Wireless Access

I was working with a customer yesterday who complained of slow wireless performance.  Their environment has a 650 controller (was 6.1.3 code), with about 8 AP-105 APs.  I noticed right away the customer didn't have enough APs for the size building they were in.  ARM had the APs maxed out, and they had Band-Steering enabled.  They had a lot of neighboring wifi with >20 SNR radios competing for airtime.  In the Arm profile they had Client Aware enabled, and the Arm profile was single band only.

I changed the Arm profile to Multi-Band, disabled Band-Steering, and disabled client aware.  I figured this way they could get clients back on the stronger 2.4 ghz signal, and the APs would perform better by scanning better and changing channels without worrying over clients who would just sit there and try their best.  I also upgraded them to 6.3.1.4 code, which I hoped would allow Client Match to help any roaming issues work more smoothly.

The customer did report clients "looked" better.  However, the CEO came around and said his iPhone was periodically getting poor results going to www.speedtest.net.  He was quite upset.

I tried to explain why that was not a valid test, but he persisted.  We ended up with 2 more iPhones and my Dell laptop all sitting there repeatedly trying his speed test over and over.  Very seldom did one fail, but when it did, the client was briefly unable to surf the web at at all, for a second or two.  A "show ap debug client-table ap-name xxx" command never showed any loss of SNR, or transmit/receive rates, but the client would "stumble" every now and then.

I was debugging my client at the time, and I've gone over the logs, and I don't see anything that is a red flag.  I have a tech support log from their controller, and the AP in question.  All I can see is the AP radios have like 96k buffer overflows in around 4 hours (from the "show ap monitor debug status ap-name xx123" command).  None the less, the customer isn't very happy because they believe they are still having intermittent wireless issues.

The link here:  http://community.arubanetworks.com/t5/Technology-Blog/Removing-the-Bottleneck-in-Wireless/ba-p/77978 has everything that I would check..

Why disable ARM Client-Aware? In that case ARM could change channels when there are clients associated to a radio, this can be disruptive.

You don't need to enable multi-band scan when you have AP-105's, multi-band scan is for single radio AP's only.

Have you done a site-survey with AirMagnet/Ekahau to verify the coverage? In my experience I don't see that much difference in SNR between 2.4GHz and 5GHz with the AP-105's, but this of course depends on the building.

Overall, if your clients can do 5GHz they should use it, 2.4GHz could get you a better signal, but 2.4GHz is usually way more crowded than 5GHz. You can look at channel utilization numbers and noise levels in the controller to get a sense of this.

In the default configuration with the AP105's the 2.4GHz radio will do 2*2 MIMO with 20MHz channels and the 5GHz radio will do 2*2 MIMO with 40MHz channels. This means 5GHz can also get you higher raw throughput because of wider channels (but note: if you start re-using 40MHz channels because of high density this will not always mean more throughput).

In addition to what's been posted:

• When ClientMatch is enabled, it overrides your band steering configuration.
• Personally, I would not disable client aware.  I do not want my APs changing channels with clients connected.  I've seen arguments for disabling/enabling, but believe you will have to do your own tests to determine how this affects your clients.
• Have you configured min/max tx power levels for both bands?  Highly recommended to cap the max tx power.
• To arjan_k's point, you should look to see if channel bonding is in use for 5GHz.  Depending on the environment, enabling 40MHz channels can be detrimental.  If you disable 40MHz channels, be sure to disable both in the HT SSID and ARM profile.