| 1. |
- Castillejo, Pedro, et al.
(author)
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Integration of wearable devices in a wireless sensor network for an E-health application
- 2013
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In: IEEE wireless communications. - 1536-1284 .- 1558-0687. ; 20:4, s. 38-49
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Journal article (peer-reviewed)abstract
- Applications based on Wireless Sensor Networks for Internet of Things scenarios are on the rise. The multiple possibilities they offer have spread towards previously hard to imagine fields, like e-health or human physiological monitoring. An application has been developed for its usage in scenarios where data collection is applied to smart spaces, aiming at its usage in fire fighting and sports. This application has been tested in a gymnasium with real, non-simulated nodes and devices. A Graphic User Interface has been implemented to suggest a series of exercises to improve a sportsman/woman s condition, depending on the context and their profile. This system can be adapted to a wide variety of e-health applications with minimum changes, and the user will interact using different devices, like smart phones, smart watches and/or tablets.
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| 2. |
- Ding, Zhiguo, et al.
(author)
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On Combating The Half-Duplex Constraint In Modern Cooperative Networks : Protocols And Techniques
- 2012
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In: IEEE wireless communications. - 1536-1284 .- 1558-0687. ; 19:6, s. 20-27
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Journal article (peer-reviewed)abstract
- A key issue that characterizes cooperative wireless networks is the half-duplex constraint (HDC), which refers to the inability of current modems to receive and transmit data in the same frequency at the same time. This hardware limitation results in inefficient use of system resources (bandwidth loss) as it requires dedicated bandwidth allocation for relay transmissions. Methods to overcome the HDC have been studied intensively in the literature of cooperative networks in recent years, and several approaches have been proposed. In this article we highlight four different techniques which combat the HDC by using existing technology. The first approach is non-orthogonal protocols, which allow the source to be active during relay transmissions. The second approach is the overlap of several relaying transmissions in order to mimic an ideal full-duplex operation. The third solution is the two-way relay channel where two sources exchange data via the assistance of a shared relay. Finally, the fourth approach incorporates cooperation on the "network" level and uses the cognitive radio concept to enable relay transmissions during silent periods of source terminals. These techniques summarize some of the most significant HDC solutions that cover both the physical and network layers.
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| 3. |
- Hwang, Youngju, et al.
(author)
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Scenario making for assessment of secondary spectrum access
- 2012
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In: IEEE wireless communications. - 1536-1284 .- 1558-0687. ; 19:4, s. 25-31
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Journal article (peer-reviewed)abstract
- Secondary spectrum access, through which secondary users opportunistically access the underutilized radio spectrum, has emerged as a solution to cope with the perceived spectrum scarcity. The potential of secondary spectrum has therefore attracted industry players and regulators worldwide. To assess the real-life benefits of the secondary spectrum, it is crucial to estimate the amount of spectrum available for secondary use. This estimation requires a well defined set of models and parameters, which are collectively termed a scenario. In this article, we demonstrate the importance of scenario making in the quantitative assessment of secondary spectrum access. We first describe the elements that constitute a comprehensive secondary access scenario: a primary system and spectrum, a secondary system and usage, and the methods and context of spectrum sharing. Then we demonstrate how the assessment results of the spectrum availability differ depending on the scenario elements. We also illustrate the crucial aspects of a scenario in the business analysis, which, together with the technical assessment, is the input for the regulatory decision.
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| 4. |
- Laya, Andres, et al.
(author)
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Device-to-device communications and small cells : Enabling spectrum reuse for dense networks
- 2014
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In: IEEE wireless communications. - 1536-1284 .- 1558-0687. ; 21:4, s. 98-105
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Journal article (peer-reviewed)abstract
- 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.
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| 5. |
- Lo, Anthony, et al.
(author)
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A cellular-centric service architecture for machine-to-machine (M2M) communications
- 2013
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In: IEEE wireless communications. - : IEEE Communications Society. - 1536-1284 .- 1558-0687. ; 20:5, s. 143-151
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Journal article (peer-reviewed)abstract
- A machine-to-machine (M2M) communications system is a large-scale network with diverse applications and a massive number of interconnected heterogeneous machines (e. g., sensors, vending machines and vehicles). Cellular wireless technologies will be a potential candidate for providing the last mile M2M connectivity. Thus, the Third Generation Partnership Project (3GPP) and IEEE 802.16p, have both specified an overall cellular M2M reference architecture. The European Telecommunications Standards Institute (ETSI), in contrast, has defined a service-oriented M2M architecture. This article reviews and compares the three architectures. As a result, the 3GPP and 802.16p M2M architectures, which are functionally equivalent, complement the ETSI one. Therefore, we propose to combine the ETSI and 3GPP architectures, yielding a cellular-centric M2M service architecture. Our proposed architecture advocates the use of M2M relay nodes as a data concentrator. The M2M relay implements a tunnel-based aggregation scheme which coalesces data from several machines destined to the same tunnel exit-point. The aggregation scheme is also employed at the M2M gateway and the cellular base station. Numerical results show a significant reduction in protocol overheads as compared to not using aggregation at the expense of packet delay. However, the delay rapidly decreases with increasing machine density.
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| 6. |
- Rantakokko, Jouni, et al.
