Prioritized Delay Optimization for NOMA-Based Multi-UAV Emergency Networks
Lan Lin, Wenjun Xu, Wei Chen, Fengyu Wang, Guojun Li, Miao Pan
Abstract
In emergency networks, it is significant to jointly consider users’ priorities and communication delays for post-disaster users. To this end, we propose an essential metric by integrating these two factors, namely <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">prioritized delay</i> . Moreover, we formulate a min-max prioritized delay problem for non-orthogonal multiple access (NOMA)-based multi-unmanned aerial vehicle (UAV) emergency networks, where the powers of all users are concurrently optimized to balance prioritized delay among users while suppressing multi-user interference introduced by NOMA and multiple UAVs. The problem is found to be non-convex, and we propose the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">substitution-decomposition-scaling-block successive upper bound minimization</i> (SDS-BSUM) algorithm to address this issue. Specifically, the originally-formulated problem is first transformed into a standard form through variable <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">substitution</i> , followed by problem <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">decomposition</i> into single-UAV subproblems through exploiting its separable structure, and the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">scaling</i> of non-convex constraints into tight convex ones. Finally, the converted problem is fitted into <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">BSUM</i> for solving. Simulation results reveal that compared with the existing schemes, the proposed SDS-BSUM not only reduces the prioritized delay by up to 70 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\%$</tex-math></inline-formula> , but also achieves an excellent delay fairness commensurate with users’ priorities.