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MOB_SCN-REQ Scanning Interval Allocation Request message

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The MOB_SCN-REQ (Mobility Scanning Interval Allocation Request) message is a control plane message used in 5G networks to request the allocation of a scanning interval for a UE (User Equipment). In this article, we will explain in detail what MOB_SCN-REQ messages are, what their purpose is, and how they are used in 5G networks.

Background

As the name suggests, the MOB_SCN-REQ message is related to the mobility of a UE in a 5G network. When a UE moves from one cell to another, it needs to perform cell selection and reselection procedures to maintain the communication with the network. These procedures involve scanning the available cells in the network to find the best one to connect to. Scanning consumes significant battery power and can also cause delay in the UE's ability to receive and transmit data.

To mitigate these issues, 5G networks allow UEs to request the allocation of scanning intervals. A scanning interval is a period of time during which the UE can scan for available cells. By requesting the allocation of a scanning interval, the UE can conserve battery power and reduce delays in receiving and transmitting data.

The MOB_SCN-REQ message is used by the UE to request the allocation of a scanning interval from the network. The message contains information about the UE's scanning requirements, such as the minimum and maximum scanning intervals, the maximum number of cells to be scanned, and the priority of the scanning request.

MOB_SCN-REQ Message Structure

The MOB_SCN-REQ message is a binary message that is transmitted over the air interface between the UE and the network. The message consists of three parts: the message header, the information element (IE) container, and the optional padding bits.

The message header is 8 bits long and contains information about the type of message and the size of the IE container.

The IE container contains one or more IEs, which are used to carry the information about the UE's scanning requirements. The IE container is variable in length and can contain up to 255 octets.

The padding bits are optional and are used to align the message to a 32-bit boundary. If the message length is not already a multiple of 32 bits, padding bits are added to the end of the message to align it.

The MOB_SCN-REQ message can contain the following IEs:

  • UE Identity (UEID): This IE identifies the UE that is requesting the scanning interval allocation.
  • MOB_SCN_PRIORITY: This IE specifies the priority of the scanning request. The priority can be set to high, medium, or low, depending on the urgency of the UE's scanning requirements.
  • MOB_SCN_INTERVALS: This IE specifies the minimum and maximum scanning intervals that the UE requires. The scanning interval is specified in milliseconds and can range from 20 ms to 160 ms.
  • MOB_SCN_MAX_NR_CELLS: This IE specifies the maximum number of cells that the UE is allowed to scan during each scanning interval. The maximum number of cells can range from 1 to 16.
  • MOB_SCN_BLACK_LIST: This IE specifies a list of cells that the UE should not scan. The blacklisted cells are identified by their Cell Global Identifier (CGI).
  • MOB_SCN_WHITE_LIST: This IE specifies a list of cells that the UE should scan. The whitelisted cells are identified by their CGI.

MOB_SCN-REQ Message Flow

The MOB_SCN-REQ message is initiated by the UE when it requires the allocation of a scanning interval. The UE sends the MOB_SCN-REQ message to the network over the air interface.

When the network receives the MOB_SCN -REQ message, it validates the message and checks if the UE is authorized to request a scanning interval. If the UE is authorized, the network allocates a scanning interval to the UE and sends a MOB_SCN-CONF (Mobility Scanning Interval Configuration) message to the UE.

The MOB_SCN-CONF message confirms the allocation of the scanning interval and contains information about the allocated scanning interval, such as the actual scanning interval, the number of cells to be scanned, and the duration of the scanning interval.

If the network cannot allocate a scanning interval to the UE, it sends a MOB_SCN_REJ (Mobility Scanning Interval Rejection) message to the UE. The MOB_SCN_REJ message contains information about the reason for the rejection, such as insufficient resources or conflicting scanning requests.

Conclusion

The MOB_SCN-REQ message is an important control plane message used in 5G networks to request the allocation of a scanning interval for a UE. By requesting the allocation of a scanning interval, UEs can conserve battery power and reduce delays in receiving and transmitting data.

The MOB_SCN-REQ message contains information about the UE's scanning requirements, such as the minimum and maximum scanning intervals, the maximum number of cells to be scanned, and the priority of the scanning request. The message flow involves the UE sending the MOB_SCN-REQ message to the network, the network validating the message and allocating a scanning interval, and the network sending a MOB_SCN-CONF or MOB_SCN_REJ message to the UE.

Overall, the MOB_SCN-REQ message is an essential feature of 5G networks that helps to improve the mobility and performance of UEs.