Rafael Asorey Cacheda

Universidad Politécnica de Cartagena | UPCT · Department of Information and Communication Technologies

Piezoelectric transducers are widely used for generating acoustic energy, and choosing the right radiating element is crucial for efficient energy conversion. In recent decades, numerous studies have been conducted to characterize ceramics based on their elastic, dielectric, and electromechanical properties, which have improved our understanding of...

The Internet of Nano-Things (IoNT) is an emerging paradigm in which devices sized to the nano scale (nanonodes) and transmitting in the Terahertz (THz) band can become decisive actors in future medical applications. Flow-Guided Nanonetworks are well-known THz networks aimed at deploying the IoNT inside the human body, among other issues. In these n...

Deficient air quality in industrial environments creates a number of problems that affect both the staff and the ecosystems of a particular area. To address this, periodic measurements must be taken to monitor the pollutant substances discharged into the atmosphere. However, the deployed system should also be adapted to the specific requirements of...

In this paper, the automation of the evacuation process of a military ship is studied in real time. For this purpose, a scenario is reconfigured to produce a failure or damage. Then, an optimal network of alternative escape routes is computed. The resulting escape route map can be indicated by lighting the appropriate corridors on the ship. Through...

Este artículo analiza el proceso de co-creación de una obra de arte digital en el contexto del conflicto armado colombiano. El artículo sitúa este proceso dentro de un panorama más amplio de experiencias artísticas dedicadas a para transformar, testimoniar o bien generar memoria sobre el conflicto. Todas estas prácticas son parte del actual “boom d...

Cardiovascular events occurring in the bloodstream are responsible for about 40% of human deaths in developed countries. Motivated by this fact, we present a new global network architecture for a system for the diagnosis and treatment of cardiovascular events, focusing on problems related to pulmonary artery occlusion, i.e., situations of artery bl...

We are witnessing the full integration of the Internet of Things (IoT) into many social and economic sectors. Part of this unprecedented growth is due to the emergence of new communication technologies such as Low Power Wide Area Networks (LPWAN), which have been the catalyst for previously unfeasible smart applications. Efforts to optimize energy...

Background Computer Generated Animations (CGA), when applied to three-dimensional (3D) city models (3DCM), can be used as powerful tools to support urban decision-making. This leads to a new paradigm, based on procedural modeling, that allows the integration of known urban structures. This paper introduces a new workflow for the development of high...

Terahertz-based nano-networks are emerging as a groundbreaking technology able to play a decisive role in future medical applications owing to their ability to precisely quantify figures, such as the viral load in a patient or to predict sepsis shock or heart attacks before they occur. Due to the extremely limited size of the devices composing thes...

Flow-guided nanocommunication networks comprise a new paradigm that enables among other things, new medical applications for monitoring, information gathering, and data transmission inside the human body. Although promising, this type of network is conceived to operate in a very hostile environment (e.g. blood circulatory system) where nano-node mo...

Continuous progress of nanocommunications and nano-networking is opening the door to the development of innovative yet unimaginable services, with a special focus on medical applications. Among several nano-network topologies, flow-guided nanocommunication networks have recently emerged as a promising solution to monitoring, gathering information,...

Terahertz-based nano-networks are emerging as a groundbreaking technology able to play a decisive role in future medical applications owing to their ability to precisely quantify figures, such as the viral load in a patient or to predict sepsis shock or heart attacks before they occur. Due to the extremely limited size of the devices composing thes...

Implicit Error Correction (IEC) is a near Video-on- Demand (nVoD) scheme that trades bandwidth utilization for initial playback delay to potentially support an infinite number of users. Additionally, it provides error protection without any further bandwidth increase by exploiting the implicit redundancy of nVoD protocols, using linear combinations...

Flow-guided nanocommunication networks have recently emerged as a promising solution to monitor, gather information, and data communication inside the human body. This paper presents an analytical study on the behavior of these networks with the objective of evaluating the maximum channel utilization and determining an optimal frame length.

The deployment of wireless sensor networks in smart cities for environmental monitoring is a complex issue. One of the main problems is to determine the most appropriate places for these tasks. This paper proposes the use of information from crowdsourcing to identify places of interest from the environmental point of view to deploy the sensor netwo...

