Tenoux T.,Siradel |
Lostanlen Y.,Siradel Wireless Expertise and Research Center
Physical Communication | Year: 2012
Depolarization is herein investigated for urban radio propagation. First, a theoretical study on some fundamental depolarizing mechanisms along one path, involving single and double reflection as well as wedge diffraction, is presented. Significant parameters impacting on XPR (cross polarization ratio) as the oblique incidence angle on walls or streets orientation with regards to the transmitter-receiver axis are studied thanks to simple theoretical models.XPR is also analyzed using deterministic propagation simulations in a realistic typical urban environment. The conclusions drawn in the theoretical study for single phenomena are also observed at the scale of several streets combining several paths: XPR decreases in proportion to these parameters change. These observations have been confirmed by polarimetric measurements conducted in Tokyo which are given in the last part. © 2012 Elsevier B.V. Source
Agency: Cordis | Branch: FP7 | Program: CP | Phase: ICT-2009.1.1 | Award Amount: 3.45M | Year: 2010
Currently, femtocells and macrocells are seen as isolated networks, competing for the resources available in the common spectrum band, at the cost of injecting interference to the whole system. FREEDOM project will face key technical and industrial concerns about the foreseen mid-term massive deployment of femtocells by adopting a new approach based on cooperative/coordination paradigms, enabled by the limited ISP backhaul link. The project will not disregard the approach of isolated networks because it is met when there is not enough backhaul link connecting the femtocells and macrocell. In order to guarantee a strong focus and efficiency, FREEDOM will focus on: advanced interference-aware cooperative PHY techniques; improvement of the control plane procedures for seamless connectivity and system-level and hardware feasibility evaluation of the proposed femto-based network architecture.
Agency: Cordis | Branch: FP7 | Program: CP | Phase: ICT-2007.1.1 | Award Amount: 3.88M | Year: 2008
Ultra-Wide Band (UWB) is a wireless technology which exhibits unique features such as spectrum coexistence with other wireless services, RF front-end simplicity (enabling potential low cost terminals), good radio wave propagation (robustness against multi-path fading, material penetration) and high bitrate. \nCurrent UWB implementations target short-range ultra-high bitrate point-to-point wireless communication. UCELLS project will develop the required technology to enable the cellular operation of UWB transceivers. This cellular operation enables the seamless provision of UWB communication along a medium range user area, e.g. a whole office or home.\nCellular operation of UWB transceivers requires the spectral coexistence of UWB wireless communications with other wireless licensed services operating in the same band. Strong concerns exist nowadays regarding this coexistence. These concerns are reflected in the strict maximum radiated power imposed by the Spectrum Regulation Agencies (e.g. FCC and ETSI) in current UWB regulation to avoid UWB-induced interferences.\nThe cellular UWB technology in UCELLS guarantee that regulated radiation limits are meet in a given coverage area, despite a large number of UWB transmitters are in operation and/or the transmission limits are locally exceeded. In UCELLS radiated power limits could be locally relaxed in some frequency sub-bands, which is reflected it larger UWB range, higher bitrate and larger user capacity.\nUCELLS monitors spectral radiation limits at the cellular coverage area boundary by a real-time spectrum monitor. This system with unique features (large bandwidth, high dynamic range and good spectral resolution) is implemented using a photonic analogue-to-digital converter (Ph-ADC). The associated spectral analysis algorithms to optimise both the system performance and an efficient spectrum utilisation of cellular UWB communication are also developed in UCELLS.
Agency: Cordis | Branch: FP7 | Program: CP | Phase: ICT-2007.1.1 | Award Amount: 5.55M | Year: 2008
To increase ubiquitous and mobile network access and data rates, scientific and technological development is more and more focussing on the integration of radio access networks (RANs). For an efficient usage of RANs, knowledge of the position of mobile terminals (MTs) is valuable information in order to allocate resources or predict the allocation within a heterogeneous RAN infrastructure.\nThe main objective of WHERE is to combine wireless communications and navigation for the benefit of the ubiquitous access for a future mobile radio system. The impact will be manifold, such as real time localization knowledge in B3G/4G systems that allow them to increase efficiency. Satellite navigation systems will be supplemented with techniques that improve accuracy and availability of position information.\nThe WHERE project addresses the combination of positioning and communication in order to exploit synergies and to improve the efficiency of future wireless communication systems.\nThus, the estimation of the position of MTs based on different RANs is the main goal in WHERE. Positioning algorithms and algorithms for combining several positioning measurements allow to estimate the position of MTs. Appropriate definitions of scenarios and system parameters together with channel propagation measurements and derived models will allow to assess the performance of RAN based positioning. Based on the performance of RAN positioning, location based strategies and protocols will be developed in order to optimise as well as to cross-optimise different OSI layers of communication systems and RAT selection policies. Performance assessment of the algorithms is provided by theoretical studies and simulations. Hardware signal processing will provide a verification of the performance of dedicated algorithms under realistic conditions. \nAll the tasks are covered by different work packages, which are in close interaction to ensure an integral research of positioning and communications.
Agency: Cordis | Branch: FP7 | Program: CP | Phase: ICT-2009.1.1 | Award Amount: 7.45M | Year: 2010
The availability of position information plays an increasing role in wireless communications networks already today and will be an integral part of future systems. They inherently can offer the ability for stand-alone positioning especially in situations where conventional satellite based positioning systems such as GPS fail (e.g., indoor). In this framework, positioning information is an important enabler either for location and context-aware services or even to improve the communications system itself.The WHERE2 project is a successor of the WHERE project and addresses the combination of positioning and communications in order to exploit synergies and to enhance the efficiency of future wireless communications systems. The key objective of WHERE2 is to assess the fundamental synergies between the two worlds of heterogeneous cooperative positioning and communications in the real world under realistic constraints. The estimation of the position of mobile terminals (MTs) is the main goal in WHERE2. The positioning algorithms combine measurements from heterogeneous infrastructure and complement them by cooperative measurements between MTs, additional information from inertial sensors, and context information. Based on the performance of the geo-aided positioning strategies (in the sense of accuracy, complexity, overhead of signalling, reliability of the provided information, etc.) the impact on coordinated, cooperative, and cognitive networks is assessed. This is done under realistic scenarios and system parameters following on-going standardization processes. A joint and integrated demonstration using multiple hardware platforms provides a verification of the performance of dedicated cooperative algorithms.All the tasks in WHERE2 are covered by different work packages, which are in close interaction to ensure an integral research of cooperative positioning and communications.