Research On Channel Estimation And Channel Equization In OQAM/FBMC System

Although Orthogonal Frequency Division Multiplexing(OFDM)technology plays an important role in modern wireless communicationi,it is facing great challenges in terms of spectrum utilization,user experience rate and traffic density with the rapid industrial development such as Internet of Things and smart cities.The Filter Bank Multi-Carrier technology(FBMC)uses a prototype filter with good time-frequency characteristics to obtain higher spectrum utilization,smaller out-of-band leakage,and more flexibility,which makes FBMC technology find a wide range of applications in wireless communication.However,the offset quadrature amplitude modulation used by the FBMC system to ensure transmission rate relaxes the conditions of subcarrier orthogonality,which causes the system to generate inherent interference and degrades the system channel estimation and equalization performance.The thesis mainly studies the channel estimation and equalization technology of OQAM / FBMC system.First,the thesis summarizes the principles of the OFDM system and analyzes the characteristics of its filter bank.Then the principles of FBMC and OQAM modulation technology are described in detail.The transmission characteristics of the wireless channel and its effect on the OQAM / FBMC system are introduced.Then,in the channel estimation technology of OQAM/FBMC system,the research includes the system's channel estimation model,pilot structure and existing channel estimation algorithms' processing methods for inherent interference.paired pilot method(POP)and interference approximation method(IAM)based on the block pilot are conducted,and then the theoretical derivation and analysis of the formula for the signal-to-noise ratio gain after smoothing filtering are carried out.In response to the flaws of the smoothing filtering algorithm,a channel estimation algorithm based on iterative preprocessing is proposed.This algorithm performs iterative smooth filtering on the channel estimation values on subcarriers based on the correlation between the subcarriers.Then it was compared with the smoothing algorithm to analyze the signal-to-noise ratio processing gain and complexity.Based on the scattered pilot structure,a detailed theoretical analysis and simulation verification of the auxiliary pilot method(AP)and the modified interference approximation method(MIMA)are carried out,and for the fast fading scenarios,a feedback interference calculation method is optimized.This algorithm calibrates the pseudo-pilot estimation information by the secondary pilot before performing the iterative interference calculation,thereby improving the accuracy of channel estimation.Simulation results show that the algorithm performs well under fast fading channels.Finally,in the channel equalization technology of the OQAM/FBMC system,an in-depth study are carried out,which mainly involves the system's demodulation mathematical model,the existing linear equalization algorithm and the iterative interference cancellation equalization algorithm(IIC),and the theoretical analysis and performance of these algorithms simulation are carried out.Then based on the IIC algorithm,a MMSE-IR-IIC equalization algorithm is proposed to improve the channel equalization performence.In this algorithm,the suppression of interference and noise in the pre-estimation of transmitted symbols are considered,so it obtains a better channel equalization performence.Simulation results show that the algorithm has a great improvement in equalization performance compared to the traditional IIC algorithm.