Introduction to the IJWIN Special Issue: ‘Physical Layer Engineering for Emerging Wireless Applications’

Abstract

In 2007 we had the honor and responsibility to serve as chairs of the Technical Programme Committee (TPC) of the prestigious IEEE PIMRC (Personal Indoor and Mobile Radio Communications) conference. The conference attracted more than 1,200 participants and included several excellent contributions covering all aspects of the contemporary wireless telecommunications landscape. We personally had the chance to read almost all papers, and attend to a large number of interesting talks during the conference. Furthermore, we came directly in touch with many authors that excelled in the conference. In the scope of this special issue we extended an invitation to excellent authors, with a view to publishing the next steps of their works in this special issue. The five papers of this issue cover a number of different topics ranging from channel characterization and localization to smart antennas. Specifically, the first paper is titled ‘Analysis of Scattering in Mobile Radio Channels based on Clustered Multipath Estimates’ is co-authored by Maurice Kwakkernaat and Matti Herben from the Department of Electrical Engineering of the Eindhoven University of Technology. The paper deals with the accurate estimation of the propagation effect in smart-antenna and MIMO systems. The authors capitalize on a 3-D high-resolution channel sounder, which was developed based on a 3-D antenna array in combination with a multi-dimensional version of the Unitary ESPRIT algorithm. This system is capable of accurately measuring the angle-delay characteristics in azimuth conditions, as well as under mobile conditions. The authors also compare the results from deterministic propagation models to the clustered highresolution angle-of-arrival (AoA) estimates. Comparison results show that: (a) a significant amount of multipath components (MPCs) was missing and (b) the spreads in delay and angle are much larger in the measurements, (c) The MPCCs (MPCs clusters) tend to evolve rather slow along the trajectory, which may allow for interpolation techniques to reduce simulation time. The title of the second paper of the issue is ‘Identification of the Absence of Direct Path in ToA-Based Indoor Localization Systems’. The authors of the paper (namely Mohammad Heidari, Ferit Ozan Akgul, Nayef Alsindi and Kaveh Pahlavan from the Worcester Polytechnic Institute) introduce a methodology to identify and mitigate the undetected direct path (UDP) conditions, which can substantially improve the overall indoor positioning accuracy of Ultra-wideband (UWB) positioning systems based on time of arrival (ToA) techniques. The methodology relies on a novel UDP identification and mitigation technique that is based on analyzing the statistics of the propagation channel. The paper introduces the fundamentals of ToAbased localization and describes the metrics being used for UDP identification. Accordingly it presents results of binary likelihood ratio tests for UDP identification. In deriving these results the outcome of the hypothesis tests are compared to a certain threshold, in order to determine if a receiver is in DDP or UDP condition. The contribution is validated based on simulation results for a sample indoor environment. J. Soldatos (&) Athens Information Technology, 0.8 km Markopoulou Ave., P.O. Box 68, 19002 Peania, Athens, Greece e-mail: jsol@ait.edu.gr