Itziar Angulo

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.

Software tool for the analysis of potential impact of wind farms on radiocommunication services

The prediction of the potential impact of a wind farm on the existing radiocommunication services before its installation allows the planning of alternative solutions to ensure the coexistence of wind energy and telecommunication facilities. Although some guidelines for safeguarding radiocommunication services have been recently published, the precise impact on a specific service can only be determined on a case-by-case basis, due to the multiple factors that must be considered in the analysis. This paper presents a software tool that allows the accurate analysis of the degradation of the different radiocommunication systems. The calculations are based on the configuration of a specific wind farm and the different transmitters and receivers over a terrain database containing high resolution altimetry data. For each type of service, suitable calculation algorithms and interference criteria are applied. Graphic and numerical results of the analysis are presented on a map, which allows an on-the-spot evaluation of the degradation mechanisms for each wind turbine.

Performance Study of Layered Division Multiplexing Based on SDR Platform

Two of the main drawbacks of the current broadcasting services are, on the one hand, the lack of flexibility to adapt to the new generation systems requirements, and on the other hand, the incapability of taking a piece of the current mobile services market. In this paper, layered division multiplexing (LDM), which grew out of the concept of Cloud Txn, is presented as a very promising technique for answering those challenges and enhancing the capacity of broadcasting systems. The major contribution of this paper is to present the first comprehensive study of the LDM performance behavior. In particular, in this paper, the theoretical considerations of the LDM implementation are completed with the first computer based simulations and laboratory tests, covering a wide range of stationary channels and the mobile TU-6 channel. The results will support LDM as a strong candidate for multiplexing different services in the next generation broadcasting systems, increasing both flexibility and performance.

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.

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.

Planning Large Single Frequency Networks for DVB-T2

The final coverage and associated performance of a single frequency networks (SFNs) is a joint result of the properties of all transmitters in the SFN. Due to the large number of parameters involved in the process, finding the right configuration is quite complex. The purpose of this paper is to find optimal SFN network configurations for second generation digital terrestrial broadcast system (DVB-T2). Offering more options of system parameters than its predecessor DVB-T, DVB-T2 allows large SFN networks. However, self-interference in SFNs gives rise to restrictions on the maximum intertransmitter distance and the network size. In order to make optimum use of the spectrum, the same frequency can be reused over different geographical areas-beyond the reuse distance to avoid co-channel interference. In this paper, a methodology based on theoretical network models is proposed. A number of network architectures and network reference models are considered here for different reception modes in order to study the effects of key planning factors on the maximum SFN size and minimum reuse distance. The results show that maximum bitrate, network size, and reuse distance are closely related. In addition, it has been found that the guard interval is not the only limiting parameter and that its impact strongly depends on the rest of DVB-T2 mode parameters as well as on the network characteristics (equivalent radiated power, effective height, and intertransmitter distance). Assuming that the carrier to noise ratio requirements are in the vicinity of 20 dB and bitrates over 30 Mb/s, it has been found that the network can be as large as 360 × 360 km (delivering 39.2 Mb/s) or even 720 × 720 km (delivering 37.5 Mb/s). The reuse distance will also have a complex dependency on the DVB-T2 mode and especially the network parameters, ranging from below 100 to 300 km.

Error propagation in the cancellation stage for a multi-layer signal reception

Cloud-Txn is a new broadcasting approach, which proposes the usage of the layer-division-multiplexing (LDM) to meet the requirements of the new generation digital TV services. Cloud Txn has been proposed as one of the candidate technologies for the Next Generation DTV systems. This technology is considered as an attractive alternative to the commonly used Time Division (TDM) and Frequency Division (FDM) multiplexing. Its main advantage lies in being more efficient as the RF channel is continuously used both in time and frequency, while the flexibility for each layer configuration is maintained. Nevertheless, the performance of this technique is closely related to the accuracy of the cancelation process required to decouple the multi-layered signals. The main objective of this paper is to analyze the possible error propagation due to the cancellation stage and the corresponding impact on the layers performance.

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.

Methodology for the empirical analysis of the scattering signals from a wind turbine

This study proposes a field data-based methodology to characterize the scattered signals from wind turbines. The method is based on the scattering pattern of the wind turbine, empirically obtained from the estimation of the channel impulse response, which allows the accurate estimation of the amplitude and the time variation of the scattered signals. The analysis of the Channel Impulse Response at different situations, such as the rotation speed, the orientation of the turbine or the elevation and azimuth angles of the receiver location, will allow the proper characterization of this phenomenon, and therefore, the development of an empirical model for the estimation of the potential interference of wind farms.

A Measurement-Based Multipath Channel Model for Signal Propagation in Presence of Wind Farms in the UHF Band

Scattering signals on wind turbines may lead to degradation problems on the communication systems provided in the UHF band, such as terrestrial television broadcasting, broadband wireless systems or public safety services. To date, despite the continuous requests from the International Telecommunication Union for studies on this field, no channel model has been developed to characterize signal propagation under these particular conditions. In response to this necessity, this paper presents a complete Tapped Delay Line (TDL) channel model to characterize multipath propagation in presence of a wind farm, including novel scattering modeling and Doppler spectra characterization. As proved later, this channel model, which is based on both theoretical development and empirical data obtained in the surroundings of a real wind farm, is adaptable to the particular features of any case under study: wind turbine dimensions, working frequency, and relative location of the wind farm, transmitter and receivers.