Research On Peak-to-Average Power Ratio Reduction In SFBC MIMO-OFDM Systems Without Side Information

Multi-input multi-output (MIMO) exploits spatial diversity of wirelesscommunication systems to increase capacity and spectrum efficiency by employingmultiple transmitting and receiving antennas. On the other hand, orthogonal frequencydivision multiplexing (OFDM) can fight against frequency selective fading effectively.Therefore, a combination of MIMO and OFDM is able to provide large capacity androbustness to multipath fading. However, one of the significant challenges ofMIMO–OFDM systems is the high peak-to-average power ratio (PAPR).In this thesis, we propose two methods to tackle the PAPR problem inMIMO-OFDM systems with space frequency block coding (SFBC) without sideinformation. The first one is a tone reservation (TR) method. In the proposed TR method,signals on both antennas are taken into consideration to design the original peakreduction signal. Then, SFBC operations are taken to generate peak reduction signals forsignals on both antennas. Both theoretical and simulation results demonstrate that theproposed method can significantly reduce the PAPR for signals on both antennas.The second proposed method is a novel selective mapping (SLM) method withouttransmitting side information (SI). In this method, we innovatively link the positions of asmall number of null subcarriers in MIMO-OFDM systems with the indexes of the phasesequences of the SLM method. At the receiver, energy detection is adopted to find out thepositions of the null subcarriers, from which the index of the optimal phase sequence,called side information (SI) can be recovered. Simulation results show that the proposedmethod can get the same PAPR reduction with the traditional SLM method. Besides, theproposed SLM method does not need to transmit any side information, but it can achieve the same bit error rate (BER) performance with the traditional SLM method with perfectside information.