Orthogonal frequency division multiplexing (OFDM) technology can combat multipath fading and eliminate inter-symbol interference. OFDM has a very high spectral efficiency and it is widely used in HDSL, ADSL, WLAN and other areas. However, OFDM technology has many disadvantage. The main shortcoming of OFDM is high of ratio about peak to average power . This Paper discusses about the high peak to average power ratio of OFDM system, and study the companding algorithms of reducing the PAPR using simulating method with matlab software. Main work is as follows:
First, paper reviews the OFDM development process, explains the principle of OFDM technology, illustrates the advantages and disadvantages of the technology, and simulates the OFDM system. Then, the definition of peak to average power ratio is given. The reasons for high peak to average power ratio is analyzed. Finally, the companding algorithm is realized and analyzed using MATALB software. Simulation results show that companding algorithm can reduce PAPR, but the bit error rate of OFDM system by applying companding algorithm is to be increased, which verifies the theory.
Keywords: orthogonal frequency division multiplexing, peak-to-average power ratio, Compression expansion transformation
