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  • 2014 INFOCOM Best Demo Award

     Alonso Zárate, Luis Gonzaga; Tuset-Peiro, Pere; Alonso-Zárate, Jesús; Vázquez-Gallego, Francisco; Vilajosana, Xavier
    Award or recognition

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    Standardized low-power wireless communication technologies for distributed sensing applications  Open access

     Vilajosana, Xavier; Tuset-Peiro, Pere; Vázquez Gallego, Francisco; Alonso-Zárate, Jesús; Alonso Zárate, Luis Gonzaga
    Sensors
    Date of publication: 2014-02-10
    Journal article

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    Recent standardization efforts on low-power wireless communication technologies, including time-slotted channel hopping (TSCH) and DASH7 Alliance Mode (D7AM), are starting to change industrial sensing applications, enabling networks to scale up to thousands of nodes whilst achieving high reliability. Past technologies, such as ZigBee, rooted in IEEE 802.15.4, and ISO 18000-7, rooted in frame-slotted ALOHA (FSA), are based on contention medium access control (MAC) layers and have very poor performance in dense networks, thus preventing the Internet of Things (IoT) paradigm from really taking off. Industrial sensing applications, such as those being deployed in oil refineries, have stringent requirements on data reliability and are being built using new standards. Despite the benefits of these new technologies, industrial shifts are not happening due to the enormous technology development and adoption costs and the fact that new standards are not well-known and completely understood. In this article, we provide a deep analysis of TSCH and D7AM, outlining operational and implementation details with the aim of facilitating the adoption of these technologies to sensor application developers.

    Recent standardization efforts on low-power wireless communication technologies, including time-slotted channel hopping (TSCH) and DASH7 Alliance Mode (D7AM), are starting to change industrial sensing applications, enabling networks to scale up to thousands of nodes whilst achieving high reliability. Past technologies, such as ZigBee, rooted in IEEE 802.15.4, and ISO 18000-7, rooted in frame-slotted ALOHA (FSA), are based on contention medium access control (MAC) layers and have very poor performance in dense networks, thus preventing the Internet of Things (IoT) paradigm from really taking off. Industrial sensing applications, such as those being deployed in oil refineries, have stringent requirements on data reliability and are being built using new standards. Despite the benefits of these new technologies, industrial shifts are not happening due to the enormous technology development and adoption costs and the fact that new standards are not well-known and completely understood. In this article, we provide a deep analysis of TSCH and D7AM, outlining operational and implementation details with the aim of facilitating the adoption of these technologies to sensor application developers.

  • Is the random access channel of LTE and LTE-A suitable for M2M communications? A survey of alternatives

     Laya Romero, Andres Ernesto; Alonso Zárate, Luis Gonzaga; Alonso-Zárate, Jesús
    IEEE Communications Surveys & Tutorials
    Date of publication: 2014
    Journal article

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    The 3GPP has raised the need to revisit the design of next generations of cellular networks in order to make them capable and efficient to provide M2M services. One of the key challenges that has been identified is the need to enhance the operation of the random access channel of LTE and LTE-A. The current mechanism to request access to the system is known to suffer from congestion and overloading in the presence of a huge number of devices. For this reason, different research groups around the globe are working towards the design of more efficient ways of managing the access to these networks in such circumstances. This paper aims to provide a survey of the alternatives that have been proposed over the last years to improve the operation of the random access channel of LTE and LTE-A. A comprehensive discussion of the different alternatives is provided, identifying strengths and weaknesses of each one of them, while drawing future trends to steer the efforts over the same shooting line. In addition, while existing literature has been focused on the performance in terms of delay, the energy efficiency of the access mechanism of LTE will play a key role in the deployment of M2M networks. For this reason, a comprehensive performance evaluation of the energy efficiency of the random access mechanism of LTE is provided in this paper. The aim of this computer-based simulation study is to set a baseline performance upon which new and more energy-efficient mechanisms can be designed in the near future.

  • Client-weighted medium-transparent MAC protocol for user-centric fairness in 60GHz radio-over-fiber WLANs

     Kalfas, George; Maniotis, Pavlos; Markou, Stamatia; Tsiokos, D.; Pleros, Nikos; Alonso Zárate, Luis Gonzaga; Verikoukis, Christos
    Journal of optical communications and networking
    Date of publication: 2014-01
    Journal article

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    We present a novel client-weighted medium-transparent medium access control (CW-MT-MAC) protocol with enhanced fairness service delivery properties accompanied by a low-loss remote access unit (RAU) architecture for use in indoor, Gbps-capable, 60 GHz radio-over-fiber (RoF) wireless local area networks (WLANs). Our approach relies on incorporating a client-weighted algorithm (CWA) in the optical capacity allocation mechanism employed in the MT-MAC scheme, so as to distribute the available wavelengths to the different antenna units according to the total number of active users served by each individual antenna. The protocol¿s throughput and delay fairness characteristics are evaluated and validated through both simulations and analytic modeling for saturated network traffic operational conditions. In addition, extended simulation-based performance analysis for nonsaturated network conditions and for different end-user distributions, traffic loads, and available optical wavelengths at 1 Gbps data rates is presented. Our results confirm that complete throughput equalization can be achieved even for highly varying user population patterns when certain wavelength availability conditions are satisfied. At the same time, the presented scheme manages to equalize the average packet delays amongst packets generated by all RAUs while concurrently dropping the packet delay variation metric that is essential for quality of service delivery. Finally the proposed RAU design reduces insertion losses by almost 14 dB compared to RAU elements used in MT-MAC-compatible bus networks, extending in this way the number of supported RAUs by an order of magnitude and enabling the formation of extended-reach, high-speed RoF WLANs.

    We present a novel client-weighted medium-transparent medium access control (CW-MT-MAC) protocol with enhanced fairness service delivery properties accompanied by a low-loss remote access unit (RAU) architecture for use in indoor, Gbps-capable, 60 GHz radio-over-fiber (RoF) wireless local area networks (WLANs). Our approach relies on incorporating a client-weighted algorithm (CWA) in the optical capacity allocation mechanism employed in the MT-MAC scheme, so as to distribute the available wavelengths to the different antenna units according to the total number of active users served by each individual antenna. The protocol’s throughput and delay fairness characteristics are evaluated and validated through both simulations and analytic modeling for saturated network traffic operational conditions. In addition, extended simulation-based performance analysis for nonsaturated network conditions and for different end-user distributions, traffic loads, and available optical wavelengths at 1 Gbps data rates is presented. Our results confirm that complete throughput equalization can be achieved even for highly varying user population patterns when certain wavelength availability conditions are satisfied. At the same time, the presented scheme manages to equalize the average packet delays amongst packets generated by all RAUs while concurrently dropping the packet delay variation metric that is essential for quality of service delivery. Finally the proposed RAU design reduces insertion losses by almost 14 dB compared to RAU elements used in MT-MAC-compatible bus networks, extending in this way the number of supported RAUs by an order of magnitude and enabling the formation of extended-reach, high-speed RoF WLANs.

