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Spatial diversity analysis for digital TV systems

Spatial diversity for digital TV systems has been studied using the results of a measurement campaign of the radio channel complex frequency response for two different situations: an outdoor-indoor channel and an indoor-indoor channel. It is shown that the actual improvement of spatial diversity is not only the mean level increase, but the reduction of both the level crossing rate (LCR) and the average fade duration (AFD). The mean level gain is in the range 1.2-3 dB for the indoor-indoor channel and within 1.4-2.9 dB for the outdoor-indoor channel and the LCR/AFD improvement is between 9.5 and 15 dB for both environments. To explain the behavior of the diversity system, high resolution angle of arrival and delay information was obtained. It is concluded that it is the interference of the direct propagation path with the main reflections that causes the received field to follow a standing wave pattern and shapes the spatial diversity gain behavior.