Research On Waveform And Multiple Access Technologies In 5G Uplink

With the rapid development of communication technology,the 5G era has arrived,and the requirements for the communication system are also higher and higher.Higher transmission rate,ultra large capacity,ultra low communication delay,better user experience,and higher spectrum efficiency and so on.This paper mainly focuses on improving the spectrum efficiency and communication overloading problems.To improve the spectrum efficiency,orthogonal frequency division multiplexing(OFDM)is a kind of important multi-carrier technology,not only has been widely used in the 4G,but also as a very important candidate wave in 5G.However,compared with the previous generations mobile communication systems,5G can not only consider the mobile broadband services,but also needs to consider the massive machines connection,high reliability and low delay problems.OFDM has some inherent shortcomings:it is sensitive to the frequency synchronization error,asynchronization,and Doppler expansion.For the future more diversified business,higher spectrum efficiency and mass connection,it is not enough to continues to use OFDM waveform technology in 5G.So this paper mainly focuses on the theoretical analysis and comparison of several new technologies of OFDM deformation.Based on the LTE link level simulation platform,different modulation methods,user interference,delay,multipath interference,peak to average power ratio/cubic metric,and error vector magnitude are simulated.The advantages and disadvantages of different waveforms are shown in different cases.In order to solve the problem of communication congestion in communication overloading,the competition based random access mechanism has become a hot research topic of the physical layer in 5G.However,the simultaneous transmission of multi-user will result in signal aliasing,that will make receiver can not complete signal detection normally.This paper designs a novel structure of preamble.Collisions of multiple users can be detected based on well-designed structure of the preamble.Furthermore,channel state information can be estimated as a byproduct in the process of collision detection.And the proposed preambles are applied in flat-fading channel,multipath channel and asynchronous scenario.The simulation results validate the accuracy and robustness of the proposed scheme.