Beamforming MISO-OFDM PAPR Reduction: A Space-User Perspective

A novel space-user approach to multiple-input-single-output (MISO) OFDM peak-to-average-power ratio (PAPR) reduction is examined. We propose two techniques that significantly reduce PAPR for MISO-OFDM at various userloads. The first exploits the degrees of freedom in the channel’s null-space (transmit weight optimization), while the second provides a more robust and higher reduction by further relaxing the constraint on the constellation domain (constellation-beam modification) with modest computational overhead. Both methods can be implemented by lowcomplexity projection-onto-convex-set (POCS) iterations, have no data rate loss, and are fully compatible with various constellation choices and receiver structure in practical systems. The algorithms proposed achieve up to 6.65 dB reduction in peak power for an 8-antenna MISO transmitter. Index Terms Orthogonal frequency multiplexing (OFDM), peak-to-average-power ratio (PAPR), multiple-input-single-output (MISO), beamforming.