What’s in Your Spectrum?
2019-06-28 | 6 min read
Today’s world is brimming with wireless communications signals. Think of all the devices people have in their homes or even on their persons compared to 10 to 20 years ago. Those devices provide greatly increased functionality, such as the ability to send and receive data. They boast multiple antennas to support various wireless technologies, from closer-range Bluetooth through WiFi and cellular. As frequency bands grow increasingly crowded, however, it’s more likely that networks will suffer from interference or even communications failure. Spectrum must increasingly be monitored for three issues: elusive events undermining spectral security, increased interference resulting from crowded spectrum, and the potential for some wireless signals to cause harm.
Elusive Signal Events
Elusive signal events are particularly difficult to detect. For example, interferers may affect communications—especially clarity or audibility of sound—by creating noise or distortion. If the system and the interferer are on the same frequency, the two signals will be right on top of each other when looked at with a spectrum analyzer. Some signal events are elusive in a different way: They only occur occasionally, maybe once a month or year. Yet they still can cause major problems, depending on their frequency.
Pinpointing signals that occur very infrequently involves the use of monitoring systems that will run continuously—say, for a year—without user intervention. Because of the constant evolution of technology and consumer access to so many wireless solutions, it is not uncommon that a system runs with no issues for a period of time and then suddenly is negatively impacted by a new signal.
Mitigating Interference in a Crowded Spectrum
Risk mitigation in communications calls for preventing or isolating interference in a crowded spectrum. In a theme park or stadium, for example, police, staff, and medical professionals communicate by radio in case someone at the location needs help or another issue arises. Yet such environments are often filled with people using their own devices to make calls, post on social media, text, etc. The right interfering signal could take out those emergency communications.
To find the source of such interference, sensors perform RF monitoring in a perimeter around the area of concern, with software showing the data collected by each sensor. Given the band and other information, it is usually possible to tune for a specific frequency with a unique shape of “fingerprint.” Discovery of that fingerprint triggers geo-location, which leads to the emitter location. Another possible step involves using a handheld vector network analyzer in conjunction with a directional antenna.
Wireless Signals with Potential for Harm
Spectrum monitoring also can detect unwanted communications, which may often be used for questionable intentions. In a secure facility, for example, it may be advisable to monitor for communications going to the outside world via a cell phone or other devices. Drone detection currently generates a great deal of interest as well. As drones become cheaper, smaller, and more prevalent, they can be used for wonderful as well as malicious things, such as surveillance of a targeted location, bringing drugs across a border, or even dropping a substance onto a crowd or area. It is therefore critical to be able to locate both the drone and the controller.
The worst example of a signal used to do harm is as a bomb trigger or improvised explosive device (IED) mechanism. If a cell phone performs that step, a change has been made to the cell phone to connect the switch configured for this purpose. It could be possible to detect the cell-phone modification. However, it is very difficult to detect such things at this point. The best approach is to continuously monitor in search of anomalies.
Device makers and operators are increasingly concerned about unexpected issues like interference and their potential to affect communications. If an interfering signal appears, they want to be notified immediately. For this process to be effective, they must cover the spectrum as quickly as possible to make sure nothing is missed. With the signal environment growing more crowded and different threats emerging, spectrum monitoring only becomes more critical to safeguarding communications.
Learn how Keysight’s solutions can help you with your spectrum monitoring needs by clicking here. We also offer comprehensive tools for spectrum monitoring, interference analysis, signal identification, and geolocation.