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  • An energy efficient vertical handover decision algorithm

     Pons, Xavier; Mesodiakaki, Agapi; Gruet, Christophe; Naviner, Lirida; Adelantado Freixer, Ferran; Alonso Zárate, Luis Gonzaga; Verikoukis, Christos
    IEEE Global Communications Conference
    p. 1145-1150
    DOI: 10.1109/GLOCOMW.2014.7063587
    Presentation's date: 2014-12-12
    Presentation of work at congresses

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    As wireless communications evolve towards heterogeneous networks, mobile terminals have been enabled to handover seamlessly from one network to another. At the same time, the continuous increase in the terminal power consumption has resulted in an ever-decreasing battery lifetime. To that end, the network selection is expected to play a key role on how to minimize the energy consumption, and thus to extend the terminal lifetime. Hitherto, terminals select the network that provides the highest received power. However, it has been proved that this solution does not provide the highest energy efficiency. Thus, this paper proposes an energy efficient vertical handover algorithm that selects the most energy efficient network that minimizes the uplink power consumption. The performance of the proposed algorithm is evaluated through extensive simulations and it is shown to achieve high energy efficiency gains compared to the conventional approach.

  • 2014 GLOBECOMM Best Paper Award

     Alonso Zárate, Luis Gonzaga; Bousia, Alexandra; Kartsakli, Elli; Antonopoulos, Angelos; Verikoukis, Christos
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  • Sharing the small cells for energy efficient networking: how much does it cost?

     Bousia, Alexandra; Kartsakli, Elli; Antonopoulos, Angelos; Alonso Zárate, Luis Gonzaga; Verikoukis, Christos
    IEEE Global Communications Conference
    p. 2649-2654
    DOI: 10.1109/GLOCOM.2014.7037207
    Presentation's date: 2014-12-08
    Presentation of work at congresses

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    The explosive data traffic demands stress the need for additional capacity in cellular systems, which can be achieved through the exploitation of Small Cells (SCs). However, the deployment of SCs implies higher energy consumption in the network, something that translates into higher financial cost for the operators. To that end, the existence of a third party that provides a common SC infrastructure for the operators has been introduced as an appealing “green” solution, raising though important issues with regard to the cost sharing for the operators. In this paper, we effectively address this issue by proposing an accurate cost model for the SCs and employing different stateof-the-art techniques to share this cost. In addition, taking into account the impact of the traffic pattern on this cost, we propose a novel hybrid cost sharing policy that provides a fair outcome for the operators. Our results highlight the potential energy efficiency gains in the network along with different ways of sharing the cost of the deployed SCs.

  • Offloading with IFOM: the uplink case

     Miliotis, Vasileios; Alonso Zárate, Luis Gonzaga; Verikoukis, Christos
    IEEE Global Communications Conference
    p. 2661-2666
    DOI: 10.1109/GLOCOM.2014.7037209
    Presentation's date: 2014-12-08
    Presentation of work at congresses

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    Mobile data offloading has been proposed as a solution for network congestion. However, the majority of the state-of-the-art is focused on the downlink offloading, while the change of mobile user habits, like mobile content creation and uploading, makes uplink offloading a rising issue. In this work we focus on the uplink offloading using Ip Flow Mobility (IFOM). IFOM allows a LTE mobile User Equipment (UE) to maintain two concurrent data streams, one through LTE and the other through WiFi access technology, that presents uplink limitations due to the inherent fairness design of IEEE 802.11 DCF. In this paper, we propose two uplink offloading algorithms to improve the energy efficiency of the UEs and to increase the offloaded data volume under the concurrent use of access technologies that IFOM provides. In the first algorithm, UEs with heavy traffic are promoted and are given priority in accessing the WiFi Access Point (AP) to offload their data. In the second algorithm, we propose a proportionally fair bandwidth allocation over the data volume needs of the UEs. We theoretically analyse the proposed algorithms and evaluate their performance through simulations. We compare their performance with the 802.11 DCF access scheme and with a state of the art access algorithm under different number of offloading UEs. Through the provided evaluation we show that there is room for improvement in the uplink access scheme of the WiFi that affects the energy efficiency of a UE during IFOM uplink offloading.

  • Joint uplink and downlink cell selection in cognitive small cell heterogeneous networks

     Mesodiakaki, Agapi; Adelantado Freixer, Ferran; Alonso Zárate, Luis Gonzaga; Verikoukis, Christos
    IEEE Global Communications Conference
    p. 2643-2648
    Presentation's date: 2014-12-08
    Presentation of work at congresses

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    In the next few years, small cells (SCs) are about to be densely deployed to achieve sustainable capacity enhancement. Due to the expected high SC density, some SCs will not have a direct connection to the core network, and thus will forward their traffic to the neighboring SCs through a multi-hop backhaul (BH). In such multi-hop architectures, the user association problem becomes challenging with BH energy consumption playing a key role. On the other hand, the ever-increasing need to minimize the user equipment (UE) transmission power along with the uplink (UL) and downlink (DL) traffic asymmetry, predicate the joint study of UL and DL. Thus, in this paper, we study the joint UL and DL cell selection problem aiming at maximizing the total network energy efficiency, without compromising the UE quality of service. The problem is formulated as an optimization problem, which is NP-hard. Therefore, we propose a heuristic algorithm that exploits context-aware information to associate the UEs in an energy-efficient way, while considering both access and BH energy consumption in UL and DL. We evaluate the performance of the proposed algorithm and we show that it can achieve significantly higher energy efficiency than the reference algorithms, while maintaining high spectral efficiency and low UE power consumption.

  • Cooperative compressed sensing schemes for telemonitoring of vital signals in WBANs

     Kartsakli, Elli; Antonopoulos, Angelos; Tennina, Stefano; Di Renzo, Marco; Alonso Zárate, Luis Gonzaga; Verikoukis, Christos; Lalos, Aristeidis
    IEEE Global Communications Conference
    p. 2387-2392
    DOI: 10.1109/GLOCOM.2014.7037165
    Presentation's date: 2014-12-08
    Presentation of work at congresses

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    Wireless Body Area Networks (WBANs) are composed of various sensors that either monitor and transmit real time vital signals or act as relays that forward the received data packets to a nearby Body Node Coordinator (BNC). The design of an accurate and energy efficient wireless telemonitoring system can be achieved by: i) minimizing the amount of data that should be transmitted for an accurate reconstruction at the BNC, and ii) increasing the robustness of the telemonitoring system to link failures due to the nature of wireless medium. To this end, we present a novel Compressed Sensing (CS) based telemonitoring scheme, called Cooperative Compressed Sensing (CCS), that exploits the benefits of Random Linear Network Coding (RLNC) along with key characteristics of the transmitted biosignals in order to achieve an energy efficient signal reconstruction at the BNC. Simulation studies, carried out with real electrocardiographic (ECG) data, show the benefits of: i) employing RLNC, compared to the case where relays simply store and forward the original data packets, and ii) applying the proposed CCS scheme, compared to traditional CS recovery approaches.

  • CAMAD 2014 BEST DEMO AWARD

     Alonso Zárate, Luis Gonzaga; Tennina, Stefano; Di Renzo, Marco; Kartsakli, Elli; Graziosi, Fabio; Antonopoulos, Angelos
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  • Model based compressed sensing reconstruction algorithms for ECG telemonitoring in WBANs

     Lalos, Aristeidis; Alonso Zárate, Luis Gonzaga; Verikoukis, Christos
    Digital signal processing
    Vol. 35, p. 105-116
    DOI: 10.1016/j.dsp.2014.08.007
    Date of publication: 2014-12-01
    Journal article

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    Wireless Body area networks (WBANs) consist of sensors that continuously monitor and transmit real time vital signals to a nearby coordinator and then to a remote terminal via the Internet. One of the most important signals for monitoring in WBANs is the electrocardiography (ECG) signal. The design of an accurate and energy efficient ECG telemonitoring system can be achieved by: i) reducing the amount of data that should be transmitted ii) minimizing the computational operations executed at any transmitter/receiver in a WBAN. To this end, compressed sensing (CS) approaches can offer a viable solution. In this paper, we propose two novel CS based ECG reconstruction algorithms that minimize the samples that are required to be transmitted for an accurate reconstruction, by exploiting the block structure of the ECG in the time domain (TD) and in an uncorrelated domain (UD). The proposed schemes require the solutions of second-order cone programming (SOCP) problems that are usually tackled by computational demanding interior point (IP) methods. To solve these problems efficiently, we develop a path-wise coordinate descent based scheme. The reconstruction accuracy is evaluated by the percentage root-mean-square difference (PRD) metric. A reconstructed signal is acceptable if and only if PRD < 9%. Simulation studies carried out with real electrocardiographic (ECG) data, show that the proposed schemes, operating in both the TD and in the UD as compared to the conventional CS techniques, reduce the Compression Ratio (CR) by 20% and 44% respectively, offering at the same time significantly low computational complexity. (C) 2014 Elsevier Inc. All rights reserved.

