This is our first PTP 670 link. We are replacing an AirFiber5x link that was not very stable. So far the link has been stable, but the capicity is super low compared to what we thought we would get. Link Planner showed we should get 373mb. I would settle for half that at this point. Using 2 foot Dishes.
Are we doing something wrong?
Our Transmit Modulation Mode (master) is always showing very low and Single. But the receive Modulation Mode sits at 256 QAM. Would this indicate interference on the Master side or Slave side?
I know that Adaptive Link Symmetry is a cool feature, but I find it is helpful to set Symmetry to 1:1 while debugging problems with a link. It makes it easier to see what's happening.
Also, remember that it is the receiver that determines modulation mode. Please could you post the System Status for the Slave ODU?
You have a lot of interference at your peer recieve end. It's fighting thru -65db of noise and your recieve signal is only -54, -64, -57. 8dBm isn't gonna be enough to do much. Bigger antenna, figure out where your noise is coming from and eliminate, or change frequencies.
Try moving yourself to the 5792 center channel, or free up other noise in the spectrum if you can.
Yea, thanks. Its interference. I moved our AP that is next to the slave to a different frequency, then put the center frequency on 5832. We are now getting abotu 170-200mb capacity.
I am using a 2 foot dish from Lcom. But I am not sure it is the best at isolation from interference. What have you guys found to be a good 2 foot dish to use with the ptp670?
Leave the local on 5742, and then move the peer to 5792. See how that works out and then change to adaptive or a 3/1 ratio in the direction you need the most BW. I also would bet money that if you use DSO it would have automatically picked 5792... of course that doesn't give you the flexibiity that fixed mode gives allowing use of two different channels. I'd also try using a 20MHz channel width. I've had instances where using a smaller channel width actually delivers more BW in a noisy environment.
As far as antennas are concerned, we've used the RadioWaves 2' dish that Cambium recommends, and we modified it for a dual-slant polarity in order to fight some interference a little better. The antennas are very expensive and I don't know if I actually saw really any additional performance over any other well built 2' dish. If I had to do it all over again, I'd really like to try out RF Elements UltraHorn antennas now that they have an N connectorized version. We're going to be testing a PMP450i connectorized SM that's using a cheap 2' dish right now, and swap it out for one of these UltraHorns and we'll have a pretty good idea of how they compare soon.
Building upon Eric's comments, I would highly recommend using DSO for the frequency setup (versus fixed frequency), even if you are going to use a fixed frequency setup. DSO should select the 'best' channel available on startup and you can configure the radio to 'bar' specific channels from being selected by DSO. Essentially you can bar all of the undesired channels, fixing the frequency at a certain channel. This allows flexibility in the future, if you need to change channels (un-bar new frequency desired and bar current frequency). More information on DSO here.
In your particular environment, you will benefit from Asynchronous DSO (different Tx channels on each end of the link). Eric mentions this in a fixed frequency environment, but it is also possible using DSO. Under the spectrum expert page of the master, you can enable A-DSO, but I would also recommend changing the hopping parameters to the following:
Hopping Margin: 5dB or greater (typically 6-8dB). This will prevent the radio from changing channels due to small environment variance
Hopping Period: 600 (10 min) or greater. This will prevent the radio from changing channels too often due to isolated interference bursts. Basically that the interference is permanent.
Interference Threshold: Environment specific. If the measured interference on a channel exceeds the specified threshold, then DSO will instruct the wireless to immediately move to a better channel. If a better channel cannot be found the PTP 670 Series will continue to use the current active channel. (Default –85 dBm). In your environment, a value of -75dBm should be sufficient.
If setup properly and optimal radio operation, the PTP670 should stay on the current local channel (5742) and move to 5792 or 5802 on the remote channel.
It may also be worthwhile to setup this link within LINKPlanner and specify the corresponding noise floor/interference values for each end of the link. You can also verify predicted RSL on both ends to ensure optimal alignment. As will all unlicensed links, interference will signficantly impact performance. Moving to a smaller channel may also push more more throughput through the link, and this scenario can be predicted using LINKPlanner (with interference values entered).
In your particular environment, you will benefit from Asynchronous DSO (different Tx channels on each end of the link). Eric mentions this in a fixed frequency environment, but it is also possible using DSO. Under the spectrum expert page of the master, you can enable A-DSO, but I would also recommend changing the hopping parameters to the following:
Hopping Margin: 5dB or greater (typically 6-8dB). This will prevent the radio from changing channels due to small environment variance
Hopping Period: 600 (10 min) or greater. This will prevent the radio from changing channels too often due to isolated interference bursts. Basically that the interference is permanent.
Interference Threshold: Environment specific. If the measured interference on a channel exceeds the specified threshold, then DSO will instruct the wireless to immediately move to a better channel. If a better channel cannot be found the PTP 670 Series will continue to use the current active channel. (Default –85 dBm). In your environment, a value of -75dBm should be sufficient.
If setup properly and optimal radio operation, the PTP670 should stay on the current local channel (5742) and move to 5792 or 5802 on the remote channel.
Wow... thanks Chris.. my mind is blown... I didn't know that that's what async DSO meant on the Spectrum Expert page. I've been dealing with some really hairy interference on a link and I finally got it dialed in with fixed frequencies but I was litterally wishing that Cambim had this feature! So cool, I'm going to play with this tonight!
Here's what I'm dealing with now... any pointers for me Chris?
I have a new issue. Instead of just low capacity, the capacity will go really high for a bit and then really low. Like 250mb in 30mhz back to 30mb. It does this with what seems like clockwork. It takes 10 seconds to get the capacity up to 250mb, then it crashes back down.
Spectrum Expert does not show any cyclical interference. We get an occasional spike every 30 minutes, but nothing that would cause it to fluctuate a just a normal cycle.
Figured I would try to ask this one more time before we put the Airfibers back up. I have tried everything to for this link. All frequencies, DSO, Different Link symmetry, replaced dishes with UltraDishes. Nothing will stop the TX Data rate from cycling from 200mb to 20mb every 10 seconds. The TX does not do this.
There has to be a mechanisim in the 670 that causes this to happen on a set interval.
Figured I would try to ask this one more time before we put the Airfibers back up. I have tried everything to for this link. All frequencies, DSO, Different Link symmetry, replaced dishes with UltraDishes. Nothing will stop the TX Data rate from cycling from 200mb to 20mb every 10 seconds. The TX does not do this.
There has to be a mechanisim in the 670 that causes this to happen on a set interval.
This is a very strange.... so what happens when you actually push traffic through it? Is it actually reducing your throughput down to 20mbps? We have a bunch of 650's and 670's in the field and have never seen this happen. There's no mechanisim that I can think of or have seen that would cause this to happen. Perhaps a bad radio on one side?
I guess the last test would be to bench test them and use attenuators and/or power turned down all the way between them and see if you can reproduce it on the bench... if it does it on the bench then you'd need to RMA one or both of them.
I think the best idea is for you to gather the field diagnostics files, and to share them with Customer Support. It's hard to make confident suggestions without this information. We can generally see what's happening from the field diags.
