A Perspective On802.11 WiFi RF Spectrum Analysis
On-Site RF Spectrum Analysis Services For Noise and Interference IdentificationAlthough RF Spectrum Analysis services that were offered through Connect802 Corporation prior to 2020 are no longer availablewe felt it was valuable to leave this information on-line as a reference. Please contact Maui Communications Networks if you have any questions.
What is "RF Spectrum Analysis" and why is it important?
802.11 WiFi signals, like any radio frequency transmission, consist of energy that is propagating outwards from the transmitter at the speed of light. Each transmitter operates in a narrow range of frequencies known as a "channel" and a transmission is accessible only to other devices operating on the same channel. RF spectrum analysis is the process by which an engineer uses a tool (an RF spectrum analyzer) which displays a representation of the electromagnetic behavior in a variety of formats. RF spectrum analysis is the task whereby an engineer analyzes and evaluates the data presented by the RF spectrum analyzer and draws conclusions regarding the characteristics of the signals, their quality, and their usability for 802.11 WiFi data transmission. If there are issues "in the air" then user's data as well as 802.11 control and management data is going to be corrupted or lost during transmission.
What types of problems can be identified during an 802.11 WiFi RF Spectrum Analysis engagement?
WiFi 802.11 Wireless LAN spectrum analysis discloses issues related to noise, interference, channel utilization, signal quality, and other aspects of the electromagnetic RF signals being transmitted. The quality and characteristics of the RF signals directly impacts an 802.11 device's ability to successfully and optimally transmit data.
An RF spectrum analyzer displays basic signal metrics like signal strength and the channels in use but those measurements are available from any number of other alternative WLAN design and analysis tools (like the ones used to perform a WiFi Site Survey and create a coverage heatmap). The RF spectrum analyzer, through its visual depiction of electromagnetic energy, goes far beyond simple metrics to provide an in-depth picture of what's happening in the air. Some of the RF signal transmission characteristics that an RF engineer can observe with the spectrum analyzer relate to the following:
- The Spectral Signature: Each 802.11 transmission consists of a pattern of electromagnetic signals referred to as the "spectral signature" of the transmission. There are various patterns used to vary (modulate) an electromagnetic transmission to represent data bits. More intricate and complex modulation patterns provide higher bit rates but, because of their intricacy, they are more easily corrupted by environmental noise. When an 802.11 device is unable to receive acknowledgements at a high bit rate they drop to a lower bit rate with a less intricate modulation pattern. By evaluating the spectral signature on each WiFi channel an RF engineer can evaluate whether or not excessive data corruption is expected as a result of an environmental noise or interference source.
- Non-WiFi Coherent Intentional Radiators (Interference): A "coherent" transmitter is one that is sending a signal that represents something meaningful. An "intentional radiator" is a device that is implemented for the purpose of transmitting something. Bluetooth, 802.22 WiMAX, some baby monitors, and some security systems are examples of devices that are coherent, intentional radiators but they aren't 802.11 WiFi. These radiators do not adhere to the 802.11 rules for accessing the medium (transmitting into the air). Consequently, non-WiFi coherent intentional radiators may "walk on top of" and corrupt a WiFi transmission. Each of these has its own unique spectral signature (signal pattern) and an RF engineer can isolate and describe their presence and gauge the degree to which WiFi performance degradation may occur.
- Incoherent Radiators (Noise): An "incoherent radiator" is sending out RF signal energy but there is no data encoded in it. Airport and shipboard radar are common examples of intentional incoherent radiators (found in the 5 GHz WiFi bands) and microwave ovens are unintentional incoherent radiators that create noise in the 2.4 GHz WiFi band. Incoherent radiators have unique spectral signatures that can be identified by an RF engineer so that appropriate steps can be taken to mitigate the impact on the 802.11 WiFi network system.
- Background Noise: The RF spectrum analyzer allows an RF engineer to observe the level of background noise present in an environment. This is random noise caused by the electromagnetic world (and galaxy!) around us. Background noise may include electromagnetic energy from fluorescent lights, industrial motors, and photovoltaic rooftop panels. An RF engineer can quantify the levels of background noise in an environment to confirm that they are normal and unremarkable.
