Transmission and detection of side information for selected mapping in MIMO OFDM

In order to reduce the peak-to-average power ratio (PAR) of multi-antenna orthogonal frequency-division multiplexing (MIMO OFDM) systems selected mapping (SLM) and its MIMO extensions are considered. With SLM the transmission of some side information is necessary. In this paper, we focus on the approach of embedding the side information into the OFDM frame using combinations of unrotated and π/4 rotated QAM constellations, known for single-antenna systems, and extend it to the MIMO scenario. Moreover, we analyze the detection and estimation of the side information at the receiver. We analyze soft decision for the side information and derive strategies for joint estimation (within one MIMO OFDM frame) of the embedded side information. Numerical results show that the PAR reduction performance behaves conversely to the side information error performance. For instance, directed SLM exhibits the best PAR reduction performance of the SLM variants discussed in this paper but is slightly more prone to transmission errors. However, applying the schemes mentioned above is beneficial to the side information error performance of directed SLM.