Design Of Sub-Band Filter For Filtered-OFDM System

OFDM(Orthogonal Frequency Division Multiplexing)is widely used in 4G mobile communication as a multi-carrier technology,but because of the many defects in technology itself,it is not the best waveform generation technology in the current era.The shortcomings of OFDM are mainly manifested in the following aspects:OFDM spectrum structure is too single,OFDM spectrum out-of-band leakage is very serious,OFDM time-frequency synchronization requirements are extremely strict.So the high capacity,wide coverage,fast rate,low latency as the criterion of 5G technology came into being.In this paper,Filtered-OFDM,one of the 5G alternative waveforms,is the main research object.As Filtered-OFDM is a major improved OFDM waveform,it overcomes many shortcomings of OFDM.Due to the addition of subband filters,limiting the OFDM symbol spectrum excessive leakage,and because the filter was added so that each sub-band energy of formation between isolated physically interfere with each other;interfere with each other because each sub-band may employ a different modulation and coding schemes,so Filtered-OFDM can support multiple modulation and coding modes at the same bandwidth,the waveform is very flexible;and supports asynchronous transmission.But there is no more specific filter design methods,so here we self-designed Filtered-OFDM downlink,and select one of the two sub-bands,were added for each sub-band filter bandwidth,and repeated attempts by adjusting The order of the filter is used to find the filter which is most suitable for the target subband.At the same time,the bit error rate of the receiver is compared with that of the different subband protection bandwidth.Finally,considering the filter order and the protection bandwidth,OFDM system simulation performance,and select a better filter as Filtered-OFDM waveform generation sub-band filter.