Research On The Spectrum And Energy Efficiency In Multiple-Mode OFDM-IM

With the rapid development of the wireless communication industry,people are demanding communication of faster speed and more energy-efficient.As a multi-dimensional modulation technology that effectively improves the spectrum and energy efficiency of wireless communication systems,index modulation(IM)technology has become a hot topic in today's research.Orthogonal frequency division multiplexing with index modulation(OFDM-IM)technology,which applies IM to frequency domain dimension,has the advantages of high energy efficiency,but the spectral efficiency still needs to be improved.Multiple-mode OFDM-IM(MM-OFDMIM)and its in-phase and quadrature(IQ)dimension extension techniques have higher spectral efficiency,but do not retain the advantages of the high energy efficiency of OFDM-IM technology.Therefore,this paper takes the OFDM-IM technology as the background to deal with the problem of optimizing energy and spectrum efficiency of the system.The main contents of the research are as follows:1.In order to improve the energy efficiency of MM-OFDM-IM(-IQ)system,a multiple-mode OFDM with subcarrier index modulation(MM-OFDM-SIM)system model is proposed,and subsequently extended to the IQ dimension.The system transmits part of the information through no-load mode without energy consumption,and achieves a compromise between spectral efficiency and energy efficiency by changing the ratio of no-load mode to other modes.The effect of the no-load mode on the bit error rate(BER)performance is analyzed,and the multiple-mode constellation after adding no-load mode is optimized accordingly.In addition,a general low complexity maximum likelihood(ML)detection algorithm is proposed to solve the problem of different permutation rules of constellation mode.Moreover,it can further reduce the detection complexity of mode permutation without reducing the BER performance in the high signal-to-noise ratio(SNR)region.The simulation results show that in high SNR region of Rayleigh fading channel,compared with MM-OFDMIM(-IQ)system,the lower spectral efficiency configuration is,the more SNR gain MM-OFDM-SIM(-IQ)system has;the higher spectral efficiency is,the less SNR gain MM-OFDM-SIM(-IQ)system has.2.In order to further improve the spectral efficiency of MM-OFDM-IM(-IQ)system,a multiple permutation and multiple-mode OFDM-IM(MP-MM-OFDM-IM)system model is proposed,and subsequently extended to the IQ dimension.On the premise of not reducing the minimum euclidean distance(MED)between sub-blocks,the system increases the number of kinds of constellation mode permutation,so that the amount of information carried by the index is increased,and the complexity of the system remains almost unchanged.In addition,MM-OFDM-HIQ-SIM and MP-MMOFDM-SIM system models are proposed to combine the advantages of improved energy and spectral efficiency.Then,MP-MM-OFDM-IM mode is extended to the IQ dimension.The simulation results show that MP-MM-OFDM-IM(-IQ)system can not only improve the spectral efficiency,but also obtain a small amount of SNR gain in the high SNR region compared with MM-OFDM-IM(-IQ)system.MM-OFDM-HIQ-SIM and MP-MM-OFDM-SIM(-IQ)systems have better performance.