I have an Airtel dongle (GSM) with Airtel 3G SIM and 2G plan. I want to increase my download speed. How can I do it?
If you are using 2G plans,then you won't get good speeds at all.3G is built for good data speeds which you subscribe for it,then you'll get good download speed.
Sounds pretty simple to me - upgrade your plan to a 3G plan. If you have a 3G-capable SIM but are only paying for 2G Internet access, then you are going to be bottlenecked at 2G speeds. 2G (GPRS) is incredibly slow compared with 3G (and glacial compared to 4G). This might not be the answer you hope for, but it's the only one that's actually going to work: pay Airtel more money for a faster speed.
If they're too expensive, try shopping around for a better deal!
Alternatively, if you use a smartphone with a 3G plan (most smartphones rely on a 3G plan) then you could look into tethering, though this is probably an even more expensive way of doing it.