Xbox Wire, the news channel of Microsoft's entertainment department, revealed more details about the requirements necessary in order to play on Xbox One.
In order to have an optimal experience, Microsoft recomends using a broadband connection of 1.5Mbps. Microsoft took this decision based on a study done by Akamai, which said average global internet connection speed is 2.9 Mbps. It was also confirmed that you will be able to use a mobile broadband connection on Xbox one in lue of an Ethernet connection.
A broadband connection will be required once every 24 hours. In case you don't do this, playing will be an impossible task. However, even without this requirement, features such as watching TV, and DVD or Blu-ray movies on Xbox One will be possible. Also, if you're playing on your account on an Xbox One that isn't your primary console, you have to connect it online every hour.
Microsoft justifies this by claiming that the system and features will automatically be installed in order to avoid players waiting before playing. Also, games that are designed to take advantage of the cloud may require a connection.
Source: Xbox Wire