Research On Key Techniques Of Generalized Frequency Division Multiplexing

Generalized Frequency Division Multiplexing(GFDM)is a new waveform based on OFDM technology and filter bank multi-carrier technology.It has the advantages of low peak-to-average ratio,low out-of-band radiation,high spectrum utilization,etc.It is a potential physical layer waveform in the future of mobile communications.At present,most of the studies on GFDM do not consider the impact of the channel.However,synchronization and channel estimation are problems that must be solved in system design.Therefore,it is of great significance to study synchronization techniques and channel estimation techniques.This thesis focuses on the preamble-based GFDM synchronization techniques and pilot interference cancellation algorithms in channel estimation.The main work of this thesis is as follows:1.The related theory of GFDM system has been studied,including modulation and demodulation principle of GFDM,low-complexity GFDM modem,and the system's shaping filter design.2.The preamble-based synchronization technique for GFDM has been studied.(1)Aiming at the problem that the synchronization performance is degraded due to the influence of large frequency offset in the existing algorithms,an improved GFDM time-frequency synchronization algorithm is proposed,which can correct large frequency deviations.The simulation results show that the improved algorithm has better synchronization performance than the existing algorithms in the case of large frequency offset,and the frequency estimation range can reach the entire system bandwidth.(2)For the problem of timing advancement of the first path when the number of available subcarriers is smaller than the total number of subcarriers,a GFDM timing synchronization algorithm based on statistical optimization is proposed.The simulation results show that when the SNR is greater than 4dB,the first-path detection performance of the improved algorithm is much better than the existing algorithm.(3)For flat fading channel,a low-complexity GFDM time-frequency synchronization algorithm based on special receiver processing flow is proposed.The timing synchronization of this algorithm is not interfered by other side peaks,and the timing is accurate.The frequency offset estimation range up to the entire system bandwidth.3.The pilot interference cancellation algorithm in GFDM channel estimation has been studied.(1)In the first type of model,for the problem that the channel estimation performance loss caused by the interference approximating processing of the Pilot-IC algorithm and the problem that the unsatisfactory spectral performance of the Tx-IC algorithm when the total number of time slots is even,an improved pilot interference cancellation algorithm based on ZF receiver is proposed.The simulation results show that the channel estimation performance of the proposed algorithm is superior to that of the Pilot-IC algorithm,and its spectral performance is much better than that of the Tx-IC algorithm.(2)In the second type of model,for the problem of serious pilot interference of the OP algorithm and the HM algorithm,an interference-free pilot design concept was introduced and applied to the GFDM system.The simulation results show that the interference-free pilot algorithm eliminates the channel estimation mean square error and error rate platforms of the OP and HM algorithms.(3)A interference-free pilot in a full-duplex GFDM system is designed,a full-duplex GFDM platform is built,and its digital domain self-interference suppression capability is simulated.The simulation results show that the full-duplex GFDM system based on the interference-free pilot can obtain the digital self-interference suppression ability comparable to that of the full-duplex OFDM system.