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    A survey on M2M systems for mHealth: a wireless communications perspective  Open access

     Kartsakli, Elli; Lalos, Aristeidis; Antonopoulos, Angelos; Tennina, Stefano; Di Renzo, Marco; Alonso Zárate, Luis Gonzaga; Verikoukis, Christos
    Sensors
    Vol. 14, num. 10, p. 18009-18052
    DOI: 10.3390/s141018009
    Date of publication: 2014-10-01
    Journal article

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    In the new era of connectivity, marked by the explosive number of wireless electronic devices and the need for smart and pervasive applications, Machine-to-Machine (M2M) communications are an emerging technology that enables the seamless device interconnection without the need of human interaction. The use of M2M technology can bring to life a wide range of mHealth applications, with considerable benefits for both patients and healthcare providers. Many technological challenges have to be met, however, to ensure the widespread adoption of mHealth solutions in the future. In this context, we aim to provide a comprehensive survey on M2M systems for mHealth applications from a wireless communication perspective. An end-to-end holistic approach is adopted, focusing on different communication aspects of the M2M architecture. Hence, we first provide a systematic review of Wireless Body Area Networks (WBANs), which constitute the enabling technology at the patient's side, and then discuss end-to-end solutions that involve the design and implementation of practical mHealth applications. We close the survey by identifying challenges and open research issues, thus paving the way for future research opportunities.

  • Device-to-device communications and small cells: enabling spectrum reuse for dense networks

     Laya, Andrés; Wang, Kun; Ahmed, Ashraf Awadelkarim Widaa; Alonso Zárate, Jesús; Markendhal, Jan; Alonso Zárate, Luis Gonzaga
    IEEE Wireless communications
    Vol. 21, num. 4, p. 98-105
    DOI: 10.1109/MWC.2014.6882301
    Date of publication: 2014-08
    Journal article

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    In the evolution of communication networks, there has always been a need to increase the capacity to cope with the continuous growing demand for data transmission. However, with the arrival of the Internet-of-Things and the commoditization of broadband access through smartphones, tablets, smart-watches, and all types of connecting devices, future networks must be capable of providing higher bandwidth and Quality of Experience, as wellas operating in dense networks with a massive number of simultaneous connections. This high number of connections will be very heterogeneous, spanning from highly-demanding data rate applications to low-complexity and high energy-efficient Machine-to-Machine communications. In such a dense and complex scenario, a more flexible use of spectrum resources is deemed to be the way to meet the growing requirements for data transmission. In particular, this article focuses on Device-to-Device communications and small cell deployments as emerging facilitators of such a demanding and heterogeneous scenario. The pros and cons of both complementary strategies are identified from both a technical and a business point of view, and main standardization activities are discussed. The aim of this article is to identify and describe open challenges and to inspire new areas for research that make viable the next generation of dense networks.

  • 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
    Vol. 18, p. 40-54
    DOI: 10.1016/j.adhoc.2013.03.006
    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.

  • Energy-efficient user association in cognitive heterogeneous networks

     Mesodiakaki, Agapi; Adelantado Freixer, Ferran; Alonso Zárate, Luis Gonzaga; Verikoukis, Christos
    IEEE communications magazine
    Vol. 52, num. 7, p. 22-29
    DOI: 10.1109/MCOM.2014.6852079
    Date of publication: 2014-07
    Journal article

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    Due to the ever increasing data traffic demands, which are directly connected to increased energy consumption, it becomes challenging for operators to achieve capacity enhancement while limiting their electric bill. To that end, exploiting the context awareness of future cognitive networks is expected to play a key role. Next generation cellular networks are about to include a plethora of small cells, with users being able to communicate via multiple bands. Given that small cells are expected to be eventually as close as 50 m apart, not all of them will have a direct connection to the core network; thus, multihop communication through neighboring small cells may be required. In such architectures, the user association problem becomes challenging, with backhaul energy consumption being a definitive parameter. Thus, in this article, we study the user association problem in cognitive heterogeneous networks. We evaluate the existing approaches in terms of energy efficiency and show the potential of exploiting the available context-aware information (i.e., users' measurements and requirements, knowledge of the network architecture, and the available spectrum resources of each base station) to associate the users in an energy-efficient way, while maintaining high spectrum efficiency. Our study considers both the access network and backhaul energy consumption, while the performance of the association algorithms is evaluated under two different case study scenarios.

