Effect of active sub-carriers' Number on OFDM-IM systems and numerical optimization

Abstract

This paper builds an OFDM-IM simulation system, analyzes the system bit error rate (BER) and the system signal-to-noise ratio (SNR) changes under different activated sub-carrier values. The conclusion is that when only BER is considered, activating a small number of sub-carriers will get better results. Then it analyzes the change rule of the optimal solution number of activated sub-carriers with the total number of sub-carriers, and obtains a general mathematical formula description, and combines relevant data such as the proportion of the optimal number of activated sub-carriers, and the theoretical transmission speed optimization rate, Compared with the OFDM system, the conclusion is that when the subcarriers carry more information, the addition of the IM system does not significantly improve the performance of the system, but increases the complexity of calculation and coding. In the above case, the optimal number of activated subcarriers is almost equivalent to the total number of sub-carriers, so adding IM modulation at this time does not make much sense.