Research Into The Algorithm Of Reducing PAPR With Low Computational Complexity In OFDM Systems

Orthogonal Frequency Division Multiplexing (OFDM) is an effective technique for multi-carrier parallel transmission, it has high bandwidth efficiency and good capability to resist multi-path interferences. So it has been widely used in several areas such as Asymmetrical Digital Subscriber Line (ADSL), Digital Audio Broadcasting (DAB), High Definition TV (HDTV) and Wireless Local-Area Networks (WLAN). However, it has an intrinsic weakness of high Peak-to-Average Power Ratio (PAPR) of the transmitted signal. This weakness makes a high request for the linearity of power amplifier in transmitter and receiver, and increases the complexity of A/D and D/A convertor. High PAPR is one of main bottlenecks of OFDM technology for practical application. It has significance to reduce PAPR in OFDM systems.Based on introducing the basic OFDM principle, we analyze the reason and influence of high PAPR in OFDM systems, give out PAPR's mathematic definition and depict regularities of distribution for statistic characteristics. Based on analyzing the previous works of reducing PAPR, we introduce methods of PTS and companding transform, and propose an improved PTS algorithm with low computational complexity. Whereas companding transform can deteriorate Bit-Error-Rate (BER) performance of system, we propose a new PTS-optimized companding transform algorithm. Simulation results show that the algorithm keeps companding transform original advantage in reducing PAPR aspects, meanwhile it evidently improves BER performance of system.