Research On Pre-distortion Algorithm Of OFDM Modulation In Wideband Wireless Communication System

With users and business needs of the wireless communication system, limited spectrum will become increasingly crowded. Because the broadband communication technology has high spectrum efficiency, it has become one of the development trends of wireless communication. The OFDM technology has a variety of advantages, including anti-interference ability, high spectrum efficiency, high-capacity broadband communication support, etc. Since, it widely applied in wireless communication system. But OFDM has some huge disadvantages, one of which is high Peak-to-Average-Power Ratio problem. The PRAR of OFDM signal is high, making it particularly sensitive to non-linear amplifier and easy to produce nonlinear distortion. Because the broadband signal is the one transmitted in the broadband wireless communication system, the memory of broadband amplifier distortion can not be ignored. Currently, the research on nonlinear distortion and memory distortion of broadband power while maintaining its linear amplification range, has become one of the hotspots of broadband linear amplifier.In order to solve the non-linear broadband amplifier and memory distortion, better application of OFDM technology to the broadband wireless communication system, while improving the efficiency of the power amplifier in response to the country's national policy. This paper studies the basic OFDM technology, broadband power amplifier distortion characteristics and broadband amplifier model, and proposes two adaptive pre-distortion algorithms for OFDM modulation. The first technical solution is to be separated from the time domain adaptive pre-distortion algorithm. The program extracts the memory and non-linear characteristics of broadband amplifier by sending a reasonable test sequence and separating algorithm. It uses two lookup tables for memory and non-linear distortion correction and adaptive update respectively. The program has been used in the actual project. Its effect is obvious. ACLR is less than 40 d B, and power amplifier efficiency has been increased by 10% to 15%. The second technical solution is a new frequency-domain pre-distortion technology, which is based on the characteristics of signal of OFDM. Currently the program has applied for a national patent. By using a lookup table simulates nonlinear and memory characteristics of broadband power amplifier, which can redress the distortion from nonlinear and memory of broadband amplifier. The simulation results are obvious. The frequency domain OFDM pre-distortion scheme, the structure of which is simple and practical, can facilitate the improvement of the whole star power amplifier efficiency. Furthermore, it can reduce the complexity of the system and save cost. So, it is significant to research on the application of the two schemes to the broadband wireless communication system.