Research On Spectrum Efficiency Improvement Technology Of Multi-mode Carrier Index Modulation

Improving the spectral efficiency of the system,utilizing the resources in efficient ways and reducing the complexity of the signal detection are some of the key problems in the field of wireless communication research.Orthogonal frequency division multiplexing with index modulation(OFDM-IM)is one of the potential IM technique in the frequency domain to improve the energy efficiency of wireless communication system.The spectral efficiency(SE)of the system,however,is limited,since the null mode itself does not modulate any information and the activated subcarriers only adopt the same modulation mode.Motivated by this,a novel IM scheme,called multiple-mode OFDM-IM(MM-OFDM-IM),has been proposed for OFDM systems to improve the SE by conveying information through multiple distinguishable modes and their full permutations.The number of permutations in MM-OFDM-IM is also limited so there is still room for improvement in spectral efficiency.In order to improve the SE of MMOFDM-IM technology,this thesis studies the multi-antenna extension system of MM-OFDMIM and expands the index domain of MM-OFDM-IM technology,three main contributions of this thesis are summarized as follows:1.Firstly,based on multiple antenna MM-OFDM-IM scheme,index bit mapping rules is presented.Secondly,the basic criteria for mode selection and application strategy selection are given for scenarios with given constellation mode order and carrier quantity.Finally,based on the maximum likelihood detection algorithm and minimum mean square error detection algorithm,a new detection method named minimum mean square error(MMSE)Vitebri algorithm is proposed,which gives tradeoffs between the detection complexity and error performance.The numerical simulation results are also introduced.2.Firstly,a composite multiple-mode OFDM-IM(C-MM-OFDM-IM)scheme is proposed in order to increase the SE of MM-OFDM-IM systems by extending the indexing to the energy and activation domains.In C-MM-OFDM-IM,the information bits are mapped not only to the subcarrier activation patterns and modulation symbols,but also to the energy allocation patterns and constellation activation patterns.Secondly,in order to make full use of the constellation pattern,by re-establishing the new mapping rule of constellation activation patterns,an optimized C-MM-OFDM-IM scheme named C-MM-OFDM-IM-II is proposed.Finally,based on the maximum likelihood detection,upper-bounded bit error rate and lower bounded achievable rate are both derived in closed-form to evaluate the performance of C-MM-OFDM-IM(-II).3.In order to improve the spectral efficiency of C-MM-OFDM-IM(-II)scheme,two extension schemes named GC-MM-OFDM-IM(-II)and C-MM-OFDM-IQ-IM(-II)are proposed in this thesis,where the former jointly considers all subcarrier activation patterns,energy allocation patterns,constellation activation patterns and modulated symbols,while the latter expands the index implementation to the in-phase and quadrature constellation domains.For proposed schemes,a log-likelihood ratio based low-complexity detection is also proposed to detect the transmitted signal.Simulation results show that the proposed schemes have better error performance.