AP Co-location

What should I do here?

I have a couple of 900 AP’s that are loaded up with 50+ users.
I have started getting complaints of slowness from customers on these AP’s and we have verified the slowness during peak times.

The main cluster is at 150’ using 906,915,924.

Can I add another AP to carry some of the load?

Can I add an AP to the same tower, say, 40’ lower on one of the same freq’s without causing myself more grief?

If not, any suggestions?

Thanks in advance,


How many APs on this cluster?

How many SMs connected to each AP?

What is the control slot settings on the AP?

QoS settings on the SMs?

6 AP’s

35-55 SM’s on each

Control slots = 2

Sustained Uplink Data Rate : 512
Sustained Downlink Data Rate : 2000
Uplink Burst Allocation : 600
Downlink Burst Allocation : 3000

How much bandwidth is fed to this tower?

Are there any other 900 towers around either owned by you or another company?

Direct 100Mbs fiber connection to a 45 Mbs DS3 with about 20 Mbs of available head space.

Well what i would do is try to figure out where the bottleneck/problem is. I would connect an SM with the same QoS settings as your customers and try to connect to each AP and see if I could duplicate the speed results they are complaining of.

What are the link test results of the customers complaining?

Where is the CMM located on the tower? If it is on the bottom how do you connect to the APS? Is it by fiber or ethernet?

Is there anything like high-powered FM that could be causing your ethernet on the tower to be losing packets?

You need to determine where the problem is. Whether it be between the SM and the AP, or packets lost between the AP & CMM, or from the CMM to your bandwidth connection.

We have been able duplicated the issue.

It is only on the two heaviest loaded AP’s, those with 47-55 SM’s during peak times.

I can plug in at the CMM and get 40-45 Mbs to our dedicated speed server.

From the SM’s BW varies from 800 Kbs to 1.2 Mbs during peak times and 1.5 to 3 off peak.

The AP’s in question graph out on MRTG at 2-3Mbs during peak.

It appears to me that they are just loaded to capacity.

The bottleneck appears to be in the AP.

As I understand it each 900 Mhz AP will only pass 3 Mbs aggregate bandwidth.

About 8% of these SM’s have a strong enough link to enable 2x and are set up so.

For now the complaints aren’t that numerous. Problem is, I could easily double the customer count in this area in the next 6 months.


Sustained Uplink Data Rate : 512
Sustained Downlink Data Rate : 2000
Uplink Burst Allocation : 600
Downlink Burst Allocation : 3000

I beleive this is your main problem. Open it up if you have 45MB running there. Personally, I don't like setting the APs to burst, because under load my ping times go crazy. Try setting all APs to 7000, and rate limit on the SM.

I don't use 900Mhz, but I wonder if it's the best choice for dense SM population bacause this freq does not provide as high speeds as the other bands due to its reduced bandwidth (8mhz instead of 20mhz) I am not sure what the max is, but I would think it around 4mbit, so, at busy times, a few 384k users could bring the AP to it's knees.

Those settings are on the SM’s, the AP’s are wide open.

AP config:
Sustained Uplink Data Rate : 20000
Sustained Downlink Data Rate : 500000
Uplink Burst Allocation : 20000
Downlink Burst Allocation : 500000

On the AP you have it set for the Configuration Source to be SM correct?

One of our 900 AP clusters ranges from 38-65 users and our bandwidth settings are actually set faster than your for our customers but they (as far as I know) are working fine.

Sounds like you are hitting limit. You might have to consider an alt freq like 5.7 to colocate on that tower and start switching over high priority clients to it.

That is correct. SM is the config source.

What kind of speeds can you get accross those links?

What kind of speed does the AP graph out at?

Should I see more on the AP’s MRTG than 2-3 Mbs?

5.7 bandwidth would be great and I would do it if the local terrain was not so hilly with huge oaks and pines.

Isn’t 5.7 strict LOS?


Just a suggestion, consider removing bursting and setting people to a static 512/512. The reason is, at busy times, several people bursting at the same time will max a 900 AP. We switched out our busy 5.7s to static speeds, and complaints dropped significantly, and our bandwidth became a lot more stable, especially for gamers and you tubers. We average 4.5d and 1up on MRTG our non advantage gear.

yes, 5.7 is restricted LOS. We actually have pretty good luck with moderate foliage on 5.2.

I’ll try that. Thanks

2 of our APs have 65 and 1 has 71 SMs connected on it.

Looking at the graphs for the past week they have not maxed out yet.


What is your max?

We set our sustained download to 768 and burst to 50000. I haven’t had a complaint off that tower regarding speeds in quite a long time, and when we did it was because we had faulty equipment on the tower.

I mean what is the max thruput on that AP (aggregate)