If some one uses up 30-40 Gb and that too in wireless- one should have minimum one GSM 7.2 mbps data card + another GSM 21 mbps data card each with a prepaid 3G sim.In chennai Airtel,Vodafone,Idea (on borrowed Voda network),BSNL,Aircel 3G works very well.One has to check signal strength in their home. I have got 2-5 mbps in Voda & Airtel networks. BSNL too is not bad though not consistent.Aircel has impreved nowadays and gives minimum 1.5-3 mbps. No Docomo/Reliance in south.10 Gb data pack in each sim .(can not depend on one operator only) Approximate budget 2500-3500 minimum. Keep renewing every 30 days.CDMA mobile BB like Tataphoton/Net connect/MTS not considered at all.