(author)
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Accurate and Reliable Soldier and First Responder Indoor Positioning : Multi-Sensor Systems and Cooperative Localization
- 2011
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In: IEEE wireless communications. - : IEEE Communications Society. - 1536-1284 .- 1558-0687. ; 18:2, s. 10-18
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Journal article (peer-reviewed)abstract
- A robust, accurate positioning system with seamless outdoor and indoor coverage is a highly needed tool for increasing safety in emergency response and military urban operations. It must be lightweight, small, inexpensive, and power efficient, and still provide meter-level accuracy during extended operations. GPS receivers, inertial sensors, and local radio-based ranging are natural choices for a multisensor positioning system. Inertial navigation with foot-mounted sensors is suitable as the core system in GPS denied environments, since it can yield meter-level accuracies for a few minutes. However, there is still a need for additional supporting sensors to keep the accuracy at acceptable levels during the duration of typical soldier and first responder operations. Suitable aiding sensors are three-axis magnetometers, barometers, imaging sensors, Doppler radars, and ultrasonic sensors. Furthermore, cooperative positioning, where first responders exchange position and error estimates in conjunction with performing radio-based ranging, is deemed a key technology. This article provides a survey on technologies and concepts for high accuracy soldier and first responder positioning systems, with an emphasis on indoor positioning.
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| 7. |
- Tombaz, Sibel, et al.
(author)
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Energy- and cost-efficient ultra-high-capacity wireless access
- 2011
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In: IEEE wireless communications. - 1536-1284 .- 1558-0687. ; 18:5, s. 18-24
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Journal article (peer-reviewed)abstract
- Mobile communication networks alone today consume 0.5 percent of the global energy supply. Meeting the rapidly increasing demand for more capacity in wireless broadband access will further increase the energy consumption. Operators are now facing both investing in denser and denser networks as well as increased energy cost. Traditional design paradigms, based on assumptions of spectrum shortage and high cost base station sites, have produced current cellular systems based on 3G and 4G (LTE) standards. The latter ones are characterized by very high spectrum efficiency, but low energy efficiency. Deployment has favored strategies with few high-power bases stations with complex antenna systems. The key method for indoor coverage has so far been to literally "blast signals through walls" - a solution that is neither energy-efficient nor very sound from a radiation perspective. As environmental aspects may be perceived as important from a societal perspective, the cost remains the short-to medium-term concern for operators of future mobile broadband systems. What becomes evident now is that the so far mostly neglected energy cost will be a major concern. Future system deployment has to balance infrastructure deployment, spectrum, and energy cost components. Ongoing incremental improvements in electronics and signal processing are bringing down the power consumption in the base station. However, these improvements are not enough to match the orders-of-magnitude increase in energy consumption cause by demands for more capacity. It is clear that solutions to this problem have to be found at the architectural level, not just by increasing the efficiency of individual components. In this article we propose a framework for a total cost analysis and survey some recent, more radical, "clean slate" approaches exploiting combinations of new spectrum opportunities, energy-efficient PHY layers, and novel deployment and backhauling strategies that target minimizing overall system cost. The latter involve network deployment tightly tailored to traffic requirements, using low-power micro base stations tailored specifically to decrease the power consumption compared to today's high-power macro base station schemes. To illustrate our findings, a power consumption model for mobile broadband access networks taking backhaul into account is presented, and the main trade-offs between infrastructure, energy, and spectrum costs are analyzed. We demonstrate optimal deployment strategies in some simple scenarios where a certain capacity has to be provided in a dense interference-limited scenario.
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| 8. |
- van de Beek, Jaap, et al.
(author)
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How a layered rem architecture brings cognition to today's mobile networks
- 2012
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In: IEEE wireless communications. - 1536-1284 .- 1558-0687. ; 19:4, s. 17-24
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Journal article (peer-reviewed)abstract
- In this article, we present a layered radio environment map architecture along with its applications to the self-organizing network functionalities of heterogeneous LTE radio access networks comprising macrocells and femtocells. In this architecture, the functional blocks reappear with different spatial and temporal granularity at different architectural layers. Although the radio environment map is one of the key promising technologies to enable future cognitive radio networks, it can be already applied to provide limited cognitive capabilities to today's commercial networks too. We explain why, and show how, this architecture can support today??s LTE self-organizing network functions like automatic neighbor relation and minimization of drive tests, and also allow the smooth introduction of new radio access technologies through refarming. We also demonstrate some of the quantitative benefits adopting radio environment map technologies can bring using the minimization of drive tests as an example.
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| 9. |
- Zander, Jens, et al.
(author)
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On the scalability of cognitive radio: : Assessing the commercial viability of secondary spectrum access
- 2013
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In: IEEE wireless communications. - 1536-1284 .- 1558-0687. ; 20:2, s. 28-35
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Journal article (peer-reviewed)abstract
- We report results from the recently finished QUASAR project, which has studied overall system aspects of cognitive radio technologies and has paid attention particularly to the economic viability of different use cases. We find that successful secondary sharing goes far beyond the detection of spectrum holes. Large-scale commercial success requires that secondary systems are scalable so that a large number of users can be served in an economically viable fashion. Our key finding is that secondary spectrum use is not an attractive method for most of the commercially interesting scenarios, from neither a business nor technical perspective. Perhaps somewhat surprisingly, the likely commercial "sweet spot" for secondary sharing in the lower frequency bands is short-range indoor communications. We also find that regulation does not currently present a significant barrier in Europe or the United States.
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| 10. |
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