PAPR Reduction in MIMO OFDM Using Unitary Matrix Precoding

Abstract:
Peak to Average Power Ratio (PAPR) plays an important role in orthogonal frequency division multiplexing (OFDM) systems, and therefore has been addressed extensively in the literature, resulting in diverse mitigation techniques. OFDM systems employing multiple transmit and receive antennas (MIMO) have received less attention. These have mostly been considered as an extension of OFDM and have been addressed by similar techniques. In this paper we propose a new approach to PAPR reduction in OFDM MIMO, which is based on precoding with general unitary matrices. We exploit the fact that in certain MIMO transmission schemes, the capacity is invariant to unitary matrix precoding, and reveal new degrees of freedom allowing the minimization of PAPR. We propose a new unitary matrix based selective mapping (SLM) technique that jointly precodes all transmit antennas. The proposed method exhibits significant PAPR reduction at low computational complexity. Index Terms—OFDM, MIMO, PAPR, SLM.