iOS 3G & WiFi Connections

Question

I made a test program that log the download speed of a big file.

I start downloading the file using WiFi with an average speed of 180KB/s.

Then I start the app again downloading the file using 3G with an average speed of 20KB/s. After a few minutes of download, I enable WiFi. In the status bar the WiFi icon appear but the download speed don't change.

I was expecting that iOS switch between connections from 3G to WiFi. But it looks that although WiFi is enable, 3G is also enable. Is that correct?

In case that 3G speed is faster than WiFi, iOS switch to the better connection automatically?

In case both connections are enable it is posible to decide which one of the connection use?

If it posible to test 3G and WiFi download speed at same time?

Answer 1

My best guess is that once a networking connection is established, the established connected stays alive until it finishes. For example, if you start a download over a cellular data connection, the download will complete on that same connection. If that is, in fact, the case then enabling WiFi in the middle of a download won't affect the download speed for that current download, but if you start a new download after establishing the WiFi connection, the new download should transfer at WiFi speeds.