Here is the answers to your first two questions:
If the channel is set to Auto on the AP’s, wouldnt the AP use a different channel from the one thats closest? Because in checking, wifi1’s channels are set to Auto on pretty much all our AP’s.
Auto channel assignment is enough usually but its not perfect and some network environments may require you to either have static channel plan OR have Auto channel assignment select the channels and then you tweak the channels as needed. It is more important in networks where only limited no. of channels are available for use, which means channels will be repeated many times over on different APs which may create CCI. I am not sure what your channel profile looks like, if you are using all non-DFS channel or just UNII-1 channels are being used. The recommendation would be to skip DFS channels and use all the remaining channels. I assume this is most likely already the case.
This issue only applies to AP’s close to each other AND using the same channel, right? For instance, in one building there is an AP on channel 161, and then in a different building - a long distance away - there is another AP thats on channel 161. Because of the distance, we wont have the issue you explained, correct?
That’s correct, the issue will surface only when you have APs in the hearing range of each other while using the same channel. The following diagram should help visualize that; here channel 6 is the cause of CCI since two APs can hear each other on channel 6 which will cause the APs and their associated clients to compete for channel access.
We seem to have the rx/tx retries in one place more than others, the SU Lecture Hall. My first screenshot was of that one. I just checked it, and its not on the same channels as the 3 closest AP’s. At least its not now, but of course this is many hours after the issue.
In this particular location, your problem may not be the CCI due to other APs but If you have a large no. of concurrent clients on this AP which are all:
- Actively doing Tx/Rx
- Using any application that utilizes broadcast/multicast etc.
- Legacy 802.11b/g clients which are slower and drag the faster clients with them
- Clients that are located far from the AP will also increase retries, because these clients won’t get Tx opportunity as often as the clients located closer to the AP, hence they keep re-trying.
- Clients that are sticky and not roaming away from the lecture hall AP when they really should move on to the next better AP. This is a very common problem with hand-held client devices. These clients will kill the performance of the AP.
- If its a large lecture hall and the network is designed to cover the hall with single AP, you may have too many clients for a single AP, adding another AP will help load balance the clients across the two APs and free up the channel. But this should only be considered if the above mentioned conditions are not found to be true.
You should investigate this AP in the light of above and check what’s the cause of high channel utilization and retries. Let me know if this helps.