arXiv subjects

Xavier Vilajosana

Publications and source records attributed to Xavier Vilajosana.

16 recordsLinked to original sources

arXiv2024

Adapting LoRaWAN to the Open-RAN Architecture

This article proposes O-LoRaWAN, an adaptation of the LoRaWAN architecture into a modular network architecture based on the Open RAN (O-RAN) principles. In our vision, standardization of the network components and interfaces will enable the reuse of network functions, and thus, foster an accelerated tailoring of the network functions to the changing application demands. LoRaWAN shares similarities to cellular networks and becomes an interesting candidate for a transformation to the O-RAN standard. In the article we draw several transition strategies, these include the reorganization of the LoRa gateway functions into Radio and Distributed Units; enhancing network performance with RAN Intelligent Controllers exploiting the network data; and the standardization of the management and orchestration of network components. Key for that adaptation are the O-RAN interfaces. Along the article, we analyze them and suggest protocol extensions or adjustments for compatibility and interoperability between network components, advocating for the design of extensible protocols

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arXiv2023

LoRa Multi-Hop Networks for Monitoring Underground Mining Environments

Internet of Things applications have gained widespread recognition for their efficacy in typical scenarios, such as smart cities and smart healthcare. Nonetheless, there exist numerous unconventional situations where IoT technologies have not yet been massively applied, though they can be extremely useful. One of such domains is the underground mining sector, where enhancing automation monitoring through wireless communications is of essential significance. In this paper, we focus on the development, implementation, and evaluation of a LoRa-based multi-hop network tailored specifically for monitoring underground mining environments, where data traffic is sporadic, but energy efficiency is of paramount importance. We hence define a synchronization framework that makes it possible for the nodes to sleep for most of the time, waking up only when they need to exchange traffic. Notably, our network achieves a sub 40us proven synchronization accuracy between parent-child pairs with minimum overhead for diverse topologies, rendering it highly viable for subterranean operations. Furthermore, for proper network dimensioning, we model the interplay between network's throughput, frame size, and sampling periods of potential applications. Moreover, we propose a model to estimate devices' duty cycle based on their position within the multi-hop network, along with empirical observations for its validation. The proposed models make it possible to optimize the network's performance to meet the specific demands that can arise from the different subterranean use cases, in which robustness, low power operation, and compliance with radio-frequency regulations are key requirements that must be met.

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arXiv2022

Challenges and Opportunities for Simultaneous Multi-functional Networks in the UHF Bands

Multi-functional wireless networks are rapidly evolving and aspire to become a promising attribute of the upcoming 6G networks. Enabling multiple simultaneous networking functions with a single radio fosters the development of more integrated and simpler equipment, overcoming design and technology barriers inherited from radio systems of the past. We are seeing numerous trends exploiting these features in newly designed radios, such as those operating on the mmWave band. In this article, however, we carefully analyze the challenges and opportunities for multi-functional wireless networks in UHF bands, advocating the reuse of existing infrastructures and technologies, and exploring the possibilities of expanding their functionality without requiring architectural changes. We believe that both modern and legacy technologies can be turned into multi-functional systems if the right scientific and technological challenges are properly addressed. This transformation can foster the development of new applications and extend the useful life of these systems, contributing to a more sustainable digitization by delaying equipment obsolescence.

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arXiv2020

LR-FHSS: Overview and Performance Analysis

Long Range-Frequency Hopping Spread Spectrum (LR-FHSS) is the new physical layer designed to address extremely long-range and large-scale communication scenarios, such as satellite IoT. At its core is a fast frequency hopping technique designed to offer higher network capacity while offering the same radio link budget as LoRa. Additionally, LR-FHSS finely manages packet transmission thanks to its design principles, enabling QoS policies on a per-packet basis. Given the notorious adoption of LoRaWAN in the IoT application landscape, this article is a reference for understanding how exactly LR-FHSS works, the performance it can offer, and its limitations and research opportunities.

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arXiv2020

Debunking Wireless Sensor Networks Myths

In this article we revisit Wireless Sensor Networks from a contemporary perspective, after the surge of the Internet of Things. First, we analyze the evolution of distributed monitoring applications, which we consider inherited from the early idea of collaborative sensor networks. Second, we evaluate, within the current context of networked objects, the level of adoption of low-power multi-hop wireless, a technology pivotal to the Wireless Sensor Network paradigm. This article assesses the transformation of this technology in its integration into the Internet of Things, identifying outdated requirements and providing a critical view on future research directions.

