Roaming issue

Question

Users complain that wireless device would lost wireless network connection when they moved from one AP coverage to another AP coverage.  They have to reconnect to the wireless network again.
In our wireless environment, all APs are connecting to a single loacl controller which anchor to two remote controllers.  WLC 5508 with 7.2.11.3.
Thanks,

Answer 1

Configuring Client Roaming
The Cisco UWN Solution supports seamless client roaming across lightweight access points managed by the same controller, between controllers in the same mobility group on the same subnet, and across controllers in the same mobility group on different subnets. Also, in controller software release 4.1 or later releases, client roaming with multicast packets is supported.
You can adjust the default RF settings (RSSI, hysteresis, scan threshold, and transition time) to fine-tune the operation of client roaming using the controller GUI or CLI.
CCX Layer 2 Client Roaming
The controller supports five CCX Layer 2 client roaming enhancements:
•Access point assisted roaming—This feature helps clients save scanning time. When a CCXv2 client associates to an access point, it sends an information packet to the new access point listing the characteristics of its previous access point. Roaming time decreases when the client recognizes and uses an access point list built by compiling all previous access points to which each client was associated and sent (unicast) to the client immediately after association. The access point list contains the channels, BSSIDs of neighbor access points that support the client's current SSID(s), and time elapsed since disassociation.
• Enhanced neighbor list—This feature focuses on improving a CCXv4 client's roam experience and network edge performance, especially when servicing voice applications. The access point provides its associated client information about its neighbors using a neighbor-list update unicast message.
• Enhanced neighbor list request (E2E)—The End-2-End specification is a Cisco and Intel joint program that defines new protocols and interfaces to improve the overall voice and roaming experience. It applies only to Intel clients in a CCX environment. Specifically, it enables Intel clients to request a neighbor list at will. When this occurs, the access point forwards the request to the controller. The controller receives the request and replies with the current CCX roaming sublist of neighbors for the access point to which the client is associated.
For more information you can refer the following link-
http://www.cisco.com/en/US/docs/wireless/controller/7.0/configuration/guide/c70ccfg.html#wp1098538