EMM (EPS mobility management)

Introduction:

EPS (Evolved Packet System) mobility management (EMM) is a critical part of the EPS architecture, which is used to manage the mobility of devices across different networks in a mobile communication system. EMM ensures that the devices remain connected to the network, while also providing seamless handover between different network elements. In this article, we will explore the architecture of EMM, its functions, and how it works to manage device mobility.

EMM Architecture:

EMM is part of the EPS architecture, which is a core component of the 4G LTE (Long-Term Evolution) mobile communication system. The EPS architecture comprises of two main elements: the Evolved UMTS Terrestrial Radio Access Network (E-UTRAN), and the Evolved Packet Core (EPC). The E-UTRAN consists of the base stations (eNodeBs) and the mobile devices (UEs), while the EPC comprises of the network elements that provide connectivity to the core network and other external networks.

EMM is a protocol that operates between the UE and the EPC, and it comprises of two sub-protocols: the Attach and the Tracking Area Update (TAU). The Attach protocol is used to establish a connection between the UE and the network, while the TAU protocol is used to manage the mobility of the UE within the network.

EMM Functions:

The primary function of EMM is to manage the mobility of the UE within the EPS network. This involves ensuring that the UE remains connected to the network, even when it moves from one location to another. EMM also ensures that the UE can seamlessly handover between different network elements, such as base stations, without losing connectivity.

The Attach procedure is the first step in establishing a connection between the UE and the network. It involves the UE sending a request to the network, which includes its International Mobile Subscriber Identity (IMSI) and other relevant information. The network responds with a message that includes the information required for the UE to establish a connection, such as the assigned IP address and the security parameters.

Once the UE is attached to the network, the TAU procedure is used to manage its mobility within the network. This involves updating the UE's location information, such as its current cell and tracking area, with the network. The TAU procedure is triggered when the UE moves out of its current tracking area and enters a new one. This ensures that the network is aware of the UE's location, and can route incoming calls and messages to the appropriate network elements.

EMM also manages the security of the connection between the UE and the network. This involves the use of authentication and encryption protocols to ensure that the connection is secure and cannot be intercepted by unauthorized parties. EMM uses the Authentication and Key Agreement (AKA) protocol to authenticate the UE and generate session keys that are used to encrypt and decrypt the data transmitted over the connection.

EMM also manages the Quality of Service (QoS) of the connection between the UE and the network. This involves ensuring that the UE is provided with the required network resources, such as bandwidth and latency, to support the services it is using. EMM uses the QoS parameters negotiated during the Attach procedure to ensure that the UE is provided with the required QoS.

EMM also manages the mobility of the UE between different networks. This involves ensuring that the UE can seamlessly handover between different networks, such as from LTE to 3G, without losing connectivity. This is achieved through the use of inter-system handover procedures, which allow the UE to transition from one network to another while maintaining the connection.

EMM also manages the mobility of the UE between different operators. This involves ensuring that the UE can roam between different networks operated by different operators, while maintaining connectivity. This is achieved through the use of roaming agreements between operators, which allow the UE to connect to the network of the visited operator while maintaining its connection to its home operator.

EMM also manages the power consumption of the UE. This involves optimizing the use of network resources to minimize the power consumption of the UE while ensuring that it remains connected to the network. EMM achieves this through the use of techniques such as network-assisted device-to-device communication and optimized network scheduling.

How EMM works:

The EMM protocol operates between the UE and the EPC, and it comprises of two main procedures: the Attach and the TAU. The Attach procedure is used to establish a connection between the UE and the network, while the TAU procedure is used to manage the mobility of the UE within the network.

The Attach procedure is initiated by the UE when it is powered on or when it moves into an area where it has not previously established a connection. The UE sends an Attach Request message to the network, which includes its IMSI and other relevant information. The network responds with an Attach Accept message, which includes the information required for the UE to establish a connection, such as the assigned IP address and the security parameters.

Once the UE is attached to the network, the TAU procedure is used to manage its mobility within the network. The TAU procedure is triggered when the UE moves out of its current tracking area and enters a new one. The UE sends a TAU Request message to the network, which includes its current location information and other relevant information. The network responds with a TAU Accept message, which includes the updated location information for the UE.

During the TAU procedure, the network may also update the security and QoS parameters for the connection between the UE and the network. This ensures that the connection remains secure and that the UE is provided with the required QoS.

Conclusion:

EPS mobility management (EMM) is a critical part of the EPS architecture, which is used to manage the mobility of devices within a mobile communication system. EMM ensures that the devices remain connected to the network, while also providing seamless handover between different network elements. The EMM protocol operates between the UE and the EPC, and it comprises of two main procedures: the Attach and the TAU. The Attach procedure is used to establish a connection between the UE and the network, while the TAU procedure is used to manage the mobility of the UE within the network. EMM also manages the security, QoS, power consumption, and mobility of the UE within and between different networks and operators. With the rapid growth of mobile communication systems, EMM plays an increasingly important role in ensuring that the devices remain connected and mobile within the network.