Luis M. Correia

Challenges and enabling technologies for energy aware mobile radio networks

Mobile communications are increasingly contributing to global energy consumption. In this article, a holistic approach for energy efficient mobile radio networks is presented. The matter of having appropriate metrics and evaluation methods that allow assessing the energy efficiency of the entire system is discussed. The mutual supplementary saving concepts comprise component, link and network levels. At the component level the power amplifier complemented by a transceiver and a digital platform supporting advanced power management are key to efficient radio implementations. Discontinuous transmission by base stations, where hardware components are switched off, facilitate energy efficient operation at the link level. At the network level, the potential for reducing energy consumption is in the layout of networks and their management, that take into account slowly changing daily load patterns, as well as highly dynamic traffic fluctuations. Moreover, research has to analyze new disruptive architectural approaches, including multi-hop transmission, ad-hoc meshed networks, terminal-to-terminal communications, and cooperative multipoint architectures.

An overview of wireless broadband communications

A brief overview of wireless broadband communication systems, those providing a data rate higher than 2 Mb/s and up to 155 Mb/s, is done by addressing some of the applications and services that are foreseen, as well as some of the technical challenges that need to be solved, and by referring to some safety considerations. After an introduction, the need for high data rates is justified, and possible applications are listed and compared, concerning user mobility and bandwidth. Then an analysis of the propagation aspects at the bands foreseen for these systems-microwaves, millimeter waves and infrared-is presented, also addressing the issue of the antennas and batteries for these systems.

Estimation of materials characteristics from power measurements at 60 GHz

The RACE-MBS (Mobile Broadband System) project deals with the development of a mobile communications system at the 60 GHz band, which means that its propagation models, both for indoor and outdoor environments, have to be developed for that specific frequency band. The article presents estimated values, at 60 GHz, for the electrical characteristics of several building materials (only for flat surfaces), namely the relative dielectric constant, the loss tangent, and the attenuation coefficient. The estimations are based on power reflection and transmission measurements of the material samples, and the multiple internal reflections in a dielectric slab are used as a model. A least-square approach is used to obtain the numerical values of the parameters from the measurements. The attenuation coefficient ranges from 1 dB/cm to 8 dB/cm.

Content, connectivity, and cloud: ingredients for the network of the future

A new network architecture for the Internet needs ingredients from three approaches: information- centric networking, cloud computing integrated with networking, and open connectivity. Information-centric networking considers pieces of information as first-class entities of a networking architecture, rather than only indirectly identifying and manipulating them via a node hosting that information; this way, information becomes independent from the devices they are stored in, enabling efficient and application- independent information caching in the network. Cloud networking offers a combination and integration of cloud computing and virtual networking. It is a solution that distributes the benefits of cloud computing more deeply into the network, and provides a tighter integration of virtualization features at computing and networking levels. To support these concepts, open connectivity services need to provide advanced transport and networking mechanisms, making use of network and path diversity (even leveraging direct optical paths) and encoding techniques, and dealing with ubiquitous mobility of user, content and information objects in a unified way.

The way 4WARD to the creation of a future internet

In this paper, we describe the approaches taken in the 4WARD project to address the challenges of the network of the future. Our main hypothesis is that the Future Internet must allow for the fast creation of diverse network designs and paradigms, and must also support their co-existence at run-time. We observe that a pure evolutionary path from the current Internet design will not be able to address, in a satisfactory manner, major issues like the handling of mobile users, information access and delivery, wide area sensor network applications, high management complexity, and malicious traffic that hamper network performance already today. Moreover, the Internetpsilas focus on interconnecting hosts and delivering bits has to be replaced by a more holistic vision of a network of information and content. This is a natural evolution of scope requiring nonetheless a re-design of the architecture. We describe how 4WARD directs research on network virtualisation, novel InNetworkManagement, a generic path concept, and an information centric approach, into a single framework for a diversified, but interoperable, network of the future.

