Quick survey of 3G network in Kolkata

Kolkata is flooded with 3G (UMTS, WCDMA) services from BSNL, Reliance, Vodafone and Aircel.
BSNL:
BSNL provides UMTS based technology with 900 MHz (yea unusual!) band, provides theoretical maximum speed of 3.1 Mbps. In practice you will experience a speed from 120 to 200 KBps. But this has the cheapest tariff of all other 3G data services. BSNL sites are not updated in regular, you have to rely on customer care for tariff. In worst case you may have to consider more than one of them as even they may confuse you with wrong information. Still for your information you can check http://www.bsnl.co.in/service/3G/3GHomepage.htm (URL may be outdated or may expire in future).
Vodafone:
Vodafone is HSPA (HSDPA+HSUPA) based technology, which should provide a theoretical maximum speed of 21.1 Mbps, though with a 7.2 Mbps HSDPA
device I have experienced a maximum of 300 KBps. The infrastructure seems yet to be developed to ensure the speed with full capacity and full coverage in outer areas of Kolkata. It is moderately costly. Check http://www.vodafone.in/3gworld/pages/3g_serivces.aspx for tariff.
Reliance:
Reliance 3G is also an HSPA technology. With a 7.2 Mbps HSDPA device this provides an average speed 500 KBps and the maximum possible speed
even rises further to 600 to 700 KBps. With a 21.1 Mbps device the speed should rise even higher. It is a little costlier than Vodafone 3G for higher bandwidth plans. But this is quite fair regarding their wide coverage and best data rate handling infrastructure.
http://www.rcom.co.in/Rcom/personal/3G/HTML/index.html
Others:
No survey is done on Aircel 3G but it seems to provide a comparable speed.
http://www.aircel.com/AircelWar/appmanager/aircel/kolkata?_nfpb=true&_pageLabel=B1800786561300341649097

Services like Idea 3G, Tata Docomo 3G, Airtel 3G are not available in Kolkata yet for commercial reasons. But Docomo and Airtel are expected to come in near future by tying up with existing networks.

Other telecom network technologies:
There are certain other technologies commercially available in Kolkata such as EV-DO (BSNL), HSIA (Tata Photon+). In general the tariff for those network services are cheaper than WCDMA and the speed is theoretically 3.1 Mbps, i.e., comparable to UMTS.