A Study Of The Methods To Reduce Peak-to-average Power Ratio Of MIMO-OFDM System

With the rapid development of wireless communication, higher data transmission rate service such as telephone conference is an urgent need. Current communication system can not meet a requirement of higher data transmission rate. Orthogonal frequency division multiplexing (OFDM) technology not only effectively overcomes the frequency selective fading of a wireless channel, but also has higher spectrum efficiency. Multiple input multiple output (MIMO) technology can obtain spatial diversity gain and enhance the channel capacity without increasing spectral resources and the transmit power. A hybrid of the two is called MIMO-OFDM, which opens a bright path to realize the high-speed and reliable data wireless transmission.There is a serious peak-to-average power ratio (PAPR) problem of MIMO-OFDM for its multi-carrier modulation. A large PAPR requires devices such as power amplifiers with large dynamic range, or it will result in a nonlinear distortion and reduce the performance of the system. Therefore, studying how to effectively reduce the PAPR of the MIMO-OFDM system is significant.The thesis is organized as follows: it firstly provides an overview of the OFDM theory and its PAPR property, followed by an introduction to the MIMO-OFDM system and three common space-time coding methods. Then, the signals characteristics for the MIMO-OFDM system with space-time block codes (STBC) is analyzed. At the end, the methods to reduce the PAPR of the MIMO-OFDM system are discussed.In this work, the study on PAPR mainly focuses on non-distortion methods. Several methods based on selective mapping (SLM) and partial transmit sequence (PTS) to reduce the PAPR of MIMO-OFDM are first introduced, followed by an analysis of their computational complexity and side information. Then, some methods are proposed based on the characteristics of STBC-OFDM system to resolve the high complexity and much side information. At last, a more efficient method without side information called carrier interference is proposed for STBC-OFDM system.This work intends to find a method with lower computational complexity and less side information to reduce the PAPR in MIMO-OFDM system. It mainly solves the PAPR problem for MIMO-OFDM system coded with STBC.