Commentary | Conquering Interference
Satellite services are widely used by military commanders to provide key tactical communications capabilities to their forces anywhere in the world. Satellite interference, either unintended or deliberate, is becoming a major threat to maintaining assured and reliable communications links.
Let’s look at the main sources of interference in satellite communications links and the military’s role in resolving it.
Satellite Interference in Perspective
Satellite interference is an issue in our industry, but in reality it affects only a small number of services. At a recent panel at the International Broadcasting Convention, Chris Grogan ofhelped with that perspective, stating that although they typically have two to three interference events per day, interference in general affects 1-2 percent of the total bandwidth available. However, the satellite industry strives for perfection and despite its being a small proportion, it can have a significant impact on satellite services and takes time and resources to resolve.
Indeed, a recent survey conducted by the Satellite Interference Reduction Group (IRG) and Newtec found that 93 percent of respondents suffer from satellite interference. The same survey also proved that we have come a long way in recent years and the various initiatives for resolving interference are beginning to have an impact. For example, 6 percent of respondents have already implemented Carrier ID, a broadcaster identification stamp that enables the operators to identify sources of unintentional interference to their satellite transmissions. A further 10 percent say they will be implementing it within six months and another 18 percent within one year. That gives us 34 percent that will be implemented by this time next year.
The survey also found overwhelming support for training both broadcasters and satellite operators across the globe to reduce human error. The Global VSAT Forum (GVF), along with its partner organizations, has already trained more than 8,000 satellite operatives worldwide, and has recently made a number of enhancements to its global training initiatives. That said, there may still be 20,000 to 40,000 untrained field technicians out there, and that is something GVF is aiming to address.
Ensuring the Right Equipment
It is clear that the military relies on satellite technology for vital communications links and therefore the service needs to be assured at all times and in all locations. Of course, satellite interference affects the entire industry and any user. One of the biggest challenges for military users is the very nature of their communication links; they are often using remote terminals in hostile conditions, so the equipment needs to be able to withstand those conditions. Also, satellite communications on the move (COTM) places sever restrictions on the size of the antenna used as profile drag and limited footprint are key design elements for vehicles where these terminals are mounted. In many cases this entails the use of ultrasmall aperture terminals that are inherently restricted in their focusing ability and thus produce wider beams. The combination of these wider beams with the increased risk of mispointing, due to the dynamic nature of the platform on which these terminals are mounted, makes it critical to ensure that these terminals don’t cause excessive levels of interference.
To that end, the Global VSAT Forum recently issued document GVF105, “Performance and Test Guidelines for Type Approval of ‘Comms on the Move’ Mobile Satellite Communications Terminals.” The document is intended to serve as a best-practices guide for interpreting international regulatory specifications for the purpose of GVF type approval of COTM very small aperture terminals. It adds guidance for testing parameters that are unique to COTM terminals. GVF is also in coordination with the U.S. Department of Defense regarding COTM Earth station testing and approvals.
Thankfully, there are a great deal of high-quality products on the market today that make the process extremely simple and efficient. Modern terminals are fully automatic and will recover even from inevitable (but brief) outages due to blocking (shadowing) and heavy rain. Therefore, except on the rare occasion of something breaking, “operating” satellite equipment needn’t be a complicated process for those responsible.
Users can increase the likelihood of things running smoothly by ensuring the equipment purchased is of the best quality possible. GVF is working closely with a number of equipment manufacturers, and the GVF Quality Products Framework aims to highlight those that meet a certain level of quality, aiding users to select the best equipment possible to ensure the best possible service.
Although satellite equipment is not generally complicated, training those tasked with using it will also help them better understand the equipment and give them much needed confidence. Equally, there are a few characteristics of satcom terminals that need to be explained to the users, such as rain and blockage, along with basic instructions like how to determine the difference between a fault and a temporary outage, and how to do simple maintenance and simple first-level troubleshooting.
GVF works with partners to provide a wide range of satellite training courses both online and across the globe. The courses vary in degrees of proficiency desired, from simple understanding of what the equipment does, how to recognize its hardware components, how it responds to normal phenomena and how to check it for healthy operation to in-depth technical understanding of antenna pointing.
GVF recently launched an Enhanced Training Services program that enables organizations to reach out to customers and support industry initiatives, such as interference prevention through sponsorships. It also enables them to rapidly deploy a training system for their staffs that integrates the GVF curriculum with a custom-branded portal and customized courses. GVF’s training content and administration provider, SatProf Inc., has crafted a range of options by building on the extensibility and partitioning capabilities of the GVF online learning system and website. These include sponsorship administration, listing on the new GVF Training Partners Web page, a custom-branded training portal, reference document libraries, courses and learning paths customized for the organization, on-site classroom administration support, and training manager administration access.
Carrier ID Demystified
Carrier ID (CID) is a signal embedded into a video or data transmission path, and it is an important part of the solution to mitigate carrier interference, as it helps to pinpoint the source of interference quickly, enabling faster resolution. The Digital Video Broadcasting Project recently approved a CID specification (DVB-CID) that enables much more efficient resolution thanks to the addition of a low power spread spectrum carrier underneath the host carrier it will identify. This specification applies to all types of single channel per carrier and multiple channels per carrier transmissions.
There is a common misconception with CID, especially among the military, that data will be shared. However, this is not the case. Other users or operators will not be able to view any sensitive information.
The CID database will be managed by the Space Data Association. The only people with access to that database will be the satellite operators, and the only information displayed will be the satellite operator responsible for the carrier identified and its identification number. When interference occurs, the satellite operator experiencing the interference will use the database to identify which operator to contact to resolve it. The satellite operator whose customer is causing the interference will then use its own internal database to determine who that is and how to contact the customer in order to resolve it.
Another common misconception surrounding CID is that it will be expensive to implement. However, CID is in most equipment, so whenever equipment is replaced it is likely to have CID. The satellite operators on the whole are geared up for CID already. Therefore, largely for the user, the investment is minimal. In fact, for many users, CID is already in their equipment and it simply is a question of turning it on. They can contact their manufacturer to find out how to do this.
The Next Steps
These initiatives are having a great impact on reducing satellite interference by helping to identify interference when it occurs, as well as proactively reducing both human error and equipment failure. Now we need to extend that further by instigating a widespread implementation of the new DVB-CID standard, training even more operators across the globe, and educating users about purchasing only type approved products. If we work together, we can resolve interference.
David Hartshorn is secretary general of the Global VSAT Forum and Martin Coleman is executive director of the Satellite Interference Reduction Group. The Global VSAT Forum and Satellite Interference Reduction Group, together with Cobham Technical Services and, will be jointly hosting a workshop Nov. 4 at Global Milsatcom in London on “Conquering Interference: The Next Big SatCom Challenge.”