latform element and ME application life cycle, rules, and requirements. MEPM has been investigated by ETSI in [207] and [208]. 3. System-level entity: It involves the user application life cycle management proxy, operations support system (OSS), and mobile edge orchestrator. The user application life cycle proxy is responsible on some application services such as instantiation and termination. In addition, it provides a security gateway between the third-party applications and OSS. Meanwhile, the OSS receives the requests of UE and third-party applications. It verifies and grants resources for these requests and then forward them into the MEC orchestrator. The MEC orchestrator has a global view on the available MEC resources, services, and topology. Furthermore, it manages the MEC system, functionalities, services, and resources as well as third-party and UE applications. In addition, it verifies and achieves the requested resources and QoE for the applications. M. Alfaqawi et al. MEC entities communicate via reference points categorized into ME platform functionality (Mp), management reference points (Mm), and interfacing with external entities (Mx). These three reference points are detailed and explained in [165] and [201]. 1.5 5G Development and Experimentations Mobile operators, telecom enterprises, and Academia are collaborating on develop- ing simulation tools to validate and analyze the cellular networks with or without an actual implementation of hardware. These simulation tools are targeting the RAN, core, edge/cloud, and application layer. This section presents several 5G RAN and core simulation tools and projects for the edge/cloud and application layer. 1.5.1 5G Development Platforms for R&D Various 5G and LTE platforms, e.g., srsLTE and Radisys, for RAN and core have been investigated in depth in [209]. Besides these platforms in [209], additional simulation tools for 5G networks are compared in Table 1.10. As illustrated in Table 1.10, the LTE and 5G simulators for RAN involve three layers as follow