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Interference: Operators Making Advances In Fight

By | June 1, 2008

      Satellite interference costs commercial operators and end users millions of dollars per year when factoring in lost revenue opportunities, specialized personnel costs and the price of interference detection systems. Many different groups are becoming more active in their efforts to combat the problem, and new work and technology are helping operators make headway in the fight.
      Satellite interference is a fact of life for operators, broadcasters and service providers. It is a pain that ranges from awkward to agonizing. Humans are error prone and make mistakes. Factor in fatigue, stress and lack of sleep and the average uplink operator or VSAT installer’s performance degrades even further.
      Bob Ames, president and CEO of the Satellite Users Interference Reduction Group (SUIRG), a non-profit organization that acts as a clearinghouse of information and best practices, outlines the different types of interference to satellites, including: human error, cross-poll problems, equipment malfunction, terrestrial interference, piracy and malicious interference. Ames also can cite several case studies to provide a sense of scale of the economic impact.
      • A large global operator experienced ongoing regional interference lasting more than a year, forcing the operator to abandon 18 megahertz of spectrum. Cost: $550,000 per year.
      • A $100 million contract held up for two months until the interference problem could be resolved. Cost: $750,000
      • Lost revenue due to reduced value of transponders operated in “backed-off mode.” Cost: $3.5 million per year
      • A major TV broadcaster lost live programming, causing them to re-feed. Cost: More than $2.4 million to resolve the interference issue.
      Ames also can point to other interference related problems in which the financial impact is harder to calculate. They included the loss of live satellite newsgathering shots, lost data for industry and government clients as well as the slow down or network interruptions of data traffic across VSAT networks.
      SUIRG has developed several initiatives to help minimize satellite interference. “One of the first things we did was develop a checklist that all operators can use before they activate a carrier on a satellite,” says Ames. “The checklist is just like the ones airline pilots use. The checklist includes things like polarization, power and modulation scheme. At first we got some pushback from old hands who felt we were questioning their industry knowledge. Once they recognized that a checklist minimizes their headaches, they started buying into the program.”
      Ames also points to work SUIRG initiated with manufacturers of satellite communications gear to embed uplink identification into their carriers. The overhead would include source locations, latitude and longitude, and contact information for the operator. “If the operator’s information was embedded into the carrier, we could quickly determine where the interference was coming from and remedy the situation,” he says. SUIRG also has initiated training and certification programs. Once a satellite operator has completed the SUIRG certification, its name is put into SUIRG’s database, where potential employers can find certified uplink operators.
      Tools of the Trade
      “Most people behave themselves,” says Bob Potter, president of SAT Corp., a subsidiary of Integral Systems. “Experience and the SUIRG report indicate that 98 percent of all incidents of interference are accidental.” SAT’s system analyzes spectrum automatically and detects when things begin to go bad — before they cause network interruptions. The system allows users to analyze the characteristics of rogue carriers, including modulation, type, forward error correction and symbol rate. Personnel can then use the information like a fingerprint and go through a database to identify potential interferers. SAT also provides a geolocation tool that targets a specific geographic region when the interference is coming from. “We can see when antennas become misaligned due to weather problems, when there is cross-pole leakage and intermodulation problems. Sometimes all the service providers on a particular transponder begin inching the power up when they start to see errors. They think that they will improve their performance by boosting the power, but in reality, power creep causes mutual interference. Our system allows a satellite operator to recognize when it is happening and ask everyone to back off,” he says.
      Glowlink Communications Technologies also provides an interference detection and geolocation system. Jeff Chu, president of Glowlink, is a 25-year veteran of the interference detection business and has seen quantum leaps in the functionality of today’s systems, of which many are direct off-shoots from governments-funded research and technology programs. “The older systems weren’t engineered using best engineering practices from a commercial perspective,” he says. “The legacy systems are very costly and aren’t nearly as effective as today’s tools. Interference detection and geolocation systems have dropped in price from several million dollars to several hundred thousand, while their performance has increased by a factor of ten. This allows all commercial operators to deploy system allowing them to detect interference and then find the uplink causing the problem,” he says.
