An EPS bearer uniquely identifies traffic flows that receive a common QoS treatment between a UE and a PDN GW for GTP-based S5/S8.
Whenever a UE attaches to a PDN, there will always be a Default bearer which gets created. This EPS bearer which is first established for a new PDN connection and remains established throughout the lifetime of the PDN connection. Any additional EPS bearer that is established for the same PDN connection is referred to as a Dedicated bearer.
Each EPS bearer is assigned a EBI (EPS Bearer Identity) by MME. This EBI is of 4 bits. Hence 16 combinations are possible. In those 16, first 5 (0-4) are reserved. It means EBI values range from 5-15. Hence the total number of bearers that a UE can have per PDN is 11.
An EPS bearer is referred to as a GBR bearer if dedicated network resources related to a Guaranteed Bit Rate (GBR) value that is associated with the EPS bearer are permanently allocated (e.g. by an admission control function in the eNodeB) at bearer establishment/modification. Otherwise, an EPS bearer is referred to as a Non-GBR bearer.
** A dedicated bearer can either be a GBR or a Non-GBR bearer. A default bearer shall be a Non-GBR bearer.
Ref: 3GPP TS 23.401
Whenever a UE attaches to a PDN, there will always be a Default bearer which gets created. This EPS bearer which is first established for a new PDN connection and remains established throughout the lifetime of the PDN connection. Any additional EPS bearer that is established for the same PDN connection is referred to as a Dedicated bearer.
Each EPS bearer is assigned a EBI (EPS Bearer Identity) by MME. This EBI is of 4 bits. Hence 16 combinations are possible. In those 16, first 5 (0-4) are reserved. It means EBI values range from 5-15. Hence the total number of bearers that a UE can have per PDN is 11.
An EPS bearer is referred to as a GBR bearer if dedicated network resources related to a Guaranteed Bit Rate (GBR) value that is associated with the EPS bearer are permanently allocated (e.g. by an admission control function in the eNodeB) at bearer establishment/modification. Otherwise, an EPS bearer is referred to as a Non-GBR bearer.
** A dedicated bearer can either be a GBR or a Non-GBR bearer. A default bearer shall be a Non-GBR bearer.
Ref: 3GPP TS 23.401
Nice explanation
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