On-Site 802.11 RF Spectrum Analysis Service Descriptions
List of Services
-
Standard Channel and Noise AssessmentList Item 3
Using an RF spectrum analyzer, a walk-through of the site is performed to isolate and describe normal, unusual, and problematic characteristics related to noise or interference.
Noise and interference are called out and described with particular attention to Bluetooth and microwave oven interference in the 2.4 GHz WiFi band and airport or shipboard radar that would require the configuratoin of channel restrictions in the 5 GHz band.
This is the RF spectrum analysis service associated with on-site troubleshooting of RF-related problems. Normal behavior is generalized and only abnormal or significant types of conditions are called out in the deliverable report.
-
Expanded RF Spectrum AnalysisList Item 1
A complete site walk is performed and the RF spectrum is evaluated in real-time. A representative example of the normal RF spectrum along with detailed presentations of any significant spectrum events (noise, interference, etc.) are provided in the deliverable report. In addition to the overall site walk, spectrum analysis measurements are made at key locations at the site where noise or interference problems are most likely to be critical. Noise or interference sources are identified, photographed, and their RF characteristics are measured and detailed in the delivered report. Normal RF characteristics are documented and each specific noise or interference source is individually called out and documented. Microwave ovens may be powered on and an assessment is made regarding the degree of 2.4 GHz noise/leakage visible from the oven.
This is the 802.11 RF Spectrum Analysis service called for when an in-depth RF analysis is required, when focusing on an RF-related troubleshooting issue, or when evaluating a critical WiFi infrastructure such as might be found in a hospital (for wireless medical telemetry or medical robots).
-
Wireless Medical Telemetry (WMTS) Spectrum AnalysisList Item 2
In addition to providing engineering services for 802.11-based patient medical telemetry, Connect802 has one of very few RF engineering teams that is experienced with troubleshooting and analyzing the older 608-614 MHz Wireless Medical Telemetry (WMTS) systems still used for patient monitoring in many hospitals and medical facilities today.
When WMTS patient telemetry monitors disconnect, we've identified problems ranging from nearby Channel 36 UHF television transmitters (now obsolete) to faulty power supplies in portable ultrasound equipment interferring with the WMTS telemetry monitors, and even a faulty fire alarm alert siren. We know how to isolate problems between the WMTS A- and B-antenna systems as well as through coax splitters in the Wireless Medical Telemetry antenna system.
For non-WiFi WMTS Wireless Medical Telemetry System patient monitor consulting engagements we use a sophisticated Anritsu spectrum analyzer and provide an in-depth report of the findings.
Talk To The Experts At Connect802 When You Need On-Site Resources To Perform:
- Office Building RF Spectrum Analysis and Wireless Interference Troubleshooting Services
- Apartment Complex RF Spectrum Analysis and Wireless Interference Troubleshooting Services
- Hospital RF Spectrum Analysis and Wireless Interference Troubleshooting Services
- Research Lab RF Spectrum Analysis and Wireless Interference Troubleshooting Services
- Hospitality RF Spectrum Analysis and Wireless Interference Troubleshooting Services
- Resort RF Spectrum Analysis and Wireless Interference Troubleshooting Services
- Hotel RF Spectrum Analysis and Wireless Interference Troubleshooting Services
- Automotive Car Dealership RF Spectrum Analysis and Wireless Interference Troubleshooting Services
- Marina and Boat Yard RF Spectrum Analysis and Wireless Interference Troubleshooting Services
- Museum and Aquarium RF Spectrum Analysis and Wireless Interference Troubleshooting Services
- School and University RF Spectrum Analysis and Wireless Interference Troubleshooting Services
- Warehouse RF Spectrum Analysis and Wireless Interference Troubleshooting Services
- Military Base RF Spectrum Analysis and Wireless Interference Troubleshooting Services
- Outdoor RF Spectrum Analysis and Wireless Interference Troubleshooting Services
Perspective on RF Spectrum Analysis Services
When users complain that browsing is slow, they're dropping their WiFi connections, wireless dead zones are here and there in the building, or their voice-over-IP call quality is bad - this may be the time to bring in an RF spectrum analyzer and see what's happening with the wireless signals in the space.
