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The commercialization of Cloud-RAN, and Open-RAN in particular, is a key factor to enable 5G cell densification by providing lower cost and more agile deployment of small cells. In addition, the adoption of multi-access edge computing (MEC) is important to support the ultra-low latency and high reliability required by mission-critical applications, which constitute a milestone of the 5G and beyond vision of a fully connected society. However, connecting antenna site, C-RAN processing, and MEC at low cost is challenging, as it requires high-capacity, low-latency connectivity delivered through a highly inter-connected topology. While passive optical networks (PONs) are being considered as a solution for providing low-cost connectivity to C-RAN, they only allow data transmission from the endpoints (e.g., hosting the radio unit, RU, at the antenna site) toward a central node (e.g., the central office, hosting computing equipment), and thus cannot support traffic from RUs toward MEC end nodes that could host the distributed unit (DU) and possibly central unit (CU) and network core. This has led to research into the evolution of PON architectures with the ability to provide direct communications between endpoints, thus supporting mesh traffic patterns required by MEC installations. In this context, virtualization plays a key role in enabling efficient resource allocation (i.e., optical transmission capacity) to endpoints, according to their Communication patterns. In this article, we address the challenge of dynamic allocation of virtual PON slices over mesh-PON architectures to support C-RAN and MEC nodes. We make use of a mixed analytical-iterative model to compute optimal virtual PON slice allocation, with the objective of minimizing the use of MEC node resources, while meeting a target latency threshold (100 µs in our scenario). Our method is particularly effective in reducing computation time, enabling virtual PON slice allocation in timescales compatible with real-time or near real-time operations. [ABSTRACT FROM AUTHOR]

Cloud radio access networks (C-RANs) are considered one of the most promising candidates for implementing 5G mobile communication systems. C-RAN enables centralization of baseband processing, enabling advanced coordination between base stations, such as coordinated multi-point and inter-cell interference cancellation. In addition, it allows pooling of resources across several cells, providing statistical multiplexing gains of computing resources. However, the link between the remote radio unit and the baseband unit requires high transmission capacity, making the fronthaul link a potential bottleneck for future dense cell deployments. One of the current solutions to this issue is to compress the fronthaul transmission rate. A second under standardization is to adopt a different functional split that can reduce the transmission capacity requirement. While this solution decreases the capacity requirements on the transport link, it decentralizes some of the computational resources, requiring a more complex remote radio unit (e.g., compared with a CPRI type of solution), whose resources cannot be utilized by other cells when not in use. It is thus expected that in the future, multiple solutions (different functional splits and CPRI) will coexist. In this paper, we introduce the concept of variable rate fronthaul (VRF) for C-RAN. This scheme operates on a CPRI type of interface (e.g., one that transmits I/Q data samples) with the novelty of dynamically changing the cell bandwidth, and consequently the fronthaul data rates, depending on the cell load, with the support of a software defined network (SDN) controller. This allows for a more efficient transport of C-RAN cells’ data over a shared backhaul. We first propose a mathematical analysis of the VRF performance using a queuing theory approach based on the Markov model. We then provide the results of our simulation framework both for validation and in support of the mathematical analysis. Our results show that the proposed VRF scheme provides significantly lower blocking probability over a shared backhaul than standard CPRI. [ABSTRACT FROM AUTHOR]

Radiation detectors have been fabricated on 8 mm\,\times\,8 mm substrates, \sim390\ \mum in thickness, diced from a (0001) 4H-SiC semi-insulating (SI) wafer (\geq10^12 Ohm-cm). The crystals used for detector fabrication have been characterized by x-ray diffraction (XRD), electron beam induced current (EBIC), chemical etching, cross-polarized imaging, and Raman spectroscopy. Current-voltage (I-V) characteristics showed very low leakage current (\leq50 pA at -800 V) and the capability of detector's operation \geq470 K. EBIC investigations revealed that the screw dislocations produce dark EBIC contrast indicating high leakage current in the defective regions. Thermally stimulated current (TSC) measurements and high temperature resistivity measurements revealed deep level centers with activation energies 1.1–1.2 eV, and 1.56 eV. The TSC peak at \sim460 K associated with the \sim1.2 eV center was much stronger than the other high temperature peaks (e.g., 370 K due to vanadium impurity, 0.95 eV below of conduction band edge), indicating that this level along with the 1.56 eV level should dominate in controlling the resistivity and carrier lifetime in the studied 4H-SiC. Based on the literature data, we associate these centers with intrinsic defects and/or V-related complex. Nuclear detection measurements on the single-element SiC detectors with ^241Am X-\gamma ray source clearly detected 59.6 keV and other low energy x-rays. [ABSTRACT FROM AUTHOR]

In this work we investigated a new method of growing detector grade large GaTe layered chalcogenide single crystals. GaTe ingots (2^\prime\prime diameter) were grown by a novel method using graphite crucible by slow crystallization from a melt of high purity (7 N) Ga and zone refined (ZR) Te precursors in an argon atmosphere. GaTe samples from the monocrystalline area of the ingot have been cleaved mechanically and characterized using x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive analysis by x-rays (EDX), atomic force microscopy (AFM), x-ray photoelectron spectroscopy (XPS), transfer length method (TLM), resistivity measurements using van der Pauw technique, Hall effect, and capacitance-voltage (C-V) measurements. Our investigations reveal a novel method of growing superior quality GaTe crystals for large volume inexpensive nuclear radiation detectors. [ABSTRACT FROM AUTHOR]

Presents information on a study which described a technique for synthesizing totally symmetric Boolean functions for path-delay fault testability of logic circuits. Synthesis of consecutive symmetric functions to achieve robust testability; Reduction of logic by algebraic factorization; Conclusions.