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    Experimental energy consumption of Frame Slotted ALOHA and Distributed Queuing for data collection scenarios  Open access

     Tuset-Peiro, Pere; Vázquez-Gallego, Francisco; Alonso-Zárate, Jesús; Alonso Zárate, Luis Gonzaga; Vilajosana, Xavier
    Sensors
    Vol. 14, num. 8, p. 13416-13436
    DOI: 10.3390/s140813416
    Date of publication: 2014-07
    Journal article

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    Data collection is a key scenario for the Internet of Things because it enables gathering sensor data from distributed nodes that use low-power and long-range wireless technologies to communicate in a single-hop approach. In this kind of scenario, the network is composed of one coordinator that covers a particular area and a large number of nodes, typically hundreds or thousands, that transmit data to the coordinator upon request. Considering this scenario, in this paper we experimentally validate the energy consumption of two Medium Access Control (MAC) protocols, Frame Slotted ALOHA (FSA) and Distributed Queuing (DQ). We model both protocols as a state machine and conduct experiments to measure the average energy consumption in each state and the average number of times that a node has to be in each state in order to transmit a data packet to the coordinator. The results show that FSA is more energy efficient than DQ if the number of nodes is known a priori because the number of slots per frame can be adjusted accordingly. However, in such scenarios the number of nodes cannot be easily anticipated, leading to additional packet collisions and a higher energy consumption due to retransmissions. Contrarily, DQ does not require to know the number of nodes in advance because it is able to efficiently construct an ad hoc network schedule for each collection round. This kind of a schedule ensures that there are no packet collisions during data transmission, thus leading to an energy consumption reduction above 10% compared to FSA.

  • Two-tier cellular random network planning for minimum deployment cost

     Mekikis, Prodromos Vasileios; Kartsakli, Elli; Antonopoulos, Angelos; Lalos, Aristeidis; Alonso Zárate, Luis Gonzaga; Verikoukis, Christos
    IEEE International Conference on Communications
    p. 1248-1253
    DOI: 10.1109/ICC.2014.6883492
    Presentation's date: 2014-06-10
    Presentation of work at congresses

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    Random dense deployment of heterogeneous networks (HetNets), consisting of macro base stations (BS) and small cells (SC), can provide higher quality of service (QoS) while increasing the energy efficiency of the cellular network. In addition, it is possible to achieve lower deployment cost and, therefore, maximize the benefits for the network providers. In this paper, we propose a novel method to determine the minimum deployment cost of a two-tier heterogeneous cellular network using random deployment. After deriving the coverage probability of the two-tier deployment by using stochastic geometry tools, we identify the tier intensities that provide the minimum deployment cost for a given coverage probability. Extensive simulations verify the existence of a unique set of intensities for different coverage constraints.

  • Energy analysis of a contention tree-based access protocol for machine-to-machine networks with idle-to-saturation traffic transitions

     Vázquez-Gallego, Francisco; Alonso-Zárate, Jesús; Tuset-Peiro, Pere; Alonso Zárate, Luis Gonzaga
    IEEE International Conference on Communications
    p. 1094-1099
    DOI: 10.1109/ICC.2014.6883467
    Presentation's date: 2014-06-04
    Presentation of work at congresses

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    Machine-to-Machine (M2M) area networks must provide connectivity between an M2M gateway and a large number of energy-constrained M2M devices. Attaining high energy efficiency is essential in order to prolong devices lifetime. In this paper, we consider a wireless M2M area network composed of hundreds or even thousands of dormant devices that wake up periodically to transmit data upon request from a gateway. We theoretically analyze the energy efficiency of a Medium Access Control (MAC) protocol that uses a tree-splitting algorithm to resolve the collisions among devices: the Distributed Queuing (DQ) access. Computer-based simulations have been carried out to validate the accuracy of the analytical model and to evaluate and compare the energy consumption of devices using also a basic Contention Tree Algorithm (CTA) and Frame Slotted-ALOHA (FSA). Results show that DQ can reduce energy consumption in more than 35% with respect to CTA and in more than 80% with respect to FSA in dense M2M area networks with devices in compliance with the IEEE 802.15.4 physical layer.

