A combined SLM and closed-loop QO-STBC for PAPR mitigation in MIMO-OFDM transmission

A closed-loop quasi-orthogonal space time block coding scheme developed by Toker, Lambothoran and Chambers has much attraction due to its full diversity and full rate. This scheme exploits feedback from the receiver to the transmitter and rotation of certain antenna transmitted symbols by a particular phase value to achieve an effectively orthogonal code matrix. This technique however ignores the effect of increased peak-to-average power ratio (PAPR) introduced by the phase rotations, and the associated demands on the range of linearity of transmission power amplifiers. This work focuses on jointly achieving full diversity and full rate whilst minimizing PAPR. Two symbols within an orthogonal frequency division multiplexing (OFDM) frame are therefore either used for transmitting selected mapping side information or for PAPR mitigation thereby retaining the diversity gain of the multiple antennas whilst being able to perform the PAPR mitigation. For an OFDM system with 128 subcarriers and QPSK data symbols, the new scheme shows that the multiple antenna PAPR can be effectively reduced.