WiMax deployments could "wipe out" satellite services on the C-band, disrupting crucial television transmissions, and even pose a potential threat to 2010 Soccer World Cup broadcasting, delegates at SatCom Africa 2007 heard.
VSAT Forum general-secretary David Hartshorn, addressing the Sandton conference yesterday, said global broadcasters use the C-band range to distribute content around the world. In SA, a single C-band uplink will distribute a signal from the tip of Africa across the continent.
However, he warned that for the WiMax and satellite services to coexist, an exclusion zone of between 50km to 60km around a WiMax base station is required to ensure it does not create an interference risk to satellite services.
As local telecoms operators gear up to deploy WiMax networks, many have put pressure on the government to allocate the necessary spectrum, while some operators have already begun rolling out test WiMax networks.
Hartshorn said there have been widespread reports of transmission interference linked with WiMax deployments globally. "The most notable of these occurrences was in Bolivia last year, during the World Cup, when 30% of the nation`s television transmission went down."
He claimed that, at the time of the blackout, a WiMax system was being piloted within the extended C-band range, which created so much interference that it "wiped out" standard C-band services.
Hartshorn added this was not an isolated incident. "Governments that have invested heavily in [WiMax] technology such as the Hong Kong administration, France, Singapore and Brazil, have noted similar occurrences and have begun tests to establish the root cause of the interruption."
Can WiMax and satellite services co-exist?
However, he acknowledged WiMax supporters` argument that the outages may not be caused by WiMax deployments. "The WiMax community defines a WiMax terminal as a terrestrial wireless system, certified by the WiMax Forum to be a WiMax terminal."
It may be, he said, that WiMax terminals, or even a form of terrestrial wireless system not certified by the WiMax Forum, are causing the interferences, and not the WiMax standard itself.
"What we do know from all test results from the various governments is that WiMax, as defined by the WiMax Forum, cannot coexist with satellite services in the C-band range, without causing out-of-band interferences."
Malcolm Clark, MD of Johannesburg-based Rapid Cloud Technology, disagrees with Hartshorn. He says all interference can be avoided easily through careful wireless network planning.
"WiMax and C-band transmissions can quite happily co-exist if WiMax networks use frequencies that are not the same as the 3.5GHz frequency used by C-band," he explains.
Clark says WiMax networks in SA can use any frequency from 3.3GHz to 3.8GHz, and therefore can operate on other frequencies without causing any interference.
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