OFDM with index modulation-based alternative waveform designs for future wireless systems

Orthogonal frequency division multiplexing with index modulation (OFDM-IM), which transmits information bits through ordinary signal constellation symbols and indices of active subcarriers, is a promising multicarrier transmission scheme and has attracted the attention of researchers due to its several benefits such as flexibility and simplicity. Nonetheless, OFDM-IM cannot satisfy many needs of future wireless communication services such as, ultra-reliable low-latency communications (URLLC) and enhanced mobile broadband (eMBB) since providing superior reliability, high data rates, and low complexity is challenging due to its null subcarriers and unsufficient error performance. Therefore, several novel waveforms have been proposed by utilizing the flexible nature of the OFDM-IM to meet the diverse needs of eMBB and URRLC services. In this thesis, two novel OFDM-IM based multicarrier transmission schemes have been proposed by utilizing the aforementioned advantages of OFDM-IM. Firstly, a novel transmission scheme named as coordinate interleaved OFDM with power distribution IM (CI-OFDM-PIM), which applies coordinate interleaving and power distribution in subcarriers to achieve a diversity gain that is equal to the number of subcarriers in a subblock, is proposed. The average bit error probability (ABEP) for the CI-OFDM-PIM was derived and the superior error performance of the proposed scheme over benchmarks has been shown via computer simulations. Next, a novel OFDM-IM based scheme called coordinate interleaved OFDM with repeated in phase/quadrature IM (CI-OFDM-RIQIM), which provides superior error performance and enhanced spectral efficiency due to its diversity order of two and clever subcarrier activation pattern (SAP) detection mechanism, is proposed. Furthermore, a log-likelihood ratio (LLR) based low-complexity detector is designed for the proposed scheme. Theoretical analyses are performed and an upper bound on the bit error probability is derived. Comprehensive computer simulations under perfect and imperfect channel state information (CSI), are conducted to compare the proposed and reference schemes. It is shown that CI-OFDM-RIQIM shows superior results and can be considered as a promising candidate for next generation wireless communication systems.