Peak power reduction in MIMO OFDM via active channel extension

High peak to average power ratio (PAR), a major drawback in single-input-single-output (SISO) systems using orthogonal frequency division multiplexing (OFDM), has already found many methods of reduction. The active channel extension (ACE) method reduces analog PAR by as much as 3.5 dB with no reduction in data rate by altering constellation points. We present an extension of this original method for PAR reduction for multi-input-multi-output (MIMO) systems in general. This new scheme, compatible with variable power allocation, minimizes PAR on each antenna in a similar manner as in the SISO system. It also supports any number of unique constellations and number of antennas by moving outer constellation points appropriately depending on the constellation for the particular channel and antenna. Simulations with 4 antennas at both transmitter and receiver show analog peak reductions of more than 3 dB overall for all 4 antennas.