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arXiv2020

Exploiting the Solar Energy Surplus for Edge Computing

In the context of the global energy ecosystem transformation, we introduce a new approach to reduce the carbon emissions of the cloud-computing sector and, at the same time, foster the deployment of small-scale private photovoltaic plants. We consider the opportunity cost of moving some cloud services to private, distributed, solar-powered computing facilities. To this end, we compare the potential revenue of leasing computing resources to a cloud pool with the revenue obtained by selling the surplus energy to the grid. We first estimate the consumption of virtualized cloud computing instances, establishing a metric of computational efficiency per nominal photovoltaic power installed. Based on this metric and characterizing the site's annual solar production, we estimate the total return and payback. The results show that the model is economically viable and technically feasible. We finally depict the still many questions open, such as security, and the fundamental barriers to address, mainly related with a cloud model ruled by a few big players.

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arXiv2019

Experimental Interference Robustness Evaluation of IEEE 802.15.4-2015 OQPSK-DSSS and SUN-OFDM Physical Layers

In this paper, we experimentally evaluate and compare the robustness against interference of the OQPSK-DSSS (Offset Quadrature Phase Shift Keying - Direct Sequence Spread Spectrum) and the SUN-OFDM (Smart Utility Network - Orthogonal Frequency Division Multiplexing) physical layers, as defined in the IEEE 802.15.4-2015 standard. The objective of this study is to provide a comprehensive analysis of the impact different types of interference produce on these modulations, in terms of the resulting PDR (Packet Delivery Ratio) and depending on the length of the packet being transmitted. The results show that the SUN-OFDM physical layer provides significant benefits compared to the ubiquitous OQPSK-DSSS in terms of interference robustness, regardless of the interference type and the packet length. Overall, this demonstrates the suitability of choosing the SUN-OFDM physical layer when deploying low-power wireless networks in industrial scenarios, specially taking into consideration the possibility of trading-off robustness and spectrum efficiency depending on the application requirements.

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arXiv2019

Authenticated Preambles for Denial of Service Mitigation in LPWANs

In this article we introduce authentication preambles as a mechanism to mitigate battery exhaustion attacks in LPWAN networks. We focus on the LoRaWAN technology as an exponent of industrial LPWANs. We analyze the impact of DoS attacks in Class B deployments and implement authentication preambles to limit attacker options when forcing nodes to overhear class B beacons. The article presents realistic results demonstrating significant energy savings (91% energy saving when a network is attacked) versus a 4% energy overhead of the mechanism in normally operating networks.

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arXiv2019

Experimental Clock Calibration\\on a Crystal-Free Mote-on-a-Chip

The elimination of the off-chip frequency reference, typically a crystal oscillator, would bring important benefits in terms of size, price and energy efficiency to IEEE802.15.4 compliant radios and systems-on-chip. The stability of on-chip oscillators is orders of magnitude worse than that of a crystal. It is known that as the temperature changes, they can drift more than 50 ppm/°C. This paper presents the result of an extensive experimental study. First, we propose mechanisms for crystal-free radios to be able to track an IEEE802.15.4 join proxy, calibrate the on-chip oscillators and maintain calibration against temperature changes. Then, we implement the resulting algorithms on a crystal-free platform and present the results of an experimental validation. We show that our approach is able to track a crystal-based IEEE802.15.4-compliant join proxy and maintain the requested radio frequency stability of +/-40 ppm, even when subject to temperature variation of 2°C/min.

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arXiv2019

A Channel Measurement Campaign for mmWave Communication in Industrial Settings

Industry 4.0 relies heavily on wireless technologies. Energy efficiency and device cost have played a significant role in the initial design of such wireless systems for industry automation. However, high reliability, high throughput, and low latency are also key for certain sectors such as the manufacturing industry. In this sense, existing wireless solutions for industrial settings are limited. Emerging technologies such as millimeter-wave (mmWave) communication are highly promising to address this bottleneck. Still, the propagation characteristics at such high frequencies in harsh industrial settings are not well understood. Related work in this area is limited to isolated measurements in specific scenarios. In this work, we carry out an extensive measurement campaign in highly representative industrial environments. Most importantly, we derive the statistical distributions of the channel parameters of widely accepted mmWave channel models that fit these environments. This is a highly valuable contribution, since researchers in this field can use our empirical model to understand the performance of their mmWave systems in typical industrial settings. Beyond analyzing and discussing our insights, with this paper we also shareoour extensive dataset with the research community.

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arXiv2019

Exploring the Performance Boundaries of NB-IoT

NarrowBand-IoT has just joined the LPWAN community. Unlike most of its competitors, NB-IoT did not emerge from a blank slate. Indeed, it is closely linked to LTE, from which it inherits many of the features that undoubtedly determine its behavior. In this paper, we empirically explore the boundaries of this technology, analyzing from a user's point of view critical characteristics such as energy consumption, reliability and delays. The results show that its performance in terms of energy is comparable and even outperforms, in some cases, an LPWAN reference technology like LoRa, with the added benefit of guaranteeing delivery. However, the high variability observed in both energy expenditure and network delays call into question its suitability for some applications, especially those subject to service-level agreements.

