RSSI

Received Signal Strength Indicator (RSSI) is an estimated measurement of how good a device can hear, detect and receive signals from any access point or from a specific router. A signal is indicated through RSSI. Most of the time, it measures how good a particular radio can hear other connected client’s radios. The good thing about RSSI is that it helps you determine and know if a signal is sufficient to establish a wireless connection.[1] When broadcasting to a larger distance, the signal becomes weaker and the bandwidth of the wireless data connection becomes slower. This leads to a weaker overall data output. This RSSI is usually invisible to the user of a receiving device but since the signal strength varies greatly and affects the function of a wireless connection, the devices sometimes make the measurement available to users. In a nutshell, RSSI is the most common name for a signal value, it refers to the strength that one device is hearing from another device.

Functionality

RSSI or this signal value is measured in decibels from 0 (zero) to -120 (minus 120). The closer the value to 0 (zero), the stronger the signal will be.[2] With this, the common spot for neighboring nodes is between -55 (minus 55) and -65 (minus 65). An RSSI of -55 (minus 55) is a stronger signal than -70 (minus 70). This RSSI can be found between the APs by clicking them in the map view and going through the neighbor’s tab.[3] If measured in negative numbers, a number that is closer to 0 usually means a better signal, a number that is -50 (minus 50) is a pretty good signal, a number of -70 (minus 70) is reasonable while a number that is -100 (minus 100) has no signal at all.[4] The number of neighbors must also be limited to a maximum of 5 because going beyond this range would cause problems with performance, most often caused by signal interferences. RSSI can also be used internally in a wireless networking card. This is to determine when the amount of radio energy in the channel is below a certain threshold. At which point, the network card is clear to send. If the card is already cleared to send, there is a packet of information that will be sent. The end user will be able to observe the RSSI value in measuring the signal strength of a wireless network through the use of a wireless monitoring tool such as Wireshark, kismet or insider. In order to measure the received signal strength at a specific location and time, you can use a Wi-Fi scanner application. If you are using a computer that is Mac OS X, you can get the RSSI even without installing any applications through the following:

  1. Press and hold the Alt key while clicking the Wi-Fi icon on the status menu.
  2. On the list of available networks, find the name of the network you are connected to and the connection information including RSSI will be displayed immediately below.

If you want to map the signal strength for the entire place, you can use the heat mapping tool instead of a Wi-Fi scanner. This tool helps you visualize the wireless coverage in different areas of your place.[5]

Signal Strength

The measurement of RSSI represents the relative quality of a signal that will be received on a device. RSSI indicates the power level that is being received after any possible loss at the antenna and cable level. Hence, the higher the value of RSSI, the stronger the signal is.

Signal Quality

This higher the number, the better the quality is. These are only theoretical numbers for ideal conditions but it also depends on the system and the device used which can be determined differently.[6]

Channel Width

If the channel is wider, normally it has a lower value of RSSI. With this, it is recommended to have the smaller channel widths in all but some special circumstances.

dBm

RSSI and dBm may have different units of measurement but both of them represent the same thing. They both represent the signal strength of a network. The difference between the two is that RSSI is a relative index while dBm is considered as an absolute number representing power levels in mW (milliwatts). Hence, the closer to 0dBm, the better the signal is.

Acceptable Signal Strengths

Signal Strength (dBm) Rating
-30 dBm Amazing
-67 dBm Very Good
-70 dBm Okay
-80 dBm Not Good
-90 dBm Unusable

There are numerous localization protocols in wireless sensor networks that are based on RSSI.[7] The reason for this is that absolute positioning is not always available. This is why localization based on RSSI is popularly used. Furthermore, there is no extra hardware that is needed unlike other alternatives.[8]

Common Issues

People may experience problems even when an acceptable signal strength already exists. If there is already a good signal strength based on the scanning app, then the problem may involve signal interference. While the Computer's built-in Wi-Fi system can enable users to identify a select type of interferences, a spectrum analysis tool may be required in some cases.[9]


  1. https://www.metageek.com/training/resources/understanding-rssi.html ↩︎

  2. https://community.cisco.com/t5/wireless-mobility-documents/snr-rssi-eirp-and-free-space-path-loss/ta-p/3128478 ↩︎

  3. https://help.cloudtrax.com/hc/en-us/articles/202211270-What-should-my-RSSI-levels-look-like- ↩︎

  4. https://www.netspotapp.com/what-is-rssi-level.html ↩︎

  5. https://eyesaas.com/wi-fi-signal-strength/ ↩︎

  6. https://www.netspotapp.com/what-is-rssi-level.html ↩︎

  7. https://www.metageek.com/training/resources/understanding-rssi.html ↩︎

  8. https://www.researchgate.net/publication/254028520_Is_RSSI_a_Good_Choice_for_Localization_in_Wireless_Sensor_Network ↩︎

  9. https://www.metageek.com/training/resources/understanding-rssi.html ↩︎