Link Efficiency

Hi All,

I'm having troubles with one of my SMs; the  SNR is flectuating between 22 and 12 and when it's at 12 

a link test gives the following 

Downlink Rate: 7120896 bps (7.12 Mbps)
Uplink Rate: 3391488 bps (3.39 Mbps)
Aggregate Rate: 10512384 bps (10.51 Mbps,  853 pps)
      Pkt Xmt (Act/Exp): 552/0 (276 pps)
      Pkt Rcv (Act/Exp): 1154/0 (577 pps)

      Downlink Efficiency: 99 Percent
            Downlink Index (Act/Max): 99/100
            Frag Count (Act/Exp): 27833/27816
            Signal to Noise Ratio: 12 dB

      Uplink Efficiency: 51 Percent
            Uplink Index (Act/Max): 51/100
            Frag Count (Act/Exp): 25615/13248
            Signal to Noise Ratio: 0 dB

what could explain a downlink efficiency of 99% and uplink effeciency of 51% ?

Thanks for your help



Hi Mehdi,

Did you run the spectrum analysis tool.   I believe that there is a high level of interference there.

Hi Mohamed,

Please see attached the spectrum analysis results




Hi Mehdi,

To get an accurate spectrum analysis you have to power-off your AP and start the scam from SM side.

Then chose the clearere channel as the operating carrier frequncy.

Do not forget to change the carrier frequency for all operating SMs.

With the later firmware versions, doing a timed spectrum from the AP will also cause the SMs to do spectrums while the AP isn't broadcasting, so you can get spectrums for an entire sector in one go.  In this case, the spectrum from the AP side is where you need to look.

OFDM equipment is very finicky about alignment.  If the usual methods of aligning an AM don't work, you may have to use 5 second link capacities in between small adjustments until you get the best spot.  Metrics like RSSI and S/N can lie to you, capacity is ultimately what matters.

I also find that vertical alignment can be a big deal when dealing with uplink issues.  A little bit of vertical uptilt can make a huge difference.