MAC-Oriented Programmable Terahertz PHY via Graphene-based Yagi-Uda Antennas

Graphene is enabling a plethora of applications in a wide range of fields due to its unique electrical, mechanical, and optical properties. In the realm of wireless communications, graphene shows great promise for the implementation of miniaturized and tunable antennas in the terahertz band. These unique advantages open the door to new reconfigurable antenna structures which, in turn, enable novel communication protocols at different levels of the stack. This paper explores both aspects by, first, presenting a terahertz Yagi-Uda-like antenna concept that achieves reconfiguration both in frequency and beam direction simultaneously. Then, a programmable antenna controller design is proposed to expose the reconfigurability to the PHY and MAC layers, and several examples of its applicability are given. The performance and cost of the proposed scheme is evaluated through full-wave simulations and comparative analysis, demonstrating reconfigurability at nanosecond granularity with overheads below 0.02 mm$^{2}$ and 0.2 mW.Comment: Accepted for presentation in IEEE WCNC '1

VHF band-pass filter based on a single CMOS-MEMS doubleended tuning fork resonator

AbstractThis paper presents a single Double-Ended Tuning Fork (DETF) MEMS resonator-based band-pass filter fabricated on a commercial standard CMOS technology. The accurate design of this resonator demonstrates the ability to perform filtering without the need of coupling multiple resonators. The main characteristic is to define the out-of-phase mode resonance frequency of the DETF smaller than the in-phase mode frequency. The electrical characterization shows that this stand-alone band-pass filter presents a 44.4MHz central frequency with a 0.6% bandwidth in air

Scale up your In-Memory Accelerator: Leveraging Wireless-on-Chip Communication for AIMC-based CNN Inference

Analog In-Memory Computing (AIMC) is emerging as a disruptive paradigm for heterogeneous computing, potentially delivering orders of magnitude better peak performance and efficiency over traditional digital signal processing architectures on Matrix-Vector multiplication. However, to sustain this throughput in real-world applications, AIMC tiles must be supplied with data at very high bandwidth and low latency; this poses an unprecedented pressure on the on-chip communication infrastructure, which becomes the system's performance and efficiency bottleneck. In this context, the performance and plasticity of emerging on-chip wireless communication paradigms provide the required breakthrough to up-scale on-chip communication in large AIMC devices. This work presents a many-tile AIMC architecture with inter-tile wireless communication that integrates multiple heterogeneous computing clusters, embedding a mix of parallel RISC-V cores and AIMC tiles. We perform an extensive design space exploration of the proposed architecture and discuss the benefits of exploiting emerging on-chip communication technologies such as wireless transceivers in the millimeter-wave and terahertz band

Terahertz Dielectric Resonator Antenna Coupled to Graphene Plasmonic Dipole

This paper presents an efficient approach for exciting a dielectric resonator antenna (DRA) in the terahertz frequencies by means of a graphene plasmonic dipole. Design and analysis are performed in two steps. First, the propagation properties of hybrid plasmonic onedimensional and two-dimensional structures are obtained by using transfer matrix theory and the finite-element method. The coupling amount between the plasmonic graphene mode and the dielectric wave mode is explored based on different parameters. These results, together with DRA and plasmonic antenna theory, are then used to design a DRA antenna that supports the $TE_{y}^{112}$ mode at 2.4 THz and achieves a gain (IEEE) of up to 7 dBi and a radiation efficiency of up 70%. This gain is 6.5 dB higher than that of the graphene dipole alone and achieved with a moderate area overhead, demonstrating the value of the proposed structure.Comment: Accepted for presentation at EuCAP 201

Evaluation of Spanish institutional repositories based on criteria related to technology, procedures, content, marketing and personnel

