Research On Peak-to-Average Power Ratio Reduction And ICI Self-cancellation In Universal Filtered Multicarrier Systems

Universal Filtered Multicarrier(UFMC)technology is one of the candidate technologies for the Fifth Generation(5G)mobile communication.It is evolved from orthogonal frequency division multiplexing(OFDM)technology and filter bank multicarrier technology(FBMC).Compared with OFDM technology,UFMC technology replaces rectangular filters in OFDM technology with prototype filters with better performance.Compared with FBMC technology,UFMC technology reduces the length of time-domain filters for a group of subcarriers and achieves joint gain of OFDM and FBMC technology.However,UFMC belongs to multi-carrier modulation technology,and has the same peak-to-average power ratio(PAPR)problem as OFDM and FBMC.In addition,the subcarriers in the UFMC subband are still orthogonal,and carrier frequency offset will damage the orthogonality between subcarriers,resulting in deterioration of system performance.This chapter studies the above problems,and the specific research results are as follows:In order to solve the problem of high peak-to-average power ratio in UFMC system,the power threshold can reduce the number of sample signals in time domain of peak power in the traditional PTS method,thus reducing the computational complexity of the traditional PTS method.The multi-level optimization PTS method can solve the problem that the calculation amount of the traditional PTS method increases exponentially with the number of elements in the phase set.In order to further reduce the computational complexity of the traditional PTS method,a PTS method combining multi-level optimization and power threshold is proposed in this article.In addition,theoretical analysis shows that the proposed method can adopt the same fixed threshold at all stages,which can further simplify the structure of multi-level PTS optimization method based on power threshold.The proposed multi-level PTS algorithm based on fixed power threshold can not only guarantee the PAPR performance of UFMC system,but also significantly reduce the computational complexity of traditional PTS algorithm.Aiming at the problem of inter-subcarrier interference caused by carrier frequency offset in UFMC system,two ICI self-cancellation algorithms under UFMC system are proposed.The ICI self-cancellation algorithm performs 1/2 special coding on the original data in the frequency domain of the transmitter,and uses the characteristics that the adjacent subcarriers have similar interference coefficients when the carrier frequency offset is small,and can be combined and received to get better system performance when the carrier frequency offset is small.The proposed algorithm performs theoretical analysis on the 1/2 code rate based encoding with half of the repeated information in a transmission symbol,and concludes that there is a relational expression about the frequency offset in the signal after the frequency domain equalization at the receiver.Using the frequency offset expression estimates the frequency offset,and the frequency domain estimated frequency offset is fed back to the time domain for frequency offset compensation,and then the ICI self-cancellation algorithm is used,which can make the frequency offset of the ICI self-cancellation algorithm wider and the system bit error rate performance better;The frequency offset estimated in the frequency domain is directly compensated in the frequency domain,and then the ICI self-cancellation algorithm is used,which not only obtains better bit error rate performance,but also reduces the computational complexity of time-domain frequency offset compensation scheme.The above work is of great value to the further development of UFMC technology.