-preserving constraints, in order to minimize the peak magnitude. This scheme simultaneously decreases the bit error rate slightly while substantially reducing the peak magnitude of an OFDM transmit block and requiring no side information. PAR reduction for an approximated analog signal is considered, and a 4.5 dB reduction is obtained for 256-channel QPSK OFDM. The results show great promise for use in commercial systems.