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Abstract-This paper considers the end-to-end scheduling for all-optical data center networks with zero in-network buffer and non-negligible reconfiguration delay. It is known that in the regime where the scheduling reconfiguration delay is nonnegligible, the rate of schedule reconfiguration should be limited in such a way as to minimize the impact of reduced duty-cycles and to ensure bounded delay. However, when the scheduling rate is restricted, the existing literature also tends to restrict the rate of monitoring and decision processes. We first present a framework for scheduling with reconfiguration delay that decouples the rate of scheduling from the rate of monitoring. Under this framework, we then present two scheduling algorithms for switches with reconfiguration delay, both based on the well-known MaxWeight scheduling policy. The first one is the Periodic MaxWeight (PMW), which is simpler in computation, but requires prior knowledge of traffic load. The other is the Adaptive MaxWeight (AMW), which, in contrast, requires no prior knowledge. We show the stability condition for both algorithms and evaluate their delay performance through simulations.

5G and future cellular networks intend to incorporate low earth orbit (LEO) satellite communication systems (SatCom) to solve the coverage and availability problems that cannot be addressed by satellite-based or ground-based infrastructure alone. This integration of terrestrial and non terrestrial networks poses many technical challenges which need to be identified and addressed. To this aim, we design and simulate the downlink of a LEO SatCom compatible with 5G NR, with a special focus on the design of the beamforming codebook at the satellite side. The performance of this approach is evaluated for the link between a LEO satellite and a mobile terminal in the Ku band, assuming a realistic channel model and commercial antenna array designs, both at the satellite and the terminal. Simulation results provide insights on open research challenges related to analog codebook design and hybrid beamforming strategies, requirements of the antenna terminals to provide a given SNR, or required beam reconfiguration capabilities among others.

Auger electron spectroscopy (AES) and x-ray photoelectron spectroscopy (XPS) measurements have been carried out on the β-SiC(100) surface simultaneously. The AES and XPS results differ significantly in the bonding state of oxygen for both as-grown surfaces and as-etched surfaces. Differences in the same carbon-KLL Auger spectra induced by both electron beams and x rays from the same surface suggest that the electron beam used in AES removed considerable amounts of carbonaceous species in the contaminant layers. Furthermore, comparison of the Si 2p and Si LVV spectra revealed that the SiOx (x<2) species on the surface was also reduced by the electron beam used in AES. Although previous AES results have shown that both as-grown and as-etched surfaces of β-SiC(100) were covered with only submonolayer coverage of oxygen bonded to Si atoms, with no detectable carbonaceous contaminants, this work shows that the real surfaces, however, are covered with several tens of contaminant layers, including SiO, CC, CH, and CO bonds.