  • CooPNC: a cooperative multicast protocol exploiting physical layer network coding

     Miliotis, Vasileios; Alonso Zárate, Luis Gonzaga; Verikoukis, Christos
    Ad hoc networks
    Date of publication: 2014-03
    Journal article

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    In this paper we present a multicast protocol for short range networks that exploits the characteristics of physical layer network coding. In our proposed protocol, named CooPNC, we provide a novel cooperative approach that allows collision resolutions with the use of an indirect inter-network cooperation scheme. Through this scheme, we provide a reliable multicast protocol for partially overlapping short range networks with low control overhead. We show that with CooPNC higher throughput and energy efficiency are achieved, while it presents lower delay compared to state of the art multicast protocols. We provide an overview of our protocol with a simple scenario of overlapping networks and we then generalise its operation for a scalable scenario. Through mathematical analysis and simulations we prove that CooPNC presents significant performance gains compared to the state of the art in multicast communications for short range networks.

    In this paper we present a multicast protocol for short range networks that exploits the characteristics of physical layer network coding. In our proposed protocol, named CooPNC, we provide a novel cooperative approach that allows collision resolutions with the use of an indirect inter-network cooperation scheme. Through this scheme, we provide a reliable multicast protocol for partially overlapping short range networks with low control overhead. We show that with CooPNC higher throughput and energy efficiency are achieved, while it presents lower delay compared to state of the art multicast protocols. We provide an overview of our protocol with a simple scenario of overlapping networks and we then generalise its operation for a scalable scenario. Through mathematical analysis and simulations we prove that CooPNC presents significant performance gains compared to the state of the art in multicast communications for short range networks.

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    A cloud-assisted random linear network coding medium access control protocol for healthcare applications  Open access

     Kartsakli, Elli; Antonopoulos, Angelos; Alonso Zárate, Luis Gonzaga; Verikoukis, Christos
    Sensors
    Date of publication: 2014-03
    Journal article

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    Relay sensor networks are often employed in end-to-end healthcare applications to facilitate the information flow between patient worn sensors and the medical data center. Medium access control (MAC) protocols, based on random linear network coding (RLNC), are a novel and suitable approach to efficiently handle data dissemination. However, several challenges arise, such as additional delays introduced by the intermediate relay nodes and decoding failures, due to channel errors. In this paper, we tackle these issues by adopting a cloud architecture where the set of relays is connected to a coordinating entity, called cloud manager. We propose a cloud-assisted RLNC-based MAC protocol (CLNC-MAC) and develop a mathematical model for the calculation of the key performance metrics, namely the system throughput, the mean completion time for data delivery and the energy efficiency. We show the importance of central coordination in fully exploiting the gain of RLNC under error-prone channels.

    Relay sensor networks are often employed in end-to-end healthcare applications to facilitate the information flow between patient worn sensors and the medical data center. Medium access control (MAC) protocols, based on random linear network coding (RLNC), are a novel and suitable approach to efficiently handle data dissemination. However, several challenges arise, such as additional delays introduced by the intermediate relay nodes and decoding failures, due to channel errors. In this paper, we tackle these issues by adopting a cloud architecture where the set of relays is connected to a coordinating entity, called cloud manager. We propose a cloud-assisted RLNC-based MAC protocol (CLNC-MAC) and develop a mathematical model for the calculation of the key performance metrics, namely the system throughput, the mean completion time for data delivery and the energy efficiency. We show the importance of central coordination in fully exploiting the gain of RLNC under error-prone channels.

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    WSN4QoL: a WSN-oriented healthcare system architecture  Open access

     Tennina, Stefano; Di Renzo, Marco; Kartsakli, Elli; Graziosi, Fabio; Lalos, Aristeidis; Antonopoulos, Angelos; Mekikis, Prodromos Vasileios; Alonso Zárate, Luis Gonzaga
    International journal of distributed sensor networks
    Date of publication: 2014-05-06
    Journal article

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    People worldwide are getting older and this fact has pushed the need for designing new, more pervasive, and possibly cost effective healthcare systems. In this field, distributed and networked embedded systems, such as wireless sensor networks (WSNs), are the most appealing technology to achieve continuous monitoring of aged people for their own safety, without affecting their daily activities. This paper proposes recent advancements in this field by introducing WSN4QoL, a Marie Curie project which involves academic and industrial partners from three EU countries. The project aims to propose new WSN-based technologies to meet the specific requirements of pervasive healthcare applications. In particular, in this paper, the system architecture is presented to cope with the challenges imposed by the specific application scenario. This includes a network coding (NC) mechanism and a distributed localization solution that have been implemented on WSN testbeds to achieve efficiency in the communications and to enable indoor people tracking. Preliminary results in a real environment show good system performance that meet our expectations.

    People worldwide are getting older and this fact has pushed the need for designing new, more pervasive, and possibly cost effective healthcare systems. In this field, distributed and networked embedded systems, such as wireless sensor networks (WSNs), are the most appealing technology to achieve continuous monitoring of aged people for their own safety, without affecting their daily activities. This paper proposes recent advancements in this field by introducing WSN4QoL, a Marie Curie project which involves academic and industrial partners from three EU countries. The project aims to propose new WSN-based technologies to meet the specific requirements of pervasive healthcare applications. In particular, in this paper, the system architecture is presented to cope with the challenges imposed by the specific application scenario. This includes a network coding (NC) mechanism and a distributed localization solution that have been implemented on WSN testbeds to achieve efficiency in the communications and to enable indoor people tracking. Preliminary results in a real environment show good system performance that meet our expectations.

  • Analysis of energy efficient distributed neighbour discovery mechanisms for Machine-to-Machine Networks

     Vazquez Gallego, Francisco; Alonso Zárate, Luis Gonzaga; Dohler, Mischa
    Ad hoc networks
    Date of publication: 2014-07-01
    Journal article

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    Energy efficiency is one of the main challenges of Machine-to-Machine (M2M) networks, since they aim at connecting devices with limited access to power sources and operate without human intervention. It has been shown in the past that the use of short-range cooperation between wireless devices equipped with multiple Radio Access Technologies (RATs) can achieve energy savings and extend the lifetime of cellular wireless networks. Devices with cellular connectivity can become temporary gateways to provide energy-constrained devices within the short-range cluster with access to the long range cellular infrastructure. To this end, the devices need to discover their neighbours using their short-range radio interface to identify and select potential gateway candidates. Existing neighbour discovery mechanisms perform poorly in terms of delay and energy consumption to maintain, continuously at each device, complete neighbourhood information, and thus may not be suitable for energy-constrained M2M networks. In this paper, we focus on distributed neighbour discovery mechanisms that are initiated dynamically and spontaneously by a single device to discover only its single-hop neighbours. We formulate accurate delay and energy models of three discovery mechanisms based on frame slotted-ALOHA and contention tree algorithms, and compare their performance in terms of delay and energy consumption. (C) 2013 Elsevier B.V. All rights reserved.

