Research On Frequency Offset Estimation And Channel Estimation For GFDM

Mobile Internet and Internet of Things are two driving forces of mobile communication at present.Both of them jointly give birth to a mobile internet society characterized by huge traffic and widely used scenarios.The increase of access equipment,explosive growth of data flow and the development of new service have put forward higher requirements for transmission delay,connection density and spectrum utilization.OFDM technology is widely used in 4G because of its simple implementation and anti-multipath fading.But it also has the disadvantages of serious out of band leakage and low frequency spectrum efficiency,which is difficult to meet the diversified needs of 5G environment.As the key technology of 5G,the new multicarrier technology has been widely concerned in recent years.This paper mainly focuses on the research of the new type of multi carrier technology of generalized frequency division multiplexing(GFDM).The research focuses on the frequency synchronization,channel estimation and joint estimation of the two technologies.The specific research contents are as follows:Firstly,the basic principles of GFDM transmitter and receiver are described in detail,and the advantages and disadvantages of GFDM and OFDM in performance indexes such as out of band leakage,self-interference and PAPR are simulated and analyzed.The simulation results show that GFDM has low out of band leakage,and the out of band leakage decreases with the increase of roll off coefficient;In addition,GFDM has lower PAPR and higher spectral efficiency.The above characteristics make GFDM can better meet the needs of 5G mobile communication.Secondly,GFDM time-frequency synchronization technology is studied,and a carrier frequency offset estimation scheme with higher estimation accuracy is proposed.Symbol Timing Error and Carrier Frequency Offset will degrade the performance of GFDM system,so an effective estimation scheme is needed for time-frequency synchronization.The existing Data-Aided synchronization schemes still have room for improvement in estimation accuracy,but the blind estimation scheme has the problem of high computational complexity.To solve this problem,this paper proposes a leading symbol based on multiple repeated sub symbols.Simulation results show that the frequency offset estimation using this preamble is better than the existing methods.Finally,the joint estimation technology of carrier frequency offset and channel is studied,and a joint estimation scheme of GFDM based on EM algorithm is proposed.At present,the joint estimation scheme for GFDM system is very deficient.In order to solve this problem,this paper establishes a probability model for GFDM receiver signal,which makes EM algorithm suitable for joint estimation of CFO and channel.Simulation results show that the proposed method can effectively estimate the two parameters,and the estimation accuracy is better than the existing methods.