Peak-to-Average Power Reduction in MIMO OFDM by Spatial Nulling

In this paper, a novel method of reducing the peak- to-average-power ratio (PAR) of multi-antenna OFDM systems is presented. The PAR is reduced by the addition of a PAR reduction signal to the transmitted signal. This PAR reduction signal is constrained to lie within the null space of the channel. Hence, only the original transmitted signal is received at the receiver because the channel nulls out the reduction signal. In this scheme, with the help of partial channel state information, the need for sending side information or allocating reserved tones (required for several existing PAR reduction schemes) is eliminated. We also present simulation results showing the performance improvement in the bit-error-rate curves while using the spatial nulling technique.