If u are an ISP u have to use the 5GHz band. Connect the 2.5Ghz card o/p to an upconverter and PA to generate 5Ghz.
Adding to it if you want to provide ISP related services in Class A Zone (which covers all the Metroes in India, e.g. Mumbai, Delhi, Calcutta, Chennai, Blore etc) you need to apply for ISP license and a bank gaurantee of INR 20,00,000 + Registration fees, you can find more information on www.dotindia.com
Class A means you get license to provide service India wide any location. Lots of minute clauses (like maintaining logs for 5 years for all the users on your network etc etc ..)
This was the scenario when i setup an ISP at Mangalore 3 years back, things might have improved a lot, its better you refer to latest rules and regulation on DOTIndia's website.
Let me know if you need further information, Best Regards, Mitul Limbani CTO, Enterux Solutions The Enterprise Linux Company (TM) http://www.enterux.com/
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