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Outdoor RSSI and Acceptable Signal Strength

RSSI stands for Received Signal Strength Indicator. It is an estimated measure of power level that a RF client device is receiving from an access point or router.

At larger distances, the signal gets weaker and the wireless data rates get slower, leading to a lower overall data throughput. Signal is measured by the receive signal strength indicator (RSSI), which in most cases indicates how well a particular radio can hear the remote connected client radios. For point-to-(multi)point applications, the optimal RSSI on each end of the wireless link is between -48 dBm and -65 dBm to achieve the highest possible data rates.

  • The best practice is to pre-configure the radios with a transmit power of 15 dBm and validate that a link is properly established (which serves to validate security and MAC address settings as well). Once the access points are physically mounted in place, look at the RSSI readings on each radio and adjust the transmit power settings on each side of the link up or down to get the RSSI to within the -48 dBm to -65 dBm range.
  • If the signal strength is greater than -35 dBm (typical for wireless links under 50 feet), then the electronic amplifiers get saturated because the signal is too strong, which degrades throughput performance. In such scenarios, turning down the power to minimum (11 dBm) may be insufficient, and if so we recommend purposely misaligning the antennas.
  • If the signal strength is less than -75 dBm (typical for very long distance shots over 4 miles), it may be difficult to sustain a link reliably or to achieve high throughputs, especially in the presence of external interference. For long distance shots, EnGenius recommends using laser tooling to optimize the antenna alignment so as to maximize the signal.

Desired RSSI:    -40 dBm to -50 dBm
Usable RSSI:    -35 dBm to -70 dBm
Above -35 dBm: Signal is too strong, saturated amplifiers
Below -70 dBm: Signal is too weak, subject to external interference

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