5G will be applied to the large-scale Internet of things, which means billions of devices will be connected to each other. 5G is bound to improve the efficiency of multi-transmission to meet the challenge of large-scale Internet of things. In order that the adjacent bands do not interfere with each other, the signal radiation in and out of the band must be as small as possible. OFDM can realize post-processing of waveform, such as adding window in time domain or filtering in frequency domain to improve frequency localization