Multiple Hop With Master Between Slaves

Require Configuration of Multi Hop With BH Master betwween Slaves.

What will be Frequency on each module ?
What will be the Color Code ?

Basicaaly We want communication between Location “A” BH Slave and Location “C” BH Slave. At Location “B”, We will configure Bh Master alongwith CMM2.

Require Urgent Response.


You could, if needed, use the same frequency on both pairs, but you’d then also have to set DataDown to 50%. You’re better off simply using two different frequencies (at least 25MHz apart); you can then alter the DataDown to more closely match your needs.

In your situation, however, you need to set each pairs’ DataDown in opposite fashion; 75% on one pair, 25% on the other pair, for the following result:

[Location A]BHs ------ BHm(75%)-BHm(25%) ------ [C]BHs

If you instead made the Location B units a Master and a Slave, the DataDown would be set the same:

[Location A]BHs ------ BHm(75%)-BHs ------ [C]BHm(75%)

ColorCode can be any setting, but make sure each pair uses matching ColorCodes. Because you plan to have both masters together at Location B, there’s a possibility the slaves will “see” both masters (check the slaves’ AP Eval pages). If this happens, you should force the slaves to connect to their respective master by either limiting the slaves’ RF Scan list, or making each links’ ColorCode different.

Something else to consider: If you have no other Canopy components to synchronize with, then you don’t need the CMM. The timing pins on the units at Location B can instead simply be tied together.

Good luck!

Hey Teknix …

Not to butt in…
I thought that a BHM & a BHS could not co-exist at the same location. Is that not really true?


wew have 5.7 BH master and 5.7 BH slave on the same tower about 80 feet separation vertically with dishes pointing about 180 degrees apart. We have no interferrence noted after a year. (The units are not synced together) What we don’t know is how much less than 80 feet we could get by with.

Remember that when syncing masters together the downlink percentage needs to be the same so the length of tx on time will not overlap. You can’t then have one back to back 75% down with one 25%down which you would need to keep going down a line over multiple bh’s.


The practice of co-locating a BH master and slave – as well as an SM and “remote” AP – and connecting their timing ports together without a CMM will work, but Motorola doesn’t recommend or support it.

Apparently, this method introduces a slight timing delay. As a Canopy network grows, accurate synchronization becomes more and more critical. Motorola explains that it’s common for this type of non-CMM timing to work for months, but then inexplicably stop working.


Co-located BH masters do not have to have identical DataDown settings the way clustered APs do.


I was incorrect in my previous post: the co-located BH masters can be set to the same frequency and still be able to adjust their DataDown settings to something other than 50%.

Yea, I knew about the SM/AP relay - we have 4 or 5 of them running. I was just curious about the BHM/BHS colocate. We are setting our 4th cluster tower right now, and that “taboo” set-up would make the backhaul to it easier. I guess I’ll just stick with the status quo for now.

BTW - did you know you can run multiple RAP’s off one SM - with timing? We just tried it. I spliced the timing relay and fed 3 Remote AP’s. They all got sync, and so did all the relayed SM’s. Cleaned up the jitter from 4/5 to 1/3 instantly :slight_smile:


For Mohsan’s situation, I presumed he would be using identical pairs of BackHaul units for both hops. I should have stated my assumption.

Motorola does support tying the the timing ports together without a CMM, but only when you’re connecting units with different frequency bands (e.g., 5.2 and 5.7 GHz.) I presume this is what you’re doing in your SM/AP relay example. Motorola should also support connecting a BHs directly to a BHm if they use different frequency bands.

However, they don’t support either a BHs/BHm co-locate or an SM/AP relay when the units are all operating in the same band – even when the units are set to different frequency channels.

You guys have this sussed! But you do need to still watch the Downlink Data % on collocated same-frequency-band BHMs to give them the same transmit/receive ratio, else, part of each cycle one of the collocated BHMs will interfere with the other when one transmits while the other is receiving.

But here is another insight: If the offered throughput is low, the interfering BHM will not be actually transmitting during the end of its transmission phase, so there is no problem (it doesn’t transmit unless it has something to send). However, as throughput cranks up to full capacity, the interference may cause bad fragments, retransmissions, and lowered delivered capacity.

The solution to get full capacity is to gain spectral separation by using different frequency bands, or physical separation by vertical distance on the tower. And with enough vertical distance (and reflectors, always use reflectors on backhauls if you possibly can), you can run a BHM and a BHS on the same tower in the same frequency band.

sussed? !


can I get a w00t!