2,2-Dimethyl-5-{[(4-nitro­phen­yl)amino]­methyl­idene}-1,3-dioxane-4,6-dione

In the title compound, C13H12N2O6, the dihedral angle between the benzene ring and the amino­methyl­ene unit is 5.42 (16)°, while the angle between the amino­methyl­ene unit and the dioxane ring is 3.06 (43)°. The dioxane ring shows a half-boat conformation, in which the C atom between the dioxane ring O atoms is 0.464 (10) Å out of the plane. An intra­molecular N—H⋯O hydrogen bond stabilizes the mol­ecular conformation. In the crystal, a three-dimensional framework is built up via inter­molecular N—H⋯O hydrogen bonds

4-[4-(Piperidin-1-yl)piperidin-1-yl]benzonitrile

In the title compound, C17H23N3, both piperidine rings adopt chair conformations. In the crystal packing, intermolecular C—H⋯N hydrogen bonds and C—H⋯π interactions are present

5-(4-Chloro­anilinomethyl­ene)-2,2-dimethyl-1,3-dioxane-4,6-dione

The title compound, C13H12ClNO4, is approximately planar, with a dihedral angle of 8.23 (4)° between the mean plane of the amino­methyl­ene unit and the planar part of the dioxane ring. The dioxane ring has a half-boat conformation, in which the C atom between the dioxane O atoms is −0.464 (8) Å out of the plane of the other five atoms. In the mol­ecule there is an intra­molecular N—H⋯O hydrogen bond, involving the NH H atom and the adjacent dioxane carbonyl O atom. In the crystal, weak intermolecular C—H⋯O hydrogen-bonding contacts, result in the formation of sheets parallel to the ab plane

5-[(2-Chloro-4-nitro­anilino)methyl­idene]-2,2-dimethyl-1,3-dioxane-4,6-dione

In the title compound, C13H11ClN2O6, the dihedral angles between the benzene ring and the amino­methyl­ene unit and between the amino­methyl­ene group and the dioxane ring are 8.19 (14) and 1.39 (17)°, respectively. The dioxane ring has a half-boat conformation, in which the C atom between the dioxane O atoms is 0.662 (4)Å out of the plane through the remaining ring atoms. Intra­molecular N—H⋯O and N—H⋯Cl inter­actions occur

3-Fluoro-4-nitro­phenyl 4-methyl­benzene­sulfonate

In the title compound, C13H10FNO5S, the dihedral angle between the benzene rings is 47.63 (14)°. In the crystal, π–π stacking occurs between nearly parallel benzene rings of adjacent mol­ecules, the centroid–centroid distance being 3.7806 (16) Å. Weak inter­molecular C—H⋯O hydrogen bonding is also present in the crystal structure

Differential Modulation for Short Packet Transmission in URLLC

One key feature of ultra-reliable low-latency communications (URLLC) in 5G is to support short packet transmission (SPT). However, the pilot overhead in SPT for channel estimation is relatively high, especially in high Doppler environments. In this paper, we advocate the adoption of differential modulation to support ultra-low latency services, which can ease the channel estimation burden and reduce the power and bandwidth overhead incurred in traditional coherent modulation schemes. Specifically, we consider a multi-connectivity (MC) scheme employing differential modulation to enable URLLC services. The popular selection combining and maximal ratio combining schemes are respectively applied to explore the diversity gain in the MC scheme. A first-order autoregressive model is further utilized to characterize the time-varying nature of the channel. Theoretically, the maximum achievable rate and minimum achievable block error rate under ergodic fading channels with PSK inputs and perfect CSI are first derived by using the non-asymptotic information-theoretic bounds. The performance of SPT with differential modulation and MC schemes is then analysed by characterizing the effect of differential modulation and time-varying channels as a reduction in the effective SNR. Simulation results show that differential modulation does offer a significant advantage over the pilot-assisted coherent scheme for SPT, especially in high Doppler environments.Comment: 15 pages, 9 figure