Incorrect RSSI values at AP force 2000 VS what the CPE actually reads

We are running several force 2000 units one with 3.0 and one with 3.1 both exhibit this issue.

We log into the AP force 2000 Ver 3.1 and have it say on channel 5835. We look at the RSSI of the clients connected and they are showing unbeleavable RSSI some in the range of -35 we log into the CPE's and the ones showing -35 at the AP are actually more like -65 at the CPE which is more believable. We switch channels to something else like 5235 or 5770 and the RSSI at the AP shows more correct.

Whats going on?

I have the same issue with 3.0 + software.  I had a post about it a while ago but I didn't press the issue.

Post is HERE although there is not much information in it.

bummer I wonder if they know about it and will fix it but when your trying to look at signals and you went from say -70 on the ap to a -40 your thinking WOW this Epmp 2000 is WAY better then I expected almost like false advertisement...

I knew it was to good to be true thats why I logged into the CPE to confirm I wonder why its only on certain channels?

Hi Matt, 

As explained in the post you referenced (as well as the AP GUI information bubble on this field), the DL RSSI displayed on the AP is an estimated measure. The DL RSSI reported on the SM/CPE is accurate. 

We have to make an enhancement where the SM/CPE sends the accurate DL RSSI measurement to the AP via a management message. That mechanism is not in place at this time. 

Thanks,

Sriram


@accelwireless wrote:

bummer I wonder if they know about it and will fix it but when your trying to look at signals and you went from say -70 on the ap to a -40 your thinking WOW this Epmp 2000 is WAY better then I expected almost like false advertisement...

I knew it was to good to be true thats why I logged into the CPE to confirm I wonder why its only on certain channels?


We in no way intend to do any false advertisement. I'm sorry it it appears that way. If you are running the latest firmware, 3.1 or 3.2, we say right on the AP's GUI that this DL RSSI measurement displayed on the AP is an estimated measurement (click the blue information bubble). 

The difference in measurements on different channels could be because the AP sees a different noise floor on each channel. The DL RSSI measurement displayed by the AP is a measurement based on its own noise floor (not the SM/CPE's noise floor). 

Hope this helps. 

Thanks,
Sriram

Not saying EPMP is trying to pull one over on anyone I meant it as  false advertising just in general its relaying false info back to us from the AP.

I would think this would be an important thing to address as this is what we go by when looking at problems or choosing a good channel. We do use the spectrum tool too but when you look at RSSI values in -60 or below you dont expect to have issues due to noise like we have experienced before then we log into the CPE and notice hey its not -60 ts -80 or so.

So its a HUGE guage as to how the CPE are performing at a glance. I mean who wants to log into 30-70 CPE to see signals when you can go to the AP and at a glance view a general idea of what CPE are doing. Its a HUGE timesaver.

That's fair. Like I mentioned before, this is something that has been pending implementation where the SMs send thier DL measurements to the AP.  I'll discuss with the team again on this and see if we can get this in a near future release. 

Thanks,

Sriram

Thanks Sri,

I should have stated that I notcied this on firmware 3.0.1.  I have not upgraded any of our radios to 3.1 or 3.2 so I was not aware of the bubble.

Yes something has changed in the firmware to make this issue worse or broke it all together. Before when we had the Epmp 1000 we were almost perfect from what the AP and CPE rssi were for downlinnk no matter which unit you logged into.

Now with Force 2000 and the "better recieve" capability we see HUGE increases in signal but in the end its false because the actual RSSI from the AP to the CPE is 10-15 dB worse than what it shows in the AP.

Just now troubleshooting a customer who at the AP this is what he has for signal -65 / -68 and us thinking he has been okay for some time now when in reality its been very low.

Log into his radio it is

STA DL RSSI
-75 dBm
 
Throughput has gone significantly way down since installing the force 2000 at the tower so now I need to figure out do we ditch these units until we get firmware that is showing correct values and or better throughput and put back the AP-1000. Seems since this is getting / guessing the RSSI from the CPE is affecting throughput as well, I can only assume the AP is trying to switch to a higher MCS then the CPE can handle and thus creating issues with speed?
 
Please enlighten us on how this works becuase if the numbers dont match that cant be a good thing.

Thanks

@accelwireless wrote:

Yes something has changed in the firmware to make this issue worse or broke it all together. Before when we had the Epmp 1000 we were almost perfect from what the AP and CPE rssi were for downlinnk no matter which unit you logged into.

Now with Force 2000 and the "better recieve" capability we see HUGE increases in signal but in the end its false because the actual RSSI from the AP to the CPE is 10-15 dB worse than what it shows in the AP.

Just now troubleshooting a customer who at the AP this is what he has for signal -65 / -68 and us thinking he has been okay for some time now when in reality its been very low.

Log into his radio it is

STA DL RSSI
-75 dBm
 
Throughput has gone significantly way down since installing the force 2000 at the tower so now I need to figure out do we ditch these units until we get firmware that is showing correct values and or better throughput and put back the AP-1000. Seems since this is getting / guessing the RSSI from the CPE is affecting throughput as well, I can only assume the AP is trying to switch to a higher MCS then the CPE can handle and thus creating issues with speed?
 
Please enlighten us on how this works becuase if the numbers dont match that cant be a good thing.

Thanks

Hi, 

If the issue is mismatch in DL RSSI being reported between the CPE and AP, I have already explained why that is the case. Maybe I misunderstood your question and you can expand on it a little bit?

As far as ePMP 2000 is concerned, is the issue that the DL RSSI has gone down or has not changed since you swapped from the ePMP 1000? Once again compare the RSSI on the SM/CPE. It may be the case that even with ePMP 1000, the SM/CPE was reporting -75 but you were looking at the AP reported DL RSSI. 

Are you using the same sector antenna you used with the ePMP 1000 or are you using the new sector antenna recommended with the ePMP 2000? If using the new antenna, remember that it comes with 2 degrees electrical down tilt and has 2 dBi additional gain. Hence you will have to adjust it 2 degrees mechanically compared to the old sector antenna. With proper adjustments, you should see 1-2 dB improvement in DL RSSI at the SM/CPEs with the new antenna. If you are using the existing antenna, then no improvement is expected. 

The AP does not switch MCS based on guessing the RSSI. The AP switches MCS based primarily on PER (Packet Error Rate) and a few other paramters to a lesser extent and arives at the most optimal MCS for that link. So no, the fact that there is a mimatch of the DL RSSI reported on the AP vs. the CPE does not matter with MCS selection. 

Have you tried contacting our support engineers at support@cambiumnetworks.com? If not it may be worth a call OR PM me a number I can reach you at so one of our engineers can call you directly and help troubleshoot the ePMP 2000 issues you are having. 

Thanks,

Sriram

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