timing sync

Here is a question. I fully understand the need for sync and timing in the canopy system.

However what I don’t understand is that if one AP is on channel 5735 and the next AP is on centre frequency 5810, then if they are not synced how they would interfere with eachother, they are on different frequency…

and further to that, how come you can co-locate Orthogon in a Canopy cluster in the same band and don’t have to worry about timing ?

Why is synchronization of AP’s and BH masters required?

Author: Knowledge Base Administrator

Canopy radios use time division duplexing (TDD) on the outbound transmission and time division multiple access (TDMA) on the inbound frame. Canopy radios transmit and receive but not all at the same time. If one AP were to transmit while another is receiving the possibility for interference or de-sensing exists. AP’s and BH masters must be synchronized to prevent interference and de-sensing.

and its always better to wear seat belts even when sleeping !!

so the risk is not to do with interference but more to do with de-sensing.

Does this not apply to orthogon kit, as that does not operate with timing

De-sensing is a form of interference. Self interference. You can get this by improper timing or even to good a rx signal. Lets say the noise floor in the ares is -90db you install a sm and log into the sessions page on the AP. You have 6 sm’s listed 5 show a rx signal at the AP of -75db their 15 miles out. The one you just installed shows a -55db it’s only half a mile. When the sm’s transmit the AP’s reciever is going to be de-sensatized by the -55 and might have issues with the further signals getting threw. The same is true with an AP and BH that are at the same location dut are not timed properly. TDD uses GPS to determin when transmitters should transmit and recievers should recieve. In TDD outbound and inbound transmissions occur over the same frequency but in alternating fashion. OFDM transmits data on multiple beams to enhance the probability of successful transmission. the beams behave diffarent so they don’t interfear. The beam’s can be on multiple frequencies or sub-carriers or the waveform can modulate in a diffarent way. This does not mean that colocation on the same band with Canopy and orthogon wont cause problems they still have to be on diffarent freq at least 20mhz away or thay will interfear. The 150.300 has to be 30Mhz away.


I’ve never experienced problem of a close by SM de-sensing the AP, we have SM ranging from 0.5 to 10 miles.

Can an AP on frequency 5735 be de-sensed by an SM/AP not synced on 5740.

If you were to look at the spectrum when an AP is transmitting, you would see that there is energy spread from either side of the center frequency. This is why there is a lower number of non-overlapping channels than there are available frequencies in any given band. You can probably get away with not having two AP’s generate their own sync at opposite ends of the spectrum as you have, however it’s better to have the AP’s in sync.

It really starts being a problem when you have multiple AP’s in a cluster as you are not able to get the channel spacing far enough apart to avoid self interference.

If it’s the cost of the CMM that is stopping you from syncing the AP’s, then use one of the sync-pipes from packetflux.com. It will allow you to sync the two you have now for very little cost, and then add a sync splitter from the same company as you add AP’s later.

its not a cost issue, all our RF is fully synced.

I am just curious as to why 2 AP’s need to be synced if they are on different frequencies.

So from what you are syaying is that if the centre frequency is 5735, and we know that canopy uses 20MHz of bandwidth, i.e. 5725-5745Mhz to operate, then from what you are saying that we have a bleed beyond this boundary where an AP set to 5735 will bleed beyond 5745 and possibly cause an issue in the 5750 space.

Well here is another question, if I get two AP’s and put them next to eachother, set them both to 5735, what will happen at the RF level. I know we can’t do it, I have tried it and I know the results but curious to know what is happening at the RF level.

In my view, both AP’s will transmit and receive at the same time, so where is the problem ? Is it that the SM registered to AP1 end up causing interference to AP2 and vice versa ?