Controllerless Networks

My office was running 4 Aruba IAP-93's.  I ran into significant slowness on the 2.4Ghz band due to a high number of neighboring access points, so the band was switched to 5GHz to increase speed.  I saw our 5mbps jump to 20mbps just like that.

Two of these access points were consistently over untilized and needed to be upgraded to meet the demand of the clients connecting to them.

I've replaced two of the IAP-93's with Aruba IAP-135s but I'm struggling to force both radios to the 5GHz band - radio one always remains at 2.4GHz even though the configuration is set to force it to 5GHz. I've looked through the manual and researched online but haven't been able to find a solution.  Does anyone know if this is even possible?

Leaving one radio on the 2.4GHz band, or turning it off, defetes the purpose of upgrading the AP.  I need both radios on 5Ghz, can anyone help?

Thanks.

You cannot change the 2.4GHz radio over to 5GHz on dual-radio IAPs or our controller based APs.  The only platform we offer that allows this are the Outdoor AirMesh products.

The "Force 5GHz" setting is for the Band-Steering feature and forces all dual-band capable clients to connect to the 5GHz radio. Clients that are 2.4GHz capable only will still connect to the 2.4GHz radio.

Your users should see improved performance with the IAP-135 over the IAP-93 as it has a faster processor.

Answer to your question of why its not recommended to have 2 radios in an AP in the same band (5GHz band) is - Adjacent Channel Interference.

Unlike wired, in wireless addition radios don't necessarily mean additional bandwidth. Since WLAN is a shared medium, it backfires if the distance of separation between radios is not good enough.

The formula for free space path loss is:

If the distance between is very less, as in case of 2 radios being in same band in same AP, is going to be in centimeters or millimeters, the attenuation is going to be very less even if we allocate them different channels with in the band.

Below is the graph of attenuation. You can see that even in feets its very less for some initial distance.

So by using 2 radios in the same AP, it will kill most possible communication.

To put it simple, if you have 2 radios in same band in same AP, what is happening in 2.4 between you and your neighbor aps will happen between your Radio1 and radio 2 in 5ghz with in your AP.

While I have given why its not recommended to have 2 radios in same band in the same AP (some vendors do but not very successful), I can say that with AP 135s you can get 150 Mbps of extra throughput compared to AP 93s. And I hope that what you want.

The industry solution for improving throughput with a single radio is to go for multiple Spatial streams, from a concept called MIMO ( Multiple in Multiple Out) introduced with 11n.

With 3 spatial streams an AP can provide data link rates of 450 Mbps inplace of 300 Mbps by a 2x2 AP. This improves your throughput by 150 Mbps i.e 50%. As good as having another radio. This is the industry practise.

With this in combination with Band steering, that is force 5Ghz, you can move all 5Ghz capable clients to 5ghz band.

So rest assured that you have made the right investment.

Great info all around, thank you.  I was concerned about clients hoping on the 2.4GHz band and ending up right back where we started, but as long as capable client are being forced to 5GHz that shouldn't be an issue. 

This also solves a minor problem I was facing after the switch; some older machines and and a wireless printer didn't have dual band radios, so they weren't able to connect until the 135's were brought in.

If I understand the responses correctly, the 135 is the best of both worlds, even if the single band 2.4GHz radio clients continue to experience congestion from neighboring APs.

Out of curiosity; which Aruba IAP is capable to handling the most clients and throughput, but only broadcasts at 5GHz (with a single radio obviously)?

AP 135 is the best bet. For two reasons:

1) There are no single Radio Aps that are having 3 spatial streams i.e 450 Mbps.

2) By default AP with highest priority in IAP is AP 135. Example when there are 100 APs of different various models in a subnet all powered up at the same time, then only an IAP 135 will become master.

The AP-93 is the only single-radio AP.  Our highest performance AP, in terms of throughput and number of clients, is the AP-22x.  This is a dual-radio 802.11ac AP.  If you really don't want to use the 2.4GHz radio you can configure, on a per SSID basis, to broadcast on 5GHz only.