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Publications
Publications (99)
The introduction of low-cost sensors (LCSs) in air quality Internet of Things (IoT) monitoring platforms presents the challenge of improving the quality of the data that these sensors provide. In this paper, we propose two algorithms to perform denoising and calibration for LCSs used in IoT monitoring platforms. Sensors are first calibrated in-situ...
Air pollution monitoring platforms play a very important role in preventing and mitigating the effects of pollution. Recent advances in the field of graph signal processing have made it possible to describe and analyze air pollution monitoring networks using graphs. One of the main applications is the reconstruction of the measured signal in a grap...
The simultaneous measurement of soil water content and water table levels is of great agronomic and hydrological interest. Not only does soil moisture represent the water available for plant growth but also water table levels can affect crop productivity. Furthermore, monitoring soil saturation and water table levels is essential for an early warni...
Recently, the monitoring of air pollution by means of low-cost sensors has become a growing research field due to the study of techniques based on machine learning to improve the sensors’ data quality. For this purpose, sensors undergo a calibration process, where these are placed in-situ nearby a regulatory reference station. The data set explaine...
The analysis of sensor networks for air pollution monitoring is challenging. Recent studies have demonstrated the ability to reconstruct the network measurements with graphs derived from the acquired data, thus describing the complex relationships between the sensors that compose the network. In this work, we propose a graph-based data reconstructi...
The use of low-cost sensors in conjunction with high-precision instrumentation for air pollution monitoring has shown promising results in recent years. One of the main challenges for these sensors has been the quality of their data, which is why the main efforts have focused on calibrating the sensors using machine learning techniques to improve t...
Today's air pollution sensor networks pose new challenges given their heterogeneity of low-cost sensors and high-cost instrumentation. Recently, with the advent of graph signal processing, sensor network measurements have been successfully represented by graphs depicting the relationships between sensors. However, one of the main problems of these...
Air pollution monitoring platforms play a very important role in preventing and mitigating the effects of pollution. Recent advances in the field of graph signal processing have made it possible to describe and analyze air pollution monitoring networks using graphs. One of the main applications is the reconstruction of the measured signal in a grap...
The calibration of low-cost sensors using machine learning techniques is a methodology widely used nowadays. Although many challenges remain to be solved in the deployment of low-cost sensors for air quality monitoring, low-cost sensors have been shown to be useful in conjunction with high-precision instrumentation. Thus, most research is focused o...
The H2020 CAPTOR project deployed three testbeds in Spain, Italy and Austria with low-cost sensors for the measurement of tropospheric ozone (O3). The aim of the H2020 CAPTOR project was to raise public awareness in a project focused on citizen science. Each testbed was supported by an NGO in charge of deciding how to raise citizen awareness accord...
Existing air pollution monitoring networks use reference stations as the main nodes. The addition of low-cost sensors calibrated in-situ with machine learning techniques allows the creation of heterogeneous air pollution monitoring networks. However, current monitoring networks or calibration techniques have limitations in estimating missing data,...
This paper investigates the calibration of low-cost sensors for air pollution. The sensors were deployed on three IoT (Internet of Things) platforms in Spain, Austria, and Italy during the summers of 2017, 2018, and 2019. One of the biggest challenges in the operation of an IoT platform, which has a great impact on the quality of the reported pollu...
This paper shows the result of the calibration process of an Internet of Things platform for the measurement of tropospheric ozone (O
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). This platform, formed by 60 nodes, deployed in Italy, Spain, and Austria, consisted of 140 metal–oxide O
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New advances in sensor technologies and communications in wireless sensor networks have favored the introduction of low-cost sensors for monitoring air quality applications. In this article, we present the results of the European project H2020 CAPTOR, where three testbeds with sensors were deployed to capture tropospheric ozone concentrations. One...
Growing progress in sensor technology has constantly expanded the number and range of low-cost, small, and portable sensors on the market, increasing the number and type of physical phenomena that can be measured with wirelessly connected sensors. Large-scale deployments of wireless sensor networks (WSN) involving hundreds or thousands of devices a...
