A New Analytical Model for SIM–OFDM Contradicts the Previously Claimed Features

Abstract

The Subcarrier Index Modulation OFDM (SIM–OFDM) appeared in 2009 promising a –3 dB transmitted power reduction without affecting the system performance. Therefore, it became an attractive choice to upgrade the communication systems with researchers’ increasing interest. Despite the research efforts in SIM–OFDM field, there was no in-depth investigation for such transmitted power reduction or the system’s performance. The claimed power reduction relies on probabilistic assumptions that were not validated considering system operation concepts. This paper provides a new analytical model that characterizes the actual SIM–OFDM behavior. The contribution of this model is the inclusion of the majority condition in the derivation of 1’s pmf which modifies the 1’s pmf into a complex nonlinear function that is always higher than 1/2. The new pmf effect upon the power reduction, synchronization, and the overall Bit Error Rate (BER) is investigated. The new analytical model shows that the –3 dB power reduction cannot be achieved. Also, no successful synchronization can be established unless extra subcarrier is added that will create a frame like communication system. Such scheme increases BER if the carrier is falsely detected creating a Frame Error Rate (FER) which might lead to serious problem.