Susana Mota

Estimation of the Number of Clusters in Multipath Radio Channel Data Sets

This communication deals with the grouping of the multipath radio channel components. The estimation of the number of clusters that a given data set exhibits is an important step in channel modeling and parameterization. We present a performance assessment of several cluster validity indices using Monte Carlo simulations. Synthetic channels were generated by means of the extended Saleh-Valenzuela model and used as input to a clustering algorithm which outputs several solutions with different number of clusters. The cluster validity indices allow the selection of the best solution. Finally, an example is presented where the best performing indices were applied to an experimental data set.

Software Tools for Teaching Wave Propagation in Transmission Lines [Education Corner]

This article describes a demonstrator comprising four software tools that was developed to assist the teaching of some fundamental concepts about wave propagation in transmission lines and that can also serve as a student virtual laboratory. The tools, developed in MATLAB, are easy to use and offer a new approach, which intends to explore the physical basis of transmission line theory, including the transmission line model as a ladder inductor-capacitor circuit, the concept of traveling waves and their interaction in the transmission line, the nature of transmission line input impedance, and impedance matching issues. The tools are made available online to be used, modified, or improved by the community.

Detailed Analysis of Directional Radio Channel Measurements

Physical models describe the radio channel by characterizing the multipath propagation. Also, measurements are frequently employed in the establishment of such models, or for tuning the existing ones. This paper presents a systematic analysis of double-directional radio channel data, obtained by combining two single-input multiple-output measurements (forward and reverse), each, containing the channel frequency responses at the locations of a virtual rectangular antenna array. The measurement setup uses a vector network analyzer, which, together with the adopted data processing, represents an affordable, but very consistent, alternative to more sophisticated equipment, given that, a physical analysis of the identified channel contributions provided sensible results. The study comprised three main steps: 1) the characterization of each single-directional channel by employing a high-resolution algorithm to obtain the parameters of a chosen number of multipath components (MPCs); 2) the classification of the obtained MPCs in a twofold way, first, by grouping MPCs using clustering tools, and, second, by classifying these clusters according to their type of interaction with the propagation scenario; and 3) the extraction of typical values for the number of clusters, the number of MPCs per cluster, rules for power decay, and statistical distributions for inter and intracluster delays and azimuths.

Results from a First Approach to a Point-Scatter Simulator for MIMO Radio Channel Modeling

This paper presents some results obtained from a first approach to a point-scatter simulator for multiple-input multiple-output (MIMO) radio channel modeling. Specifically, we present the comparison of capacity obtained using the point- scatter simulator with that obtained with the Kronecker model. Capacity results obtained from measured propagation data are also presented. Ideas to enhance the simulator, which include the development of a statistical-based generative channel model for MIMO systems, are discussed.

Radio Transmission and Experimental Channel Characterisation Usingan MBS Platform Operating in the 40 GHz Band

This paper focuses on results obtained in the ACTS SAMBA project. Theprojects main objective was the implementation of a Trial Platformproviding a full duplex radio link of 34 Mbit/s to prove the technicalfeasibility with todays technology and to evaluate the main MBSfunctionality for the public cellular MBS segment. Thus, extensive fieldtrials were carried out in the city of Aveiro, Portugal, in differentenvironments and using the 40 GHz band. The paper starts with anintroductory analysis of the radio channel impairments and discusses thevarious appropriate mitigation techniques. A brief description of theSAMBA Trial Platform used in the measurements campaign is presentedconcentrating on the description of the main technical solutions relatedwith the physical layer. Then, representative measurements resultscollected in an urban and in an indoor environment are analysed so as toevaluate the system performance, focusing on the cell coverage area andtransmission quality. This study is made analysing parameters such as:received power level, bit error rate, fitted Rice distributionparameters to model the small-scale fading, power level cumulativedistribution functions, level crossing rate and average fade duration ofthe signals received in the two diversity antennas and the resultedsignal after combination. The achieved results constitute a significantforward step for the MBS development.