Sample Indexed Spatial Orthogonal Frequency Division Multiplexing

Optical spatial modulation (OSM) is a multiple-transmitter technique that can provide higher data rates with low system complexity as compared to single-input singleoutput (SISO) systems. Orthogonal frequency division multiplexing (OFDM) is widely implemented to achieve better spectral efficiency in wireless channels. Asymmetrically clipped optical OFDM (ACO-OFDM) and DC-biased optical OFDM (DCO-OFDM) are two well-known optical OFDM (O-OFDM) techniques suitable for intensity-modulation direct-detection (IM/DD) optical systems. In this work, sample indexed spatial OFDM (SISOFDM) is proposed to combine OSM and O-OFDM in a novel way and achieve significant performance gain. By assigning time-domain samples of the O-OFDM transmit symbol to different transmitters, SIS-OFDM achieves much better spectral efficiency and reduced computational complexity at the transmitter as compared to previous work that combines OSM with O-OFDM in the frequency-domain. We also consider the impact of optical source biasing on overall performance, and the relative performance of imaging (ImR) versus non-imaging receiver (NImR) design for our proposed SIS-OFDM technique. Results indicate that for a Ntx×Nrx MIMO configuration where Ntx = Nrx = 4, SIS-OFDM using ImR can achieve up to 135dB of signal-to-noise ratio (SNR) gain over comparable system using a NImR. Also, using Nsc number of O-OFDM subcarriers provides up to Nsc × log2(Ntx) additional bits per symbol of spectral efficiency over techniques that combine OSM and O-OFDM in the frequency domain. 1In Chin. Opt. Lett., 2014, 12(09): pp.090602 doi:10.3788/COL201412.090602 This work is supported by the NSF under grant No. CNS-0435353. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.