Enhanced subcarrier index modulation (SIM) OFDM

A novel modulation technique coined SIM-OFDM was recently proposed. SIM-OFDM uses different frequency carrier states to convey information and leads to increased performance in comparison to conventional OFDM. Additionally, its innovative structure can lead to a decrease of the peak system power, which is highly beneficial in the context of optical wireless communication. One of the issues of the original SIM-OFDM scheme is a potential bit error propagation which could lead to significant burst errors. The current paper proposes a modified technique which avoids bit error propagation whilst retaining the benefits of the concept.

I. Introduction

SIM-OFDM is a modification of the classical OFDM modulation scheme. In OFDM a number of different frequency carriers are modulated with a signal from a scheme such as Quadrature Amplitude Modulation (QAM). The novel approach of SIM-OFDM tries to exploit an additional “new” dimension in the OFDM frame coming from the state of each subcarrier – active or inactive. This additional dimension is employed to transmit information in an On-Off Keying (OOK) fashion. A detailed description of SIM-OFDM can be found in [1].