satellite communication designers

Abstract: Pinching-antenna systems (PASS) reconfigure the wireless channel by positioning dielectric antennas along a waveguide. A single waveguide, however, confines its antennas to one line, so that good coverage of an area has relied on several waveguides or waveguide segments with separate feeds. This paper proposes X-PASS, in which a hub feeds radially deployed waveguide arms, one pinching antenna on each, and drives them by arm selection, aggregation or multiplexing. It models the hub with its insertion losses, derives a unified signal-to-noise ratio expression for these three operating modes, and derives in closed form a radius inside which aggregation outperforms selection. Numerical results validate the analysis and compare the coverage of X-PASS with that of the other layouts at equal transmit power.

Abstract: Airy beams are often proposed in array beamforming to bend beams around obstacles. We prove that, for a single-antenna receiver, conventional beamfocusing maximizes the received power regardless of how many antennas are blocked and, in expectation, even with phase errors in the channel state information. This also holds for multi-antenna receivers under a phase-separability condition that is satisfied in rank-one channels. Numerical results confirm that unmodified beamfocusing is optimal for physically small receivers (i.e., those that fit within the beamwidth) when an obstacle is present. For physically larger receivers, the optimal precoding deviates from beamfocusing to better illuminate the receiver's unobstructed parts, but will not become Airy beams. While Airy beams can be configured to perform well, their ability to follow a bent trajectory in front of an obstacle does not maximize the received power behind it.

Abstract: Movable and rotatable-antenna systems treat element placement as a design resource, but the supporting theory is largely position-only. We prove that element orientation is an effective spatial resource in its own right, complementary to position. For collinear or coplanar arrays, the angular-domain rank is capped by the number of projection-ambiguity classes of the scattering directions, for every common element orientation and pattern. Orientation-diverse elements with sufficiently rich analytic patterns restore the maximal rank min(N,L) for almost every orientation draw. A closed-form correlation expression, strictly monotone in orientation spread under isotropic scattering, quantifies the gain within the scalar-pattern model, and Monte Carlo simulations corroborate the exact-rank and capacity behavior.

Abstract: We study the identification capacity of discrete-time Gaussian multiple-input multiple-output (MIMO) channels under per-antenna, per-symbol peak-amplitude constraints. We establish upper and lower bounds on the identification capacity that scale linearly with the channel rank $r.$ The number of reliably identifiable messages can grow super-exponentially with blocklength $n,$ following $M_n(R)=2^{(n\log n)R},$ where $R$ is an achievable rate. The channel rank provides a spatial-multiplexing advantage, enabling higher achievable rates and, consequently, stronger super-exponential codebook growth. These results characterize the rank-dependent gain in achievable identification performance.