Session counts incrementing, no re-regs

I’ve recently turned up a new site consisting of (3) 5750APs synced using a LMG CTM. All modules are P10 running 9.4. The noise floor at this tower site is about -78. Customers on these APs are having their sessions reset once or twice a day. There seem to be no other performance problems. SMs stay in 2x mode, received power at AP for all SMs is in the mid -60’s, jitter is at 4-10. Received power at SMs is around -50. Linktests are 99/98. The session count for all SMs keep incrementing. Re-reg counts do not increment. APs have matching maxrange, control slots, downlink percentage. 25 MHz channel separation between APs.

There are two SMs on this site right now, both are within 1/2 mile of the tower. Here are stats from one of the SMs:

Transmit Unicast Data Count : 4046513
Transmit Broadcast Data Count : 27
Receive Unicast Data Count : 5673772
Receive Broadcast Data Count : 1319143
Transmit Control Count : 38
Receive Control Count : 38
In Sync Count : 305
Out of Sync Count : 286
Overrun Count : 7451


Your problem is most likely sync… when the sync pulse shifts, this causes the sm to register using the new timming pulse without triggering a re-reg.

The last mile gear CTM emulates sync when it losses GPS… but the clock on the device shifts off very quickly (unlike the claimed 24hrs)… if the GPS is lost for about a min, it will start causing the sm’s to re-register just like what you were describing.

Hmm. I don’t see any messages in the CTM log about loss of GPS sync since the site was being set up. Also nothing in the AP logs regarding GPS after they get their first sync pulse upon booting. Are there any other statistics I can look at that would point to a sync issue?

not really… some versions of the CTM had firmware on it that would fill up then show nothing when it loss sync… not sure if this is the case here?

You could try putting more separation between the AP’s… something around 40mhz if possible then set all 3 to generate sync… see if this helps. If it does, this would point to sync issue.

The CTM is at the latest firmware version (211.02) and shows GPS loss if the GPS antenna is disconnected- so I think we’re good there.

One AP has no customers on it, so I will shut it off and have the other two APs (at opposite ends of the spectrum) generate sync and see what happens. Seems like even with a ton of freq. separation, this is a recipe for receiver overload, though.

Update: After changing some settings on the problematic AP last night, it appears that the AP itself is bad. The higher the frequency is set on the AP, the worse the received power at the SM is. At 5735 MHz, the SM sees the AP at -50 dBm. At 5840, the AP shows up at -77. Spectrum is clean according the built in spec-ans at both the AP and SM.

The AP is being changed out tomorrow, hopefully that will resolve the problem.

One SM (on the seemingly defective AP) has its session reset every few hours, the other (on a different AP) once every day or two.

Is the AP shooting across water or a metal roof or some other RF reflective surface?

We had an AP shooting across a small lake and the higher the frequency the worse the connections were. wasn’t much we could do except put some of the SMs in dishes even tho they were only 1-2 miles away. the dish narrowed the beam enough that the water surface didn’t create a multi-path issue any more.

Okay, there were two problems here. First- bad CMM. Replaced it and sessions stay stable. Second- multipath. Will be moving one of the SMs to fix this.

Registrations increments after an SM has been disconnected >5 minutes (session timeout).

Re-Reg increments when the SM disconnects and reconnects in the same session <5min.