Distributed jamming has important applications not only in the military context but also in the civilian context where spectrum sharing is increasingly used and inadvertent jamming becomes a reality. In this paper, we derive the capacity bounds of wireless networks in the presence of jamming. We show that when the density of jammers is higher than...

Wireless Sensor Networks (WSN) pose several problems in terms of scalability and energy consumption. Many of them have been treated in the literature by means of optimization techniques. Depending on the optimization goal and constraints, a great number of these problems are solved using Linear Programming (LP) techniques whenever possible or the n...

Cultural heritage is a fragile, nonrenewable resource that constitutes the basic record of past human activities, and as such, it should be protected (Vecco 2010). The protection and management of cultural heritage include materials characterisation, archaeological prospecting and structural stability analysis. Regarding archaeological surveys, the...

Ground penetrating radar is a well-established technique for civil engineering applications. However, the method still needs improvements and new developments when interpreting the reflection profiles produced. Advances are therefore required both for automated detection and better understanding of the GPR signal propagation. The development of new...

This work presents the evaluation of a medieval masonry bridge that has suffered different restorations throughout history. Ground penetrating radar was used to define the internal state of the structure. Given that the heterogeneity in masonry complicates the interpretation of field data, numerical modelling was employed to improve such interpreta...

Disclosed embodiments include a method and an apparatus for digital content transmission that comprise: (a) partitioning the digital content into a plurality of sequential segments; (b) selecting a plurality of transmission time instants for each of the sequential segments as a function of their order; (c) generating a plurality of linear combinati...

Future wireless communications are heading towards an all-Internet Protocol (all-IP) design, and will rely on the Session Initiation Protocol (SIP) to manage services, such as voice over IP (VoIP). The centralized architecture of traditional SIP has numerous disadvantages for mobile ad hoc services that may be possibly overcome by advanced peer-to-...

The extension of the network lifetime of Wireless Sensor Networks (WSN) is an important issue that has not been appropriately solved yet. This paper addresses this concern and proposes some techniques to plan an arbitrary WSN. To this end, we suggest a hierarchical network architecture, similar to realistic scenarios, where nodes with renewable ene...

Implicit Error Correction is a near Video-on-Demand (nVoD) schema that trades bandwidth utilization for initial playback delay while potentially allowing an infinite number of users. Additionally, it provides error protection without further bandwidth increase by exploiting the implicit redundancy of nVoD protocols, using linear combinations of the...

This paper addresses the modeling of specific Smart Grid (SG) communication requirements from a data networking research perspective, as a general approach to the study of different access technologies suitable for the last mile (LM). SGLM networks serve customers' Energy Services Interfaces. From functional descriptions of SG, a traffic model is d...

This paper studies mutual information in a novel scenario combining cooperative diversity and cognitive radio based on spectrum leasing. In the scenario there is a primary transmitter subject to random channel fading, with full spectrum rights available, and a secondary transmitter without any spectrum rights, which offers its cooperation to the pr...

In this paper we extend Continuous Derivative Free (CDF) algorithms that solve optimization models with continuous variables to the solution of optimization models with both continuous and discrete variables. The algorithm fits naturally to the solution of discretized models arising from continuous models. Roughly speaking, the finer the discretiza...

Distributed network protocols operate similar to periodic state machines, utilizing internal states and timers for network coordination, which creates opportunities for carefully engineered radio jamming to target the protocol operating periods and disrupt network communications. Such periodic attacks targeting specific protocol period/frequency of...

This paper addresses specific smart grid communication requirements. It considers a last-mile network based on an IEEE 802.16 cell deployed to cover a group of customers and serve their Energy Services Interfaces. Based on the communication requirements of smart grid last-mile applications and entities, we propose a traffic priority model and setup...

This paper studies the Implicit Error Correction (IEC) near-Video on Demand (nVoD) schema, which relies on the intrinsic redundancy of nVoD protocols, in channels that deliver damaged data. The results rather than discard show that IEC provides good protection against errors without increasing the bandwidth requirements of other schemas for the sam...

Diversity, i.e. transmitting multiple replicas of a signal, may mitigate fading in wireless networks. Among other diversity techniques, the space diversity of multi-antenna systems is particularly interesting since it can complement other forms of diversity. The recent cooperative diversity paradigm brings the advantages of multi-antenna space dive...