    Energy efficiency is one of the main challenges of Machine-to-Machine (M2M) networks, since they aim at connecting devices with limited access to power sources and operate without human intervention. It has been shown in the past that the use of short-range cooperation between wireless devices equipped with multiple Radio Access Technologies (RATs) can achieve energy savings and extend the lifetime of cellular wireless networks. Devices with cellular connectivity can become temporary gateways to provide energy-constrained devices within the short-range cluster with access to the long range cellular infrastructure. To this end, the devices need to discover their neighbours using their short-range radio interface to identify and select potential gateway candidates. Existing neighbour discovery mechanisms perform poorly in terms of delay and energy consumption to maintain, continuously at each device, complete neighbourhood information, and thus may not be suitable for energy-constrained M2M networks. In this paper, we focus on distributed neighbour discovery mechanisms that are initiated dynamically and spontaneously by a single device to discover only its single-hop neighbours. We formulate accurate delay and energy models of three discovery mechanisms based on frame slotted-ALOHA and contention tree algorithms, and compare their performance in terms of delay and energy consumption.

  • Secure and high speed cooperative small cells for cost and energy effective 5G network - 5GNET

     Alonso Zárate, Luis Gonzaga
    Participation in a competitive project

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  • Low-overhead heuristic algorithms for spectrum sensing in cognitive radio networks

     Miliotis, Vasileios; Koutsopoulos, Iordanis; Alonso Zárate, Luis Gonzaga; Verikoukis, Christos
    European Wireless Conference
    Presentation's date: 2014-05
    Presentation of work at congresses

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    Cognitive Radio (CR) has matured as a research field and has the goal to improve the utilization of spectrum. This technology enables a CR user to function in unlicensed or licensed bands without causing interference to primary users. In order to achieve this functionality a CR user needs to sense the spectrum and exploit efficiently the transmission opportunities. In this paper we propose two heuristic sensing algorithms for adhoc CR networks with low computational requirements, where each user tries to exploit ??spectrum holes?? based only on its own observations. The first algorithm refers to an immediate reward approach, according to which, each time a ??spectrum hole?? is detected, it is used instantaneously. The second refers to an immediate-versus-future-reward approach, where the CR may wait to sense the next channel instead of transmitting in the current one, if the expected reward when using the next channel is greater than the instant. In our proposed algorithms we examine both known and unknown statistics of channels. For the case of unknown channel parameters we introduce an initial sensing time and we investigate through simulations the impact of different sensing periods on the system's throughput.

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    Multiuser MAC schemes for high-throughput IEEE 802.11n/ac WLANs  Open access

     Kartsakli, Elli; Zorba Barah, Nizar; Alonso Zárate, Luis Gonzaga; Verikoukis, Christos
    Date of publication: 2013-12
    Book chapter

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    In the last decade, the Wireless Local Area Network (WLAN) market has been experiencing an impressive growth that began with the broad acceptance of the IEEE 802.11 standard [1]. Given the widespread deployment of WLANs and the increasing requirements of multimedia applications, the need for high capacity and enhanced reliability has become imperative. Multiple-Input Multiple-Output (MIMO) technology and its single receiving antenna version, MISO (Multiple-Input Single-Output (MISO), promise a signi¿cant performance boost and have been incorporated in the emerging IEEE 802.11n standard.

    In the last decade, the Wireless Local Area Network (WLAN) market has been experiencing an impressive growth that began with the broad acceptance of the IEEE 802.11 standard [1]. Given the widespread deployment of WLANs and the increasing requirements of multimedia applications, the need for high capacity and enhanced reliability has become imperative. Multiple-Input Multiple-Output (MIMO) technology and its single receiving antenna version, MISO (Multiple-Input Single-Output (MISO), promise a signi¿cant performance boost and have been incorporated in the emerging IEEE 802.11n standard.

  • 2013 EURASIP Best Paper Award for the Journal on Advances in Signal Processing

     Alonso Zárate, Luis Gonzaga; Kartsakli, Elli; Verikoukis, Christos; Alonso, L.
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  • Energy Efficient Schemes for Base Station Management in 4G Broadband Systems

     Bousia, Alexandra; Kartsakli, Elli; Antonopoulos, Angelos; Alonso Zárate, Luis Gonzaga; Verikoukis, Christos
    Date of publication: 2013-12
    Book chapter

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  • Enhancing quality of life with wireless sensor technology

     Kartsakli, Elli; Antonopoulos, Angelos; Tennina, Stefano; Lalos, Aristeidis; Mekikis, Prodromos Vasileios; Alonso Zárate, Luis Gonzaga; Graziosi, Fabio; Di Renzo, Marco; Verikoukis, Christos
    IEEE LifeSciences
    Date of publication: 2013-12
    Journal article

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    A co-operative project involving both industry and academia is designing an innovative Wireless Sensor Network for more effective healthcare of elders. The median age of the world population has shown a steady increase over the last 50 years, mainly due to the reduction of fertility and the 20-year increase in the average life expectancy. These factors, combined with the elevated birth rate observed in many countries during the decades following World War II, have led to a shift in the distribution of the population towards older ages in most regions of the planet. On the other hand, the average lifespan worldwide is expected to increase by 10 years by 2050.

    A co-operative project involving both industry and academia is designing an innovative Wireless Sensor Network for more effective healthcare of elders. The median age of the world population has shown a steady increase over the last 50 years, mainly due to the reduction of fertility and the 20-year increase in the average life expectancy. These factors, combined with the elevated birth rate observed in many countries during the decades following World War II, have led to a shift in the distribution of the population towards older ages in most regions of the planet. On the other hand, the average lifespan worldwide is expected to increase by 10 years by 2050.

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  • Cross layer access point selection mechanisms for a distributed queuing MAC protocol

     Antonopoulos, Angelos; Kartsakli, Elli; Alonso Zárate, Luis Gonzaga; Verikoukis, Christos
    Telecommunications systems and services directory
    Date of publication: 2013-07
    Journal article

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    The Distributed Queuing with Collision Avoidance (DQCA) Medium Access Control (MAC) protocol has been presented in the literature as a high-performance protocol for WLANs. Previous work regarding DQCA is focused on the operation of a single cell, where no interaction with neighboring sites is considered. In this paper, we define specific handoff procedures (channel sensing, discovery and reassociation functions) that enable the roaming of users in a scenario consisting of several DQCA access points (APs) deployed in a specific area using non-overlapping channel frequencies. Furthermore, we introduce a number of AP selection mechanisms in order to provide efficient reassociation decision criteria in the context of DQCA. These mechanisms are based either on a single metric such as the Signal to Noise Ratio (SNR) or the traffic load, or on cross-layer design by combining the information fromThe Distributed Queuing with Collision Avoidance (DQCA) Medium Access Control (MAC) protocol has been presented in the literature as a high-performance protocol for WLANs. Previous work regarding DQCA is focused on the operation of a single cell, where no interaction with neighboring sites is considered. In this paper, we define specific handoff procedures (channel sensing, discovery and reassociation functions) that enable the roaming of users in a scenario consisting of several DQCA access points (APs) deployed in a specific area using non-overlapping channel frequencies. Furthermore, we introduce a number of AP selection mechanisms in order to provide efficient reassociation decision criteria in the context of DQCA. These mechanisms are based either on a single metric such as the Signal to Noise Ratio (SNR) or the traffic load, or on cross-layer design by combining the information from different layers. Finally, our proposed solutions are evaluated by means of computer simulations. different layers. Finally, our proposed solutions are evaluated by means of computer simulations.

