ded across all non GBR bearers and across all PDN connections of the same APN. Each UE in state EMM-REGISTERED (EPS Mobility Management) is associated with UE-AMBR. The UE AMBR limits the aggregate bit rate that can be expected to be provided across all non GBR bearers of a UE. 3.9.2 Radio Resource Management The role of RRM is essential to ensure that radio resources are efficiently utilized, taking advantage of the various optimization techniques, and to serve users according to their QoS attributes. LTE employs a number of techniques for RRM including QoS-aware bearer admission control, multi-user time and frequency domain packet scheduling, hybrid automatic repeat request (HARQ) management, and link adaptation with dynamic switching between different transmission modes. The available transmission modes include single- and dual-codeword transmissions for multi-antenna configurations, and localized and distributed subcarrier transmission. These mechanisms will be placed in eNodeBs to have a better RRM than GSM and UMTS. Figure 3.29 shows an overview of the user plane and control plane protocol stack at the base station, as well as the corresponding mapping of the primary RRM related algorithms. The primary difference between the two planes is at the layer 3 level where the user plane is composed of PDCP whereas RRC is present in the control plane. The family of RRM algorithms at the base station exploits various functionalities from layer 1 to layer 3 as illustrated in Figure 3.29. Some of these RRM techniques are as follows [22]: 3.9.2.1 RRM Techniques Some key RRM techniques and processes are discussed in the following sections [14]: 3.9.2.1.1 Admission Control Based on QoS profile, the admission control functionality decides whether requests for new bearers (data flows) in the cell are granted or rejected. Admission control can take into account the resource situation in the cell, the QoS requirements for the new bearer, as well as the priority level and the currently provided QoS of the active sessions in t