B5-Lite Strangeness


#1

Sorry for the ominous topic, but I have no other way to describe it. I’ll start with the setup, then move into the strangeness.

We recently got a B5-Lite link kit for a 1.8km link from our existing tower to a fairgrounds building. Our link calculation software and Mimosa’s calculator indicated around -65dBm link and clear line of sight. This existing tower has fiber to the base, so all we have on the tower is 6x degree sectors powered by Cambium ePMP1000’s @ 100ft elevation utilizing GPS sync. the B5-Lite is mounted @ 50ft elevation; and is pointing in the same direction as our SouthEast 60 degree Cambium sector. The Cambium is running 5745Mhz @ 20Mhz channel width, so we decided to go with 5810Mhz @ 80mhz for the B5 Link initially to test.

Upon installing the B5Lite at the tower, everything went as expected, 5810 @ 80Mhz looked clear on the local analyzer, we could see our channel at 5745, but the B5 kept on suggesting to use this channel if we were to turn on “auto everything” which we did not. (strangeness #1)

I pointed the B5 as best I could (verified line of sight no problems) and went to the fairgrounds. The fairgrounds B5 saw similar spectrum readings as the tower, 5810 was clear. as soon as the B5 Link established; all my customers on the SE Cambium sector briefly stopped passing traffic. they did not disassociate with the AP, the AP did not record any issues, my ping/SNMP monitoring software simply couldn’t communicate with anyone off the SE sector for a brief time while the B5 Lite link established, once the B5 was connected everyone on the Cabium AP resumed traffic as normal. (strangeness #2)

it turns out that the noise levels in the B5 once the link was established was considerably higher than the spectrum analysis indicated before the link was established - I was getting 1db SNR and barely holding a steady link. I changed to other channels not overlapping with my Cambiums and tried 40Mhz channel width. At every channel the noise was considerably higher once the link established and I couldn’t get good SNR. I eventually went to a DFS channel - 5510@ 40mhz. due to power restrictions, my overall signal dropped to -77dBm, but I had a 10db SNR and a steady link that negotiates 180Mbps PHY in both TX/RX. (strangeness #3) **also every time the B5 link re-established link - the SE Cambium couldn’t pass traffic to its subscribers for a brief moment again - referencing strangeness #2.

I was the only one working this project, and had to point the B5 lites by myself one side at a time, I was able to peak in the fairgrounds side, but did not get back to peak in the tower side. I realize some of this could be related to a misaligned link, but all of it seems like a stretch. any ideas?


#2

These are my readings:
-59.7 dBm
PHY Tx/Rx (Mbps): 650 / 780
MAC Tx/Rx (Mbps): 390 / 468

Center Frequency 5450 MHz DFS
Channel Width 80 MHz
Tx Power 23 dBm
Link Length 4.2 km / 2.6 mi

Chain Tx Power (dBm) Rx Power (dBm) Rx Noise (dBm) SNR (dB) Center Freq. (MHz) Pol
1 20 -62.7 -86.4 24 5450 DFS H
2 20 -62.9 -86.4 24 5450 DFS V

I guess you have a problem there.


#3

Can you share Combined spectrum here to help you to choose right settings ?

Anyway I give you my actual settings:

-67.2 dBm
PHY Tx/Rx (Mbps): 260 / 390
MAC Tx/Rx (Mbps): 156 / 234

Center Frequency 5910 MHz
Channel Width 80 MHz
Tx Power 23 dBm
Link Length 755.0 m / 2477 ft

MIMO Status
Chain Tx Power (dBm) Rx Power (dBm) Rx Noise (dBm) SNR (dB) Center Freq. (MHz) Pol
1 20 -69.9 -85.4 16 5910 H
2 20 -70.2 -85.4 15 5910 V

Traffic Split: AUTO
TDMA Window: AUTO
Rate Adaption Criteria: PER
PHY Rate: Aggressive


#4

Your link is not alligned at all. RX Power should be 20dBm more than your current readings. Spend some time realligning or look for obstacles.


#5

Yes I know. This is why I have showed you that value. If in my case I have this real bandwidth, you should have a real better situation.


#6

OK, I think we are in agreement that the link needs some alignment. I think I may have mentioned that in the original post. so what about strangeness #2 about causing my other radio’s on other channel, in some cases 20+Mhz spacing - to stop passing traffic when the B5’s link up to each other, and #3 - the noise level difference between spectrum analyzer mode and linked up?? is Mimosa just really noisy or what??