  • Energy-efficient context-aware user association for outdoor small cell heterogeneous networks

     Mesodiakaki, Agapi; Adelantado Freixer, Ferran; Alonso Zárate, Luis Gonzaga; Verikoukis, Christos
    IEEE International Conference on Communications
    p. 1614-1619
    DOI: 10.1109/ICC.2014.6883553
    Presentation's date: 2014-06-04
    Presentation of work at congresses

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    To meet the ever-increasing traffic demands, future cellular networks are about to include a plethora of small cells (SCs), with user equipments (UEs) being able of communicating via multiple bands. Given that SCs are expected to be eventually as close as 50 m apart, some of them will not have a direct connection to the core network, and thus will forward their traffic to the neighboring SCs until they reach it. In such architectures, the user association problem becomes challenging with backhaul (BH) energy consumption playing a key role. Thus, in this paper, we study the user association problem aiming at maximizing the network energy efficiency. The problem is formulated as an optimization problem, which is NP-hard. Therefore, we propose a cognitive heuristic algorithm that exploits context-aware information (i.e., UE measurements and requirements, the HetNet architecture knowledge and the available spectrum resources of each base station (BS)) to associate the UEs in an energy-efficient way, while considering both the access and the BH energy consumption. We evaluate the performance of the proposed algorithm under two study-case scenarios and we prove that it achieves significantly higher energy efficiency than the reference algorithms, while maintaining high spectral efficiency.

  • A protocol architecture for energy efficient and pervasive eHealth systems

     Tennina, Stefano; Di Renzo, Marco; Kartsakli, Elli; Graziosi, Fabio; Lalos, Aristeidis; Antonopoulos, Angelos; Mekikis, Prodromos Vasileios; Alonso Zárate, Luis Gonzaga; Verikoukis, Christos
    IEEE-EMBS International Conferences on Biomedical and Health Informatics
    p. 452-455
    DOI: 10.1109/BHI.2014.6864400
    Presentation's date: 2014-06-01
    Presentation of work at congresses

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    The design of new and more pervasive healthcare systems has been fostered by the increased expectancy of life in the coming years. In this field, distributed and networked wireless embedded systems, such as Wireless Sensor Networks (WSNs), suit well with the requirements of continuous monitoring of aged people for their own safety, without affecting their daily activities. WSN4QoL is a Marie Curie project which involves academic and industrial partners from three EU countries, and aims to propose new WSN-based technologies to meet the specific requirements of pervasive healthcare applications. This paper focuses on presenting a protocol stack architecture designed to support the solutions proposed in that project to enhance energy efficiency.

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    Energy consumption optimisation for duty-cycled schemes in shadowed environments  Open access

     Predojev, Tatjana; Alonso-Zárate, Jesús; Dohler, Mischa; Alonso Zárate, Luis Gonzaga
    International journal of distributed sensor networks
    Vol. 2014, num. 2014, p. 1-10
    DOI: 10.1155/2014/709135
    Date of publication: 2014-05-28
    Journal article

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    The focus of this study is the optimal configuration of a wireless low-power duty-cycled network with respect to the minimal energy consumption. Precisely, the energy consumption of a truncated-ARQ scheme in realistic shadowing environments is examined for the reference IEEE 802.15.4e standard protocol and for its cooperative extension that is presented in the paper. We show how to choose between the direct or multihop forwarding and the cooperative version of the two. We determine the optimal forwarding strategy for both loose and strict reliability requirements. Low-power links are parametrised by the interdevice distance and the corresponding outage probability, for the fixed output transmission power. It is shown that significant amounts of energy can be saved when the most adequate scheme of the three is applied. All analytical results are validated in the network simulator ns-3.