Growing progress in sensor technology has constantly expanded the number and range of low-cost, small, and portable sensors on the market, increasing the number and type of physical phenomena that can be measured with wirelessly connected sensors. Large-scale deployments of wireless sensor networks (WSN) involving hundreds or thousands of devices a...
Tropospheric ozone (O3) is an environmental pollutant of growing concern, especially in suburban and rural areas where the density of air quality monitoring stations is not high. In this type of areas citizen science strategies can be useful tools for awareness raising, but sensor technologies must be validated before sensor data are communicated t...
Duty-cycle at the media access control (MAC) layer plays a key role in energy savings and network lifetime extension. It consists in putting a node's radio in the sleep state as soon as it has no communication activity. Traditional wireless sensor network MAC protocols are designed with short duty-cycles at the cost of long delays. Careful design i...
Optimizing energy consumption and end-to-end (e2e) packet delay in energy-constrained, delay-sensitive wireless sensor networks is a conflicting multiobjective optimization problem. We investigate the problem from a game theory perspective, where the two optimization objectives are considered as game players. The cost model of each player is mapped...
To minimize pesticide use it is necessary to detect at the early stage the present of plant disease and perform local treatment instead of global systematic treatment. To achieve this goal, one of the techniques may be used is image processing through the deployment of WMSN in the cultivated field. However, transmitting massive image data wirelessl...
A Spontaneous Area Network (SPAN) is formed by mobile and fixed nodes using wireless transmission links between nodes, usually in a nearby geographical area. Applications allow users to create, join, leave, and manage SPANs and groups in a SPAN. Automatic procedures allow nodes to join other SPANs. Transmission power of the wireless network interfa...
This paper gives a state-of-art of wireless sensor network (WSN) technologies and solutions applied to precision agriculture (PA). The paper first considers applications and existing experiences that show how WSN technologies have been introduced in to agricultural applications. Then, a survey in hardware and software solutions is related with spec...
In this paper we discuss the architecture of MStack, a data-centric communications stack specifically designed for mobile intermittent networking environments. MStack contains native support for delay tolerant connections, it is resilient to disconnections, and solves other problems associated with mobile devices. The architecture and its main prot...
This paper presents a Medium Access Control (MAC) protocol for broadband wireless LANs based on the ATM transfer mode, together with the evaluation of its performance in terms of throughput and access delay. Important characteristics of the MAC protocol are the way information between the Mobile Stations (MSs) and the Base Station (BS) is exchanged...
As the evolution of multi-core multi-threaded processors continues, the complexity demanded to perform an extensive trade-off analysis, increases proportionally. Cycle- accurate or trace-driven simulators are too slow to execute the large amount of experiments required to obtain indicative results. To achieve a thorough analysis of the system, soft...
Wireless nodes such as smart-phones in which the WiFi wireless card is continuously on, consume battery energy in just a few hours. Moreover, in many scenarios, an always-on wireless card is useless because there is often no need for transmission and/or reception. This fact is exacerbated in Delay/Disruptive Tolerant Network (DTN) environments, in...
This article presents a low coordination overhead cooperative Automatic Repeat reQuest (ARQ) scheme with an integrated frame
combiner, which exploits space diversity and cooperation between neighbouring nodes. A comparison between cooperation with
and without frame combiner is also performed. In channels with a strong Line of Sight (LOS) component...
Nowadays, the evolution of network services provided at the edge of Internet increases the requirements of network applications. Such applications result in complexities thus, the processors need to execute more complex workloads that can deal not only with the packet header, but also with the packet payload (e.g. Deep Packet Inspection). Unlike co...
Vehicular Ad Hoc Networks are networks characterized by intermittent connectivity and rapid changes in their topology. This paper addresses car-to-road communications in which vehicles use Access Points (AP) in a Delay Tolerant Network architecture. Results show how the combination of a Delay-Cooperative ARQ mechanism reduces packet losses and in c...
In this paper we introduce a novel cooperative forwarding mechanism for IEEE 802.11-based MANETs. The mechanism has been adapted to operate together with two well known routing protocols: AODV and LUNAR. We evaluate our proposal by means of a prototype, using pedestrian mobility inside a building. Results show that, in dense MANETs, our cooperative...