    The Distributed Queuing with Collision Avoidance (DQCA) Medium Access Control (MAC) protocol has been presented in the literature as a high-performance protocol for WLANs. Previous work regarding DQCA is focused on the operation of a single cell, where no interaction with neighboring sites is considered. In this paper, we define specific handoff procedures (channel sensing, discovery and reassociation functions) that enable the roaming of users in a scenario consisting of several DQCA access points (APs) deployed in a specific area using non-overlapping channel frequencies. Furthermore, we introduce a number of AP selection mechanisms in order to provide efficient reassociation decision criteria in the context of DQCA. These mechanisms are based either on a single metric such as the Signal to Noise Ratio (SNR) or the traffic load, or on cross-layer design by combining the information from different layers. Finally, our proposed solutions are evaluated by means of computer simulations.

  • Impact of correlated log-normal shadowing on two-way network coded cooperative wireless networks

     Lalos, Aristeidis; Di Renzo, Marco; Alonso Zárate, Luis Gonzaga; Verikoukis, Christos
    IEEE communications letters
    Date of publication: 2013-09
    Journal article

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    In this letter, we provide a novel theoretical framework for studying the effects of correlated shadowing, in the number of relays that are capable of helping two nodes (sources) to exchange their messages. The relays use network coding to simultaneously transmit the received messages to the sources. We prove theoretically and verify by means of simulations that the average number of relays that are capable of forwarding the network coded message, is independent from any correlation between the links from one source to the relays. Finally, we apply this framework, to compute the network outage probability. The presented results are essential for the theoretical study of medium access control and relay selection protocols designed for network coded cooperative communications.

    In this letter, we provide a novel theoretical framework for studying the effects of correlated shadowing, in the number of relays that are capable of helping two nodes (sources) to exchange their messages. The relays use network coding to simultaneously transmit the received messages to the sources. We prove theoretically and verify by means of simulations that the average number of relays that are capable of forwarding the network coded message, is independent from any correlation between the links from one source to the relays. Finally, we apply this framework, to compute the network outage probability. The presented results are essential for the theoretical study of medium access control and relay selection protocols designed for network coded cooperative communications.

  • Combining cooperation and physical layer network coding to achieve reliable multicast

     Miliotis, Vasileios; Alonso Zárate, Luis Gonzaga; Verikoukis, Christos
    Recent Advances in Communications and Networking Technology
    Date of publication: 2013-07
    Journal article

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    A novel cooperative scheme based on Physical layer Network Coding (PNC) for short range communication (SRC) networks is presented in this paper. We investigate a scenario of overlapping networks with multicast traffic and propose a technique for the leverage of inter-network cooperation. Our main goal is to exploit the characteristics of PNC in a solution for cooperative SRC networks, where energy efficiency is improved without degrading Quality of Service (QoS). The performance of our proposed cooperative scenario is highly energy efficient and it also presents high throughput. Comparing our scheme with a conventional protocol we show that it presents better performance. We analytically present the throughput, the delay and the energy efficiency of the neighbouring networks and we validate the mathematical analysis through extensive simulations. In addition, we provide an assessment of the impact of the capture effect on the proposed approach. Our proposal is inspired by recent patents in telecommunications that focus on interference cancellation.

  • Energy efficiency analysis of secondary networks in cognitive radio systems

     Mesodiakaki, Agapi; Adelantado, Ferran; Alonso Zárate, Luis Gonzaga; Verikoukis, Christos
    IEEE International Conference on Communications
    Presentation's date: 2013-06-09
    Presentation of work at congresses

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    In this paper, we evaluate a novel contention-aware channel selection algorithm that focuses on energy efficiency improvement of a secondary network (SN) in a scenario where other non-cooperating SNs are also using the primary resources. We present a detailed energy efficiency analysis and we study how the time between two consecutive sensing periods affects the energy efficiency. Our analysis proves that a categorization of the idle channels based on their contention level and the selection of the less contended ones can result in up to 70% gain in energy efficiency. The model is further evaluated through simulations.

    In this paper, we evaluate a novel contention-aware channel selection algorithm that focuses on energy efficiency improvement of a secondary network (SN) in a scenario where other non-cooperating SNs are also using the primary resources. We present a detailed energy efficiency analysis and we study how the time between two consecutive sensing periods affects the energy efficiency. Our analysis proves that a categorization of the idle channels based on their contention level and the selection of the less contended ones can result in up to 70% gain in energy efficiency. The model is further evaluated through simulations.

  • Cooperative multicast exploiting Physical layer Network Coding: a performance analysis

     Miliotis, Vasileios; Alonso Zárate, Luis Gonzaga; Verikoukis, Christos
    IEEE International Conference on Communications
    Presentation's date: 2013-06-09
    Presentation of work at congresses

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    In this paper, a novel cooperative scheme based on Physical layer Network Coding (PNC) for short range communication (SRC) networks is proposed. We present a scenario of overlapping networks with multicast traffic and propose a technique of indirect inter-group cooperation, based on the features of PNC. Our main goal is to exploit the characteristics of PNC to provide a solution for cooperative SRC networks, that presents high levels of energy efficiency without degrading Quality of Service (QoS). Illustrating the performance of our proposed cooperative scenario, it is proved that it is highly energy efficient and it also presents higher throughput compared to conventional cooperative schemes. The throughput, the delay and the energy efficiency of the neighbouring networks are analytically presented and the mathematical analysis is validated through extensive simulations.

  • Energy performance of distributed queuing access in machine-to-machine networks with idle-to-saturation transitions

     Vázquez-Gallego, Francisco; Alonso-Zárate, Jesús; Tuset-Peiro, Pere; Alonso Zárate, Luis Gonzaga
    IEEE Global Communications Conference
    Presentation's date: 2013-12-09
    Presentation of work at congresses

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    Machine-to-Machine (M2M) networks must be energy-ef¿cient to operate autonomously for years, or even decades. In this paper, we consider a synchronized duty-cycled M2M network composed of a huge number of dormant devices that periodically wake up to transmit data to a coordinator. We propose the use of Distributed Queuing (DQ) tree-splitting algorithms to optimize the shared access to the channel among the high number of devices, in order to improve the energy ef¿ciency and thus extend the network lifetime. We evaluate the energy performance of DQ access in this kind of dense M2M networks, and we compare it to traditional access schemes based on variations of Frame Slotted-ALOHA (FSA) and the Contention Tree Algorithm (CTA). Computer-based simulations show that DQ can reduce the energy consumption in more than a 50% with respect to FSA and CTA. Results show that there is an optimum number of contention slots which maximizes the energy ef¿ciency of DQ regardless of the number of devices. The performance evaluation presented in this paper also compares the energy consumption of DQ using low power Wi-Fi and IEEE 802.15.4 devices

  • WSN4QoL: Wireless Sensor Networks for Quality of Life

     Tennina, Stefano; Kartsakli, Elli; Lalos, Aristeidis; Antonopoulos, Angelos; Mekikis, Prodromos Vasileios; Di Renzo, Marco; Zacchia Lun, Yuriy; Graziosi, Fabio; Alonso Zárate, Luis Gonzaga; Verikoukis, Christos
    IEEE International Conference on e-Health Networking, Applications and Services
    Presentation's date: 2013-10-09
    Presentation of work at congresses

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    Life expectancy is projected to increase significantly in the coming years. This fact has pushed the need for designing new and more pervasive healthcare systems. In this field, distributed and networked embedded systems, such as Wireless Sensor Networks (WSNs), are the most suitable technology to achieve continuous monitoring of aged people for their own safety, without affecting their daily activities. This paper proposes recent advancements in this field by introducing WSN4QoL, a Marie Curie project which involves academic and industrial partners from three EU countries. The project aims to propose new WSN-based technologies to meet the specific requirements of pervasive healthcare applications. In particular, in this paper, a Network Coding (NC) mechanism and a distributed localization solution are presented. They have been implemented on WSN testbeds to achieve efficiency in the communications and to enable indoor people tracking. Preliminary results in a real environment show good system performance that meet our expectations.

