David de la Vega

Generalization of the Lee Method for the Analysis of the Signal Variability

The Lee method, which was recommended by the International Telecommunications Union (ITU) and the European Conference of Postal and Telecommunications Administrations (CEPT) to obtain the local mean values of the received signal along a route, was developed for a Rayleigh distribution in the ultrahigh-frequency (UHF) band. This paper describes the generalization of this method to any propagation channel and frequency band and describes the methodology to obtain the parameters involved. The Generalized Lee Method is based on field data samples, which allows estimating the mean values without the requirement of a priori knowing the distribution function that better fits the propagation channel. The accuracy in obtaining the averaging interval is also improved. The Generalized Lee Method is solved for ground-wave propagation at the medium-wave (MW) band, taking data from field trials of a Digital Radio Mondiale (DRM) transmission. The results show that the values considerably differ from those obtained for a Rayleigh channel and prove that the method allows the adequate differentiation of long-term and short-term signals. The Generalized Lee Method completes the results obtained by Lee and Parsons and makes better characterization of the spatial variability possible.

Medium Wave Digital Radio Mondiale (DRM) Field Strength Time Variation in Different Reception Environments

This paper examines the temporal variability in fixed reception of the ground-wave propagated DRM (Digital Radio Mondiale) signal. This field strength analysis in the medium wave band has been performed using the first Spanish DRM field trial. Several fixed reception points located along radial routes provided the field strength sample distributions in rural and suburban areas. Additionally a second measurement campaign was carried out in several dense and open areas of downtown Madrid. The maximum likelihood estimations and logarithmic functions were used to analyse the fit of the experimental data with theoretical statistical distributions. A deep analysis of the most important parameters of the distribution has been carried out in order to characterize the field strength behavior in the different reception situations. It has been taken into account the influence of environment, measurement time interval, distance to the transmitter and the presence of critical reception impairments. The most remarkable result of this study has shown that the time variability of the ground-wave medium wave DRM channel is well approximated by a Log Normal and also by a Nakagami process. The Log Normal distribution is preferred as it is the one considered by the analog medium wave broadcasts for the ground-wave propagation case

DTV reception quality field tests for portable outdoor reception in a single frequency network

This paper presents a field measurement campaign developed to study the influence of the special features of a Single Frequency Network (SFN) reception in the C/N thresholds applicable to portable DTV reception. The measurements presented here were performed inside coverage areas of the nationwide SFN which broadcasts DTV (COFDM 8 K mode) services in Spain. The aim of this paper is to present some network planning reference values for portable reception in urban environments where both multipath and multiple transmitter reception have to be taken into account to ensure a good quality of service.

DTV (COFDM) SFN signal variation field tests in urban environments for portable outdoor reception

The paper presents the measurement results obtained in an extensive field test campaign developed in two large cities of Spain (Madrid and Bilbao) with the aim of characterizing the portable outdoor reception of digital terrestrial television (COFDM - coded orthogonal frequency division multiplexed) and continue the studies carried out by the authors during the past years.

External Noise Measurements in the Medium Wave Band

This paper presents an up to date study on external noise levels in the medium wave band based on field trials carried out in Spain and Mexico during years 2004 and 2005 respectively. External noise levels predicted by the ITU-R P.372 recommendation are based on measurements carried out more than 30 years ago and no updated results for the medium wave band have been published in this time. An increment on these noise levels have been measured, which leads to a significant impact on the minimum usable field strength requirements for the broadcasting systems used in this frequency band, such as the new Digital Radio Mondiale (DRM) and In-Band/On-Channel (IBOC) systems

An Empirical Comparative Study of Prediction Methods for Estimating Multipath Due to Signal Scattering From Wind Turbines on Digital TV Services

Several authors have theoretically studied the effect of wind turbines on the propagation of electromagnetic waves in the UHF band. The International Telecommunication Union also proposes a simplified model to evaluate the impact caused to television reception by a wind turbine in the Recommendation ITU-R BT.805. This paper presents an empirical study of the above-mentioned prediction methods for estimating signal scattering from wind turbines in the UHF band, comparing predicted values with empirical data obtained from a DTV measurement campaign carried out in Spain. As signal scattering is independent of the transmission standard or modulation, the results are applicable to any broadcasting and wireless communication signals in the UHF band that may be affected by the multipath interference caused by a wind farm.

Analysis of the DVB-T Signal Variation for Indoor Portable Reception

A study of DVB-T (Digital Video Broadcasting-Terrestrial) signal variability for indoor reception environments is stated in this paper. A commercial signal was measured and analyzed in order to obtain C/N threshold values that account time and space fluctuations. In this way, results increase the accuracy of the values provided by the ETSI (European Telecommunications Standards Institute) standard and other studies that assume static propagation channels. On the other hand, the fading influence due to people walking near the reception antenna has been proved as critical for correct reception. Characterization of this effect has been made in terms of its depth and duration. The results obtained results improve DVB-T network planning and could be also relevant for other technologies sharing similar frequencies and bandwidths.

3DTV Roll-Out Scenarios: A DVB-T2 Approach

This paper presents an analysis of the characteristics of the DVB-T2 standard to deliver 3DTV contents (3DTV). The work has been based on the current state-of-the-art developments in technologies that enable 3DTV delivery, from production to displays, with special emphasis on formats and coding efficiencies. Based on bitrate and format requirements the capacity of DVB-T2 is investigated, proposing two roll-out scenarios and discussing the associated DVB-T2 configuration parameters. The target receivers are both fixed and portable, and different backward compatibility problems and solutions are highlighted. The result of this work is an estimation of the number and type of services (both 2D and 3D) that this standard will be able to deliver in the mid term future as 2D HD and 3D services become commercially available.

Analysis of the Attenuation Caused by the Influence of Orography in the Medium Wave Band

This paper presents attenuation values due to the influence of orography in the MW band, based on an analysis of data recorded in a measurement campaign. The decisive influence of the distance of the obstacle from the receiver is demonstrated, and this parameter has been considered in the analysis. Values for the range of the influence are indicated for different values of the height of a single obstacle. These attenuation values are greater than the ones assumed in classical methods, and coincide with measurement campaigns developed by DRM (digital radio mondiale) consortium members. Accuracy in calculating the attenuation due to the irregular terrain is necessary in planning the coverage of digital services, where it is necessary to provide adequate field strength in a high percentage of locations.

DVB-T BER measurements in the presence of adjacent channel and co-channel analogue television interference

This paper presents some laboratory tests carried out to measure the BER degradation caused by an analogue PAL-G television interference on a COFDM 8 K digital television signal. The tests made include co-channel and both upper and lower adjacent channel interference situations. Previously, the ITU-R has presented some protection ratios to be sought when planning DVB-T networks. The results of the work presented here include a wider range of power ratios and their effect on the BER rather than the limit protection values. The new digital services will share the same frequency bands as the conventional analogue television so the exact characterization of mutual interference is a major concern of broadcasters during the transition period when both systems have to co-exist.