The following is taken from the Cisco NetPro discussion forum, regarding cisco wireless access points which are dropping clients randomly. I thought it might interest somone so I repost the issue here:

Problem:
I have anywhere from 5-20 access points drop up and down throughout the day out of a total of around 200. I am currently trying to go through and figure out why we our access points are having some many issues and how I might be able to resolve them.

One of the logs that I commonly see is:

AP ‘exp-p13′, interface ’802.11a’ on Controller ’10.2.192.25′. Channel changed to ’44′ from ’60′ due to ‘None’. Interference Energy before update is ’0′ and after update is ’0′. Noise before update is ’0′ and after update is ’0′. Interference before update is ’0′ and after update is ’0′.

Is there anyway to determine what the cause of this is?

Controller Firmware: 4.2.130.0.
AP Model AIR-LAP1242AG-A-K9
IOS Version 12.4(10b)JA4

Solution:
Sounds like it’s just the Radio Resource Management (RRM) on the controller. You can disable this if it’s dropping clients. Go to the wireless tab, look on the left, and click on the 802.11a/n or 802.11b/g/n dropdown. Then click on the RRM dropdown, and click on Auto RF.

My advice is to change both power and channel assignment algorithms to “On Demand”. You can invoke them as needed to maintain an optimum network. By default, it automatically invokes the update every 10 minutes.

If you need a rugged wireless access point device for challenging RF environments (such as warehouses, factories, large establishments etc) then the Cisco Aironet 1240 AG series is the ideal product for your situation. This device takes into account antenna support versatility as well as environment/physical security (broad range of operating temperatures and secure mounting bracket).

The 1240AG supports the 802.11 a/b/g wi-fi standards but comes also as 802.11g single band version to be used in environments that do not allow the 5 Ghz operation of 802.11a band. Antenna support features diversity antenna connectors for both 2.4 and 5 GHz bands to provide extended range, coverage versatility, and more flexible installation options. The RF performance of 1240AG offers industry-leading transmit power, receive sensitivity, and delay spread for high-multipath environments in order to provide reliable performance and throughput under the most challenging RF environments.

The Next Generation Wireless technology came into play with the introduction of the new 802.11n Wi-Fi standard which delivers unprecedented reliability and up to five times the throughput of current 802.11a/b/g wireless networks. Some of the key advantages of the new 802.11n standard are the enhanced data rate of up to 300 Mbps and the adoption of MIMO (Multiple In – Multiple Out) radio technology which greatly increases the Wireless LAN coverage.

In terms of coverage, Cisco has also developed a new solution called ”Cisco Enterprise Wireless Mesh”, which is supported on the Cisco Aironet 1240 and 1130 Series access points. Without requiring wired connections, mesh wireless access points use the 2.4 GHz frequency to deliver network access to users in hard-to-reach areas, and use the 5 GHz frequency band to backhaul traffic to traditional access points connected to Ethernet ports. This solution will provide network wireless connectivity in indoor areas that until now have been difficult to achieve. The wireless mesh technology offers high availability through dynamic wireless mesh self-healing, and optimal network performance for the entire enterprise.