  • Energy and delay analysis of contention resolution mechanisms for machine-to-machine networks based on low-power WiFi

     Vázquez Gallego, Francisco; Alonso Zárate, Luis Gonzaga
    IEEE International Conference on Communications
    Presentation's date: 2013-06-09
    Presentation of work at congresses

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    Attaining very high energy efficiency is one of the big challenges to implement Machine-to-Machine (M2M) networks whose lifetime (without human intervention) must be measured in years. In this paper, we consider a synchronized duty-cycled M2M network composed of a large number of devices that periodically wake up their radio interfaces to transmit data to a coordinator. We theoretically analyze the delay and energy efficiency of two contention-based Medium Access Control (MAC) protocols for this kind of networks. One protocol is based on Frame Slotted ALOHA, and the other is based on a tree-splitting contention resolution algorithm. Computer-based simulations have been carried out to ensure the accuracy of the theoretical models and to evaluate and compare the performance of the two alternatives for M2M applications based on low power Wi-Fi devices.

    Attaining very high energy efficiency is one of the big challenges to implement Machine-to-Machine (M2M) networks whose lifetime (without human intervention) must be measured in years. In this paper, we consider a synchronized duty-cycled M2M network composed of a large number of devices that periodically wake up their radio interfaces to transmit data to a coordinator. We theoretically analyze the delay and energy efficiency of two contention-based Medium Access Control (MAC) protocols for this kind of networks. One protocol is based on Frame Slotted ALOHA, and the other is based on a tree-splitting contention resolution algorithm. Computer-based simulations have been carried out to ensure the accuracy of the theoretical models and to evaluate and compare the performance of the two alternatives for M2M applications based on low power Wi-Fi devices.

  • The impact of cooperative physical layer network coding on multicast short range networks

     Miliotis, Vasileios; Alonso Zárate, Luis Gonzaga; Skianis, Harry; Verikoukis, Christos
    IEEE International Conference on Communications
    Presentation's date: 2013-06-09
    Presentation of work at congresses

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    In this paper, we exploit the characteristics of physical layer network coding (PNC) in multicast short range communication (SRC) networks. We present a scalable scenario of partially overlapping SRC networks, where collisions are resolved through indirect inter-group cooperation based on the features of PNC. Our scenario consists of a central network and several peripheral networks. In our previous work we proved that the central network presents significant gains in terms of throughput, delay and energy efficiency when applying the proposed scheme. Here we explore the impact of that scenario on the peripheral networks through a decomposition approach and we prove that they also present significant performance gains.

    In this paper, we exploit the characteristics of physical layer network coding (PNC) in multicast short range communication (SRC) networks. We present a scalable scenario of partially overlapping SRC networks, where collisions are resolved through indirect inter-group cooperation based on the features of PNC. Our scenario consists of a central network and several peripheral networks. In our previous work we proved that the central network presents significant gains in terms of throughput, delay and energy efficiency when applying the proposed scheme. Here we explore the impact of that scenario on the peripheral networks through a decomposition approach and we prove that they also present significant performance gains.

  • Energy efficient techniques for 802.11n multiuser MAC WLANs

     Gajic, Danica; Kartsakli, Elli; Zorba Barah, Nizar; Liß, Christian; Alonso Zárate, Luis Gonzaga; Verikoukis, Christos
    IEEE International Conference on Communications
    Presentation's date: 2013-06-09
    Presentation of work at congresses

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    In this paper we evaluate the energy efficiency of MIMO technologies introduced in the emerging IEEE 802.11n standard for infrastructure based WLANs. The main focus is on exploiting multiuser capabilities of MIMO technologies, while studying the proper design of multiuser MAC schemes to achieve an energy efficient solution. Three different multiuser MAC schemes are presented and analyzed. Analytical models for energy efficiency are mathematically developed and verified with link-level computer simulations. The results show the feasibility of achieving higher energy efficiency with the proper adjustment of the system parameters, and without significant degradation of throughput performance.

    In this paper we evaluate the energy efficiency of MIMO technologies introduced in the emerging IEEE 802.11n standard for infrastructure based WLANs. The main focus is on exploiting multiuser capabilities of MIMO technologies, while studying the proper design of multiuser MAC schemes to achieve an energy efficient solution. Three different multiuser MAC schemes are presented and analyzed. Analytical models for energy efficiency are mathematically developed and verified with link-level computer simulations. The results show the feasibility of achieving higher energy efficiency with the proper adjustment of the system parameters, and without significant degradation of throughput performance.

  • Game theoretic approach for switching off base stations in multi-operator environments

     Bousia, Alexandra; Kartsakli, Elli; Antonopoulos, Angelos; Alonso Zárate, Luis Gonzaga; Verikoukis, Christos
    IEEE International Conference on Communications
    Presentation's date: 2013-06-09
    Presentation of work at congresses

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    The emerging increase of the number of Base Stations causes redundant energy consumption, especially during low traffic periods, when the Base Stations capacity is underutilized. In this paper, we study energy efficiency issues in multi-operator mobile networks. Our primary goal is to save energy, without compromising the offered Quality of Service, by switching off the excessive Base Stations. To this end, we propose a novel game theoretic strategy using cost-based functions to decide the best suitable Base Stations to remain active. Mathematical analysis and simulations demonstrate that the proposed scheme can significantly reduce the energy consumption.

    The emerging increase of the number of Base Stations causes redundant energy consumption, especially during low traffic periods, when the Base Stations capacity is underutilized. In this paper, we study energy efficiency issues in multi-operator mobile networks. Our primary goal is to save energy, without compromising the offered Quality of Service, by switching off the excessive Base Stations. To this end, we propose a novel game theoretic strategy using cost-based functions to decide the best suitable Base Stations to remain active. Mathematical analysis and simulations demonstrate that the proposed scheme can significantly reduce the energy consumption.

  • DPCF-M: A medium access control protocol for dense machine-to-machine area networks with dynamic gateways

     Vázquez Gallego, Francisco; Balboteo Toledano, Iván; Alonso Zárate, Luis Gonzaga
    IEEE International Workshop on Signal Processing Advances in Wireless Communications
    Presentation's date: 2013-06-16
    Presentation of work at congresses

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    Machine-to-Machine (M2M) area networks must provide connectivity between either an M2M application server or an M2M gateway and a large number of M2M devices. In this paper, we consider a densely populated M2M area network. We propose a novel duty-cycled energy-efficient Medium Access Control (MAC) protocol, called DPCF-M, which switches dynamically between contention-based access (CSMA/CA) for low data traffic periods and a dynamically scheduled access mechanism for high data traffic or high number of contending devices. We have experimentally evaluated the performance of DPCF-M in saturation conditions by real implementation on IEEE 802.15.4 standard-compliant devices. Results show that DPCF-M outperforms the CSMA/CA protocol of the IEEE 802.15.4 non-beacon mode in terms of throughput and energy-efficiency.