Hierarchical routing is a common practice in actual Internet networks. This kind of routing allows nodes and routers to get small routing tables and small routing overhead. On the opposite side, routing in MANETs is flat; therefore, nodes have to learn how to reach each node in the network. It means large routing tables, impact in the look up algor...
This paper proposes a Cooperative ARQ protocol to be used in delay-tolerant vehicular networks. The proposed scheme has been implemented and evaluated through an experimental testbed, showing that packet losses in transmissions from an access point to cars can be reduced to the half without any cost as long as cooperation takes place on areas where...
This paper evaluates a Cooperative ARQ protocol to be used in delay-tolerant vehicular networks. The scenario consists in cars downloading information from Access Points along a road. The key difference between proposed Cooperative ARQ protocols is when the cooperation takes place. Simply C-ARQ cooperation occurs in a packet-by-packet basis. In thi...
In this paper a Cooperative-ARQ (C-ARQ) with a maximum-likelihood frame combiner (ML-FC) protocol is studied. C-ARQ is well suited for wireless transmission in either infrastructure or ad-hoc networks, as it exploits some of the unique characteristics of wireless media, such as the natural broadcast of wireless transmission and receiver diversity....
In this paper a maximum-likelihood frame combiner integrated into a Cooperative-ARQ (C-ARQ) protocol is proposed and evaluated. C-ARQ is well suited for wireless transmission in either infrastructure or ad-hoc networks, as it exploits some of the unique characteristics of wireless media, such as the natural broadcast of wireless transmission and re...
This paper proposes a Cooperative ARQ protocol to be used in delay-tolerant vehicular networks. The proposed scheme has been implemented and evaluated through an experimental testbed, showing that packet losses in transmissions from an access point to cars can be reduced to the half without any cost as long as cooperation takes place on areas where...
This paper evaluates a Cooperative ARQ protocol to be used in delay-tolerant vehicular networks. The scenario consists in cars downloading information from Access Points along a road. The key difference between proposed Cooperative ARQ protocols is when the cooperation takes place. Simply C-ARQ cooperation occurs in a packet-by-packet basis. In thi...
This paper proposes a low coordination overhead cooperative automatic repeat request (ARQ) scheme with an integrated frame combiner, which exploits space diversity and cooperation between neighbouring nodes. In channels with a strong line of sight (LOS) component and low signal-to- noise ratio (SNR), the maximum achievable throughput of the propose...
Resumen En este artículo se discute la docencia de las Redes de Computadores y Sistemas Distribui-dos (RCySD) para escuelas de Ingeniería de Informática, y es fruto de la experiencia de los autores como profesores del Departamen-to de Arquitectura de Computadores (DAC) en la Facultad de Informática de Barcelona (FIB) [1] de la Universidad Politécni...
Posibilidades que ofrecen el IEEE estándar 802.16e, con respecto a los servicios que se pueden ofrecer a la industria del automóvil en sistemas inteligentes del transporte. Preprint
Information Technologies are called to play an important role in the world of transport services. One example is the combination
between mobile Internet and automotive industry. This research is focused on the design of a new automotive network architecture
called TrafficNet which, using IEEE 802.3 and 802.11 technologies, intends to support not o...
Nowadays, some of the more exciting research areas in networking are based on cooperation between network nodes. Examples
of this are ad-hoc or sensor networks, cooperative physical layer techniques known as cooperative diversity, or other new cooperative mechanisms such asCooperative ARQ. In many scenarios, this cooperation could be further exploi...
We address the design of high-speed packet buffers for Internet routers. We use a general DRAM/SRAM architecture for which previous proposals can be seen as particular cases. For this architecture, large SRAMs are needed to sustain high line rates and a large number of interfaces. A novel algorithm for DRAM bank allocation is presented that reduces...
Due to MANET topological routing algorithms are not scalable respect to the number of nodes in the network, we evaluate the
potential use of a subnet structure in MANETs. We show scenarios in which a MANET with subnet structure is applicable, present
the main technical challenges for the application of this structure and show that a reduction of ro...
