Survey of Spectrum Sharing for Inter-Technology Coexistence

Increasing capacity demands in emerging wireless technologies are expected to be met by network densification and spectrum bands open to multiple technologies. These will, in turn, increase the level of interference and also result in more complex inter-technology interactions, which will need to be managed through spectrum sharing mechanisms. Consequently, novel spectrum sharing mechanisms should be designed to allow spectrum access for multiple technologies, while efficiently utilizing the spectrum resources overall. Importantly, it is not trivial to design such efficient mechanisms, not only due to technical aspects, but also due to regulatory and business model constraints. In this survey we address spectrum sharing mechanisms for wireless inter-technology coexistence by means of a technology circle that incorporates in a unified, system-level view the technical and non-technical aspects. We thus systematically explore the spectrum sharing design space consisting of parameters at different layers. Using this framework, we present a literature review on inter-technology coexistence with a focus on wireless technologies with equal spectrum access rights, i.e. (i) primary/primary, (ii) secondary/secondary, and (iii) technologies operating in a spectrum commons. Moreover, we reflect on our literature review to identify possible spectrum sharing design solutions and performance evaluation approaches useful for future coexistence cases. Finally, we discuss spectrum sharing design challenges and suggest future research directions

60 GHz MAC Standardization: Progress and Way Forward

Communication at mmWave frequencies has been the focus in the recent years. In this paper, we discuss standardization efforts in 60 GHz short range communication and the progress therein. We compare the available standards in terms of network architecture, medium access control mechanisms, physical layer techniques and several other features. Comparative analysis indicates that IEEE 802.11ad is likely to lead the short-range indoor communication at 60 GHz. We bring to the fore resolved and unresolved issues pertaining to robust WLAN connectivity at 60 GHz. Further, we discuss the role of mmWave bands in 5G communication scenarios and highlight the further efforts required in terms of research and standardization

Hidden Resources of Coordinated XPS and DFT Studies

Electronic configuration of chemically bound atoms, at the surface or in the bulk of a solid, contains the traps for energy absorption provided by the valence band electron transitions; the core-level excitation of any origin is coupled with traps forming the multichannel route for energy dissipation. This chapter displays tracing over these channels by means of X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT). Conformity between energy losses in the XPS spectra and electron transitions in relevant unit cells is verified by the examples of the pristine and half fluorinated graphite C2F, and the Br2-embedded C2F. Perfect XPS-DFT combination can be useful for material science providing exhaustive data on state and geometry of the atoms in a sample, regardless the field of its application. The valence band is insensitive to the energy source for its excitation. It makes the behavior of energy losses in XPS spectra of the atoms to be a descriptor of bonding between these atoms in multicomponent materials. Moreover, the state of any component can be tracked through change or invariability of satellites in the relevant XPS spectra, obtained in the course of the external influence, thus revealing a wear performance of the material