sweetlysing,
It will vary based on the App's data demand, but typically 3 Mbps is the least you want to go, and 10Mbps is sufficient for most Apps. There's not an official answer, but I've tested it with different speed limits, and Netflix HD does pretty good at those speeds. (Other apps can be a little more data heavy, and require faster speeds).
Thanks for your interest in Samsung products.
--Mr. S