      Khalid Chaudhry, vice president of network operations for Intelsat, says the foundation of any interference detection system is a knowledgeable staff. “You need talented people to do the detective work. They have to investigate the characteristics of the interference and look into the types of interference that have occurred in the past,” he says. Intelsat instituted a geolocation system, dubbed Transmitter Location System (TLS), in 1998 and now operates seven TLS centers around the globe. In 2006, Intelsat added two Glowlink systems to enhance its inference resolution capabilities. “The original TLS system is comprised of several racks of equipment, making it impractical to move,” says Chaudhry. “The Glowlink system is much smaller, allowing us to transport it to a specific region if we need to.”
      Geolocation systems attempt to pinpoint the location of the interference on a map. The satellite operator can then check the characteristics of the offending signal and run the “digital fingerprint” through a database, which then suggests known uplinks within the perimeter of the ellipse. Chu points out that Glowlink’s geolocation system interfaces with Google Earth maps. “We can actually send the offending uplinker a map showing their location. We ask them, ‘Is this you?’ We usually don’t get any arguments at that point,” he says. Should the interference be malicious, military or civilian aircraft can fly over the identified territory seeking out the offender. As the accuracy of geolocation systems improves, the vertical axis of the ellipse becomes more narrow, minimizing the area to be searched. If the ellipse becomes narrow enough an aircraft can inspect the area with a single pass rather than flying a zigzag pattern.
      Satellite operators tend to take the cautious road in deploying new hardware, but active phased array antennas, which are comprised of hundreds or even thousands of electrically steered individual elements that are used to shape a beam, also are being employed in the fight. An operator can individually control the energy and the relative phase of each element, and in the event of a malicious interferer, the operator would use ground station geolocation system to identify the source of the interference and then reshape the beam to null out the offending uplink, says Dany Harel, chief scientist at SES Engineering. Had SES Americom’s AMC-14 become operational, it would have provided a test of an active phase array antenna on a commercial satellite, but the opportunity will have to wait until another satellite operator makes the commitment, he says.
      With 86 percent of all military communications now carried by commercial satellite operators, the U.S. government has even more of a stake in the development of detection systems for commercial operators, says Ames. “Any interference to a commercial satellite is going to have an impact them,” he says.
      Encryption is becoming more popular as a way of minimizing malicious interference on commercial satellites, says Jim Scheimer, CTO for Americom Government Services. The Americom fleet uses KI23 encryption on earlier spacecraft and Caribou encryption on current satellites on the command links. Both types are approved by the U.S. National Security Agency. “By encrypting the traffic it makes it difficult for bad actors to know what traffic is aimed at a particular satellite or channel on a satellite. Picking out the satellite and channel you want to interfere with is actually quite hard if the traffic is encrypted, very much like finding the needle in a haystack,” he says.
      The U.S. Department of Defense “has been pursuing protection measures such as adherence to national telemetry, tracking and control encryption policy; protection of infrastructure critical to the communications services (uninterruptible power supplies); commercial best practice network security measures (firewalls) and the ability to isolate interference,” the U.S. Defense Information Systems Agency, which procures commercial satellite capacity for the military, says. “… Most satellite operators have an inherent capability to perform such interference isolation as it is critical to their business. If unintentional interference is affecting the performance of a transponder they cannot lease that transponder, thus revenue is impacted. If a satellite operator does not have such an inherent capability, they can contract for an interference isolation service.”


      Satellite interference costs the industry millions of dollars each year, with the overwhelming majority caused by human error and equipment malfunction, which can be solved through a combination of education, rigorous attention to detail and implementation of state-of-the-art interference detection and geolocation tools. The price of these tools has dropped significantly, while performance has sky rocketed. Based on the value that these systems deliver, there is no longer a reason for any commercial satellite operator not to integrate them into their operations.

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