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Applied for the first time to mobile radio propagation modeling at the beginning of the nineties, ray tracing is now living a second youth. It is probably the best model to assist in the design and planning of future short-range, millimeter-wave wireless systems, where the more limited propagation environment with respect to UHF frequencies allows to overcome traditional high-CPU time limitations while the higher operating frequency makes ray-optics approximations less drastic and allows to achieve an unprecedented level of accuracy. An overview of ray tracing propagation modeling is given in this paper, with a special attention to future prospects and applications. In particular, frontiers of ray-based propagation modeling such as extension to diffuse scattering, multidimensional channel characterization, multiple-input multiple-output (MIMO) capacity assessments, and future applications such as real-time ray tracing are addressed in the paper with reference to the work recently carried out at the University of Bologna.

The investigation of the modulated, backscattered contribution from UHF RFID Transponders is a crucial issue for the reliable evaluation of the behavior and the performance of RFID systems. The backscattered, radiated field by a UHF Transponder is described by means of a simple and complete analytical expression. The tag radar cross section (RCS) and the bit error rate (BER) at the Reader are evaluated by means of the achieved formula, and the results are in perfect agreement with previous available publications.

The use of large-size antenna arrays to implement pencil-beam forming techniques is becoming a key asset to cope with the very high throughput density requirements and high path-loss of future millimeter-wave (mm-wave) gigabit-wireless applications. Suboptimal beamforming (BF) strategies based on search over discrete set of beams (steering vectors) are proposed and implemented in present standards and applications. The potential of fully adaptive advanced BF strategies that will become possible in the future, thanks to the availability of accurate localization and powerful distributed computing, is evaluated in this paper through system simulation. After validation and calibration against mm-wave directional indoor channel measurements, a 3-D ray tracing model is used as a propagation-prediction engine to evaluate performance in a number of simple, reference cases. Ray tracing itself, however, is proposed and evaluated as a real-time prediction tool to assist future BF techniques.INDEX TERMS MIMO, beamforming, ray tracing, millimeter-wave propagation, channel measurements. 1314 2169-3536 2014 IEEE. Translations and content mining are permitted for academic research only.Personal use is also permitted, but republication/redistribution requires IEEE permission. See http://www.ieee.org/publications_standards/publications/rights/index.html for more information. VOLUME 2, 2014 ROBERT MÜLLER received the M.S. degree in electronic engineering from His areas of interest include high-frequency components design in Rogers and LTCC technology. Furthermore, he is also working on high-frequency front-end design, antenna design, ultrawideband system design, and special antenna array design for channel sounding applications. His research is focusing on channel sounding measurements system and analysis for further communication system in the field of V2V and cellular networks.CHRISTIAN SCHNEIDER received the Diploma degree in electrical engineering from the Ilmenau University of Technology, Ilmenau, Germany, in 2001, where he is currently pursuing the Dr.Ing. degree with the Institute for Information Technology. His research interests include space-time signal processing, turbo techniques, adaptive techniques, multidimensional channel sounding, channel characterization and analysis, and channel modeling for single and multiuser cases in cellular and vehicular networks. He was a recipient of the Best Paper Award at the European Wireless Conference in 2013.

Abstract-The World Radiocommunications Conference WRC15 identified a number of frequency bands between 24-86 GHz as candidate frequencies for future cellular networks. In this paper an extensive review of propagation characteristics and challenges related to the use of millimetre wave in future wireless systems is presented. Reference to existing path loss models including atmospheric and material attenuation in recommendations of the International Telecommunication Union is given and the need for new multidimensional models and measurements is identified. A description of state of the art mm wave channel sounders for single and multiple antenna measurements is followed by a discussion of the most recent deterministic, semi-deterministic and stochastic propagation and channel models. Finally, standardization issues are outlined with recommendations for future research.

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In this work, a flexible and extensive digital platform for Smart Homes is presented, exploiting the most advanced technologies of the Internet of Things, such as Radio Frequency Identification, wearable electronics, Wireless Sensor Networks, and Artificial Intelligence. Thus, the main novelty of the paper is the system-level description of the platform flexibility allowing the interoperability of different smart devices. This research was developed within the framework of the operative project HABITAT (Home Assistance Based on the Internet of Things for the Autonomy of Everybody), aiming at developing smart devices to support elderly people both in their own houses and in retirement homes, and embedding them in everyday life objects, thus reducing the expenses for healthcare due to the lower need for personal assistance, and providing a better life quality to the elderly users.