Hi Uzma,

It is likely in this day and age that when creating a Large WLAN that you will be using a "Lightweight" architecture. Here are some good "getting started" Cisco docs (and link to a video) which might help with your initial steps. Don't forget to pay special attention to your Site Survey (best to hire a professional firm for this key function);

Wireless LAN Design Guide

http://www.cisco.com/web/about/ciscoitatwork/design_guides/dg-wlan.html

Wireless Site Survey FAQ

http://www.cisco.com/en/US/tech/tk722/tk809/technologies_q_and_a_item09186a00805e9a96.shtml

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! And best of luck.

Rob