OFDM With Subcarrier Number Modulation

A new modulation technique, named orthogonal frequency division multiplexing (OFDM) with subcarrier number modulation, is proposed for efficient data transmission. In this scheme, the information hits are conveyed by changing the number of active subcarriers in each OFDM subblock. The idea behind this scheme is inspired from the integration of OFDM with pulse width modulation, where the width of the pulse represents the number of active subcarriers corresponding to specific information bits. This is different from OFDM with index modulation (OFDM-IM), where the information bits are sent by the indices of the subcarriers instead of their number. The scheme is shown to provide better spectral efficiency than that of OFDM-IM at comparable bit error rate performances. Another key merit of the proposed scheme over OFDM-IM is that the active subcarriers can be located in any position within the subblock, thus enabling channel-dependent optimal subcarrier selection that can further enhance the system performance.