LTE : Does it mandatory to have default bearer as a non - GBR bearer ?

Question

In LTE, when UE is first time attached to a network, it is usually allocated a default non-GBR bearer. Can this bearer be converted to a GBR bearer, without releasing the UE context at eNodeB?

Answer 1

I think, its not.
LTE provides always on-IP connectivity to its users. To met this objective only a non-GBR bearer is sufficient.
However, there is no constraint, a GBR-bearer can also be used as a default bearer at the cost of more radio resource since when for a GBR bearer, eNodeB MAC scheduler need to reserve more resource as compare to non-GBR bearer.