  • NCMOB-MAC: a network coding-based MAC protocol with mobility support

     Torres, Pol; Antonopoulos, Angelos; Alonso Zárate, Luis Gonzaga; Schulte, Gerrit
    IEEE Vehicular Technology Conference
    p. 1-5
    DOI: 10.1109/VTCSpring.2014.7023000
    Presentation's date: 2014-05-18
    Presentation of work at congresses

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    In this paper, a novel Network Coding (NC)-aided Medium Access Control (MAC) protocol with mobility support (NCMOB-MAC) is presented. The proposed protocol is compatible with Automatic Repeat reQuest (ARQ) techniques and can be applied in Vehicular Ad hoc Networks (VANETs). NCMOB-MAC proposes a new way of coordinating the communication between a sender, a moving destination and a set of fixed relay nodes. The relays employ different Contention Window (CW) sizes to assign priorities and optimize the NC opportunities. Extensive simulations have been carried out to evaluate the performance of the protocol and the results show an improvement in throughput and energy efficiency compared to conventional NC-aided MAC protocols.

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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
    Vol. 2014, p. 1-16
    DOI: 10.1155/2014/503417
    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.

  • 2014 INFOCOM Best Demo Award

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

  • Performance evaluation of frame slotted-ALOHA with succesive interference cancellation in machine-to-machine networks

     Vázquez-Gallego, Francisco; Rietti, Marc; Bas, Joan; Alonso-Zárate, Jesús; Alonso Zárate, Luis Gonzaga
    European Wireless
    p. 403-408
    Presentation's date: 2014-05
    Presentation of work at congresses

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    Machine-to-Machine (M2M) area networks connect a gateway with a huge number of energy-constrained end-devices. Therefore, energy efficiency is essential to prolong the lifetime of M2M networks. In this paper, we consider an M2M area network composed of hundreds or thousands of end-devices that periodically transmit data upon request from a gateway. We propose a Medium Access Control (MAC) protocol based on Frame Slotted-ALOHA (FSA) with Successive Interference Cancellation (SIC), also referred to as SIC-FSA, for data collection applications. By means of comprehensive computer-based simulations, we evaluate the delay and the energy consumed by the gateway and the enddevices using SIC-FSA. We have compared the delay and energy performance provided by SIC-FSA with that of conventional FSA and diversity-FSA (D-FSA). Results show that SIC-FSA can reduce the delay and energy consumption of the gateway in more than 50%, and the energy consumed by an end-device in more than 10%, with respect to FSA in dense M2M networks equipped with radio-transceivers in compliance with the IEEE 802.11 physical layer.

  • Digital and physical layer network coding performance in the context of enforced fairness

     Miliotis, Vasileios; Alonso Zárate, Luis Gonzaga; Verikoukis, Christos
    International Conference on Telecommunications
    p. 72-76
    DOI: 10.1109/ICT.2014.6845083
    Presentation's date: 2014-05
    Presentation of work at congresses

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    In this paper, we investigate the performance of the so-called Cross Network operating under diverse Network Coding (NC) techniques. We study the impact of Medium Access Control (MAC) layer fairness on the throughput performance of the network for the cases of pure relaying, digital NC with and without overhearing and physical layer NC with and without overhearing. We provide a comparison among these techniques and we discuss the throughput bounds, due to MAC layer limitations, imposed to the system operation by broadly adopted short range communication protocols that provide for fair resource allocation such as IEEE 802.11. Furthermore, we show that significant coding gains are achieved with digital and physical layer NC and we discuss on the energy efficiency performance of each NC case when applied on the Cross Network.

  • Demonstrating low-power distributed queuing for active RFID communications at 433 MHz

     Tuset-Peiro, Pere; Alonso Zárate, Luis Gonzaga; Vázquez-Gallego, Francisco; Alonso-Zárate, Jesús; Vilajosana, Xavier
    IEEE International Conference on Computer Communications
    p. 157-158
    DOI: 10.1109/INFCOMW.2014.6849203
    Presentation's date: 2014-04-27
    Presentation of work at congresses

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    This paper presents a demonstrator of Low-Power Distributed Queuing (LPDQ), a MAC protocol targeted at active RFID systems operating at 433 MHz. LPDQ is based on a packet-based Preamble Sampling for network synchronization and Distributed Queuing for channel access. Compared to the MAC protocol defined in the ISO 18000-7 standard, based on an analog Preamble Sampling and Frame Slotted ALOHA, LPDQ represents a major breakthrough in terms of system performance and energy consumption. At the MAC layer system performance is close to the optimal, e.g., no collisions during data packet transmission, and tag energy consumption can be reduced by more than 10% compared to FSA.

