Realtime Multiuser Multicarrier Communications

Multiuser multicarrier communication, e.g. orthogonal frequency division multi-access (OFDMA), has been extensively investigated since the 4G era and applied in several mainstream mobile networking standards, because it holds the potential of high-throughput provision, low complexity, and flexible bandwidth allocation. In the upcoming 6G era, mobile networks are newly expected to provide deadline or hard-delay assurance for latency-sensitive traffics generated from factory automation, smart grids, telesurgery, and automatic driving, etc. However, whether the emerging hard-delay constraint can be effectively satisfied in multiuser multicarrier systems, where subcarriers are shared by users, remains open. As a result, a unified framework for realtime multiuser multicarrier communications is presented in this paper, based on the bipartite-graph model of OFDMA. In particular, we conceive a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mathcal {H}$ </tex-math></inline-formula>-matching empowered joint subcarrier allocation and power adaptation strategy, which is shown to meet the deadline requirements deterministically over frequency-selective channels with finite average transmission power. Furthermore, we leverage the theory of random bipartite graph matching to analyze the delay-constrained capacity as a function of the average transmission power, based on the approximate outage probability of the embedded matching diversity. To gain more insights, asymptotic analysis is adopted to obtain the deadline-constrained throughput when the number of independent subcarriers is huge.