Research On High Spectral Efficiency OFDM-RoF System

With the rapid development of mobile Internet and the multimedia service,the need for the transmission rate of the wireless communication shows explosive growth.The Radio over Fiber(RoF)combines the flexibility of wireless access with the large capacity and low loss of optical fiber communication,which can meet the demand for transmission rate.Orthogonal Frequency Division Multiplexing(OFDM)has drawn a lot of attention because of its high spectral efficiency and strong anti-interference ability.The OFDM-RoF system,which combines OFDM technology with RoF technology,will become one of the potential technologies for future wireless communication in the future.However,high peak-to-average power ratio(PAPR)of the OFDM-RoF system tends to cause nonlinear distortion.In this paper,the simulations to reduce the nonlinear distortion of OFDM-RoF system is established.The main content and innovations are as follows.(1)In this paper,the basic principle and the key technologies of RoF and OFDM are analyzed and the characteristics of two techniques are summarized.Three methods to generate millimeter wave and the effect of higher PAPR of OFDM signal on nonlinear distortion in OFDM-RoF system are respectively described.(2)In this paper,five methods,which are Clipping-Filtering,?-law Pressure Expansion,Selective Mapping,Partial Transmit Sequence and DFT spreading,to reduce the PAPR of OFDM signal are analyzed.In addition,the effect of four methods on the PAPR reduction of OFDM signal are verified by the simulation.Moreover,the advantages and disadvantages of the five methods are analyzed.Finally,the DFT spreading method is selected for computational complexity comparison.By comparison,the DFT spreading algorithm has lower computational complexity than the other two methods,and can effectively reduce the PAPR of OFDM signals,which provides the algorithm basis for the following system verification.(3)Through the comparison of simulation experiments,the centralized mapping DFT spread spectrum method is selected.Then,the simulation is carried out for the OFDM-RoF communication system designed in Chapter 3.Through the system,the effect of centralized mapping DFT spread spectrum to reduce PAPR is experimentally verified.The simulation results show that DFT spreading algorithm can effectively reduce the PAPR of OFDM signal,and can significantly improve the nonlinear distortion of OFDM-RoF system,which contribute to increase the transmission distance and receiver sensitivity of the system.