Non-Orthogonal Transmission Techniques for Next-Generation Communications Systems

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Next-generation wireless systems will have novel use cases that require gigabit experience of end-users to support data-hungry wireless applications (such as 4K streaming) and stringent energy consumption to support the expected massive connectivity. Such requirements pose several technical challenges for the existing wireless systems infrastructure and there is a need to explore novel techniques to improve the spectral efficiency (SE) and energy efficiency (EE) of next-generation wireless systems. Conventional communication systems follow the Nyquist theorem and use orthogonal pulses for transmission in time and/or frequency domains. This simplifies the transmitter and receiver designs; however, it also limits the performance. Intentionally relaxing the Nyquist orthogonality condition in next-generation wireless systems, on one hand, will allow higher transmission rates in the same bandwidth (i.e., improve the SE) and/or will result in lower signal-to-noise ratio to maintain the communication quality (i.e., improve the EE). On the other hand, it will result in intersymbol interference (ISI) between adjacent symbols in the time domain and/or intercarrier interference (ICI) between adjacent subcarriers in the frequency domain. Such innovative non-orthogonal physical layer transmission is commonly referred to in the literature as time-frequency packing (TFP) or faster-than-Nyquist signaling (FTNS). The long-term objective of the research program is to explore novel transmission and reception techniques to advance the state-of-knowledge on designing SE/EE wireless systems. To achieve this target, the proposed research program has the following three short term objectives: 1) developing innovative low-complexity precoding and detection techniques to remove the expected ISI and/or ICI of TFP/FTNS. 2) investigating the integration of TFP/FTNS (to fully characterize its benefits) with other candidate technologies for next-generation wireless systems such as multiple-input-multiple-output (MIMO) antennas and/or index modulation (IM). 3) analyzing and quantifying various transmission impairments, such as, in-phase and quadrature (IQ) imbalance of radio frequency (RF) front-end, phase-noise due to local oscillators instabilities, and power amplifier nonlinearities, on the performance of TFP/FTNS and developing innovative signal processing techniques to compensate for their harmful effects. The proposed research program will develop novel signal processing techniques to enable the development of SE/EE next-generation wireless systems. The findings of the research program are expected to attract the attention of the wireless/telecommunication industry, and hence, facilitate future research collaboration. The highly qualified personnel trained in this research program will acquire advanced skills in wireless communications and digital signal processing to excel in their future careers and contribute to Canada's economic growth.