The sensitivity of a radio is the minimum signal level at the input port required to demodulate and decode a signal.
Wi-Fi Receiver Sensitivity is specified in dBm and varies between -82 dBm and -48 dBm.
Wi-Fi Sensitivity Requirements
The table below from the 802.11 ac standard shows sensitivity as a function of modulation and bandwidth
The simplest modulation BPSK with the narrowest bandwidth of 20 MHz has a minimum Sensitivity of -82 dBm.
Contrast that with the most complex modulation format 256 with 160 MHz of bandwidth. In this case the minimum sensitivity is -48 dBm.
256-QAM provides a higher data rate than BPSK. The higher sensitivity requirement (-48 dBm vs -82 dBm) means the Wi-Fi client (laptop) will have to be closer to the Access Point as expected.
To get a higher data rate, the RSSI has to be higher.
RSSI to Internet Speed
This can be seen in the table below for Wi-Fi speed measurements we made. Higher levels of RSSI translate to faster upload and download speeds.
| RSSI (dBm) | Download (Mbps) | Upload (Mbps) |
|---|---|---|
| -37 | 506 | 366 |
| -43 | 379 | 341 |
| -49 | 348 | 231 |
| -51 | 341 | 208 |
| -59 | 220 | 109 |
| -66 | 81 | 126 |
| -69 | 135 | 107 |
| -72 | 44 | 61 |
| -73 | 39 | 38 |