@jcrouch wrote:
Thanks for the replies. I will try these out and let you know how they work out.
Jcrouch,
I see from another thread that you have 6 SSIDs, and that is probably limiting your bandwidth even further, due to the management traffic overhead. Depending on your environment, you probably cannot merge any of those SSIDs together anytime soon. Since you are already dropping broadcasts on all your Virtual APs, there are three things that you can do:
- Make sure that Virtual APs that are only supporting clients on one band are ONLY broadcasting on that band. If you have VOIP devices, for example, that only run on b/g, make sure that the Virtual AP's "Allowed Band" parameter is ONLY "g" and not "all". That will ensure that the management traffic from that particular wireless network does not contribute to the congestion on the "a" band. If you have a guest network, you should experiment with just turning this to g, as well so that your devices running Citrix that are on the "a" band do not have to contend with management traffic from your guest WLAN.
- Use only 20 mhz instead of 40mhz channels for 802.11n on the 802.11a band - By default, only the "a" band uses 40mhz or "bonded" channels. This provides higher throughput, but limits you to only 4 non-overlapping channels in the 5ghz side. Since you have a high-density environment, you could gain 4 more channels in the "a" band and ease some contention if you do not bond channels in the "a" band. This will allow your 802.11n clients in the "a" band to still have a maximum association rate of 130, which is plenty for Citrix, but could ease some of the congestion in a dense environment. You can change this parameter in the ARM profile. Go to Configuration> Wireless LAN> AP Configuration. Edit the AP-Group that your APs are in. Expand RF Management> Expand 802.11a Radio Profile> Expand ARM Profile. Change the "Allowed bands for 40MHz channels" parameter in the ARM profile to "none". Before you make the change, the channels that APs are on would look like "HT:36+", but after, they should look like just "HT:36". That will let you know that your WLAN is using 802.11n, but not consuming two channels per ap.
- Use the "Local Probe Request Threshold" parameter under the Advanced Tab in the SSID Profile - Many times, in high density environments, clients will stay associated to access points that are very far away from them, because the driver in the client WLAN card believes that the signal is still good. The biggest issue this creates is that a client that is far from an access point normally associates at a lower rate and transmits more slowly, because of the distance. This will also degrade the throughput of clients that are closer and associated to the same AP, because they have to wait longer for that client to transmit. If you change the "Local Probe Request Threshold" to something like 20 or 25 (dB), access points will only accept associations clients that are of a certain signal strength, limiting clients to only choose access points that are better for them. This parameter is located under the Advanced Tab of the SSID profile. To edit it, go to Configuration> Wireless LAN> AP Configuration. Edit the AP-group. Expand Wireless LAN, Expand Virtual AP, Expand SSID profile under that. Chose your SSID and go to the Advanced Tab to see the Local Probe Request Threshold parameter. The parameter is Zero By default.