Signal attenuations and quality of experience

Various environmental factors can degrade Wi-Fi performance. The factors that affect Wi-Fi signal attenuation include absorption, reflection, diffraction and multipath:

  • Absorption is a physical phenomenon in which radio waves are blocked by some material. Highly absorbent materials for Wi-Fi signals include concrete and brick. If a building contains a large amount of these materials, it is very important to take into account the effects of signal absorption.
  • Diffraction is a phenomenon in which a signal passes through a material and becomes weaker or more muddle. A wide variety of materials can cause diffraction.
  • Reflection is when a signal bounces off a surface. Reflective materials include glass, whiteboards, and plastic.
  • Multipath can cause problems with Wi-Fi performance. This happens when the client device is being bombarded with various signals, including reflected and diffracted signals.

The most spread signal strength indicator for WiFi is RSSI (Received Signal Strength Indicator) measured in dBms. RSSI depends on the distance between AP (Access Point - router) and STA (Station - client) and radio propagation issues.

Quality of experience in dependence on RSSI

RSSI directly influences bit rate: with increasing of RSSI bit rate also grows and therefore user loyalty becomes higher (and vice versa). The signal strength also relates to coverage.

Example of RSSI distribution

If there are too many devices with low RSSI, this means that placement of routers planning is needed!

In our Support Portal RSSI values are recalculated from dBm to percentages to represent relation with connection quality:

TODO

TR-069 or TR-369 protocols can be used to obtain the information required for analysis (Device.WiFi.AccessPoint.{i}.AssociatedDevice.{i} field). The list of necessary parameters is shown in the table below.

The required for analysis TR-069/TR-369 parameters
NameTypeDescription
MACAddressstring­(17)The MAC address of the associated device.
SignalStrengthint­[-200:0]An indicator of radio signal strength of the uplink from the associated device to the access point, measured in dBm, as an average of the last 100 packets received from the device.

Note, that SignalStrength parameter can be missed in some CWMP data models (e.g. in tr-098-1-8-0) and then some vendor specific parameters can play its role (examples: internetGatewayDevice.LANDevice.1.WLANConfiguration.1.AssociatedDevice.1.X_HW_RSSI InternetGatewayDevice.LANDevice.1.WLANConfiguration.1.AssociatedDevice.1.X_MGTS_RSSI ).