How to know sync is working?

Hi, we have a tower with 3 EPMP5GPS we have turned on co-locaion mode with the following settings: on the 3 AP's:

Max Range: 10KM

Subscriber Module Target Receive Level: -60

Downlink/Uplink Ratio:75/25

Frame Size: 2.5ms

Synchronization Source: GPS

Synchronization Source of  Co-located System: GPS

Does anything else has to be configured for Sync to work? How to know if it is actually working?



Can you please describe the antenna types and how they're arranged on the tower? Are these three radios sectors installed to provide 360 deg coverage?

The main benefit to GPS sync is the ability for radios in a back to back orientation to take advantage of frequency reuse, e.g. the ability for both radios to use the same frequency. There are a few requirments to this however:

1. The radios ideally should be back to back (180deg apart)

2. The distance, uplink/downlink ratio, frame size need to be set the same, and the 'front radio, back radio' settings need to be set.

3. The antennas being used should have a high front to back ratio. If you're using Cambium OEM antennas you're good to go.

4. And the most important part, clients from either sector cannot hear the opposite sector.

Assuming you're using (3) 120deg sectors on a tower to provide 360deg coverage, you won't be able to effectively use frequency reuse because clients from one sector will most likely be able to hear the other sector(s) as these radios are not 180deg apart.

For further information and tips on GPS sync and frequency reuse with ePMP, check out this knowledge base article.

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We are using APMP51790 antennas and 2 sectors are facing the same way (due to customers density) and other at 90 degrees, so we are not using frequency reuse. Are you saying that sync does't have any benefit in this scenario? Would it be better to use flexible mode?



Yes, if you are not reusing frequency and if you have enough frequency seperation between the APs, then you are better off using Flexible mode. 

Thank you both for taking the time to answer.

Cambium_Sri we have being testing the ePmp1000 for some months now and until a couple of days ago I would totally agree with your statement that in a non frequency reuse scenario flexible mode worked best but since 2.5 (which had some problems with 2.5ms sync) and now 2.5.1 that is working great I wouldn't be so sure.

I have been testing during the weekend with both and have found that using sync with 75/25 works a lot better than flexible mode, better latency and almost double throughput. The only problem I have seen so far is something I had already read in the forum that the upload speeds suffer a lot. 75/25 works more like 90/10 or 93/7, the download speeds are great but the upload speeds arent close to 25% of the bandwidth. The links in real life tests give 30 to 40 Mbps down and 1 to 2 Mbps up.