Research On The GFDM System Out-of-band Radiation And PAPR Reduction

Currently, mobile communication systems have gradually developed from 4G towards 5G. Orthogonal Frequency Division Multiplexing(OFDM) is the core technique in the application of 4G, however, it has many disadvantages such as: high out-of-band radiation, high peak-to-average power ratio(PAPR), sensitive to Carrier Frequency Offset(CFO), unable to meet the short delay requirements TI system asks for and also the data short pulse requires for Vehicle to Vehicle(V2V), so OFDM cannot be applied in 5G communications. But Generalized Frequency Division Multiplexing(GFDM)which is derived from OFDM can meet the needs of 5G communications, and it is the main candidate technologies of 5G. This thesis will analyze whether the high OOB radiation and high PAPR exist in GFDM system or not. As for the high PAPR in the GFDM system, we will take two techniques to suppress it and then compare their effectiveness. Specifically, the main contents of this paper are divided into three parts:Firstly, we study the basic principle of GFDM system. Since the pulse shaping filter existing or not is the main difference between GFDM and OFDM system, we will compare the BER performance through various filters. Here, we put the emphasis on four typical pulse-shaping filters: RC, RRC, Xia 1st and Xia 4th filter. Then, we compare the system communication performance when the roll-off factor of RC filter changes under three channels, which are Gaussian White Noise Channel(AWGN), Frequency Selective Channel(FSC) and Rayleigh Time Varying Channel(TVC).Then, we study the characteristics of GFDM system, OOB radiation and PAPR. On the one hand, since the original mission of GFDM system is to reduce the OOB radiation, so this thesis verifies the presence of high OOB radiation in OFDM system, and then give simulations on the same problem in the GFDM system. On the other hand, investigate the PAPR performance in GFDM system. Similar to the high OOB radiation problem, this paper first carries on the confirmatory test in the OFDM system and then simulates in the GFDM system, aiming to examine whether the GFDM system exists the high PAPR.Finally, we investigate two methods to reduce GFDM system PAPR. Firstly, we investigate how the Clipping technology in the OFDM system can suppress PAPR, and then explore whether Clipping can reduce PAPR in GFDM system. Lastly, apply the improved CT method in GFDM system, examine whether there is PAPR reduction, and compare the PAPR reduction ability between Clipping and MCT method. The results show that, MCT behaves better than Clipping in GFDM system PAPR suppression.