How does a dedicated bearer created in LTE?

Answer 1

UE should have default bearer before dedicated bearer can be created. However, in case of Piggybacked dedicated bearer, default and dedicated bearers are simultaneously activated. UE can create a max of 11 bearers.1 has to be default, rest can be dedicated (Every APN will have 1 default bearer.)

Network initiates the dedicated bearer creation (Dedicated bearer creation can be initiated by PGW based on local config or based on PCRF). UE can also do it by sending Bearer resource allocation

Dedicated bearer can be created in one of the following ways

Case 1: Piggybacked Create bearer request is piggybacked to create session response, Modify bearer request is piggybacked to create bearer response (Attach accept is always sent first, before activate dedicated bearer request)

Case 2: Non-Piggybacked

Comments

You can refer "UE requested bearer resource modification" section in 3GPP TS 23.401 to understand how the dedicated bearer is activated based on Request Bearer Resource Modification message sent by UE.