Distributed network protocols operate similar to periodic state machines, utilizing internal states and timers, for network coordination. This creates opportunities for carefully engineered radio jamming to target the protocol operating periods and disrupt network communications. Such periodic attacks targeting specific protocol period/frequency of...

Aeronautical electronics and communication technologies have evolved from the analog domain to the digital domain, and nowadays, planes are complex structures serviced by many standalone systems that communicate through data buses. Many of these systems have found applicability in other sectors. This paper reviews the most recent technologies in mo...

In the nVoD (near video-on-demand) paradigm, video is distributed through broadcast channels with constrained bandwidth, so that at reception there is a bounded playback start time that is independent of the number of users. In other words, there is unlimited scalability for low bandwidth cost, at the expense of a bounded start time. Thus, regardin...

In this paper, using linear programming, we formulate the problem of maximizing the α-lifetime of wireless sensor networks with solar energy sources. The α-lifetime of a sensor network is defined as the duration in which α percentage of sensor data can be collected by the base station. Our formulation takes account of varying solar energy recovery...

In a previous paper we presented a new near Video on Demand (nVoD) schema with error correcting capabilities, without any bandwidth overhead. In this paper, we compare this schema with the recent proposal by Jenkac in order to determine which one has better characteristics to be used on wireless mesh networks. After this, we extend our schema to su...

In this paper we present a novel multicast near-Video on Demand (nVoD) coding schema, which relies on the intrinsic redundancy of the underlying nVoD protocol to provide implicit error correction, by employing content segments as blocks for coding operations. As a result, this implicit error correction has zero overhead, unlike the direct applicati...

As wireless mesh networks become more widely deployed, media streaming in such networks poses a pressing research issue because of the increasing importance of multimedia applications. The challenge with wireless mesh networks is the time-varying wireless channel compounded by multi-hop transmission. However, wireless mesh networks also present an...

In a previous paper we presented a new near Video on Demand schema with error correcting capabilities, without any bandwidth overhead. In this paper, we extend this schema to support scalable video. The clients can adapt the video to quality they can support. Moreover, they can reduce quality in case of unrecovered errors, as far as the lowest qual...

In the nVoD (near video-on-demand) paradigm, video is distributed through broadcast channels with constrained bandwidth, yielding a bounded playback start time regardless of the number of users. In other words, there is unlimited scalability for low bandwidth cost, at the expense of a bounded start time. Thus, regarding bandwidth, nVoD schemas are...

In this paper, we present a bandwidth limited and error tolerant near-Video-on-Demand (nVoD) schema suitable for satellite networks. Compared to traditional nVoD schemas, such as carousels, it outperforms in terms of download start letency and packet loss tolerance. Video-on Demand (VoD) has been a topic of intense research in the past. The main pr...

In this paper we present a novel multicast near- video on demand (nVoD) schema which relies on the intrinsic redundancy of nVoD protocols to provide implicit error correction, by employing content segments as blocks for coding operations. The results in this paper show that our proposal outperforms previous approaches involving explicit error corre...

In this paper we present a novel multicast near-Video on Demand (nVoD) scheme. It relies on the intrinsic redundancy of nVoD protocols to provide implicit error correction , by employing content segments themselves as blocks for coding operations. The results in this paper show that our proposal outperforms previous schemes in terms of transmission...

In this paper, we review different architectures for near video-on-demand (NVoD) systems on satellite networks. In many scenarios, satellites are the only available option for content distribution. On the other hand, video-on-demand (VoD) has been a topic of intense research in the past. The main problem of VoD systems is that their bandwidth requi...

In this paper, the main role of satellite systems in hybrid satellite/terrestrial networks will be highlighted, as well as the main functions which should be performed to optimize the performance of these hybrid networks. Then, some typical services believed to occupy a great portion of the future telecommunication service market and benefiting fro...

The load balanced Birkhoff–von Neumann switch is an elegant VOQ architecture with two outstanding characteristics: (i) it has a computational cost of O(1) iterations and (ii) input controllers do not exchange information (as a result, it allows decoupled implementations with a low power density). The load balancing stage guarantees stability under...

Internet development and an ever-increasing demand for bandwidth are boosting the market for satellite solutions. Technological progress leading to new satellite capabilities and the availability of bandwidth at lower cost is enabling this growing role of satellites in the Internet world. Satellite solutions are being used for both broadcast/multic...

