Enabling Ultra-Reliable and Low-Latency Communications through Unlicensed Spectrum

© 2018 IEEE. In this article, we aim to address the question of how to exploit the unlicensed spectrum to achieve URLLC. Potential URLLC PHY mechanisms are reviewed and then compared via simulations to demonstrate their potential benefits to URLLC. Although a number of important PHY techniques help with URLLC, the PHY layer exhibits an intrinsic trade-off between latency and reliability, posed by limited and unstable wireless channels. We then explore MAC mechanisms and discuss multi-channel strategies for achieving low-latency LTE unlicensed band access. We demonstrate, via simulations, that the periods without access to the unlicensed band can be substantially reduced by maintaining channel access processes on multiple unlicensed channels, choosing the channels intelligently, and implementing RTS/CTS

Sub-Band Cascaded CSP-based Deep Transfer Learning for Cross-Subject Lower Limb Motor Imagery Classification

Lower limb motor imagery (MI) classification is a challenging research topic in brain-computer interface (BCI) due to excessively close physiological representation of left and right lower limb movements in the human brain. Moreover, MI signals have severely subject-specific characteristics. The classification schemes designed for a specific subject in previous studies could not meet the requirements of cross-subject classification in a generic BCI system. Therefore, this study aimed to establish a cross-subject lower limb MI classification scheme. Three novel sub-band cascaded common spatial pattern (SBCCSP) algorithms were proposed to extract representative features with low redundancy. The validations had been conducted based on the lower limb stepping-based MI signals collected from subjects performing MI tasks in experiments. The proposed schemes with three SBCCSP algorithms have been validated with better accuracy and running time performances than other common spatial pattern (CSP) variants with the best average accuracy of 98.78%. This study provides the first investigation of a cross-subject MI classification scheme based on experimental stepping-based MI signals. The proposed scheme will make an essential contribution to developing generic BCI systems for lower limb auxiliary and rehabilitation applications.National Natural Science Foundation of China (61603223); Jiangsu Provincial Qinglan Project, Suzhou Science and Technology Programme (SYG202106); Research Development Fund of XJTLU (RDF-18-02-30, RDF-20-01-18); Key Program Special Fund in XJTLU (KSF-E-34) and The Natural Science Foundat on of the Jiangsu Higher Education Institutions of China (20KJB520034)

Heterojunction structures for reduced noise in large-area and sensitive perovskite x-ray detectors

Polycrystalline perovskites can be readily fabricated into large areas using solution depositions; however, they suffer from large dark currents that are tens to hundreds times higher than industrially relevant values, limiting their application in low-dose x-ray detection. Here, we show that the application of a heterojunction structure into polycrystalline films significantly reduces the dark current density by more than 200 times to subnanoampere per square centimeter without reducing the sensitivity of the detectors. The heterojunction perovskite films are formed by laminating several membrane films filled with perovskites of different bandgaps. A gradient bandgap is formed during annealing. The detectors have a lowest detectable dose rate of 13.8 ± 0.29 nGyair s-1 for 40-keV x-ray and can conduct dynamic x-ray imaging at a low-dose rate of 32.2 nGyair s-1. Simulation and experimental analysis show that the heterojunction is tolerant of halide diffusion and can be stable for over 15 years

Surface energy engineering of graphene

Contact angle goniometry is conducted for epitaxial graphene on SiC. Although only a single layer of epitaxial graphene exists on SiC, the contact angle drastically changes from 69{\deg} on SiC substrates to 92{\deg} with graphene. It is found that there is no thickness dependence of the contact angle from the measurements of single, bi, and multi layer graphene and highly ordered pyrolytic graphite (HOPG). After graphene is treated with oxygen plasma, the level of damage is investigated by Raman spectroscopy and correlation between the level of disorder and wettability is reported. By using low power oxygen plasma treatment, the wettability of graphene is improved without additional damage, which can solve the adhesion issues involved in the fabrication of graphene devices

Enabling Technologies for Ultra-Reliable and Low Latency Communications: From PHY and MAC Layer Perspectives

© 1998-2012 IEEE. Future 5th generation networks are expected to enable three key services-enhanced mobile broadband, massive machine type communications and ultra-reliable and low latency communications (URLLC). As per the 3rd generation partnership project URLLC requirements, it is expected that the reliability of one transmission of a 32 byte packet will be at least 99.999% and the latency will be at most 1 ms. This unprecedented level of reliability and latency will yield various new applications, such as smart grids, industrial automation and intelligent transport systems. In this survey we present potential future URLLC applications, and summarize the corresponding reliability and latency requirements. We provide a comprehensive discussion on physical (PHY) and medium access control (MAC) layer techniques that enable URLLC, addressing both licensed and unlicensed bands. This paper evaluates the relevant PHY and MAC techniques for their ability to improve the reliability and reduce the latency. We identify that enabling long-term evolution to coexist in the unlicensed spectrum is also a potential enabler of URLLC in the unlicensed band, and provide numerical evaluations. Lastly, this paper discusses the potential future research directions and challenges in achieving the URLLC requirements