When we talk about reallocating spectrum assignments from the Defense Department for public use, it is easy to think that as long as key systems are protected, other frequency losses are really just inconveniences. For example, if I own radio frequencies for a six-channel radio and two RF channels are reallocated, that means I still have four channels available. In normal operations it may be true that the military can get by with reduced spectrum access, but when discussing training and readiness, reduced spectrum access can degrade our ability to train as we fight.
For example, when the 1755-1850 MHz band was identified for reallocation in 2000 to meet the growing demand from the commercial wireless industry, the DoD assessed the impact to a number of its systems. One of them was the Air Combat Training System which includes aircraft-mounted pods that transmit and receive telemetry information to provide real-time tactical training. They can be used for air-to-air, air-to-ground, and electronic warfare training with multiple combat participants. If the band were fully relocated, realistic training with the ability to replay events, watch and learn would be lost unless and until alternatives could be put in place.
If only part of the targeted band were lost, there would still be an impact: the number of aircraft able to participate simultaneously in the training would be reduced because each aircraft needs its own separate telemetry channel. This would impact the ability to train for multiple aircraft missions. Thus, even reducing access to only a part of the spectrum is not just an inconvenience; it can have significant adverse effects to certain types of training.
The impact to training becomes an important consideration to address as we view potential spectrum reduction. National priorities of spectrum assets have shifted from military use of spectrum in CONUS to providing commercial access for applications such as broadband. It seems the demand for spectrum from the public and the desire to provide spectrum by commercial entities is growing every year. Thus, it is likely that spectrum availability for the military, and especially military training, will be reduced. Can we change the model from vacating spectrum to another option? Is a paradigm shift possible? Here are some steps that may help ensure training is not degraded.
First and foremost, we must develop an accurate assessment of the effect on training and readiness so the consequences of lost spectrum are fully understood. We must first understand the level of impact before we can attempt to minimize the extent of the problem (i.e., spectral reallocation would be fought against in bands that have been identified as having an adverse impact on training.)
Can we quantify the effects of lost spectrum? How does less training express itself in effectiveness of operations? How does less training express itself in susceptibility to adversary attack? Some potential measures of effectiveness are:
- The time needed for training changes; and
- cost in training changes (e.g., training at multiple versus single location).
Second, when spectrum is targeted for reallocation, we must identify ways to still access it under certain circumstances. This implies agreeing to a sharing strategy with the public. This can be done either by schedule (time slots for use) or by regional separation (setting up areas that are exclusion zones). This coordination paradigm brings several issues to light:
- Can the government rent frequency back? This may not be as easy as it should be.
Can a frequency map be made of a region so the DoD knows where sparse spectrum areas exist?
- Can we treat spectrum as a maneuver space, in terms of power, bandwidth, frequency, time, location and altitude, for example, as in dynamic spectrum management and electromagnetic maneuver warfare?
- Can government restrict the commercial user to build to certain standards (e.g., a dual frequency option on equipment) in return for purchase of spectrum? In this option, the commercial entity would use one frequency band but could switch to another one temporarily so the DoD could use the primary frequency.
- Is military range geometry optimized to minimize spillover into commercial areas? Are the training ranges using terrain masking to contain RF transmissions within the training range?
Other solutions:
- Equipment improvements, like surgical jammers, are really a next generation solution.
- Using sea-based assets for training involving spectrum.
- Establish a spectrum reservation for training. This proposal would consolidate numerous small training facilities into a single large training area that was unfettered. Naval Surface Warfare Center (NSWC) proposed this a few years ago.
When the options outlined above cannot be realized, I suggest that the training functions be moved from the targeted spectrum to an allowed RF band and try to replicate the training.
Finally, as a last fallback, use simulators to mimic the training as closely as possible.
Stephen Munchak is a research scientist for the Center for Naval Analyses.