An E-RAB (E-UTRAN Radio Access Bearer) refers to the concatenation of an S1 bearer and the corresponding radio bearer. When an E-RAB exists, there is a one-to-one mapping between this E-RAB and an EPS bearer of the Non Access Stratum. Each E-RAB is defined by the following parameters: E-RAB ID – this element is used to identify the E-RAB on the S1 interface. E-RAB QoS – this element describes the QCI (Quality Class Identifier) that defines QoS parameters such as end to end delay, bit error rates etc. Also included are allocation and retention priorities as well as GBR (Guaranteed Bit Rate) parameters if real time services are to be supported over the E-RAB.