The trend of the networking processing is to in- crease the intelligence of the routers (i.e. security capacities). This means that there is an increment in the workload generated per packet and new types of applications are emerging, such as stateful pro- grams. On the other hand, Internet traffic contin- ues to grow vigorously. This fact involves...
The explosive and robust growth of the Internet owes a lot to the "end-to-end principle", which pushes stateful operations to the end-points. The Internet grew both in traffic volume, and in the richness of the applications it supports. The growth also brought along new security issues and network monitoring applications. Edge devices, in particula...
In this paper we propose a collaborative ARQ protocol that exploits diversity and collaboration between nodes in wireless networks. We show that when M neighboring nodes collaborate using the proposed scheme, they can achieve the BER versus SNR performance of an array of M' antennas provided that M = p/2xM' ~1.57 M', in AWGN channels or M=2M'-1 in...
The trend of the networking processing is to increase the intelligence of the routers (i.e. security capacities). This means that there is an increment in the workload generated per packet and new types of applications are emerging, such as stateful programs. On the other hand, Internet traffic continues to grow vigorously. This fact involves an in...
A critical requirement for performance evaluation and design of network elements is the availability of realistic traffic traces. There are, however, several reasons that makes it difficult to have access to them. Firstly, Internet providers are usually reluctant to make real traces public, secondly, hardware for collecting traces at high speed is...
In this paper we study the properties of a new packet trace compression method based on clustering of TCP flows. With our proposed method, the compression ratio that we achieve is around 3%, reducing the file size, for instance, from 100 MB to 3 MB. Although this specification defines a lossy compressed data format, it preserves important statistic...
The explosive and robust growth of the Internet owes a lot to the “end-to-end principle”, which pushes stateful operations
to the end-points. The Internet grow both in traffic volume, and in the richness of the applications it supports. A whole
new class of applications requires stateful processing.
This paper presents the first workload character...
Achieving QoS (Quality of Service) in Mobile Ad-hoc NETworks (MANET) has been a research topic in the last years. In this paper we describe a QoS reservation mechanism for Routing Ad-hoc Networks. The mechanism is targeted for sources requiring a bandwidth allocation. The mechanism is based on the knowledge of the bandwidth requirements of the neig...
Recently, several authors have proposed models based on power-laws to characterize Internet topologies. Most of these works use the BGP (Border Gateway Protocol) tables published by Oregon Route Views. The adjacency matrix containing AS (autonomous system) connectivity is built from a BGP table. Having access to BGP routing tables from several geog...
We address the design of a packet buffer for future high-speed routers that support line rates as high as OC-3072 (160 Gb/s), and a high number of ports and service classes. We describe a general design for hybrid DRAM/SRAM packet buffers that exploits the bank organization of DRAM. This general scheme includes some designs previously proposed as p...
In this paper, we address the design of a future high-speed router that supports line rates as high as OC-3072 (160 Gb/s), around one hundred ports and several service classes. Building such a high-speed router would raise many technological problems, one of them being the packet buffer design, mainly because in router design it is important to pro...
This paper presents a performance analysis of a fair sharing mechanism for PC-based software routers, required when the I/O
bus and not the CPU is the bottleneck. The mechanism involves changes to the OS kernel and assumes the existence of certain
NIC functions, but does not require any changes to the PC hardware architecture.
We can define a software router as a general-purpose computer that executes a computer program capable of forwarding IP datagrams among network interface cards attached to its I/O bus. This paper presents a parametrical model of a PC based IP software router. Validation results clearly show that the model accurately estimates the performance of the...
This paper presents a Medium Access Control (MAC) protocol for broadband wireless LANs based on the ATM transfer mode, together with the evaluation of its performance in terms of throughput and access delay. Important characteristics of the MAC protocol are the way information between the Mobile Stations (MSs) and the Base Station (BS) is exchanged...
this document, several methods of AC for stream traffic based on declared parameters and using bufferless multiplexing are proposed.
this document was presented at the IFIP Conference on Personal Wireless Communications (PWC'2000) in Gdansk, Poland, 14-15 September 2000
We study tree networks of discrete-time queues loaded with periodic traffic sources. By using the so-called Benes method, exact closed-form expressions are obtained for the queue length distributions. The models developed can be used to study the superposition of periodic sources emitting bursts of cells in ATM networks. The results obtained show t...