"Spectrum Analysis" is the term applied to the use of RF spectrum analyzer software and hardware tools to measure, graphically represent, document, and report radio frequency (RF) related quantities in both the 802.11 WiFi frequency bands and other communication bands. Measurements and recording of quantities such as signal strength, signal energy density, channel utilization, noise and interference levels, Signal-to-Noise Ratio (SNR), Signal-to-Interference (SIR) measurement, digital and analog transmitters, and a number of esoteric metrics ("eigenvalues", "spectral signatures") may be evaluated during a spectrum analysis consulting engagement. Spectrum analysis software tools (WiSpy, AirMagnet SpectrumXT, etc.) perform operations in software with a dedicated hardware device (typically a USB adapter) used to capture signal energy from the air. Dedicated hardware spectrum analyzers (Agilent, etc.) offer more granularity of control of the captured signals as well as wider frequency ranges of operation. RF spectrum analysis uses the spectrum analyzer software or hardware tool to discover, locate, isolate, and describe noise, interference, and other characteristics of the RF spectrum.
RF Spectrum Analysis Services Consulting to Improve and Optimize Your 802.11 WiFi Wireless Network
To improve WiFi performance and identify sources of RF noise and interference a Connect802 engineer can conduct spectrum analysis, which is a method for visualizing the radio frequency in a surveyed area and determining the strength of a signal. In addition to measuring that strength, a spectrum analyzer can find interference that would negatively impact wireless performance.
WiFi spectrum analysis services are performed throughout the lifecycle of an 802.11n, 802.11ac, or 802.11ax WLAN wireless network. Prior to deployment, spectrum analysis finds interference that may affect a wireless deployment. Interference can be isolated and described and either remediated by being located and eliminated or design considerations can be introduced to mitigate the noise or interference. After deployment, spectrum analysis determines whether interference exists and engineers often use it for troubleshooting when a WLAN is performing poorly. Spectrum analysis can help optimize a WiFi network by finding the interfering transmitter or, at a minimum, isolating and describing the impact of a noise or interference source.
802.11n, 802.11ac, and 802.11ax WiFi wireless network noise and interference degrades and disrupts user connectivity in your wireless LAN. Your wireless network is most potentially being affected by wireless interference when the symptoms like these occur: intermittent connectivity or unexpected disconnections, delays in connection and data transfer, slow network speeds, random and seemingly unexplainable (but consistent) end-user complaints regarding wireless network performance.
What is the Noise Floor and how does Out-of-Band Interference impact a WiFi network?
For an RF WiFi transmitted signal to be heard and understood by a client device's receiver circuitry, it must be received with a signal strength that's strong enough to overcome the noise floor, or background RF noise and interference in the environment. If a received RF signal isn't significantly stronger than the noise floor, the receiver won't be able to separate it from the underlying noise and understand it. This is similar to when you can't understand what another person is saying in a noisy room. In the 2.4 GHz WiFi spectrum, the noise floor is typically between -98 dBm and -102 dBm. In the 5 GHz channel space, noise floors are generally slightly higher, averaging closer to -95 dBm. Every environment will have a slightly different noise floor depending on what electromagnetic influences are present. RF energy that arrives from a device that is not an intentional radiator (not designed to be a radio transmitter) such as HVAC equipment, large electric motors (like elevator motors or water pumps), heavy industrial equipment (including floor buffing machines and electric pressure washers), or even a mobile cellular hotspot. This is referred to as "Out-of-Band Interference". Out-of-band interference is often random in nature and isn't always constant. When a large electric motor turns on or off there's often a burst of electricity that causes a spike in background noise. Such events could result in noticeable problems in a WiFi network. Using an RF spectrum analyzer, a "waterfall display" depicts the signal across a frequency range with color indicating signal amplitude. Analysis using a waterfall display can bring random noise events into view and show the presence of a temporarily heightened noise floor cause by interference from an out-of-band transmitter.