In this paper, we describe our experience in the development of a low-cost delay-tolerant network (DTN) node, based on a commercial wireless access point (AP). As far as we know, there are no previous related experiences. To achieve our goal, it was necessary to perform some changes in the original DTN stack implementation to support the AP hardwar...

The parallel hierarchical matching (PHM) algorithm is a distributed maximal size matching scheduler for virtual output-queued switches. In a previous letter, we formulated an upper bound on the maximum number of iterations PHM requires to achieve a maximal size matching in any traffic scenario. In this letter, we follow an analytical approach to fi...

In this paper we present an architecture to assist users willing to execute P2P applications in isolated networks. Our solution combines caches, multicasting for content transmissions and a transparent proxy for internal management. The simulations show that this architecture greatly improves P2P file sharing performance

In the last years, the peer-to-peer (P2P) paradigm, which replaces the client-server one, has experienced a great success. A possible reason is large-scale broadband access deployment. P2P is being used for many different applications: grid computing, telephony, mail, etc. However, P2P is mainly associated to file-sharing applications, due to their...

In this paper we propose a collaborative technique called P2P-SatBoost to improve the performance of P2P protocols over satellite networks, and we evaluate it from the perspective of user satisfaction. Highly asymmetric satellite IP connections (satellite downlink and POTS uplink, for example) may be the only reasonably fast access possibility for...

HomePlug powerline communications networks link individual computers or network segments via low-voltage power lines. The powerline medium is a harsh channel, since it varies in time and has a high attenuation. This makes difficult to communicate different devices in distant places in a building. A possible solution is the HomePlug repeater we prop...

In this paper, we evaluate the feasibility of mobile video services for IEEE 802.11b multicast networks. We show that progressive encoding (which increases content bandwidth) is not strictly necessary. Depending on the maximum number of multicast content channels in the service, it is possible to achieve negligible demand blocking and expulsion pro...

In this paper, we present a modular architecture for embed- ded sensorial-fusion systems. Each sensor is a task of a real-time operat- ing system, whose core is a Deadline Monotonic scheduler. The scheduler decides if the sensor set is admissible or not, according to user-specified deadlines. Additionally, it monitors sensor behavior to check if th...

In this paper, we present an experimental position-aware IEEE 802.11b mobile video service. For example, it may be used to deliver TV channels to PDAs in airport terminals. Instead of implementing progressive encoding -which increases content bandwidth- we rely on transcoding rate adaptation to support position-awareness.

iSLIP and parallel hierarchical matching (PHM) are distributed maximal size matching schedulers for input-buffered switches. Previous research has analyzed the hardware cost of those schedulers and their performance after a small number of iterations. In this paper, we formulate an upper bound for the number of iterations required by PHM to converg...

Strategies for converting MPEG-2 video from DVDs to MPEG-4 for next-generation home media applications.

Input-queued packet switches are more scalable than output-queued ones. However, due to HOL blocking, their throughput is poor. The virtual output queueing (VOQ) switch architecture and several buffer schedulers have been proposed to overcome this problem. Among them, the class of iterative maximal matching algorithms, with the first example being...

In this paper, we propose a real-time transcoding system to generate contents for mobile networks. Video transcoding is widely used to change storage formats. However, as far as the authors know, it has not been proposed to generate real-time contents. We implement and evaluate an indoor video service that delivers transcoded contents to wireless p...

Input-buffered packet switches boosted with high-performance schedulers achieve near-100% throughput. Several authors have proposed the use of neural schedulers. These schedulers have a fast theoretical convergence, but the standard deviation of the number of iterations required can be arbitrarily large. In a previous paper, the authors proposed a...

We present a new transcoding technique for WWW navigation on small display devices: hierarchical atomic navigation (HANd). Unlike previous techniques, HANd shows all original information in a comprehensible way, without imposing the use of a specific browser. A navigator page is used to represent original contents in a symbolic way. Unreadable e le...

INTRODUCTION Many new digital video services have been recently proposed. It has been necessary to develop new transmission protocols (DVB-S for satellite, DVB-T for terrestrial, DVB-C for cable, RTP for the Internet...) and media encoding standards (MPEG-2, MPEG-4...). Among those services, we have witnessed the exponential growth of media station...