The paper summarises the work on wireless networks inside the COST 257 project, entitled “Impact of new services on the architecture and performance of broadband networks” and chaired by Prof. Tran-Gia of the Technical University of Würzburg (Germany). This project was established for 4 years (1996–2000) and collected the researchers from 16 Europe...
This paper determines packet level performance measures of a MAC
protocol for a wireless ATM local area network. A key characteristic of
the MAC protocol is the identifier splitting algorithm with polling, a
contention resolution scheme used to inform the base station about the
bandwidth needs of a mobile station when no piggybacking can be used. W...
This paper presents a Collision Resolution Algorithm which significantly improves the performance in terms of throughput and delay of the uplink contention channel existing in Wireless ATM MAC protocols such as MASCARA (9), where slotted ALOHA is employed. FS-ALOHA groups the requests arrived at the mobile terminals during a frame length and serves...
An abstract is not available.
FIFO by sets ALOHA (FS-ALOHA) is a collision resolution algorithm for the uplink contention channel in multiservices wireless LANs. FS-ALOHA builds sets with the requests generated by the mobiles on a per-frame basis and serves them using slotted ALOHA with a FIFO discipline. In this paper the overall performance (throughput and delay) of FS-ALOHA...
This paper presents a new Medium Access Control (MAC) protocol for broadband wireless ATM Local Area Networks. Quality of Service (QoS) is provided by the support of the diierent ATM service categories. The system is TDMA with Frequency Duplexing and has a centralized architecture: one Base Station (BS) controls the access to the shared medium for...
This paper presents and evaluates the performance of a MAC
protocol for a broadband access network using an ATM passive optical
network (PON) supporting different service categories. The protocol is
an enhancement of an earlier version proposed by the authors and
implemented in the demonstrator of a project in the European RACE
programme. A request...
In this paper* we propose and analyze a Medium Access Control (MAC) protocol for high-speed ad-hoc Wireless Local Area Networks. The MAC protocol is a collision resolution algorithm and aims to approximate the delay characteristics of an ideal multiplexer with FIFO discipline. The protocol groups the packets arriving in given time intervals. Packet...
We obtain the queue length distribution in a tree of discrete time queues with constant service time whose input is periodic traffic. In the context of ATM the study could be applied to CBR sources. The tree consists of M-stages. To solve this system, we first solve a 2-stage tree network. Given this configuration, a more complex tree network can b...
When a new system is designed, different alternatives offering the same functionality have to be compared with respect to performance, reliability, modularity, robustness, hardware and software complexity, development costs etc. In particular when no implementations are available, modelling is often the only way of evaluating and comparing the alte...
In this paper we analyse a multiplexer handling a number of identical and independent Worst Case Traffic (WCT) sources. Each WCT source produces a periodic stream of cells consisting of a constant number of back-to-back cells followed by a silent period of constant duration. The WCT can model the traffic produced by a “malicious” user who sends an...
Fast Reservation Protocol (FRP) is a Traffic Control scheme intended to multiplex bursty data sources. In this paper we focus on the analysis of the FRP when different sources are multiplexed together in order to study the fairness of the protocol. We present two analytical models to analyse the case in which a set of identical sources is multiplex...
This paper deals with a traffic shaper which spaces all the cells belonging to a bundle of VCs, hence its name bundle-spacer. Although the concept of a bundle-spacer is applicable in general to situations where no VC information is available, we have focused at one particular application, namely the access control of a shared access link to an ATM...
This paper studies two different physical situations that are important to dimension User Parameter Function mechanisms and the buffers needed at the ATM Adaptation Layer: 1.(i)the cell delay variations a Constant Bit Rate traffic is subject to when mixed with Variable Bit Rate traffic in an ATM network,2.(ii)the cell loss rate when a Worst Case Tr...