| With the development of wireless technology,we have to increase the spectrum efficiency for the growing demand for spectrum resources and limited spectrum resources.Co-time Co-frequency full-duplex system has a significant performance advantage on a number of key indicators,such as system capacity,outage probability,bit error rate and diversity multiplexing gain.Thus this technology has received wide attention at home and abroad.The biggest challenge to realize full duplex communication is the elimination of the self-interference signals.This thesis is to research the impact of RF impairments on the residual self-interference signal and introduce a new self-interference cancellation method in consideration of the impact of RF impairments.In this paper,we firstly introduce the full-duplex system,with a brief introduction of the system principles and existing system models.Then various existing domestic and foreign methods to eliminate the self-interference are introduced,including antenna self-interference cancellation,analog self-interference cancellation and digital self-interference cancellation.A brief introduction to common RF impairments and their models is also given in this paper.And then we choose the full-duplex OFDM system as the research object and model the residual self-interference signal with RF impairments in the existing system compared with the signal without RF impairments.Finally,conclusions from the above comparison show that current digital self-interference scheme cannot eliminate the effects of RF impairments.Therefore,we must take the RF impairments into consideration when we want to eliminate the self-interference completely.Considering the impact of RF impairments,this paper focuses on a new improved scheme based on the current digital self-interference cancellation.The scheme is based on the output signal from the transmitter power amplifier.By introducing an addition receiver chain,we can take the output signal as the reference signal to eliminate the self-interference signal with the adaptive filter.The adaptive filter can be used to model the self-interference channel,thus we can rebuild a more accurate self-interference signal and further improve the performance of the digital self-interference cancellation.The simulation results show that the performance of new scheme based on mitigating the impact of RF impairments is better than current linear cancellation scheme,which results in about 10 dB gain. |
