Abstract: With the evolution of 5G to 6G communication,mobile communication systems are facing massive user connections and data transmission.Non-orthogonal multiple access(NOMA),as one of the candidate technologies for future communication,significantly improves spectrum efficiency by reusing user signals in the power domain,but there are problems such as high energy consumption and power allocation optimization.In order to alleviate the above problems,this paper proposes a transmission me-thod based on dual-frequency index modulation assisted non-orthogonal multiple access system(DFIM-NOMA),which combines the high spectrum utilization characteristics of non-orthogonal multiple access with the flexibility of index modulation and the advantages of high energy efficiency.At the transmitter of the system,dual-frequency index modulation is used to improve the proportion of implicit signal transmission in information transmission.At the receiver,serial interference cancellation(SIC) and maximum likelihood detection(ML) are used to demodulate the mixed transmission signal of two users.The digital model of the test system is built by MATLAB for simulation verification,and the system baseband is implemented on the field programmable gate array.Experimental results show that under the condition of using the same spectrum resources and sending the same signal,compared with the traditional index modulation assisted non-orthogonal multiple access(IM-NOMA),increasing the proportion of index modulation signals can reduce the number of actual signals to be sent;in the case of little difference in bit error rate performance,the average amplitude of the transmitted signal can be reduced by about one-third,and the transmission energy consumption can be theoretically reduced by about 50%.

Key words: Index modulation, Non-orthogonal multiple access, Maximum likelihood estimation, Bit error rate, Serial interference cancellation, FPGA