No Middle Ground Between Satellite and Telecoms

Many satellite executives believe the potential loss of C-band spectrum to terrestrial players would be catastrophic or disastrous for the industry. There is little doubt that the stakes are high for many satellite players, but is there another option than just winning or losing complete access to the bandwidth? Can the satellite and terrestrial players find a middle ground for sharing C-band spectrum that would satisfy all parties, bring new services to more users and keep revenues flowing for all companies?

WiMax and IMT players are seeking access to part of the C-band spectrum because with the world going wireless, they view use of this bandwidth as key to their future growth. Gaining access to the part of C-band spectrum running from 3.4 gigahertz (GHz) to 4.2 GHz, traditionally the domain of satellite players, would be quite a coup for the terrestrial providers, but there are some officials suggesting that there may be ways to share this section of bandwidth rather than reserving access for one technology at the expense of another.

Compromise Not An Option

While sharing the spectrum seems like a logical method to satisfy as many providers as possible, technical evidence suggests there is no easy way to keep both telecoms and satellite people happy. “Communications companies and governments throughout the world have been reporting numerous incidents where satellite telecom and broadcasting services are being severely disrupted by interference from terrestrial wireless services in the ‘extended’ and standard C-band frequencies — 3.4 to 4.2 gigahertz,” says David Hartshorn, secretary general of the Global VSAT Forum, one of the organizations leading the satellite industry’s efforts to retain exclusive use of the bandwidth.

“From an interference perspective, both in terms of what we call in-band interference and out-band interference, studies have shown that you can’t really coexist in the same geographic areas using the same frequencies,” says Kalpak Gude, vice president for regulatory affairs at Intelsat. “The out-of-band problem is that the deployed satellite infrastructure that exists out there filters signals only at the edges of the 3.4 to 4.2 gigahertz band. This means that if you put a very powerful WiMax transmitter in the 3.4 to 3.6 band, it is not being filtered for customers even if they are looking for signals in the 3.7 to 3.8 bands.

“A WiMax or IMT transmitter could then overload the satellite receiver and wipe out satellite signals in higher portions of the C-band. That is another concern we have been talking to governments about. I don’t think there is a full appreciation for the amount of deployed C-band infrastructure that exists and the costs associated with modifying this deployed base,” says Gude.

This potential disruption of satellite services provides a compelling practical reason why this part of the C-band spectrum should remain with the satellite players, says Robert Ames, CEO of the Satellite Users Interference Reduction Group. “A good example of the case for protecting the C-band spectrum comes in response to the ‘exclusion zone’ in the proposal for WiMax implementation,” he says. “The proposal suggests a minimum 150-kilometer ‘exclusion zone’ around operational earth stations where WiMax devices would not be allowed to operate so as not to interfere with the earth station. However, if you have an earth station in New York City and another in Washington, DC, both establishing a 300-kilometer-wide exclusion zone, the limitation on WiMax coverage would span the East Coast (of the United States) from Connecticut to southern Virginia.”

Ames also cites a real-life example in Latin America in 2006 which demonstrated the difficulties raised when WiMax and satellite coexist in the same spectrum. “Bolivia rolled out a test WiMax network timed with the start of World Cup soccer,” he says. “The interference from the WiMax system impacted about 30 percent of households in Bolivia receiving World Cup coverage via satellite. Needless to say, this resulted in an outcry that led to the immediate termination of WiMax testing.”

Despite examples such as this, it remains a very real possibility that the International Telecommunication Union (ITU) will authorize the terrestrial players to share C-band spectrum. “According to Article 44 of the ITU Constitution, member states shall endeavor to ensure efficient use of spectrum including the application of the latest technical advances as soon as possible,” says Danny Lau, assistant director, operations for the Office of the Telecommunications Authority, the telecoms regulator of Hong Kong. “If a decision was made purely based on this objective, WRC-07 might allocate some spectrum in the C-band to telecom players.”

Discussions are taking place between the Global VSAT Forum and the WiMax Forum to talk about coexistence. “Our organization has held extensive discussions with the WiMax Forum in an effort to come to a mutual understanding of this issue, and, surprisingly, there is not much disagreement regarding compatibility,” says Hartshorn. “Indeed, our organizations agree that adjacent operation of satellite and terrestrial-wireless services in C-band will cause unacceptable levels of interference. Independent tests conducted by various governments have also reached the same conclusion.”

There also seems to be an understanding on the part of the WiMax players about these interference issues. “The WiMax Forum recognizes that, in some countries, parts of the band in question may not be able to be used for broadband wireless access systems where ubiquitously deployed satellite earth stations use the whole band 3.4 to 4.2 gigahertz,” a WiMax Forum source says. “In some countries or regions the coexistence issues have been studied in depth and recommendations agreed to give guidance to administrations about how the service can coexist.”

However, the WiMax Forum believes in some countries coexistence is an option. “The WiMax Forum believes that both services have a role to play in countries where traditional and reliable wired telecommunications services are not in widespread use,” the source says. “The band in question is already allocated to both terrestrial and satellite services on an international basis and it is for national administrations to determine the extent to which all types of service are used with appropriate regulatory procedures in place and adherence to international coordination procedures for coexistence with services in neighboring countries.”

But Hartshorn is adamant that “terrestrial-wireless interests need to pursue spectrum other than C-band.”

Compromise Not An Option

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