Research On PAPR And Interference Of Carrier Frequency Offset In FBMC System With Carrier Aggregation

Filter bank multicarrier(FBMC) has a lower out-of-band emission than orthogonal frequency division multiplexing(OFDM), which makes it to be a candidate modulation technology for the next generation mobile communication system. Considering the requirement of 10 Gbps peak rate in next generation mobile communication system, this thesis introduces the carrier aggregation into FBMC system to expand the system bandwidth indirectly. Due to the multiple component carriers in the system, peak to average power ratio(PAPR) is further deteriorated. Considering the interference of carrier frequency offset in the system, multiple component carrier frequency offsets also need to be estimated. Aiming at these two problems in FBMC system with carrier aggregation, the corresponding algorithms are studied in this thesis and the main research content is summarized as follows:1. Considering the higher PAPR of FBMC system with carrier aggregation, the PAPR reduction techniques of discontinuous carrier aggregation and continuous carrier aggregation are studied respectively. For the discontinuous carrier aggregation in FBMC system, each component carrier is served as a naturally-divided sub-block and multiplied by different phase rotation factor to optimize PAPR, based on the principle of partial transmission sequence. At the same time, considering that the system adopts OQAM modulation to separate real and imaginary parts of signal, the phase rotation factor is multiplied by the input signal in frequency domain directly, which overcomes the problem that the original signal could not be recovered if it is multiplied by the input signal in time domain. Finally, aiming at the characteristics of symbol overlapping in the system, multi-symbol joint processing is also used to eliminate the peak value proliferation and in turn reduce PAPR. For the continuous carrier aggregation in FBMC system, considering its better out-of-band emission performance, some subcarriers in guard band between the component carriers are served as reserved subcarriers, and the cyclic clipping method is employed to fill the redundant data in those reserved subcarriers to reduce PAPR. Moreover, backward superposition method is also needed to eliminate PAPR regression derived from the symbol overlapping. Simulation results show that these two algorithms can reduce the PAPR without worsening the symbol-error-rate(SER) performance.2. Considering the problem of multiple carrier frequency offsets estimation, a joint estimation algorithm for multiple carrier frequency offsets is studied in this paper. In the algorithm, each training sequence group with good correlation performance is allocated to a component carrier, which contains a number of same training sequences to construct the periodic symbol interval. Based on the signal space method, the periodic symbol interval corresponding to training sequence on each component carrier is intercepted to construct output signal matrix. With the eigen decomposition of covariance matrix, this algorithm constructs an spectrum function of carrier frequency offset and searches for the peak values to estimate multiple carrier frequency offsets. Moreover, the peak value of cross-correlation function between the frequency offset compensation signal and the corresponding signal without frequency offset is used to complete the allocation of multiple frequency offsets to the component carriers. Simulation results show that the algorithm can effectively complete the estimation and distribution of multiple carrier frequency offsets.