Purpose The purpose of this paper is to provide, through a set of indicators, an overview of the way in which Spanish institutional repositories are run and the services they offer their respective institutions and other users. The selected descriptors are based on aspects related to technology, procedures, content, marketing and the personnel responsible for managing repositories. Design/methodology/approach In order to establish the indicators, a thorough review of the literature was carried out to identify existing indicators that are used to assess repositories. These were divided into five categories (technology, procedures, content, marketing and personnel) with a total of 48 components. An online survey was conducted with the repositories managers of 66 Spanish research institutions in order to verify the degree of fulfilment of the selected indicators. Findings The survey received forty-six responses, which represented a response rate of 69 per cent. Of these, 44 came from universities and two from research centres. In total, 65 per cent of the repositories have the capacity to import data from and export data to other university systems, mainly Current Research Information System (32 per cent). Most repositories have mechanisms for the large-scale import and export of metadata and digital objects (83 per cent). The use of altmetrics in repositories is widespread (44 per cent). Authors and librarians deposit most frequently (37 and 32 per cent, respectively), in spite of the fact that 44 per cent do not have full-time staff working in the repository. In more than 80 per cent of the repositories, between 90 and 100 per cent of the deposits are full-text documents. With respect to the tools used to promote the repository within the institution, these are primarily face-to-face training sessions (82 per cent), followed by support materials such as manuals and help pages (65 per cent). The academic authorities encourage open access among researchers in 56 per cent of cases, a significant element in repository marketing. Originality/value This work proposes a model based on five dimensions and 48 indicators to assess institutional repositories. This approach has been applied to Spanish institutional repositories to provide up-to-date information about their management procedures and promotional methods and the services they offer authors and the university community. This overview of Spanish repositories has provided an insight into the way in which repositories have evolved in recent years and allowed potential improvements to be identified based on the most advanced repositories. This model can also be exported to assess institutional repositories in other countries

Understanding the design-space of sparse/dense multiphase GNN dataflows on spatial accelerators

Graph Neural Networks (GNNs) have garnered a lot of recent interest because of their success in learning representations from graph-structured data across several critical applications in cloud and HPC. Owing to their unique compute and memory characteristics that come from an interplay between dense and sparse phases of computations, the emergence of recon-figurable dataflow (aka spatial) accelerators offers promise for acceleration by mapping optimized dataflows (i.e., computation order and parallelism) for both phases. The goal of this work is to characterize and understand the design-space of dataflow choices for running GNNs on spatial accelerators in order for mappers or design-space exploration tools to optimize the dataflow based on the workload. Specifically, we propose a taxonomy to describe all possible choices for mapping the dense and sparse phases of GNN inference, spatially and temporally over a spatial accelerator, capturing both the intra-phase dataflow and the inter-phase (pipelined) dataflow. Using this taxonomy, we do deep-dives into the cost and benefits of several dataflows and perform case studies on implications of hardware parameters for dataflows and value of flexibility to support pipelined execution.Parts of this work were supported through a fellowship by NEC Laboratories Europe, Project grant PID2020-112827GB-I00 funded by MCIN/AEI/ 10.13039/501100011033, RTI2018-098156-B-C53 (MCIU/AEI/FEDER,UE) and grant 20749/FPI/18 from Fundación Séneca.Peer ReviewedPostprint (author's final draft

ABSense: Sensing Electromagnetic Waves on Metasurfaces via Ambient Compilation of Full Absorption

Metasurfaces constitute effective media for manipulating and transforming impinging EM waves. Related studies have explored a series of impactful MS capabilities and applications in sectors such as wireless communications, medical imaging and energy harvesting. A key-gap in the existing body of work is that the attributes of the EM waves to-be-controlled (e.g., direction, polarity, phase) are known in advance. The present work proposes a practical solution to the EM wave sensing problem using the intelligent and networked MS counterparts-the HyperSurfaces (HSFs), without requiring dedicated field sensors. An nano-network embedded within the HSF iterates over the possible MS configurations, finding the one that fully absorbs the impinging EM wave, hence maximizing the energy distribution within the HSF. Using a distributed consensus approach, the nano-network then matches the found configuration to the most probable EM wave traits, via a static lookup table that can be created during the HSF manufacturing. Realistic simulations demonstrate the potential of the proposed scheme. Moreover, we show that the proposed workflow is the first-of-its-kind embedded EM compiler, i.e., an autonomic HSF that can translate high-level EM behavior objectives to the corresponding, low-level EM actuation commands.Comment: Publication: Proceedings of ACM NANOCOM 2019. This work was funded by the European Union via the Horizon 2020: Future Emerging Topics call (FETOPEN), grant EU736876, project VISORSURF (http://www.visorsurf.eu