    Machine-to-Machine (M2M) area networks must provide connectivity between either an M2M application server or an M2M gateway and a large number of M2M devices. In this paper, we consider a densely populated M2M area network. We propose a novel duty-cycled energy-efficient Medium Access Control (MAC) protocol, called DPCF-M, which switches dynamically between contention-based access (CSMA/CA) for low data traffic periods and a dynamically scheduled access mechanism for high data traffic or high number of contending devices. We have experimentally evaluated the performance of DPCF-M in saturation conditions by real implementation on IEEE 802.15.4 standard-compliant devices. Results show that DPCF-M outperforms the CSMA/CA protocol of the IEEE 802.15.4 non-beacon mode in terms of throughput and energy-efficiency.

  • Body sensors and healthcare monitoring: design and optimization of a wireless communication protocol

     Otal Ruiz, Begoña; Alonso Zárate, Luis Gonzaga; Verikoukis, Christos
    Date of publication: 2012
    Book chapter

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  • CROSS-LAYER DESIGN AND OPTIMIZATION OF MEDIUM ACCESS CONTROL PROTOCOLS FOR WLANS  Open access

     Kartsakli, Elli
    Defense's date: 2012-02-16
    Department of Signal Theory and Communications, Universitat Politècnica de Catalunya
    Theses

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    This thesis provides a contribution to the field of Medium Access Control (MAC) layer protocol design for wireless networks by proposing and evaluating mechanisms that enhance different aspects of the network performance. These enhancements are achieved through the exchange of information between different layers of the traditional protocol stack, a concept known as Cross-Layer (CL) design. The main thesis contributions are divided into two parts. The first part of the thesis introduces a novel MAC layer protocol named Distributed Queuing Collision Avoidance (DQCA). DQCA behaves as a reservation scheme that ensures collision-free data transmissions at the majority of the time and switches automatically to an Aloha-like random access mechanism when the traffic load is low. DQCA can be enriched by more advanced scheduling algorithms based on a CL dialogue between the MAC and other protocol layers, to provide higher throughput and Quality of Service (QoS) guarantees. The second part of the thesis explores a different challenge in MAC layer design, related to the ability of multiple antenna systems to offer point-to-multipoint communications. Some modifications to the recently approved IEEE 802.11n standard are proposed in order to handle simultaneous multiuser downlink transmissions. A number of multiuser MAC schemes that handle channel access and scheduling issues and provide mechanisms for feedback acquisition have been presented and evaluated. The obtained performance enhancements have been demonstrated with the help of both theoretical analysis and simulation obtained results.

  • Experimental study of bluetooth, ZigBee and IEEE 802.15.4 technologies on board high-speed trains

     Higuera, Jorge; Kartsakli, Elli; Valenzuela Gonzalez, Jose Luis; Alonso Zárate, Luis Gonzaga; Laya Romero, Andres Ernesto; Martínez, Raquel; Aguilar, Alicia
    IEEE Vehicular Technology Conference
    Date of publication: 2012
    Journal article

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    This paper studies the feasibility of using low-power wireless technologies such as Bluetooth, IEEE 802.15.4 and ZigBee in high-speed railway scenarios that involve bidirectional ground-to-train communication. The presented results have been obtained through experimental tests conducted at the Madrid- Barcelona high-speed rail line. A multiplatform communication system has been installed in a high-speed train, circulating at velocities up to 300 km/h, whereas autonomous devices have been disseminated along of the railway path to communicate with the onboard devices. The conclusions drawn from this work will be used as guidelines for the future implementation of autonomous communication platforms for high-speed rail connectivity.

  • A Survey on Prototyping Platforms for the Development and Experimental Evaluation of Medium Access Control Protocols

     Vazquez, Francisco; Verikoukis, Christos; Alonso Zárate, Luis Gonzaga
    IEEE Wireless communications
    Date of publication: 2012-02
    Journal article

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    Throughput analysis of a cooperative ARQ scheme in the presence of hidden and exposed terminals  Open access

     Alonso Zárate, Luis Gonzaga; Kormentzas, George; Tafazolli, Rahim; Verikoukis, Christos
    Mobile networks and applications
    Date of publication: 2012
    Journal article

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    Cooperative Automatic Retransmission Request (C-ARQ) schemes exploit the broadcast nature of the radio channel by allowing those users which overhear a transmission to act as spontaneous relays when a packet has been received with errors at destination. Transmission takes place in two phases. First, the source transmits to the destination. In the case of error, retransmissions are then executed by the relays, providing the system with cooperative diversity. In this paper we analyze how the addition of these relays to the communication modifies the well-known hidden and exposed terminal problems associated to any medium access control protocol based on carrier sensing. This work is focused on Carrier Sensing Multiple Access (CSMA) protocols, such as the one defined in the IEEE 802.11 Standard. The theoretical study presented in this paper has been supported by computer-based simulations.

  • Analysis of the hidden and exposed terminal effects in wireless networks with cooperative ARQ

     Alonso Zárate, Luis Gonzaga; Kormentzas, George; Verikoukis, Christos
    Lecture Notes of the Institute for Computer Sciences, Social-Informatics and Telecommunications Engineering (LNICST)
    Date of publication: 2012
    Journal article

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    Cooperative Automatic Retransmission Request (C-ARQ) schemes allow those users which overhear a transmission to act as spontaneous relays when a packet has been received with errors at destination. When these users assist a source-destination pair in the retransmission process, the area exposed to the original transmission increases in comparison with non-cooperative ARQ schemes. In addition, the extension of the transmission time, due to the retransmissions, increases the vulnerability of a transmission to the hidden terminal problem. The paper provides a performance analysis of the hidden and exposed terminal effects in an 802.11-based wireless network where a C-ARQ scheme is executed at the Medium Access Control (MAC) layer. The presented analysis is supported by computer-based simulations.

  • Comunicaciones móviles eficientes basadas en redes heterogéneas y coordinación de interferencias

     Garcia Lozano, Mario; González González, David; Laya Romero, Andres Ernesto; Pérez Diaz de Cerio, David; Valenzuela Gonzalez, Jose Luis; Lema Rosas, Maria Angel; Ruiz Boque, Silvia; Alonso Zárate, Luis Gonzaga; Olmos Bonafé, Juan José
    Participation in a competitive project

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  • Energy efficient base station maximization switch off scheme for LTE-advanced

     Bousia, Alexandra; Kartsakli, Elli; Alonso Zárate, Luis Gonzaga; Verikoukis, Christos
    IEEE International Workshop on Computer-Aided Modeling Analysis and Design of Communication Links and Networks
    Presentation's date: 2012-09
    Presentation of work at congresses

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    In this paper, we introduce a solution to a maximization problem for switching off Base Stations in an LTE-Advanced wireless network. Our scheme exploits the existence of idle periods in a cellular network during ¿night zone¿, when the traffic load is low. This work focuses on finding the optimal combination of switched on and off Bases Stations leading to the maximum energy saving. In addition, the major goal lies on increasing the energy efficiency by optimizing the power utilization of the Base Stations without sacrificing the offered Quality of Service. The proposed solution achieves significant energy saving and its performance is evaluated by means of analytical model, as well as simulations results.

