Section: A.3 Monitor of E-RAB level QoS modification
Content: When an E-RAB has been established, the QoS it experiences in the E-UTRAN is dependent upon the E-RAB level QoS parameters established for the bearer, together with settings of other bearers established in the same cell. If the QoS experienced by a bearer does not meet the expected performance, or the resource need be reassigned for other bearers, the E-RAB level QoS may be adjusted (typically with a knock-on effect onto other bearers). So the modification of E-RAB level QoS parameters needs to be monitored, and due to different priority and tolerance for different service type with different OoS level in the networks, the monitor needs to be opened on each target service type with OoS level. The E-RAB level QoS can be modified by E-RAB Modify procedure (see 3GPP TS 36.413[ Evolved Universal Terrestrial Radio Access Network (E-UTRAN); S1 Application Protocol (S1AP) ] [9]), in which the MME entity instructs the eNodeB to change one or more QoS parameters on an E-RAB using the E-RAB MODIFY REQUEST message. The eNodeB typically makes the adjustments as instructed (and adjusts the RRM applied to the bearer appropriately) but in some circumstances the bearer modification can fail. The eNodeB returns an E-RAB MODIFY RESPONSE message that tells the MME whether the modification was successful or not – for an unsuccessful modification a cause value is included. It is important for OAM to measure the failure rate of the bearer modifications, this information can be used, for example, to make adjustments to OAM CM settings.