liver extensive coverage, capacity, and low power consumption. 6.2 Network Architecture and Protocol Aspects 6.2.1 Network Architecture In order to exchange data between a NB-IoT device and an application server via NB-IoT access network, 3GPP has specified two optimizations for the cellular IoT (CIoT) in the evolved packet system (EPS): user-plane CIoT EPS and control-plane CloT EPS optimiza- tions, as shown in Fig. 6.3. These optimizations are not limited to NB-IoT devices. The control-plane CloT EPS optimization enables support of efficient transport of user data [Internet protocol (IP), non-IP, or SMS packets] over control plane via the mobility manage- ment entity (MME) without triggering data radio bearer establishment in order to reduce the latency. An NB-IoT terminal that only supports control-plane CloT EPS optimization is a UE that does not support user-plane CloT EPS optimization and S1-U data transfer, but may support other CloT EPS optimizations. The user-plane CloT EPS optimization enables Internet of Things S1-MME CloT RAN CloT Uu services Figure 6.3 NB-loT network architecture [11,19]. support for transition from EMM-IDLE mode to EMM-CONNECTED mode without invok- ing the service request procedure [6]. In other words, user-plane CloT EPS optimization allows radio resource control (RRC) con- nections to be suspended and resumed. In LTE, a new RRC context must be established when the UE moves from idle mode to connected mode. Reestablishing the context only takes about a 100 ms, but for IoT devices that only send a few bytes, it is a very significant overhead. Therefore, a method has been specified to preserve the context of an RRC con- nection and suspend it on the mobile device and network side rather than releasing it. In LTE, the control plane is used for management tasks such as authentication and connection establishment, while data is transmitted over the user plane. For high-data-rate transmis- sions, the overhead of setting up a connection on the control plane may be negligible. But, when de