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This paper investigates spectrum occupancy trends of voice services in the band of 450 MHz. An occupancy model of channel occupancy in the frequency and time domain was developed. A robust algorithm is proposed to allocate white spaces within a channel group with by primary users. The algorithm statistically identifies which channels can be used with a higher probability of having a white space, so...
The Digital Radio Mondiale (DRM) system broadcasts audio in the frequency band below 174MHz [1,2]. In this experiment in urban areas in Brazil, a hybrid signal composed of an analog AM signal and a digital DRM30 signal, with the same content, were broadcasted in diurnal and nocturnal transmissions. This paper describes the experimental setup, which employs the spectral shaping technique in simulcast...
Site-diversity measurements at 12 GHz were conducted for one year in the Amazonian region. Sky noise temperature and rainfall rate were measured at two sites 13 km apart and the results obtained are presented. The observed performance indicates that site-diversity is an effective solution for the problem of severe rain attenuation occurring in equatorial regions.<<ETX>>
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