Multiple input multiple output techniques combined

with orthogonal frequency division multiplexing (MIMO-OFDM)

provide a promising approach for wireless systems. However, a

serious drawback of the OFDM system is the high peak-toaverage

power ratio (PAPR), which may severely affect the

power efficiency of RF power amplifiers. In this paper, we

propose a simple method to reduce the PAPR of MIMO-OFDM

signals based on the use of unused subcarriers. Instead of

processing the signals at each transmitter separately, a peak

cancelling signal is generated at one antenna and is then applied

to all the others with only simple modifications. Simulation has

shown that a minimum 2 dB reduction in PAPR can be achieved

for all transmit signals using this approach. As the signal

processing is nearly all done at a single transmitter, repetition of

the operations at each transmitter is avoided, and therefore the

overall cost of the system can be significantly reduced.