Research On Hybrid Carrier Waveform Design And Detection Technology Based On Time-frequency Localization Analysis

As a compatible form of the single carrier(SC)system and the multi-carrier(MC)system,the Hybrid Carrier(HC)system based on Weighted-type Fractional Fourier Transform(WFRFT)has higher flexibility in waveform design.At the same time,compared to the SC system and the MC system,the signal energy is more evenly distributed in the time-frequency plane,which helps to obtain better bit error rate(BER)performance over doubly-selective(DS)channels.This dissertation explores the waveform design and detection method of the joint localization idea under the WFRFT framework,and demonstrates the advantages of the joint localization and averaging method.The tools used in this dissertation to reflect the idea of localization are mainly Fast Convolution(FC),partial Fast Fourier Transform(PFFT),and multi-vector interleaving algorithm.These time-frequency localization analysis tools are introduced into the HC system to further expand the flexibility of HC waveform design and detection performance.The main research work can be expressed as follows.The conventional HC system,whose resource blocks are usually not divided at the transmitter,belongs to the single-particle HC system.In the conventional single-particle HC system,the band equalization and PFFT demodulation are usually used to deal with the fading effect of the DS channels.Although its performance is better than the performance of conventional SC and MC systems after adopting the same method under DS channels,there is still room for improvement.Based on this,this dissertation further adopts timefrequency localization methods such as FC and PFFT to be combined with WFRFT,and proposes the HC detection algorithms based on the overlap-save structure of FC to remove the residual interference of the conventional hybrid carrier after banded MMSE equalization or PFFT demodulation,so as to improve the detection performance of the HC system under the DS channels.The specific detection algorithms based on the overlap-save structure of FC include the HC detection algorithm based on the overlap-save structure and PFFT demodulation and the HC detection algorithm based on the overlap-save structure and banded minimum mean square error(MMSE)equalization.These two methods have different complexity and different requirements for channel state information,thus they can be selected according to actual needs.The full knowledge of the channel state information is assumed in the previous research,then the BEM-based channel estimation is added,which considers the channel estimation algorithm research in the HC system based on the overlap-save structure and proves that the proposed algorithm outperforms the conventional one with the same pilot design and channel estimation algorithm.Aiming at the problem of interference between multi-subband of the centralized multi-particle hybrid carrier system,which treats each subband as a particle,FC is introduced to complete the frequency domain localization processing,and a filtered hybrid carrier transmission method based on FC is proposed.In order to avoid interference between subbands,the conventional HC system mainly performs waveform design based on single-particle consideration.The introduction of FC-based filtering into the HC system can not only make the waveform design of the HC system more flexible,but also reduce the complexity of filtering.The proposed FC-based multi-subband filtered hybrid carrier system can retain the advantages of HC and use the FC-based filter structure to flexibly complete the subband configuration.This dissertation studies the implementation structure of the system in detail,and analyzes its out-of-band suppression performance,Peakto-Average Power Ratio(PAPR)performance and BER performance.The system structure no longer depends on the use of CP,which improves the spectrum efficiency.Over the frequency-selective channel,this dissertation derives the closed-form expressions of BER and improves the existing equalizer to improve performance for the scenario of large delay spread;Over the doubly-selective channel,the system can be combined with the detection algorithms based on the overlap-save structure of FC to maintain the superiority of performance.Aiming at the conventional single-particle signal form of HC,the distributed localization method of multi-vector interleaving is introduced,thus the design scheme of extended HC waveform based on multi-vector interleaving and corresponding detection technology are proposed.Then the conventional single-particle HC system is extended to the distributed multi-particle HC system,which treats each HC vector as a particle.The interleaved distributed localization method and HC can be effectively combined to improve the flexibility of waveform design and the BER performance over fading channels.The performance of the proposed extended HC waveform based on multi-vector interleaving over frequency-selective channels and DS channels is analyzed in detail,and its closed-form expressions of BER over frequency-selective channels are deduced.Besides,the residual interference is analyzed to illustrate the performance advantages over DS channels.What’s more,for the proposed extended HC waveform based on multi-vector interleaving,the “WFRFT order” and “vector length” of each vector can be appropriately selected to meet the needs of different transmission environments.