Research On New Multi-carrier Transmission Technology Of Wireless Communication System

With the development of wireless communication,communication systems have profoundly changed the lifestyles of people.In the fifth generation(5G)of wireless communication systems,more and more new services and new application scenarios emerge,such as massive machine type of communication(mMTC)and Internet of things(IoT),etc.,require multi-carrier technology to support different service requirements such as low power consumption,massive connection,small data packets and asynchronous access.In addition,the emergence of new application scenarios will further aggravate the current situation of scarce spectrum resources.Therefore,how to better utilize the fragment spectrum of the existing licensed frequency bands is also one of the effective ways to solve the scarcity of spectrum resources in the future.The conventional orthogonal frequency division multiplexing(OFDM)technology has been widely used due to its simple implementation and resistance to multipath fading.However,OFDM technology also has the following disadvantages:serious out-of-band power leakage,strict synchronization,and low spectral efficiency due to the cyclic prefix(CP)added in each symbol.Therefore,in the face of 5G emerging application scenarios,these shortcomings of OFDM technology obviously cannot meet the diversified service requirements in the future.The new multi-carrier technology,as one of the key technologies of 5G,has received attention in recent years.New multi-carrier techniques typically utilize well-designed pulse shaping filter to suppress the out-of-band power leakage of the system.As a subcarrier filtering technique,the good filtering of generalized frequency division multiplexing(GFDM)and filter bank multi-carrier(FBMC)technology can also relax the time-frequency strictly synchronized requirements.In addition,GFDM and FBMC technologies reduce or eliminate the use of CP,which increases the spectral efficiency of the system.However,the introduction of pulse shaping filter also brings some drawbacks:the most important thing is that the non-orthogonal characteristics of the filter bring serious self-interference to the system,i.e.,inter-carrier interference(ICI)and inter-symbol interference(ISI),which results in a performance loss.Moreover,the impact of ICI and ISI is also not conducive to the application of existing channel estimation and multi-antenna technology in the new multi-carrier technology.This dissertation focuses on two new multi-carrier technologies,GFDM and FBMC.It aims to solve the self-interference problem in the new multi-carrier and how to use the new multi-carrier technology to meet the diversified requirements of 5G emerging application scenarios.The main research work and innovations of this dissertation can be summarized as:1.Research and performance analysis of ICI suppression based on GFDM technologyThe main research work in this part is to eliminate the interference between adj acent carriers of GFDM.Firstly,the self-interference in GFDM is analyzed.It can be seen from the analysis that ICI is the main interference.Then,two different solutions were proposed for ICI in GFDM:ICI cancellation method based on retransmission architecture and ICI cancellation method based on dual filter.In the retransmission-based method,it is mainly for the scene with retransmission.According to the characteristics of the two transmissions,the conditions for eliminating the ICI are given.Then,the pulse shaping filter that can satisfy the condition is designed and the impact of ICI can be eliminated through the combination of two information at the receiver.In the dual filter-based method,a dual-filter-based transmitter scheme is proposed first,and the condition of interference-free transmission is derived based on the scheme,and then the pulse shaping filter that can satisfy the interference-free transmission condition is designed in frequency domain;the dual-filter-based ICI cancellation method enables the GFDM to adopt a conventional channel estimation method,and can also be conveniently combined with a multi-antenna technology.2.Research on interference suppression based on FBMC technology and its simplified algorithmThe conventional FBMC/OQAM scheme is difficult to combine with existing channel estimation and multi-antenna schemes due to the use of offset quadrature amplitude modulation(OQAM).Therefore,this part focuses on the combination of FBMC and quadrature amplitude modulation(QAM).Firstly,aiming at the problem that the symbol length of FBMC/QAM matrix model is too long,a CS-FBMC/OAM scheme with shorter symbol length is proposed.In addition,in order to improve the demodulation performance of the scheme,a selection criterion of the filter is also given.The combination of FBMC and QAM can solve its difficulties in channel estimation and multi-antenna applications.Finally,in order to make the above scheme easier to implement,a simplified algorithm based on ZF receiver is proposed for FBMC/QAM and CS-FBMC/QAM schemes.3.Research on out-of-band suppression based on SCMA and new multi-carrier technologyThis part proposes a design scheme based on SCMA technology and new multi-carrier technology for the massive connection problem in 5G new application scenarios.This solution can effectively increase the number of connections,and is more suitable for application in the fragment spectrum.In addition,to further reduce interference to licensed bands,a SCMA-GFDM-AIC scheme based on active interference cancellation is proposed to further suppress the out-of-band power leakage of SCMA-GFDM.The active interference cancellation method mainly utilizes the inserted cancellation subcarrier to counteract the out-of-band power leakage of the SCMA-GFDM.Moreover,in order to eliminate the high energy of the cancellation subcarrier,a method for reducing the energy of cancellation subcarrier is also proposed.In this dissertation,the new multi-carrier technology is studied,and the problems of self-interference and complexity in the new multi-carrier technology are mainly discussed.In addition,a design scheme based on SCMA technology and new multi-carrier technology is proposed for the massive connection scenario,and a method for suppressing out-of-band power leakage of SCMA-GFDM scheme is also proposed.