  • Energy-efficient contention-aware channel selection in cognitive radio Ad-Hoc networks

     Mesodiakaki, Agapi; Adelantado, Ferran; Alonso Zárate, Luis Gonzaga; Verikoukis, Christos
    IEEE International Workshop on Computer-Aided Modeling Analysis and Design of Communication Links and Networks
    Presentation's date: 2012-09
    Presentation of work at congresses

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    In this paper, we propose a novel contention-aware channel selection algorithm that focuses on throughput and energy efficiency improvement in Cognitive Radio Ad-Hoc Networks (CRAHNs). Specifically, we study the operation and performance of a Secondary Network (SN) in a scenario where other non-cooperating CRAHNs are also using the primary resources. We prove that a channel categorization of the idle channels based on their contention level and the selection of the less contented ones can result in up to 70% improvement in throughput and up to 68% improvement in energy efficiency. Simulation results are presented for the performance evaluation of our proposed algorithm.

  • Energy analysis of distributed neighbour discovery algorithms based on frame slotted-ALOHA for cooperative networks

     Vázquez Gallego, Francisco; Alonso Zárate, Luis Gonzaga
    IEEE Global Communications Conference
    Presentation's date: 2012-12-03
    Presentation of work at congresses

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    The design of communications protocols that exploit the availability of both cellular and short-range radio access interfaces in a same terminal can be exploited to improve the energy efficiency of wireless communications networks. Devices equipped with a cellular radio interface can act as dynamic gateways to provide energy-constrained devices in its single-hop cluster with cellular connectivity. For this purpose, any device may discover its single-hop neighbourhood in order to select the appropriate gateway candidates. Conventional neighbour discovery algorithms have a great cost in terms of delay and energy consumption, and thus they are not the optimal approach for energy-constrained devices. This paper presents the energy consumption analysis of two distributed neighbour discovery algorithms based on frame slotted-ALOHA, and evaluates their performance in terms of energy consumption. In addition, it describes the conditions that minimize the energy consumption in the discovery process.

  • Extending the lifetime of M2M wireless networks through cooperation

     Botter, Giuseppe; Alonso Zárate, Luis Gonzaga; Granelli, Fabrizzio; Verikoukis, Christos
    IEEE International Conference on Communications
    Presentation's date: 2012-06
    Presentation of work at congresses

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    In this paper we show how a cooperative Medium Access Control (MAC) protocol can help extend the lifetime of Machine to Machine (M2M) networks. A comparison between non-cooperative Automatic Repeat reQuest (ARQ) schemes (retransmissions performed only from the source) and a cooperative retransmission scheme (all the stations in the network are spontaneous helpers and assist the destination during the communication) in energy-constrained networks is also presented in this work. The results shown in this paper are discussed in terms of the trade off between the network lifetime and the amount of data delivered, leading to the conditions where it is possible to optimize the lifetime of this kind of networks.

    In this paper we show how a cooperative Medium Access Control (MAC) protocol can help extend the lifetime of Machine to Machine (M2M) networks. A comparison between non-cooperative Automatic Repeat reQuest (ARQ) schemes (retransmissions performed only from the source) and a cooperative retransmission scheme (all the stations in the network are spontaneous helpers and assist the destination during the communication) in energy-constrained networks is also presented in this work. The results shown in this paper are discussed in terms of the trade off between the network lifetime and the amount of data delivered, leading to the conditions where it is possible to optimize the lifetime of this kind of networks.

  • Multi-radio cooperative retransmission scheme for reliable machine-to-machine multicast services

     Laya Romero, Andres Ernesto; Wang, Kun; Alonso Zárate, Luis Gonzaga
    IEEE International Symposium on Personal Indoor and Mobile Radio Communications
    Presentation's date: 2012
    Presentation of work at congresses

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    Mobile Machine-to-Machine (M2M) market is expected to grow dramatically in the upcoming years; predictions agree that the majority of wireless traffic will correspond to this type of communication. M2M devices deployed in proximity to each other might be handled as groups or clusters when sharing the same communication attributes and serving to achieve joint target. Moreover, devices that feature multiple radio interfaces are commonly used nowadays; they can be connected to a cellular access network, e.g., LTE, and simultaneously to a short-range network, also known as capillary network, among surrounding devices, e.g., Wi-Fi and ZigBee. For services such as over-the-air (OTA) firmware update, the same information shall be sent to all the group members over the cellular access network. A Multi-Radio Cooperative Retransmission Scheme for Reliable Multicast Services is presented as a solution to reliably manage reception errors occurred over the cellular network; by carrying out retransmissions over a short-range network it is possible to reduce both the traffic load over the cellular link and the energy consumption in error recovery. Ns-3 simulations were performed with LTE network models to analyze the scheme in terms of energy consumption and prove its usefulness in autonomous, battery driven, devices.

  • Throughput and delay fairness through an agile medium-transparent MAC protocol for 60GHz fiber-wireless LAN networks

     Maniotis, Pavlos; Kalfas, George; Alonso Zárate, Luis Gonzaga; Verikoukis, Christos; Pleros, Nikos
    IEEE Wireless Communications and Networking Conference
    Presentation's date: 2012-04
    Presentation of work at congresses

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    We demonstrate a novel Medium-Transparent MAC (MT-MAC) protocol with enhanced end-user service delivery fairness properties for use in Gbps capable, 60 GHz Fiber- Wireless (FiWi) LAN networks. Our approach relies on incorporating a Client Weighted Algorithm (CWA) in the optical capacity allocation mechanism employed in the MT-MAC scheme, so as to distribute the available wavelengths to the different antenna units according to the total number of active users served by each individual antenna. The protocols throughput fairness characteristics are confirmed through extensive simulations for different end-users distributions, varying traffic loads and multiple optical wavelength availabilities at 1 Gbps data rates. The presented results show that complete throughput and delay equalization can be achieved even for highly varying user population patterns among the different antenna units when certain wavelength availability conditions are satisfied. The performance of the proposed protocol has been compared with respective results obtained by the state-of-the-art MT-MAC scheme where a round-robin arbitration algorithm is used, clearly confirming the increased fairness capabilities of our approach. In addition, the proposed scheme is simple and remains clearly distinct from the wireless capacity arbitration process, highlighting in this way the high-level agility and flexibility of the MT-MAC platform for use in high-speed 60 GHz FiWi LANs.

