Research On Channel Estimation And Equalization Technology In FBMC System

The filter bank multi-carrier(FBMC)technology based on offset quadrature amplitude modulation(OQAM)is considered to be a promising multi-carrier technology,because of its high spectral efficiency,rapid out-of-band attenuation,and good time-frequency characteristics.However,due to the inherent interference in the FBMC/OQAM system,the traditional channel estimation and equalization algorithms cannot be directly applied to the system.Therefore,the implementation of channel estimation and equalization in FBMC/OQAM system has become a new challenge.This thesis mainly studies the channel estimation and equalization in FBMC/OQAM system.The research carries out the simulation verification on the bit error rate and normalized mean square error performance of the system,to provide a reference for the design of FBMC/OQAM system.The main work of this thesis can be summarized as follows:For the single-input single-output(SISO)FBMC system,a channel estimation algorithm with joint interpolation and feedback interference iteration is proposed,to solve excessive pilot energy or overlapping calculation windows in traditional channel estimation algorithms.Firstly,the pseudo pilot is reconstructed by the signal after equalization and demodulation.And then the channel estimation accuracy is increased by iterative operation.The proposed algorithm not only reduces the pilot energy,but also improves the channel estimation accuracy before iteration,through the interpolation with discrete prolate sequences.The simulation results show that the proposed algorithm has a significant improvement in system performance,when compared with the traditional discrete pilot algorithm.As for the multiple-input multiple-output(MIMO)FBMC system,a channel estimation algorithm based on interference cancellation is proposed,to solve large pilot overhead under the interference approximation method(IAM)pilot structure.The proposed algorithm combines the features of the PHYDYAS prototype filter,and uses the symmetry of the inherent interference to eliminate the interference.The proposed algorithm not only effectively enhances the channel estimation accuracy,but also reduces the overhead of the guard interval.The simulation results show that the bit error rate and normalized mean square error performance of the proposed algorithm are better than those of the traditional IAM algorithm.For the MIMO-FBMC system,an improved joint channel estimation and equalization algorithm is proposed,to solve the iterative interference cancellation(IIC)equalization algorithm ignores the influence of noise,and the traditional channel estimation algorithms neglect the residual interference of pilot symbols.This algorithm firstly proposes a channel estimation correction module,using the equalization information to calculate the residual interference of pilot symbols and eliminates it.Then,the minimum mean square error(MMSE)estimation algorithm with the consideration of noise correlation is used to suppress the effect of noise.Finally,the calculation accuracy of interference during equalization is continuously improved through iteration.The proposed algorithm not only validly improves the channel estimation performance through the channel correction module,but also further enhances the equalization performance by suppressing noise interference.The simulation results show that,the channel estimation and equalization performance are significantly improved of the proposed algorithm,when compared with the traditional channel estimation and equalization algorithms.