Opportunistic Sharing Between Rotating Radar and Cellular

This paper considers opportunistic primary-secondary spectrum sharing when the primary is a rotating radar. A secondary device is allowed to transmit when its resulting interference will not exceed the radars tolerable level, in contrast to current approaches that prohibit secondary transmissions if radar signals are detected at any time. We consider the case where an OFDMA based secondary system operates in non-contiguous cells, as might occur with a broadband hotspot service, or a cellular system that uses spectrum shared with radar to supplement its dedicated spectrum. It is shown that even fairly close to a radar, extensive secondary transmissions are possible, although with some interruptions and fluctuations as the radar rotates. For example, at 27% of the distance at which secondary transmissions will not affect the radar, on average, the achievable secondary data rates in down- and upstreams are around 100% and 63% of the one that will be achieved in dedicated spectrum, respectively. Moreover, extensive secondary transmissions are still possible even at different values of key system parameters, including cell radius, transmit power, tolerable interference level, and radar rotating period. By evaluating quality of service, it is found that spectrum shared with radar could be used efficiently for applications such as non-interactive video on demand, peer-to-peer file sharing, file transfers, automatic meter reading, and web browsing, but not for applications such as real-time transfers of small files and VoIP.

Spatial and temporal traffic distribution models for GSM

This paper presents models for the temporal and spatial distributions of traffic in urban areas. The models are based on the analysis of real GSM traffic data from the Lisbon urban area. Several factors are discussed, including geography (terrain occupancy, presence of main roads, etc.) and time variables (like work schedules). Models for the time variation are based on either a double-gaussian or a trapezoidal like function. Exponential, linear and a mixture of both functions are considered to model the spatial variation.

A 3D interpolation method for base-station-antenna radiation patterns

A simple method for the estimation of three-dimensional radiation patterns from the horizontal and vertical cuts is presented, which leads to lower errors compared to some common methods. In order to evaluate its reliability, the method has been tested for various theoretical cases by considering dipoles, individually or in arrays. For the case of the half-wavelength dipole, a maximum error of 12.0 dB (for directions of very low radiation) and an average error of 1.6 dB were obtained; for a uniform array of two dipoles radiating in a half-plane (which leads to a similar GSM panel-antennas radiation pattern), the average error was 1.8 dB (on the whole sphere). Measurements were also conducted in a real GSM network, and different approximations for the base-station radiation pattern were compared. The method presented here leads to a lower error, its average absolute value being 4.0 dB. This interpolation method is very useful for incorporating full three-dimensional radiation patterns into mobile-communications planning tools.

Sustainable Robots for Humanitarian Demining

This paper proposes a roadmap for the application of advanced technology (in particular robotics) for the humanitarian demining domain. Based on this roadmap, a portable demining kit to handle urgent situations in remote locations is described. A low-cost four-wheel steering robot with a biologically inspired locomotion control is the base of the kit. On going research on a method for all-terrain piloting, under the morphological computation paradigm is also introduced, along with the behavioural architecture underlying it, the Survival Kit. A multi-agent architecture, the DSAAR architecture, is also proposed as a way of promoting short time-to-market and soft integration of different robots in a given mission. A common denominator for all developments is the quest for sustainability with respect to (re-)engineering and maintainability effort, as well as economical and ecological impact. Failing to cope with these requirements greatly reduces the applicability of a given technology to the humanitarian demining domain. Finally it is concluded that biologically inspired design fits considerably well to support a sustainable demining paradigm.

The LEXNET Project: Wireless Networks and EMF: Paving the Way for Low-EMF Networks of the Future

While, according to the World Health Organization, no adverse health effects of radio-frequency (RF) electromagnetic fields (EMFs) have been established to date, EMF exposure from wireless communication networks is nonetheless often cited as a major cause of public concern and is frequently given considerable media coverage. This article presents the results of a new survey on RF-EMF exposure risk perception together with a comprehensive overview of the EMF footprint of existing and emerging networks. On the basis of these findings, we then put forward the rationale for EMF-aware networking. Subsequently, we highlight the gaps in existing systems, which impede EMF-aware networking, and outline the key concepts of the recently launched European Union (EU) Seventh Framework Programme (FP7) Integrated Project Low-EMF Exposure Future Networks (LEXNET): a new, all-encompassing, population-based metric of exposure and ways it can be used for low-EMF, quality of service (QoS)-aware network optimization.