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

     Miliotis, Vasileios; Alonso Zárate, Luis Gonzaga; Verikoukis, Christos
    Ad hoc networks
    Vol. 14, p. 35-50
    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.

  • Access to the full text
    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
    Vol. 14, num. 3, p. 4806-4830
    DOI: 10.3390/s140304806
    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.

  • Access to the full text
    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
    Vol. 14, num. 2, p. 2663-2682
    DOI: 10.3390/s140202663
    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.

  • Grup de recerca en Tecnologies i Comunicacions Sense Fils

     Olmos Bonafé, Juan José; Valenzuela Gonzalez, Jose Luis; Alonso Zárate, Luis Gonzaga; Garcia Lozano, Mario; Pérez Diaz de Cerio, David; Kartsakli, Elli; González González, David; Lema Rosas, Maria Angel; Joud, Mohammad; Arteaga Martinez, Xavier; Bousia, Alexandra; Mesodiakaki, Agapi; Miliotis, Vasileios; Mekikis, Prodromos Vasileios; Serra Pages, Albert; Ruiz Boque, Silvia
    Competitive project

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  • 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
    Vol. 16, num. 1, p. 4-16
    DOI: 10.1109/SURV.2013.111313.00244
    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
    Vol. 6, num. 1, p. 33-44
    DOI: 10.1364/JOCN.6.000033
    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.

  • 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

  • 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.

    Postprint (author’s final draft)

  • Energy Efficient Schemes for Base Station Management in 4G Broadband Systems

     Bousia, Alexandra; Kartsakli, Elli; Antonopoulos, Angelos; Alonso Zárate, Luis Gonzaga; Verikoukis, Christos
    DOI: 10.4018/978-1-4666-4888-3
    Date of publication: 2013-12
    Book chapter

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  • Access to the full text
    Multiuser MAC schemes for high-throughput IEEE 802.11n/ac WLANs  Open access

     Kartsakli, Elli; Zorba Barah, Nizar; Alonso Zárate, Luis Gonzaga; Verikoukis, Christos
    DOI: 10.5772/57129
    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.

  • 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
    p. 277-279
    DOI: 10.1109/HealthCom.2013.6720683
    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.

  • 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
    Vol. 17, num. 9, p. 1738-1741
    DOI: 10.1109/LCOMM.2013.072313.130942
    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.

  • 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
    Vol. 53, num. 3, p. 329-342
    DOI: 10.1007/s11235-013-9701-6
    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.

  • 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
    Vol. 2, num. 1, p. 41-49
    DOI: 10.2174/22117407112019990004
    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.

  • 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
    p. 490-494
    DOI: 10.1109/SPAWC.2013.6612098
    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.

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

     Miliotis, Vasileios; Alonso Zárate, Luis Gonzaga; Verikoukis, Christos
    IEEE International Conference on Communications
    p. 1010-1014
    DOI: 10.1109/ICCW.2013.6649384
    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 efficiency analysis of secondary networks in cognitive radio systems

     Mesodiakaki, Agapi; Adelantado, Ferran; Alonso Zárate, Luis Gonzaga; Verikoukis, Christos
    IEEE International Conference on Communications
    p. 4115-4116
    DOI: 10.1109/ICC.2013.6655206
    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.

  • 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
    p. 3547-3551
    DOI: 10.1109/ICC.2013.6655101
    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.

  • 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
    p. 2235-2240
    DOI: 10.1109/ICC.2013.6654860
    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.

  • 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
    p. 3655-3659
    DOI: 10.1109/ICC.2013.6655121
    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.

  • 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
    p. 4420-4424
    DOI: 10.1109/ICC.2013.6655262
    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.

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

     Alonso Zárate, Luis Gonzaga; Kartsakli, Elli; Verikoukis, Christos; Alonso, L.
    Award or recognition

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

     Predojev, Tatjana; Alonso Zárate, Luis Gonzaga; Verikoukis, Christos
    IEEE Global Communications Conference
    p. 3183-3188
    DOI: 10.1109/GLOCOM.2012.6503604
    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.

  • 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
    p. 578-583
    DOI: 10.1109/GLOCOM.2012.6503175
    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.