Comparison of the Satellite-to-Indoor Broadband Channel at 1.51 GHz and 5.2 GHz

Abstract

Receiving satellite signals indoors gains importance in research and industry. Especially for positioning applications using Global Navigation Satellite System (GNSS) a rising market can be observed. Low cost navigation receivers are currently capable of tracking the Global Positioning System (GPS) C/A signal down to a power of −159 dBm without the need of assistance. But position errors due to signal blocking, diffraction and reflection make indoor navigation with an accuracy of 1 − 2 m still impossible. To mitigate errors introduced by the wireless propagation channel by equalisation for communication systems or improved time of arrival estimation for GNSS receivers, channel propagation characteristics need to be known to aid the design process for algorithms and receivers. One possible approach to gain knowledge about the propagation channel is to perform channel sounder measurements. In such a measurement campaign the transmit signal is known to the receiver and the Channel Impulse Response (CIR) can be estimated straightforward. Because a measurement is affected by all details of the real propagation medium, channel sounder measurements for the satellite navigation multipath channel are substantially needed. For GNSS application the L-band is of most interest, where almost all GNSS based navigation signals are operating. Therefore the frequency band is crowded, which motivates investigations in other frequency bands. Currently the European Space Agency (ESA) explores the possibility of satellites-to earth transmissions operating at 5 GHz. To obtain insights into the wireless propagation channel at L and C-band the German Aerospace Center (DLR) conducted channel sounder measurements at center frequency of 1.51 GHz (L-band) as well as at 5.2 GHz (C-band). Using a broadband signal the goal is to compare the wave propagation at both center frequencies into and inside the building. The approach taken for the measurement campaign is to use elevated transmitter positions.