Research On Non-orthogonal Multicarrier Transmission Technology

The fifth generation mobile communication system(5G), as a new generation of mobile communication system, comes into being and develops to meet the human society's demand for mobile communication five years later. It will have a very high spectrum efficiency and energy efficiency; and will be an order of magnitude higher or even higher than that of 4G in utilization rate of resource and data rate. One of 5G's key technologies that are symbolic is the multicarrier transmission technology.OFDM has high spectrum efficiency and low implementation complexity, and can combat with multipath fading, so it has been adopted by various types of wireless mobile communication systems. OFDM is also very sensitive to carrier frequency offset, and has high peak to average power ratio and has much out-of-band radiation; for all of these shortcomings, OFDM is not suitable for some application scenarios of 5G. So there is a need to study a new generation of multicarrier transmission technology that can be applied in the application scenarios of 5G. This paper investigates wireless multicarrier transmission technology, focusing on non-orthogonal multicarrier transmission technology, completing the following major research:Firstly, this paper analyses the main technology in 4G, namely OFDM. Not only verification is deduced theoretically, but also shows its performance in various aspects through a specific Matlab simulation; and summarizes its disadvantages, and explains the unfavorable factors of the application in 5G.Secondly, according to the main reason for which OFDM is not suitable for 5G, this paper raises three non-orthogonal multicarrier transmission technologies, namely Filter Bank Multicarrier(FBMC), Generalized Frequency Division Multiplex(GFDM), and Universal Filtered Multicarrier(UFMC). This paper describes and analyses the principle and design criteria of each system in detail, and analyses the performance of the three kinds of multicarrier technologies theoretically through mathematical derivation. Consequently, clarifies the reason why they are suitable for the application scenarios of 5G.Thirdly, the advantages of three non-orthogonal multicarrier transmission technologies mentioned in this paper compared with OFDM is verified by combining with Matlab simulation.Finally, analyses the reason for its high complexity in GFDM system, and concludes that matrix transpose and a large number of complex multiplication operations will cause high system complexity. On this basis, puts forward an improved system transmitter design method. According to the sparse matrix on the advantages of small amount of calculation and the equivalent relationship between circular convolution in time domain and multiplication in frequency domain, and the theory that the specific filter coefficients are usually real number, this paper states the design principle of the improved transmitter and describes the equivalent implementation process of the system through mathematical derivation, and The result shows that it has lower complexity compared with the original system.