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MME (mobility management entity)

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Introduction

The Mobility Management Entity (MME) is a crucial component of the Evolved Packet Core (EPC) architecture in a Long-Term Evolution (LTE) network. It is responsible for managing and controlling the mobility of User Equipment (UE) within the LTE network. In this article, we will discuss the various functions of the MME, its architecture, and its interaction with other network elements in detail.

MME Functions

  1. Authentication and Security: The MME is responsible for authenticating the UE and providing security for the LTE network. It verifies the identity of the UE, validates its credentials, and generates session keys for secure communication between the UE and the network. The MME also provides encryption and decryption functions to ensure the confidentiality of the data transmitted over the network.
  2. UE Tracking: The MME tracks the location of the UE and maintains its current state in the network. It monitors the UE's location, mobility, and connectivity status to determine its accessibility and routing within the network.
  3. Session Management: The MME manages the establishment, modification, and termination of the UE's session within the network. It sets up the bearers (logical channels) between the UE and the serving gateway (SGW) for data transmission and manages the Quality of Service (QoS) for each session.
  4. Roaming Management: The MME is responsible for managing the UE's mobility when it moves from one LTE network to another. It interfaces with other MMEs to exchange information about the UE's location and session state to ensure seamless mobility across different networks.
  5. Paging and Notification: The MME initiates paging and notification procedures to inform the UE about incoming calls or data. It determines the location of the UE and forwards the paging request to the appropriate base station (eNodeB) to initiate communication.
  6. Handover Management: The MME manages the handover of the UE from one eNodeB to another during active sessions. It initiates the handover process by determining the target eNodeB and coordinating with the source eNodeB and SGW to transfer the UE's session to the new eNodeB.

MME Architecture

The MME is a logical entity within the EPC architecture, and it can be deployed as a standalone network element or as a part of the MME pool. The MME pool is a group of MMEs that share the load of UE management within the network. The MME architecture consists of the following components:

Control Plane: The control plane is responsible for managing signaling messages between the UE and the network. It includes the following components:

  • MME Application: It manages the signaling messages between the UE and the network and performs the functions of authentication, security, session management, roaming management, and handover management.
  • SGW: The SGW acts as a gateway between the UE and the Packet Data Network (PDN) and manages the data traffic between them. It performs the functions of packet routing, forwarding, and filtering.
  • HSS: The Home Subscriber Server (HSS) is responsible for storing and managing the subscriber's profile and credentials. It provides authentication and authorization services for the UE and the network.

Data Plane: The data plane is responsible for managing the data traffic between the UE and the PDN. It includes the following components:

  • SGW: The SGW manages the data traffic between the UE and the PDN and performs packet routing, forwarding, and filtering functions.
  • PDN: The PDN is the network that provides data services to the UE, such as the internet, multimedia messaging, and voice over IP.

MME Interaction with Other Network Elements

The MME interacts with other network elements to provide mobility management services within the LTE network. The following are the interactions between the MME and other network elements:

  1. UE: The MME communicates with the UE through the Radio Access Network (RAN) to manage its mobility and session state within the LTE network. The UE sends signaling messages to the MME to establish, modify, or terminate its session and receive paging and notification messages.
  2. eNodeB: The MME communicates with the eNodeB to manage the UE's mobility and session state within the LTE network. The eNodeB sends signaling messages to the MME to initiate the handover process or transfer the UE's session to a new eNodeB.
  3. SGW: The MME communicates with the SGW to manage the UE's data traffic within the LTE network. The SGW sends signaling messages to the MME to request session setup, modification, or termination, and receive location and mobility updates of the UE.
  4. HSS: The MME communicates with the HSS to authenticate and authorize the UE and retrieve its subscriber profile and credentials. The HSS sends signaling messages to the MME to authenticate the UE, retrieve its profile, and authorize its access to the LTE network.

Conclusion

The Mobility Management Entity (MME) is a critical component of the Evolved Packet Core (EPC) architecture in a Long-Term Evolution (LTE) network. It is responsible for managing and controlling the mobility of User Equipment (UE) within the LTE network. The MME performs various functions, such as authentication and security, UE tracking, session management, roaming management, paging and notification, and handover management. The MME architecture includes the control and data planes, which include the MME application, SGW, and HSS. The MME interacts with other network elements, such as the UE, eNodeB, SGW, and HSS, to provide mobility management services within the LTE network.