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CHIPS Articles: Electromagnetic Interference... an Achilles' Heel

Electromagnetic Interference... an Achilles' Heel
By U.S. Navy CW04 Todd D. Conley - October-December 2001
As an organization, we in the Department of Defense (DoD) fall short in our ability to detect, characterize, report and resolve electromagnetic interference or EMI. EMI is a combination of terms that broadly refers to any type of interference that can potentially disrupt, degrade or otherwise interfere with authorized electronic emissions over approved portions of the electromagnetic spectrum. Some are probably more familiar with the term "radio-frequency interference (RFI)," which is actually a specific type of EMI.

A common thought is that EMI is caused by dynamic factors, such as spurious emissions, space weather, or geomagnetic and atmospheric conditions. In other words, electromagnetic disturbances that affect electronic systems equate to EMI. However, it would be prudent for us to expand our mindset slightly in this regard to include any cause, active or passive, as electromagnetic interference. The key being, if it affects electronic emissions, it should be considered EMI. This broader definition of EMI would encompass more static causes, such as geographical and manmade obstructions.

Causes of EMI can be intentional or inadvertent, hostile or friendly, military or civil, and either foreign or domestic. They can come from a jamming device, malfunctioning equipment, or improper system operation. A mountaintop, clump of trees, building, or platform design can also be contributing factors. Regardless of the cause or intent, the effect is always the same—interference of our electromagnetic emissions.

Electronic jamming, while not common in our everyday operations, is nonetheless a potential threat against which we need to be ever ready to guard and overcome. What occurs much more frequently than is generally realized is interference from extraneous navigation and telecommunications systems, and other sources.

We can also be our own worst enemy, as we periodically interfere with our own systems through less-than-optimal equipment operation and procedures. An example that illustrates the gravity of EMI on one area of telecommunications is ultra-high-frequency (UHF) satellite communications. There are a total of 358 UHF satellite channels (i.e., sets of frequencies) available globally for use by DoD. While that number may seem large, these channels satisfy less than 44 percent of our validated requirements for this particular medium.

Imagine the impact on our ability to communicate when just one channel experiences EMI. When a channel becomes degraded or unusable due to EMI, we are many times faced with a domino effect as we attempt to find an alternate channel, usually in vain. When we do find another channel, it's at the cost of pre-empting a lower priority requirement. The fact of the matter is that on any given day as many as 20 UHF channels are degraded or completely unusable worldwide due to varying degrees and types of EMI.

There's a weakness lurking in the shadow of our EMI mitigation and resolution posture. While parts of individual service organizations work some aspects of EMI to varying degrees, these fragmented efforts are for the most part autonomous and narrowly focused with no centralized, upper-level management and oversight. In spite of this, a lot of good people are making valiant attempts to work EMI issues in their respective areas. Overall, though, we're fighting an extremely frustrating battle with rare, and then, only short-term success.

We don't have an effective means to swiftly combat and overcome EMI—detection and characterization of offending signals. Reporting and tracking of incidents, geographical location and identification of sources, and resolution are all essential phases in working an EMI event. Mitigation is also a very important part of the process. Furthermore, growing competition for portions of the frequency spectrum and equipment limitations make our ability to operate through EMI increasingly problematic. Critical actions that would enable us to improve this particular area of readiness include:

•Raise the importance of EMI mitigation and resolution to a level equal to that of our necessity to be able to navigate, communicate, and protect our forces. EMI mitigation and resolution should be bedrock to our requirements advocacy, system planning and development, and command, control, and communications architecture.

•Establish EMI resolution centers that are capable of providing near real-time geographical-location, data-analysis and correlation, and other services around the clock to all users. No core infrastructure is currently readily available to mainstream DoD units. This is not to advocate an entirely new organization, necessarily, as much as a new functional capability at existing facilities.

•Empower and staff a centralized organization with the authority, expertise, and resources to dynamically enforce and manage the EMI program.

•Realign existing signal characterization and geographical-location capabilities, and make them easily accessible to mainstream users. This could represent an expanded mission role for those entities that currently perform any of these functions.

•Revitalize the EMI Resolution Program. After much interest from multiple sources, the Joint Spectrum Center is reworking the structure and content of the Joint Spectrum Interference Resolution Procedures (CJCSM 3320.02), which should prove a very significant step toward improving the overall program.

By increasing widespread awareness and garnering upper-level support, our collective attitude toward EMI will improve giving rise to a much more effective EMI mechanism within the DoD. Our capacity for EMI mitigation and resolution is a very critical issue, basic to the successful accomplishment of the DoD mission. Whether this serves as an epiphany, confirmation of something you already know, or a point of contention, we simply cannot ignore how EMI regularly affects our operations with potentially crippling possibilities.

CWO4 Todd Conley is a career communicator with over 25 years of experience in numerous aspects of military telecommunications. He currently serves as the Military Satellite Communications Officer at Naval Space Command Headquarters in Dahlgren, Virginia where he heads the EMI Program.

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