Research On Space-Frequency-Mode Multi-dimensional Hybrid Modulation

With the increasing scarcity of radio spectrum resources,the demand for high data rate and high spectral efficiency are the key elements that drive research on future wireless communication systems.Spatial modulation(SM),as a relatively new modulation scheme for multiantenna communications,although it can alleviate the requirement of multiple transmit RF chains in MIMO schemes,the achievable spectral efficiency increases by the base-two logarithm rather than linearly with the number of antennas.The orbital angular momentum serves as a physical quantity describing the spatial distribution of the field,different OAM modes are orthogonal to each other,providing a new orthogonal resource dimension for wireless communication,but current research on orbital angular momentum in improving spectrum efficiency is relatively rare.Based on the above two points,a new modulation scheme referred as space-frequency-mode multi-dimensional hybrid modulation is proposed in this paper,which aims to further improve the achievable rate with less number of antennas.The key idea of the space-frequency-mode multi-dimensional hybrid modulation is to map a block of information bits to two information carrying units: 1)symbols chosen from a constellation diagram and 2)a subset chosen from all possible combinations of antennas,orbital angular momentum(OAM)modes and subcarriers.Specifically,the use of the second part will add three additional dimensions to conventional two-dimensional(2-D)amplitude/phase modulation techniques,which in turn improve the spectral efficiency significantly.A low complexity mapping method for space-frequency-mode multi-dimensional hybrid modulation is proposed in this paper,the main advantage of this mapping method is that we can get the unique subset straightly according to the input binary bit stream by simple calculation.In addition,the impact of the order of modulation and the number of combinations on the available rate is studied through formula derivation and simulations.For the demodulation of space-frequency-mode multi-dimensional hybrid modulation at the receivers,this paper first analyzes the channel model of single or multiple uniform circular antenna at the transceiver end.In addition,this paper sets up a mathematical model for the system's signal,and the BER performance of the space-frequency-mode multidimensional hybrid modulation is studied in Gaussian channel and LOS channel using Zero-Forcing Detection(ZF)algorithm.Finally,this paper make a comparison between the spacefrequency-mode multi-dimensional hybrid modulation and MIMO-OFDM system on BER performance under the same spectrum efficiency.Simulation results show that,the space-frequency-mode multi-dimensional hybrid modulation proposed in this paper can achieve higher achievable rate than MIMO-OFDM system under the same configuration.In addition,for the same spectral efficiency,in the case of high signal to noise ratio,the performance of space-frequency-mode multi-dimensional hybrid modulation is better than that of MIMO-OFDM both in Gaussian and LOS channel.