Joint Track-While-Scan Beam Scheduling for 6G Sub-Terahertz Multi-UE Clusters Using Resolving-Window Metrics at 140 GHz and 300 GHz

At candidate 6G sub-terahertz (sub-THz) carriers near 140 GHz and 300 GHz, half-power beamwidths of 1°-6° create a scheduling regime that 5G beam management was never designed for: a base station must simultaneously hold high-SNR beams on active user equipments (UEs), monitor UEs drifting toward the edge of resolvability, and spend scarce beam time scanning for new arrivals-all within a thermally limited duty cycle. This is structurally the track-while-scan (TWS) problem of electronically scanned array (ESA) radar. Building on a companion paper that defined per-UE resolving-window metrics (normalized range separation W_R, SNR-gated angular separation W_θ^eff, LoS-convergence urgency C_k, and beam time-to-exit T_exit), this paper converts those metrics into an implementable control plane. We (i) formulate the joint tracking-scheduling problem as a constrained multi-objective optimization over outage probability, beam mis-association (ambiguity) probability, and discovery latency, subject to an RF-chain budget B_max and a thermal duty factor η; (ii) define a three-state UE classification-stable, boundary, ambiguous-driven by the resolving-window state with radar-consistent polarity (short time-to-exit and low separability escalate a UE's state, never relax it); and (iii) propose a low-complexity, priority-driven TWS scheduler that reserves scan capacity first, stabilizes boundary UEs preventively, and serves stable UEs at relaxed revisit rates bounded by their individual T_exit.

Physics to Circuit Analysis of GaN RF Integrated Circuits versus GaAs and Silicon

The migration of radio-frequency (RF) integrated-circuit platforms from silicon to GaAs and now to gallium nitride is derived here from first principles. The hexagonal non-centrosymmetric GaN lattice admits a macroscopic polarization; elasticity and the piezoelectric tensor fix the bound sheet charge at an AlGaN/GaN interface, and Poisson's equation with triangular-well quantisation yields a degenerate quasi-two-dimensional channel of ~10^13 cm^-2 with no doping. Energy-momentum conservation for pair creation and phonon-limited energy relaxation set the breakdown field (3.3 MV/cm) and saturation velocity (2.5 x 10^7 cm/s), which combine into geometry-free limits V_brf_T = E_cv_sat/(2pi) and R_on^sp = 4V_br^2/(muepsilonE_c^3). These limits are mapped onto the low-noise amplifier, power amplifier, and switch/phase-shifter functions of a transmit/receive front end and quantified by a MATLAB device-physics model comparing GaN, GaAs, and Si up to 90 GHz. The purpose of this framework and its simulations is to identify which material platform offers the best performance at millimeter-wave frequency signals.