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.