Link Margin (also known as Fade Margin) is the difference between the received signal power and the minimum signal level required for the receiver to demodulate a signal.
The received signal power (PRx) can be estimated from the Link Budget analysis.
Enter the numbers for each (in dBm) below and the tool will provide the Link Margin in dB.
Link Margin = Received Signal Power – Receiver Sensitivity
In a Wi-Fi system, the receiver sensitivity for 256-QAM and 20 MHz bandwidth is -57 dBm.
For a received signal power of -40 dBm, the Link Margin is 17 dB.
Link or Fade margin provides an estimate of how much signal attenuation can be tolerated before the wireless communication link fails. In addition to Free space path loss, the signal can be attenuated due to multipath propagation and shadowing.
Typically the effects of fading are countered with the use of
- Antenna diversity
- Coding schemes
- Error correction
- Receiver design
The higher the value of the fade margin, the more resilient a wireless communication link will be.
How much fade margin is required?
In general, at least 10 dB of fade/link margin is required in a wireless communication system. A good number to design for is 30 dB.
 Fade Margin
 Signal Fading on Wikipedia
 IEEE Std 802.11-2020 IEEE Standard for Information Technology – Telecommunications and Information Exchange between Systems – Local and Metropolitan Area Networks – Specific Requirements – Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications.