I know that each cluster of 2 or more APs need to have a CMM and GPS attached to it. But when you have more than one cluster separated far enough so that their RF signals will not interfere, do both of those clusters need to be synced together by BHs?
If you have 1 cluster that’s 5 miles east of your NOC and 1 cluster that’s 5 miles west of your NOC. And a separate BH link from the NOC to each cluster, how do they sync together?
I know this is basic stuff to most of you, but I feel like I’m missing some small detail when it comes to syncing a network.
Thanks in advance 
What freq’s are the BH’s and clusters?
Let’s say 5.2 for the Clusters. 5.7 for the BHs.
I’d say you are probably OK. 10 miles should be good enough separation at 5.2.
But, if both sites have CMMmicro’s, they will be in sync anyway
aha! So they don’t need to be physically connected with BHs. It’s the CMM and GPS that puts everything in sync regardless of location right?
But, if both sites have CMMmicro's, they will be in sync anyway
As long as the AP's are setup exactly the same.
Scheduling, Downlink data, Control Slots...
If these are different then the modulation scheme from the AP will be different between sites, and they will not be in "time"
Why not put in one CMM at the NOC then pass it through the BH's to each site (if using Moto Canopy BH's), abd sync the cluster from the timing ports tied to the BH timing port?
That’s what the frame calculator is for…
You really want a CMMmicro at each tower for switching, VLAN support, remote power cycle, GPS, POE, etc, etc…
So in theory if you had an interference issue with a neighboring Canopy system that WAS not using a CMM, and your system was, if the neighbor installed a CMM the only way to totally avoid interference is if both systems had their AP and BH settings “identical”, correct?
If one system had their AP’s and BH’s set for 75% downlink, and the other system had their AP’s and BH’s set for 50% downlink, and both systems were using a CMM, the transmit and receive cycles of the systems would still be different, ergo not in sync?
Once they have a CMM installed, and you know all the settings on your neighbor’s AP’s, you can use the frame calulator to manipulate your radios so that they are in sync with your neighbor.
Why not put in one CMM at the NOC then pass it through the BH's to each site (if using Moto Canopy BH's), abd sync the cluster from the timing ports tied to the BH timing port?
Interesting. You would still need a CMM at each cluster though right? I mean to plug the APs and the BH into. But only one GPS would be needed at the NOC?
Ok...posted this a little late
you can use the frame calulator to manipulate your radios so that they are in sync with your neighbor.
Interesting. So that is what the Frame Calculator hyperlink is for!
How to use:
Set key values of
- Max Range
- Scheduling
- Downlink Data %
Click Apply settings, then recheck the settings. If they all look right, click Calculate
Write down value for “Uplink Rcv SQ Start” under Transmit Details
Adjust downlink data % and repeat until all AP’s are within 300 of each other.
This puts all of the APs in sync with each other.
There’s still one tiny thing that I’m not getting. :oops: It’s the GPS that provides the sync right? So if you have multiple clusters daisy-chained together, then in theory you would need only 1 GPS…is that correct? :?
Not sure what you mean by daisy chained - you mean on the same tower?
ais3101 wrote: There's still one tiny thing that I'm not getting. :oops: It's the GPS that provides the sync right? So if you have multiple clusters daisy-chained together, then in theory you would need only 1 GPS...is that correct? :?
I'm pretty sure you are talking about the same setup I'm thinking of:
http://motorola.canopywireless.com/support/community/viewtopic.php?t=2936
Not sure what you mean by daisy chained - you mean on the same tower?
No, I thought daisy-chained was cluster 'A' feeding cluster 'B' via BH and cluster 'B' feeding cluster 'C' via BH, etc. instead of one central location feeding multiple clusters like a spoke wheel design. Am I mixing up my terminology? :oops:
You can’t really carry the sync from one cluster to another. The reason being is there is no way to get the sync from the BH into the CMM to distribute it to the other AP’s and you can’t split the sync pulse 7 ways.
Each cluster gets a CMM. Each CMM has a GPS Reveiver.
You can however carry the sync to a single remote AP via a BH or an SM
CMM --> AP --------> SM --> AP
OR
CMM --> BHM -------> BHS --> AP
Ok, that actually cleared up alot. Thank you Jerry!
What if you were using this:
http://www.packetflux.com/index.php?main_page=product_info&cPath=2&products_id=2
?
If you did not want to use a CMM for your switch, but actually use a Cisco or something like that for your switch, then yes you could pass your sync on to each site in a chain.
CMM -> AP Cluster -> 1 SM which you would tie the timing port to -> 6 AP Cluster -> 1 SM which you would tie the timing port to the next and so on.
- or -
CMM -> AP Cluster + BHM -> BHS which you tie the timing port to the next Cluster and next BHM -> BHS which you tie the timing port to the next Cluster and next BHM and so on.
The first CMM is required for the initial timing though. If you use a CMM-2 then you can get timing from it, but use a Cisco switch for all the ethernet traffic. You will need a PoE switch or a Moto power supply per radio. (AP and BH) which becomes alot of power ports at every site.
It can be done, just make sure the SM or BHS has “Frame Timing Pulse Gated” disabled. Otherwise that will make every SM registered to an AP behind any one of the BHS’s or SM’s providing timing to log off.
That would be bad…