Measurement based Near Vertical Incidence Skywave channel model in the Medium Wave band

Near Vertical Incidence Sky-wave (NVIS) propagation provides wide coverage areas with only one transmitter but signals with great difficulty for reception. The NVIS channel is created by solar activity but its variability affects propagation and causes important difficulty to reception. This paper provides the first NVIS channel model in the Medium Wave (MW) band, a tap delay line (TDL) model based upon on-the-field measurements. Digital Radio Mondiale extensive field trials were carried out along 6 months at the end of the lowest activity quarter of the solar cycle, and the Impulse Responses recorded have been processed and analyzed in order to obtain the TDL models that are presented. These NVIS channel models characterize the behavior of the NVIS channel in the MW band in the periods of low solar activity thus improving channel simulators that are necessary to tune emerging digital broadcasting systems in the MW band.