The main tower site in this setup has three BHM’s which are timed by a CMM Micro. The customer wishes to add a fourth location to the network, however this location does not have LOS to the tower with the existing Backhauls. But, the fourth location does have LOS to a different tower, and this tower does have LOS to the main tower.
So, we need to shoot from this fourth location to the middle-man tower, then from the middle-man tower to the main tower with the existing BHM’s. We would like to use (1) single frequency for this double-hop shot back to the main tower which should be possible due to the position of the customer location, and the shot from the middle-man tower to the main tower.
The backhaul at the customer’s fourth location will be a BHS, connected to a BHM at the middle-man tower. There will also be a BHS at the middle-man tower connected to a BHM at the main site. If we place a CMM Micro at the middle-man tower, the link from the customer’s fourth location to the middle-man tower will be timed using the CMM micro at the middle-man tower via the BHM, but the timing for the link from the middle-man tower to the main tower will be timed via the BHM at the main tower, and this sync will be passed on to the BHS at the middle-man tower.
If we want to use the same frequency for both shots, will the timing work properly? The timing for these 2 links will be coming from two different timing sources, correct?
The timing will be identical for all the BH-masters if they’re connect to CMMs with GPS timing. That’s why there’s a GPS receiver: to synchronize the timing between remote equipment.
Your intended configuration, however, will have problems because the middle BH-slave will be receiving when the co-located BH-master is transmitting. The units will likely de-sense each other. If you can separate the co-located units enough, you might get it to work reliably, but the configuration isn’t recommended.
If you want the new double-hop to use identical frequencies, use BHs in a different frequency band than your existing tower. Make the middle units both BH-masters and connect them to a CMM. The new BH-slave at the existing tower won’t cause problems because they’re differnet frequency bands.
If you want your described configuration to work, the second hop will need to be not just a different frequency, but a different frequency band. The 2nd-hop BH master at the middle tower can get its timing from the co-located BH-slave by connecting the timing ports. This eliminates the need for a CMM or physical separation on the middle tower. If, however, you or another carrier in the area are using other Canopy units on the same frequency band as the 2nd-hop BH pair, then you should still use a CMM at the middle tower.
If you want the new double-hop to use identical frequencies, use BHs in a different frequency band than your existing tower. Make the middle units both BH-masters and connect them to a CMM. The new BH-slave at the existing tower won't cause problems because they're differnet frequency bands.
I thought about this some more last night after I made the post and I was thinking exactly what you said above, but still using the same frequency band. If I make both of the units at the middle-tower Master's, connect them to a CMM, use the same frequency for both hops, and comply with the physical seperation rules, shouldn't that work? You mention that the BHS at the existing tower won't cause problems assuming that I use a different frequency band. If I use the same frequency band as the existing tower and make sure the BHS for this new location at the existing tower is properly seperated from the existing Master's, this should not cause any desensing, or am I wrong? Every Backhaul in this network have dishes on them.
Read section 12.5 on page 110 of the v6.1 User Guide: A co-located BH-slave and AP must be on different frequency bands; I imagine the same rule applies to co-located BH-slaves and BH-masters. The physical separation listed in the User Guide applies to co-locating BH-masters and APs.
When I mentioned physical separation, I was thinking about having the thickness of a building between them. I have a pair of co-located 5.2 APs (15’ horz, 0’ vert separation) operating reliably without a CMM or any type of timing cable. There is, however, a solid metal structure between them.
I’ve found that the Canopy design rules are generally conservative – for good reason – and can sometimes be stretched or broken. I have not, however, personally tried what you’re suggesting.
For this solution to work with using the same frequency you would be to have 2BHS’s at the middle man tower and the BH masters at the customer site and the main tower.
The timing will be identical for all the BH-masters if they're connect to CMMs with GPS timing. That's why there's a GPS receiver: to synchronize the timing between remote equipment.
Perhaps this is a dumb question, but does this mean that if A BHM in California and a BHM in Pennsylvania are both connected to GPS-timed CMM's that those BHM's will transmit at the exact same time via the GPS sync should their network traffic require them to transmit at the same time? It sounds correct considering that all Canopy networks with CMM's are using a common carrier for timing (GPS) but I was under the impression that the timing was relative to individual clusters.
Msmith:
Yes, CA and PA Canopy APs will transmit simultaneously.
Mattmann72:
Good idea! That would permit everything to be in the same frequency band.