Sign in Subscribe

MM sub (Mobility Management sublayer )

Last updated on 

The Mobility Management (MM) sublayer is a critical component of the network architecture in cellular networks. This sublayer is responsible for managing the mobility of mobile devices within the network, ensuring that they are always connected to the best available network and maintaining a seamless connection as they move around.

In this article, we will discuss the MM sublayer in detail, including its purpose, components, and functions.

Purpose of MM sublayer

The primary purpose of the MM sublayer is to manage the mobility of mobile devices within the network. This includes tracking the location of devices, registering them with the network, and facilitating handovers as they move between different cells or networks.

Mobile devices in cellular networks can move around frequently and quickly, so it is important to have a system in place that can manage their mobility efficiently. The MM sublayer is responsible for ensuring that devices are always connected to the best available network, and that they can move between different networks or cells without any interruption to their service.

Components of MM sublayer

The MM sublayer consists of several components that work together to manage the mobility of mobile devices within the network. These components include:

1. Mobility Management Entity (MME)

The Mobility Management Entity (MME) is the central component of the MM sublayer. It is responsible for managing the mobility of mobile devices within the network and communicating with other network elements, such as base stations and home location registers (HLRs).

The MME performs several functions, including:

  • Authenticating and authorizing devices to access the network
  • Tracking the location of devices within the network
  • Assigning temporary identities to devices for communication purposes
  • Facilitating handovers as devices move between different cells or networks
  • Providing paging support for devices that are in idle mode

2. Serving Gateway (SGW)

The Serving Gateway (SGW) is responsible for routing data packets between the mobile device and the core network. It is located at the edge of the core network and communicates with the base station to manage the mobility of the device.

The SGW performs several functions, including:

  • Routing data packets between the mobile device and the core network
  • Acting as a mobility anchor point for the device
  • Managing the handover process as the device moves between different cells or networks

3. Packet Data Network Gateway (PDN GW)

The Packet Data Network Gateway (PDN GW) is responsible for routing data packets between the core network and the external packet data network, such as the internet. It acts as a gateway between the core network and the external network, and ensures that data is routed to the correct destination.

The PDN GW performs several functions, including:

  • Routing data packets between the core network and the external packet data network
  • Providing connectivity to external networks such as the internet
  • Allocating IP addresses to devices for communication purposes
  • Managing the quality of service (QoS) for data traffic

4. Home Subscriber Server (HSS)

The Home Subscriber Server (HSS) is responsible for storing and managing subscriber data, such as authentication credentials, service preferences, and user profiles. It is the central repository for subscriber data and is accessed by other network elements, such as the MME and the SGW.

The HSS performs several functions, including:

  • Storing and managing subscriber data
  • Authenticating and authorizing devices to access the network
  • Enforcing service policies and preferences for subscribers
  • Managing subscriber profiles and service configurations

Functions of MM sublayer

The MM sublayer performs several critical functions that are essential for managing the mobility of mobile devices within the network. These functions include:

1. Location tracking

The MM sublayer is responsible for tracking the location of mobile devices within the network. This is achieved through a process known as Location Area Management (LAM), where the network is divided into location areas, each of which is serviced by a specific base station. The MME is responsible for tracking the location of devices within each location area and updating their location information in the network database.

2. Registration and authentication

Before a mobile device can access the network, it must be registered and authenticated by the MM sublayer. This involves verifying the device's identity, checking its authentication credentials, and authorizing it to access the network. The MME is responsible for managing the registration and authentication process and maintaining a secure connection between the device and the network.

3. Handover management

As a mobile device moves around the network, it may need to switch to a different base station or network to maintain a continuous connection. This process, known as handover, is managed by the MM sublayer. The MME and SGW work together to facilitate a smooth handover process, ensuring that the device remains connected to the network without any interruption to its service.

4. Paging support

When a mobile device is in idle mode, it is not actively communicating with the network. However, it still needs to be reachable in case the network needs to send it a message or call. This is achieved through a process called paging, where the network sends a message to the device's last known location, requesting it to respond. The MM sublayer is responsible for providing paging support for devices in idle mode, ensuring that they can be reached when necessary.

5. Quality of Service (QoS) management

The MM sublayer is also responsible for managing the quality of service (QoS) for data traffic within the network. This involves prioritizing different types of data traffic based on their importance and ensuring that they are delivered with the appropriate level of quality. The PDN GW is responsible for managing the QoS for data traffic, and the MM sublayer works together with the PDN GW to ensure that the QoS requirements are met for each device.

Conclusion

In summary, the Mobility Management (MM) sublayer is a critical component of the network architecture in cellular networks. It is responsible for managing the mobility of mobile devices within the network, ensuring that they are always connected to the best available network and maintaining a seamless connection as they move around. The MM sublayer consists of several components, including the MME, SGW, PDN GW, and HSS, which work together to manage the mobility of devices. The MM sublayer performs several functions, including location tracking, registration and authentication, handover management, paging support, and quality of service management. Overall, the MM sublayer plays a crucial role in ensuring the seamless connectivity of mobile devices within the network and providing a high-quality user experience.