Intelligent and Efficient Finite Alphabet Signal Processing Technologies for Future Wireless Communications

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To date, it has been envisioned that non-orthogonal multi-access (NOMA) and massive MIMO (MaMIMO) are two major potential technologies for future wireless communications, because they meet three major requirements for future wireless communications, i.e., huge data rates, massive connectivity and low latency. The current research on NOMA focuses mainly on the channel capacity for either Gaussian inputs or finite-alphabet (FA) inputs. However, the methods for the FA signals are specifically numerical. Hence, a limited insight into the relationship between the optimal sum constellation and each individual user constellation can be drawn from the obtained solutions. On the other hand, the current research on MaMIMO has indicated that one of major factors to significantly affect its performance is pilot contamination, never vanishing, even when the number of BS antennas becomes infinity. Hence, non-coherent space-time code designs were proposed for MaMIMO. However, all the current non-coherent massive space-time code (MASTC) designs suffer a severe error floor phenomenon, never disappearing, even when SNR goes to infinity. In addition, it is also not difficult for a passive eavesdropper be equipped with a massive array, thereby; potentially and physically deteriorate uplink security. ***To address all the aforementioned significant issues, the applicant's long-term research objective is to develop advanced finite alphabet signal-processing technologies (FAST) to intelligently and efficiently manage FA interference for a general complicated wireless network topology with the uplink or the downlink having multiple base stations from the standpoint of signal estimation and detection theory. Within the next five years, the applicant targets mainly on the following three objectives: (a) to develop new FAST for FA NOMA for uplink SISO and downlink MISO systems, (b) to develop new FAST for FA uplink MaMIMO systems, and (c) to develop new FAST for physically securing FA NOMA-MaMIMO systems. In order to achieve these three objectives, the following four technical approaches are specifically proposed, i.e., (i) additively unique decomposition theory of FA signals for the design of four kinds of optimal sum constellations, (ii) multiplicatively unique decomposition theory of FA MIMO signals for the design of three kinds of optimal MASTC, (iii) super-rectangular cover theory for FA uplink MaMIMO systems for the design of an optimal MASTC when the large-scale channel is known only at the receiver, and (iv) block-equal QRS decomposition theory of MIMO channels for the design of an optimal FA precoder with ML-based block successive cancellation detection. ******Therefore, this proposed research program develops completely novel FAST for intelligently and efficiently managing FA interference for multi-user communications so that all the major benefits offered by NOMA-MaMIMO can be realized. *****