[Satellite Today – 3-4-08] WiMax communications pose a significant interference threat to satellite signals transmitted in the C-band frequency, the Satellite Users Interference Reduction Group (SUIRG), announced March 3.
    SUIRG conducted formal field tests on the compatibility of fixed satellite services (FSS) and WiMax services sharing the C-band spectrum. The primary objective of the plan was to measure interference levels generated by fixed WiMax transmissions into an FSS satellite receiving station. The method employed taking measurements of carrier/noise, interference/noise, bit error rate and spectrum plots of a satellite down link video channel during two phases – while the FSS antenna remained in a fixed location and the WiMax base unit was moved to several locations to simulate subscriber waveforms as well as while the WiMax base antenna was fixed at a height of about 50 meters and the FSS antenna was moved to different locations. 
    The testing showed that the WiMax transmit signal could cause significant problems to a satellite digital signal at a distance of more than 12 kilometers. FSS antennas cannot coexist with WiMax systems ranges from 50 to more than 200 kilometers, dependent upon the local terrain and the WiMax output levels.
     “We’re not trying to put WiMax out of business,” Robert Ames, president and CEO of SUIRG, said in a statement. “But C-band is in many ways the lifeline of the satellite industry. Protecting that spectrum from the threat of interference posed by sharing it with broadband wireless access services is of paramount importance.”