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5 - Device-to-device (D2D) communications
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- By Zexian Li, Nokia, Fernando Sanchez Moya, Nokia, Fodor Gabor, Ericsson, Jose Mairton B. Da Silva Jr., KTH - Royal Institute of Technology, Konstantinos Koufos, Aalto University
- Edited by Afif Osseiran, Jose F. Monserrat, Patrick Marsch
- Foreword by Mischa Dohler, King's College London, Takehiro Nakamura
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- Book:
- 5G Mobile and Wireless Communications Technology
- Published online:
- 05 June 2016
- Print publication:
- 02 June 2016, pp 107-136
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Summary
Direct Device-to-Device (D2D) communication, which refers to direct communication between devices (i.e. users) without data traffic going through any infrastructure node, has been widely foreseen to be an important cornerstone to improve system performance and support new services beyond 2020 in the future fifth generation (5G) system. In general, the benefits resulting from D2D operation include, among others, highly increased spectral efficiency, improved typical user data rate and capacity per area, extended coverage, reduced latency, and enhanced cost and power efficiency. These benefits are resulting from the proximity of the users employing D2D communication (proximity gain), an increased spatial reuse of time and frequency resources (reuse gain) and from using a single link in the D2D mode rather than using both an uplink and a downlink resource when communicating via the base station in the cellular mode (hop gain). The chapter starts with an overview of the fourth generation (4G) D2D development. Afterward, the challenges to be addressed in the context of 5G D2D and related key enablers are discussed. In particular, this chapter covers Radio Resource Management (RRM) for mobile broadband applications, multi-hop D2D communication, especially for public safety and emergency services, and multi-operator D2D communication.
D2D: from 4G to 5G
In the future 5G system, it is predicted that network-controlled direct D2D communication offers the opportunity for local management of short-distance communication links and allows separating local traffic from the global network (i.e. local traffic offloading). By doing this, it will not only remove the load burden on the backhaul and core network caused by data transfer and related signaling, but also reduce the necessary effort for managing traffic at central network nodes. Direct D2D communication therefore extends the idea of distributed network management by incorporating the end devices into the network management concept. In this way, the wireless user device with D2D capability can have a dual role: either acting as an infrastructure node and/or as an end-user device in a similar way as a traditional device. Further, direct D2D facilitates low-latency communication due to the local communication link between users in proximity. In fact, direct D2D has been seen as one of the necessary features to support real-time services in the future 5G system [1][2]. Another important aspect is reliability, where an additional D2D link can be employed to increase reliability through a larger extent of diversity.
Trends in excess weight and thinness among Spanish schoolchildren in the period 1992–2004: the Cuenca study
- Vicente Martínez-Vizcaíno, Mairena Sánchez López, Pablo Moya Martínez, Montserrat Solera Martinez, Blanca Notario Pacheco, Fernando Salcedo Aguilar, Fernando Rodríguez-Artalejo
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- Journal:
- Public Health Nutrition / Volume 12 / Issue 7 / July 2009
- Published online by Cambridge University Press:
- 01 July 2009, pp. 1015-1018
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- Article
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Background
In developed countries, there is abundant information on the epidemic of childhood obesity, but only a few studies on trends in the dual burden of body weight (overweight and thinness).
ObjectiveTo examine trends in overweight and thinness among 9–10-year-old Spanish children in the last decade.
MethodsData were taken from cross-sectional studies on schoolchildren in Cuenca (Spain), conducted in 1992, 1996, 1998 and 2004 with similar methods. Weight and height were measured by trained personnel with standardized procedures. Overweight (including obesity) and thinness were defined according with the International Obesity Taskforce BMI cut-offs.
ResultsThe overall prevalence of overweight increased from 24·4 % in 1992 to 30·9 % in 2004 (P = 0·07), rising from 21·2 % in 1992 to 32·0 % in 2004 (P = 0·03) among boys and from 27·7 % to 29·8 % (P = 0·67) among girls. The overall prevalence of thinness was 2·7 % in 1992 and 9·2 % in 2004 (P < 0·001); in the same period, thinness prevalence rose from 1·9 % to 9·0 % (P = 0·10) among boys and from 3·7 % to 9·5 % (P < 0·01) among girls.
ConclusionsThe dual burden of body weight has increased among children in Cuenca in the last decade. Population-based policies addressing childhood obesity, which is the most frequent problem, should not increase the risk of thinness.