Non-coherent OFDM techniques

Future indoor wireless networks will need alternative RF spectral resources to support the multi-gigabit per second (Gb/s) data speeds demanded by next generation multimedia applications. Although RF spectra in millimeter-wave, terahertz and optical bands are relatively uncongested, the communication systems operating in these frequency bands are difficult to implement, since they often suffer from stability problems due to the very high carrier frequencies. Hence, new physical layer technologies that can offer stable and low-complexity transceivers need to be developed. In this research work, non-coherent orthogonal frequency division multiplexing (OFDM) is studied to meet this demand. Non-coherent OFDMs can mitigate inter-symbol interference caused by channel frequency selectivity and achieve high spectral efficiency. Moreover, compared to conventional OFDMs, non-coherent OFDM uses simple passive direct detection without the need of complex RF frontend components such as mixers and oscillators. In this study, various non-coherent OFDM schemes with new detection enhancements are proposed to improve the performance of millimeter-wave, terahertz, optical, and optical wireless communication systems. It is shown analytically and by simulation that the proposed non-coherent OFDMs offer better bit error rate performance with much lower complexity, when compared to conventional OFDMs. In addition, a simple non-linear pre-distortion technique is explored to further improve the spectral efficiency of non-coherent OFDMs. Finally, space-time block coded (STBC) multiple-input multiple-output (MIMO) transmission schemes are incorporated with the proposed non-coherent OFDMs to offer improved system performance