E request. For UEs in RRC_CONNECTED state, dedicated RRC signaling is used for the request and delivery of the other system information. For UEs in RRC_IDLE and RRC_INACTIVE states, making the request will trigger a random access procedure [16]. As an interim step for NR deployments, 3GPP has defined a set of non-stand-alone deploy- ment configurations using dual connectivity between NR gNB and LTE eNB (or ng-eNBs). Since initial NR networks will not have full coverage, dual connectivity can be used to combine the coverage advantage of the existing LTE networks with the throughput and latency advantages of the NR. However, it requires more complex UE implementations to allow simultaneous connections with both LTE and NR networks, potentially increasing the cost of the UEs. This will require more complex UE radio capabilities including the ability to simultaneously receive downlink transmissions from NR and LTE base stations on sepa- rate frequency bands. The non-stand-alone NR deployments use architectures where NR gNBs are associated with LTE eNBs and do not require separate signaling connections to the 5GC. These architectures are classified based on the control-plane and user-plane con- nections used between eNB, gNB, EPC, and 5GC. 5G Network Architecture LTE eNB Option 2 Option 3 LTE eNB ng-eNB Option 3A Option 4 ng-eNB ng-eNB Option 4A Option 5 ng-eNB ng-eNB Option 7 Option 7A Figure 1.80 NR deployment options 34]. The deployments based on architecture option 3 use EPC as the core network as shown in Fig. 1.80. In this case, S1-C control-plane interface for the UE is established between the LTE eNB and the EPC. The gNB acts as a secondary node connected to the master node represented by the eNB. Control-plane information is exchanged between the LTE eNB and the NR gNB, and no direct control-plane interface exists between the gNB and the EPC. User-plane bearers are supported between eNB and EPC over S1-U. In option 3A, the gNB also terminates user-plane bearers with the EPC. In option 3A, those g NB terminate