With the increasing use of wireless devices, Radio Frequency spectrum has become a valuable resource. Also due to its unseen nature, conflicts of devices can be a problem for many to troubleshoot. This issue starts with the fact that there is a limited amount of frequency space available.

Image

Pretty much all available frequency space is allocated to something. Sometimes frequencies can be reallocated by using new technology to fit a given data stream in a smaller portion of the frequency space. Also higher frequency equipment (Microwave) is being developed, but with the high frequency is also a higher signal loss. Still, there is only a limited number of frequencies for a given area.

For many devices the work around is to operate them with low power, so the signal only goes a limited range. This allows other low power devices to be operated in an adjacent area. This is the principle that Cell phones and Wifi (Part 15) equipment operate on. The flaw can be when someone chooses to run more than the allotted power, or purchase equipment from out of country that is not complaint with US standards. In some cases this may result in better operation for them, at the expense of everyone else.

Radio Frequency Interference, or RFI can present itself in the form of reduced range, slower speeds for data links, dropped packets, distorted phone calls, or unreliable connections. The remedy for it would depend on the actual cause.

Much of the equipment associated with computer systems operates in either 2.4Ghz or 5Ghz bands. The trouble is that there is a lot of equipment in that space. Microwave ovens are also operating 2.4Ghz, as are cordless phones, wireless keyboards and mouse, Bluetooth and other people’s WiFi nodes. There is also an Amateur Radio allocation, which could mean something such as a television transmitter running in the area on top of your signal. By the rules assigned for the computer equipment (previously mentioned part 15) these devices must not cause, and must accept any interference. So if you interfere with a licensed service, you must stop, if they interfere with you, you are stuck with the situation.

In many cases the source of interference can be right in the office. In addition to those previously mention, we have also seen a USB 3.0 port interfere with the transponder (2.4Ghz) plugged in to it for the wireless keyboard. People setting up multiple wireless access points often set them for the same channel, or an overlapping one. Despite there being numerous channels available on the devices, many of them do overlap, and can interfere with each other. Putting more access points in to a situation like that can make things worse instead of better.

Other devices can be subject to RFI as well. Two way radios are used in some businesses and agencies to communicate, especially in emergencies. Problems can be caused though by equipment that is not properly set up, being used in areas it was not licensed and certified for, or being of poor quality. Since frequency space is a finite research, coordination of what is using it is critical. There is especially some Chinese equipment in use, which will put out extraneous signals outside of where they are supposed to be operating.

Recently, a Bitcoin miner caused interference issues with 700 MHz cellular frequencies

Steps to reduce Radio Frequency Interference -RFI

  •  Make sure devices is close proximity operate on different, non overlapping frequencies, or preferably different bands. 
  • Place the device close to the area to be covered. 
  • Most WiFi access points have multiple antennas. They should be oriented in different directions to take advantage of reflected signals. 
  • Do not place too many wireless devices in a given area
  • Scan for other devices in the same frequency space. Change channels to avoid them as much as possible. 
  • Use quality equipment. Well constructed receivers are less susceptible to Interference 

 

 

Interference Image courtesy https://www.flickr.com/photos/mikebabcock/