er request from the core network). RAC may also be executed at (initial) RRC connection request from the UE-that is, when the UE attempts to enter connected mode [14]. Although at © 2009 by Taylor & Francis Group, LLC Long Term Evolution: 3PPP LTE Radio and Cellular Technology Create dedicated bearer request (QoS Info) Bearer setup rejection is sent to MME EPS bearer setup request RAC for Allocate radio/transport resources Configure MAC/scheduler EPS bearer setup reject Create dedicated bearer response Session/Application layer specific handling (e.g SIP Reject, etc) Figure 4.4 If the radio access network cannot support the requested EPS bearer, it rejects the bearer request. Note that UE is not involved in the EPS bearer setup pro- cedure other than being notified by higher layer signaling-for example, using the session initiation protocol (SIP) between the core (service) network and the UE. this stage the UE does not specify the requested service, the RAN may reject such a connection request due to a heavy load situation. The RAN may also reserve a default bearer to the UE SO that as soon as the UE gets connected, an instant access to best effort services can be provided for the UE (as opposed to the service-specific bearers that need to configured and established according to the specific service requirements). RAC can be seen as part of the more general (overall) admission control procedure that also checks transport and hardware resources before admit- ting a new radio bearer or a radio bearer that is handed over from another eNode B. RAC is seen as a single cell RRM function and it does not require inter-eNode B communication (see Figures 4.3 and 4.4). Although RAC is mainly outside the scope of standardization, some aspects can be expected to be common for various LTE implementations. The provided QoS for the EPS bearer service (and the associated physical radio bearer) and, specifi- cally, the (average) bit rate are basically determined by: A: the number of transferred bits while the bearer is accessing (