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arXiv2019

A Square Peg in a Round Hole: The Complex Path for Wireless in the Manufacturing Industry

The manufacturing industry is at the edge of the 4th industrial revolution, a paradigm of integrated architectures in which the entire production chain (composed of machines, workers and products) is intrinsically connected. Wireless technologies can add further value in this manufacturing revolution. However, we identify some signs that indicate that wireless could be left out from the next generation of smart-factory equipment. This is particularly relevant considering that the heavy machinery characteristic of this sector can last for decades. We argue that at the core of this issue there is a mismatch between industrial needs and the interests of academic and partly-academic (such as standardization bodies) sectors. We base our claims on surveys from renowned advisory firms and interviews with industrial actors, which we contrast with results from content analysis of scientific articles. Finally we propose some convergence paths that, while still retaining the degree of novelty required for academic purposes, are more aligned with industrial concerns.

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arXiv2019

Aggressive Fragmentation Strategy for Enhanced Network Performance in Dense LPWANs

Low Power Wide Area Networks (LPWANs) are gaining ground in the IoT landscape and, in particular, for Industrial IoT applications. However, given the strict duty cycle restrictions (e.g. 1% in SubGHz bands) and the limited power supply of devices, requirements of some applications can not always be met. This paper analyzes the potential of the combination of packet fragmentation -in the direction of the IETF LPWAN working group- and negative group acknowledgement (NACK) in LoRaWAN networks, a widespread LPWAN technology. Results show that the proposed strategy can lead to significant gains in terms of goodput and energy efficiency under congested situations.

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arXiv2018

An Analysis of Packet Fragmentation Impact in LPWAN

Packet fragmentation has mostly been addressed in the literature when referring to splitting data that does not fit a frame. It has received attention in the IoT community after the 6LoWPAN working group of IETF started studying the fragmentation headers to allow IPv6 1280 B MTU to be sent over IEEE 802.15.4 networks supporting a 127 B MTU. In this paper, and following some of the recent directions taken by the IETF LPWAN WG, an analysis of packet fragmentation in LPWANs has been done. We aim to identify the impact of sending the data in smaller fragments considering the restrictions of industrial duty-cycled networks. The analyzed parameters were the energy consumption, throughput, goodput and end to end delay introduced by fragmentation. The results of our analysis show that packet fragmentation can increase the reliability of the communication in duty-cycle restricted networks. This is of especial relevance when densifying the network. We observed relevant impact in energy consumption and extra latency, and identified the need for acknowledgements from the gateway/sink to exploit some of the benefits raised by fragmentation.

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arXiv2018

The Wireless Technology Landscape in the Manufacturing Industry: A Reality Check

An upcoming industrial IoT revolution, supposedly led by the introduction of embedded sensing and computing, seamless communication and massive data analytics within industrial processes [1], seems unquestionable today. Multiple technologies are being developed, and huge marketing efforts are being made to position solutions in this industrial landscape. However, we have observed that industrial wireless technologies are hardly being adopted by the manufacturing industry. In this article, we try to understand the reasons behind this current lack of wireless technologies adoption by means of conducting visits to the manufacturing industry and interviews with the maintenance and engineering teams in these industries. The manufacturing industry is very diverse and specialized, so we have tried to cover some of the most representative cases: the automotive sector, the pharmaceutical sector (blistering), machine-tool industries (both consumer and aerospace sectors) and robotics. We have analyzed the technology of their machinery, their application requirements and restrictions, and identified a list of obstacles for wireless technology adoption. The most immediate obstacles we have found are the need to strictly follow standards and certifications processes, as well as their prudence. But the less obvious and perhaps even more limiting obstacles are their apparent lack of concern regarding low energy consumption or cost which, in contrast, are believed to be of utmost importance by wireless researchers and practitioners. In this reality-check article, we analyze the causes of this different perception, we identify these obstacles and devise complementary paths to make wireless adoption by the industrial manufacturing sector a reality in the coming years.

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arXiv2017

Understanding the limits of LoRaWAN

The quick proliferation of LPWAN networks, being LoRaWAN one of the most adopted, raised the interest of the industry, network operators and facilitated the development of novel services based on large scale and simple network structures. LoRaWAN brings the desired ubiquitous connectivity to enable most of the outdoor IoT applications and its growth and quick adoption are real proofs of that. Yet the technology has some limitations that need to be understood in order to avoid over-use of the technology. In this article we aim to provide an impartial overview of what are the limitations of such technology, and in a comprehensive manner bring use case examples to show where the limits are.

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