    We demonstrate a novel Medium-Transparent MAC (MT-MAC) protocol with enhanced end-user service delivery fairness properties for use in Gbps capable, 60 GHz Fiber-Wireless (FiWi) LAN networks. Our approach relies on incorporating a Client Weighted Algorithm (CWA) in the optical capacity allocation mechanism employed in the MT-MAC scheme, so as to distribute the available wavelengths to the different antenna units according to the total number of active users served by each individual antenna. The protocol's throughput fairness characteristics are confirmed through extensive simulations for different end-user's distributions, vaying traffic loads and multiple optical wavelength availabilities at 1 Gbps data rates. The presented results shoe that complete throughput and delay equalization can be achieved even for highly varying user population patterns among the different antenna units when certain wavelength availability conditions are satisfied. The performance of the proposed protocol has been compared with respective results obtained by the state-of-art MT-MAC scheme where a round-robin arbitration algorithm is used, clearly confirming the increased fairness capabilities of our approach. In addition, the proposed scheme is simple amd remains clearly distinct from the wireless capacity arbitration process, highlighting in this way the high-level agility and flexibility of the MT-MAC platform for use in high-speed 60 Ghz FiWi LANs.

  • Energy efficiency analysis of a cooperative scheme for wireless local area networks

     Predojev, Tatjana; Alonso Zárate, Luis Gonzaga; Verikoukis, Christos
    IEEE Global Communications Conference
    Presentation's date: 2012-12-03
    Presentation of work at congresses

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    The Persistent Relay Carrier Sensing Multiple Access (PRCSMA) Protocol has been proposed in the literature as a Medium Access Control (MAC) protocol suitable for Cooperative Automatic Retransmission Request (C-ARQ) schemes. The improvement in throughput achieved with PRCSMA is already known. In this paper, we analyze the energy efficiency of this protocol to assess application to energy-constrained networks. Towards this aim, a suitable energy model is derived. The model has been validated through computer simulations and shows that a C-ARQ based on PRCSMA can help improve the energy efficiency of wireless communications and thus increase the lifetime of devices.

  • "Green" distance-aware base station sleeping algorithm in LTE-advanced

     Antonopoulos, Angelos; Bousia, Alexandra; Alonso Zárate, Luis Gonzaga; Verikoukis, Christos
    IEEE International Conference on Communications
    Presentation's date: 2012-06-10
    Presentation of work at congresses

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    In this paper, we propose a switch on/off algorithm for Base Stations (BSs), which exploits the knowledge of the distance between the User Equipments (UEs) and their associated BS. Our novel approach hopes to provide an improvement to the problem of energy consumption. The major concern lies on reducing the energy consumption of the telecommunication networks by optimizing the power utilization without sacrificing the offered Quality of Service (QoS). Our proposed scheme achieves a significant power saving, based on switching off the Base Stations that are underutilized during low traffic periods (especially during night) in the LTE-Advanced.

  • Multicast performance bounds exploiting cooperative physical layer network coding

     Miliotis, Vasileios; Alonso Zárate, Luis Gonzaga; Verikoukis, Christos
    IEEE International Workshop on Computer-Aided Modeling Analysis and Design of Communication Links and Networks
    Presentation of work at congresses

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    In this paper we exploit the characteristics of Physical layer Network Coding (PNC) in multicast short range networks. We present a scalable scenario of partially overlapping short range networks, where collisions are resolved through indirect inter-group cooperation based on the features of PNC. Our scenario consists of a central network, which is our network of interest, and several surrounding networks. Exploring the worst case scenario of the proposed scheme, we aim to unveil the lower achievable bounds of throughput and energy efficiency and the higher bounds of delay for the network of interest. We evaluate our proposed scheme and prove that even in its lower performance it outperforms the conventional cooperative approach in terms of throughput, delay and energy efficiency.

  • Dynamic energy efficient distance-aware base station switch on/off scheme for LTE-advanced

     Kartsakli, Elli; Bousia, Alexandra; Alonso Zárate, Luis Gonzaga; Verikoukis, Christos
    IEEE Global Communications Conference
    Presentation of work at congresses

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    Reducing the energy consumption in wireless networks has become a significant problem, not only because of its great impact on the global energy crisis, but also because it represents a noteworthy cost for telecommunication operators. The Base Stations (BSs), constituting the main component of wireless infrastructure, are intended to serve their customers during peak time periods. On the other hand, they are more than sufficient when the traffic load is low. Our paper proposes a solution for the problem of inefficient use by using a dynamic BSs switch on/off algorithm. We demonstrate via analysis and simulations that we can achieve significant reduction in energy consumption when we dynamically switch off the unnecessary BSs depending on the traffic variations and the distance between the User Equipments (UEs) and their associated BS. While maintaining the Quality of Service (QoS), we calculate the maximum number of BSs that can be switched off considering the time varying characteristic of the traffic pattern.

  • Experimental study of Bluetooth, ZigBee and IEEE 802.15.4 technologies on board high-speed trains

     Higuera, Jorge; Kartsakli, Elli; Valenzuela Gonzalez, Jose Luis; Alonso Zárate, Luis Gonzaga; Laya Romero, Andres Ernesto; Martínez, Raquel; Aguilar, Alicia
    IEEE Vehicular Technology Conference
    Presentation's date: 2012-05
    Presentation of work at congresses

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    This paper studies the feasibility of using low-power wireless technologies such as Bluetooth, IEEE 802.15.4 and ZigBee in high-speed railway scenarios that involve bidirectional ground-to-train communication. The presented results have been obtained through experimental tests conducted at the Madrid-Barcelona high-speed rail line. A multiplatform communication system has been installed in a high-speed train, circulating at velocities up to 300 km/h, whereas autonomous devices have been disseminated along of the railway path to communicate with the onboard devices. The conclusions drawn from this work will be used as guidelines for the future implementation of autonomous communication platforms for high-speed rail connectivity.

    This paper studies the feasibility of using low-power wireless technologies such as Bluetooth, IEEE 802.15.4 and ZigBee in high-speed railway scenarios that involve bidirectional ground-to-train communication. The presented results have been obtained through experimental tests conducted at the Madrid-Barcelona high-speed rail line. A multiplatform communication system has been installed in a high-speed train, circulating at velocities up to 300 km/h, whereas autonomous devices have been disseminated along of the railway path to communicate with the onboard devices. The conclusions drawn from this work will be used as guidelines for the future implementation of autonomous communication platforms for high-speed rail connectivity.

  • Access to the full text
    Dealing with VoIP calls during `busy hour¿ in LTE  Open access

     Antonopoulos, Angelos; Kartsakli, Elli; Alonso Zárate, Luis Gonzaga; Verikoukis, Christos
    Date of publication: 2011
    Book chapter

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  • MAC protocols with cross-layer design

     Kartsakli, Elli; Antonopoulos, Angelos; Alonso Zárate, Luis Gonzaga
    Date of publication: 2011-11-01
    Book chapter

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  • ICC2011 Best Paper Award

     Alonso Zárate, Luis Gonzaga; Stavrou, Eirini; Stamou, Adamantia
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  • Premio a la mejor ponencia en WSN de las 5º Jornadas Científicas sobre RFID

     Alonso Zárate, Luis Gonzaga; Valenzuela Gonzalez, Jose Luis; Kartsakli, Elli; Higuera Portilla, Jorge Eduardo
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    Hybrid access techniques for densely populated wireless local area networks  Open access

     Crespo, Cristian; Verikoukis, Christos; Alonso Zárate, Luis Gonzaga
    Date of publication: 2011-03
    Book chapter

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