Satellite IRG Hones in on VSAT Interference Reduction
[Via Satellite 03-09-2015] The satellite Interference Reduction Group (IRG) plans to shift its focus this year to concentrate more heavily on mitigating VSAT interference. Martin Coleman, executive director of IRG, told Via Satellite that while carrier ID, which works by embedding a unique signal into satellite modulator or modem transmissions to identify it, remains a top priority, addressing VSAT-based interference has become more important as the number of terminals in use continues to climb.
VSATs cause satellite interference when improperly pointed, often due to poor installations or damage. Time Division Multiple Access (TDMA) bursts from misaligned VSATs end up hitting the wrong transponders in orbit, and when the number of bursts increases, it can limit the ability to fully use a satellite.
“We know that VSATs, the small burst mode TDMA systems are a big cause. I think the interesting conclusion of 2014 for me was the fact that if I were starting again in 2011, I would have tackled VSAT interference first. It’s actually creating close to 40 percent of the problem globally,” said Coleman.
VSAT interference is one of the most difficult to fix, he added, because millions of old terminals are unable to automatically cease transmitting. This requires manual corrections at remote sites that can be difficult to reach. New technologies are coming online to address interference, such as SatGuard, a VeriSat satellite interference analysis tool jointly developed with SES. Eutelsat has also developed a GSM demodulation tool to address GSM transmission, where mobile service signals are mistakenly transmitted up to satellites by Block UpConverters (BUCs) that are connected to modems by poorly installed or maintained RF cables. Coleman said industry is gaining traction with technologies that help address and prevent interference today.
“Some of these companies are starting to put better systems facilities in that actually eliminate VSAT interference, especially for the remote terminal,” he said. “Newer companies — and I use the term newer lightly — people like Newtec are already bringing their own technologies and add-ons that are making a step change to the traditional systems implemented, so we need to make sure people are aware of what’s available out there.”
The Space Data Association (SDA) is working with Analytical Graphics Inc. (AGI) to develop geolocation technology in order to better pinpoint the source of interference as well as confirming the type of interference. A big part of that for SDA is creating a common reference from for the variety of formats satellite operators use to describe the location of their satellite in orbit. Mark Rawlins, SDA chairman and Eutelsat’s director of communication system operations, told Via Satellite there are 19 different formats SDA members use that all have to be understood.
“They’ve all had to be converted to a common reference frame to enable the system to compare them,” Rawlins said. “If I needed information for geolocalization where I need to have the precise position and velocities of a satellite that might not belong to me, then the system would be able to provide it in my language.”
Rawlins expects to have a beta product by the second quarter of this year. Going forward, the SDA is also looking at ways to grow its membership with more operators, including militaries, and to be able to better track Non-Geostationary Satellites (NGSO). Today the organization tracks 139 LEO/MEO satellites from seven different operators, such as NASA, NOAA, O3b and Iridium, and 241 GEO satellites from 18 operators. A total of 24 operators participate in SDA, with more on the way.
“We have Telenor who joined us recently, and we have discussions ongoing with a number of different entities who are considering joining. We’ve also got a number of discussions going on with government bodies on having agreements on how we can work together. There are two other significant satellite operators who are currently finalizing their membership of SDA,” said Rawlins.
Regarding carrier ID, Coleman pointed to engaging militaries such as the U.S. Department of Defense and the U.K. Ministry of Defense as a highlight of 2014. The Aerospace Corporation and the Mitre Corporation, two IRG members, played a large role in building the military relationship. Coleman said a big reason for the change is that, at this point, not having carrier ID causes the military to stick out, which runs counterintuitive to their interests. In order for military to look the same, they too need carrier ID, and IRG has employed a basic method for getting it into military circles without directly connecting databases.
“Generally speaking, I think the latest carrier ID ready date we’ve heard from any manufacturer is early part of 2016. This still fits well with our rollout schedule. I would suggest that all new equipment will have carrier ID by then. At the moment we probably cover more than 80 percent of the modulator market. On the single thread encoder side I would say we are probably creeping closer to 40 to 50 percent, and that is growing faster than we can keep pace with,” Coleman said.
Regionally, he said the main push now is to engage with the Far East, where the number of smaller operators has made gaining momentum more difficult. Companies such as Hong Kong-based AsiaSat and Sky Perfect JSAT of Japan have helped lead the charge with carrier ID, along with other interference mitigation tactics, such as improved training and equipment. Companies like Arabsat and Al Jazeera are also spearheading these issues in the Middle East.
As the number of terminals in a given network grows, interference is becoming a more tangible issue, further encouraging action. Steps taken in recent years by the “Big Four” — Intelsat, SES, Eutelsat and Telesat — along with a growing number of prominent regional operators and equipment manufacturers, are helping to curb and reverse interference through education and better technology.
“If you are going to continue to increase, and instead of what was thousands is hundreds of thousands and now millions-plus of terminals in networks, if we want this growth and we want to bring in [High Throughput Satellites] HTS and other technologies, we need to make sure we get these systems actually produced better so that they don’t cause interference,” said Coleman. “We need to stop it before it starts.”