119 research outputs found
Witness-based Approach for Scaling Distributed Ledgers to Massive IoT Scenarios
Distributed Ledger Technologies (DLTs) are playing a major role in building
security and trust in Internet of Things (IoT) systems. However, IoT
deployments with a large number of devices, such as in environment monitoring
applications, generate and send massive amounts of data. This would generate
vast number of transactions that must be processed within the distributed
ledger. In this work, we first demonstrate that the Proof of Work (PoW)
blockchain fails to scale in a sizable IoT connectivity infrastructure. To
solve this problem, we present a lightweight distributed ledger scheme to
integrate PoW blockchain into IoT. In our scheme, we classify transactions into
two types: 1) global transactions, which must be processed by global blockchain
nodes and 2) local transactions, which can be processed locally by entities
called witnesses. Performance evaluation demonstrates that our proposed scheme
improves the scalability of integrated blockchain and IoT monitoring systems by
processing a fraction of the transactions, inversely proportional to the number
of witnesses, locally. Hence, reducing the number of global transactions.Comment: 6 pages, 7 figures, conference pape
Subjective quality of life in war-affected populations
PMCID: PMC3716711This is an Open Access article distributed under the terms of the Creative
Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and
reproduction in any medium, provided the original work is properly cited
Progressive feature transmission for split classification at the wireless edge
We consider the scenario of inference at the wire-less edge , in which devices are connected to an edge server and ask the server to carry out remote classification, that is, classify data samples available at edge devices. This requires the edge devices to upload high-dimensional features of samples over resource-constrained wireless channels, which creates a communication bottleneck. The conventional feature pruning solution would require the device to have access to the inference model, which is not available in the current split inference scenario. To address this issue, we propose the progressive feature transmission (ProgressFTX) protocol, which minimizes the overhead by progressively transmitting features until a target confidence level is reached. A control policy is proposed to accelerate inference, comprising two key operations: importance-aware feature selection at the server and transmission-termination control . For the former, it is shown that selecting the most important features, characterized by the largest discriminant gains of the corresponding feature dimensions, achieves a sub-optimal performance. For the latter, the proposed policy is shown to exhibit a threshold structure. Specifically, the transmission is stopped when the incremental uncertainty reduction by further feature transmission is outweighed by its communication cost. The indices of the selected features and transmission decision are fed back to the device in each slot. The control policy is first derived for the tractable case of linear classification, and then extended to the more complex case of classification using a convolutional neural network . Both Gaussian and fading channels are considered. Experimental results are obtained for both a statistical data model and a real dataset. It is shown that ProgressFTX can substantially reduce the communication latency compared to conventional feature pruning and random feature transmission strategies
Outage Analysis of Downlink URLLC in Massive MIMO systems with Power Allocation
Massive MIMO is seen as a main enabler for low-latency communications, thanks to its high spatial degrees of freedom. The channel hardening and favorable propagation properties of Massive MIMO are particularly important for multiplexing several URLLC devices. However, the actual utility of channel hardening and spatial multiplexing is dependent critically on the accuracy of channel knowledge. When several low-latency devices are multiplexed, the cost for acquiring accurate knowledge becomes critical, and it is not evident how many devices can be served with a latency-reliability requirement and how many pilot symbols should be allocated. This paper investigates the trade-off between achieving high spectral efficiency and high reliability in the downlink, by employing various power allocation strategies, for maximum ratio and minimum mean square error precoders. The results show that using max-min SINR power allocation achieves the best reliability, at the expense of lower sum spectral efficiency
Trusted Wireless Monitoring based on Blockchain over NB-IoT Connectivity
The data collected from Internet of Things (IoT) devices on various emissions
or pollution, can have a significant economic value for the stakeholders. This
makes it prone to abuse or tampering and brings forward the need to integrate
IoT with a Distributed Ledger Technology (DLT) to collect, store, and protect
the IoT data. However, DLT brings an additional overhead to the frugal IoT
connectivity and symmetrizes the IoT traffic, thus changing the usual
assumption that IoT is uplink-oriented. We have implemented a platform that
integrates DLTs with a monitoring system based on narrowband IoT (NB-IoT). We
evaluate the performance and discuss the tradeoffs in two use cases: data
authorization and real-time monitoring.Comment: 7 pages, 6 figures, Accepted in IEEE Communication Magazin
The utilization and perceived usefulness of health care and other support services by people exposed to traumatic events related to the war in the Balkans
High-Power and Safe RF Wireless Charging: Cautious Deployment and Operation
The wired charging and the need for battery replacements are critical
barriers to unlimited, scalable, and sustainable mobile connectivity,
motivating the interest in radio frequency (RF) wireless power transfer (WPT)
technology. However, the inherently low end-to-end power transfer efficiency
(PTE) and health/safety-related apprehensions about the technology are critical
obstacles. Indeed, RF-WPT implementation and operation require efficient and
cautious strategies and protocols, especially when targeting high-power
charging, which constitutes the scope of this work. Herein, we overview the
main factors affecting the end-to-end PTE of RF-WPT systems and their
multiplicative effect and interdependencies. Moreover, we discuss key
electromagnetic field (EMF) exposure metrics, safety limits, and approaches for
efficient and EMF-aware deployment and operation. Quantitatively, we show that
near-field RF charging may significantly reduce EMF exposure, and thus must be
promoted. We also present our vision of a cyber-physical system for efficient
and safe wireless charging, specify key components and their interrelation, and
illustrate numerically the PTE attained by two modern low-power multi-antenna
architectures in a simple setup. Throughout the paper, we highlight the need
for high end-to-end PTE architectures and charging protocols transparently
complying with EMF exposure regulations and outline relevant challenges and
research directions. This work expands the vision and understanding of modern
RF-WPT technology and constitutes a step towards making the technology
attractive for worldwide commercial exploitation.Comment: 8 pages, 5 figures, 1 tabl
Learning to speak on behalf of a group: medium access control for sending a shared message
The rapid development of Internet of Things (IoT) technologies has not only enabled new applications, but also presented new challenges for reliable communication with limited resources. In this work, we define a novel problem that can arise in these scenarios, in which a set of sensors need to communicate a joint observation. This observation is shared by a random subset of the nodes, which need to propagate it to the rest of the network, but coordination is complex: as signaling constraints require the use of random access schemes over shared channels, sensors need to implicitly coordinate, so that at least one transmission gets through without collisions. Unlike the majority of existing medium access schemes, the goal is to make sure that the shared message gets through, regardless of the sender. We analyze this coordination problem theoretically and provide low-complexity solutions. While a clustering-based approach is near-optimal if the sensors have prior knowledge, we provide a distributed multi-armed bandit (MAB) solution for the more general case and validate it by simulation
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