Hi Rahim,

Here some docs that explain the roles of different parts of a Lightweight (LWAPP) network;

The Cisco WCS is an optional network component that works in conjunction with Cisco Aironet Lightweight Access Points, Cisco wireless LAN controllers and the Cisco Wireless Location Appliance. With Cisco WCS, network administrators have a single solution for RF prediction, policy provisioning, network optimization, troubleshooting, user tracking, security monitoring, and wireless LAN systems management. Robust graphical interfaces make wireless LAN deployment and operations simple and cost-effective. Detailed trending and analysis reports make Cisco WCS vital to ongoing network operations.

Cisco WCS includes tools for wireless LAN planning and design, RF management, location tracking, Intrusion Prevention System (IPS), and wireless LAN systems configuration, monitoring, and management.

From this doc;

http://www.cisco.com/en/US/products/ps6305/products_configuration_guide_book09186a00806b57ec.html

There is a trend in the WLAN space toward centralized intelligence and control. In this new architecture, a WLAN controller system is used to create and enforce policies across many different lightweight access points (LWAPP). By centralizing intelligence within these devices, security, mobility, quality of service (QoS), and other functions essential to WLAN operations can be efficiently managed across an entire wireless enterprise. Furthermore, by splitting functions between the access point and the controller, IT staff can simplify management, improve performance, and increase security of large wireless networks.

From this doc;

Understanding the Lightweight Access Point Protocol (LWAPP)

http://www.cisco.com/en/US/netsol/ns340/ns394/ns348/ns337/networking_solutions_white_paper0900aecd802c18ee.shtml

Deploying Cisco 440X Series Wireless LAN Controllers

http://www.cisco.com/en/US/products/ps6366/prod_technical_reference09186a00806cfa96.html

Cisco Wireless LAN Controller Configuration Guide, Release 4.0

http://www.cisco.com/en/US/products/ps6366/products_configuration_guide_book09186a00806b0077.html

WLC Video

http://www.cisco.com/en/US/products/ps6366/index.html

Lightweight Access Point FAQ

http://www.cisco.com/en/US/products/ps6306/products_qanda_item09186a00806a4da3.shtml

Lightweight AP (LAP) Registration to a Wireless LAN Controller (WLC)

http://www.cisco.com/en/US/tech/tk722/tk809/technologies_tech_note09186a00806c9e51.shtml

Wireless - Compare Products and Solutions

http://www.cisco.com/en/US/products/hw/wireless/products_category_buyers_guide.html

Hope this helps!

Rob