Unai Gil

Cloud Transmission: System Performance and Application Scenarios

Cloud transmission (Cloud Txn) is a flexible multilayer system that uses spectrum overlay technology to simultaneously deliver multiple program streams with different characteristics and robustness for different services (mobile TV, HDTV, and UHDTV) in one radio frequency channel. Cloud Txn is a multilayer transmission system like layered-division multiplexing. The transmitted signal is formed by superimposing a number of independent signals at desired power levels to form a multilayered signal. The signals of different layers can have different coding, bit rate, and robustness. The upper layer system parameters are chosen to provide very robust transmission that can be used for high-speed mobile broadcasting. The bit rate is traded for powerful coding and robustness so that the signal-to-noise ratio (SNR) threshold at the receiver is in the range of -2 to -3 dB. The top layer is designed to withstand combined noise, co-channel interference and multipath distortion power levels higher than the desired signal power. The lower-layer signal can be a DVB-T2 signal or another new system to deliver HDTV/UHDTV to fixed receivers. The system concept is open to technological advances that might come in the future: BICM/non uniform-QAM, rotated constellations, time frequency slicing or MIMO techniques can be implemented in the Cloud Txn lower (high data rate) layer. The system can have backward compatible future extensions, adding more lower layers for additional services without impact legacy services. This paper describes the performance of Cloud Txn broadcasting system.

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

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

Carrier and Noise Measurements in the Medium Wave Band for Urban Indoor Reception of Digital Radio

This paper presents a study of indoor digital radio reception in the Medium Wave band. The results are based on a large database of measurements in indoor locations in cities in northern Spain in frequencies from 600 to 1600 kHz. The paper proposes a prediction model for indoor field strength. The results are combined with indoor noise levels to study the statistics of available C/N (Carrier to Noise) ratios. The model is intended to help broadcasters planning digital broadcasting networks in Medium Wave for indoor reception. Signal time and space variability have also been studied and reference values are provided in the paper. The paper includes curves to calculate indoor losses in respect to ground wave propagation values provided by ITU-R P.368.

Empirical Evaluation of the Impact of Wind Turbines on DVB-T Reception Quality

This paper describes the results of two extensive measurement campaigns for evaluating the potential impact of scattered signals from wind turbines on terrestrial DTV reception quality in the UHF band. A detailed description of the different propagation channels encountered is provided. Furthermore, empirical threshold carrier-to-noise requirements for Quasi Error Free reception in the DVB-T system in the area of influence of a wind farm are presented, and the situations where a significant degradation can be found are identified and characterized.

DRM (Digital Radio Mondiale) Local Coverage Tests Using the 26 MHz Broadcasting Band

The digital sound broadcasting DRM (Digital Radio Mondiale) standard has established worldwide, and the number of transmissions on air has increased significantly since the approval of the standard. This paper presents the results of the one of the first DRM field trials using the 26 MHz band for local broadcasting that were carried out in Mexico. The main objective of these trials was to test the usage of the 26 MHz frequency broadcasting band to cover a local area in a similar way to FM broadcasting. This band has been usually used to broadcast long distance transmissions mainly under high sun-spot activity. When the 26 MHz band is used for local broadcasting, the tropospheric propagation is the main mechanism instead of the ionospheric refraction used in HF. At these frequencies the first Fresnel ellipsoid is usually obstructed, and multipath at urban environments is strong. In this article, practical minimum signal-to-noise ratio and field strength levels are calculated for this novel usage of the 26 MHz frequency band

SHVC and LDM techniques for HD/UHD TV indoor reception

This paper presents a study that combines LDM (Layer Division Multiplexing) and SHVC (Scalable High Efficiency Video Coding) techniques to offer HD/UHD TV services in indoor scenarios. First, a theoretical study of the optimal configuration parameters for the LDM signal (such as constellation, code-rate and injection level) for indoor reception will be presented. Next, the results of some laboratory measurements for testing the performance in indoor scenarios will be included. For this purpose, TU6, PI, IOA and IOB channel models will be considered, being the main objective to determine the minimum receiving signal to noise ratios (SNR). These results will be useful for broadcasters for planning purposes.

Field Trials-Based Planning Parameters for DVB-T2 Indoor Reception

This paper presents the field trials carried out in Bilbao (Spain) for testing and analyzing the performance of the DVB-T2 indoor (fixed and pedestrian) reception. Test services with different DVB-T2 and T2-Lite configuration modes have been broadcasted and indoor measurements have been carried out. As a result, signal to noise ratio threshold values for DVB-T2 indoor reception have been obtained. These values update those provided by previous studies and are also valid for planning tools to be used by broadcasters in the development of DVB-T2 networks.

Use of the Channel Impulse Response of the DVB-T Service for the Evaluation of the Reflected Signals of Wind Farms

Wind turbines can cause degradation to the existing transmission systems, especially in the analogue television terrestrial broadcasting and radar services. The main effects of the interference are caused by the reflected signals in the support tower and in the rotating blades of the wind turbines. Empirical trials are necessary in order to adequately characterize the influence on the quality of the transmitted services, and to determine the parameters involved. The existing techniques to evaluate this influence are cost prohibitive or do not offer the required accuracy. In this paper, a low cost technique for evaluating the reflected signals from wind turbines is proposed, based on the analysis of the channel impulse response of the digital terrestrial television services. The results show that this technique provides accurate and reliable results.