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.

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.

Virtual organizations (VO) have been rapidly growing within collaborative business environment. However, there is need to develop work related to VO planning and launching. This paper proposes a reference model to plan and launch VOs. The reference has a three dimensional structure. The first dimension is related with VO life cycle. Second dimension shows VO modelling views supported by UML. Third dimension presents VO knowledge management structure, VO knowledge assets are structured in procedural, organizational and operational domains, which enable knowledge creation and sharing within virtual organizations. A case study is presented in order to demonstrate reference model us in VO planning and launching.