SMF Congestion Handling via DCCF for PDU Session Requests
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Solution Overview
Problem
There is a tradeoff between network load and usability due to the expiration time of the backoff timer during network congestion, where a long expiration time decreases usability while a short expiration time increases network load, making it difficult to improve both simultaneously.
Innovation Solution
Implementing an asynchronous communication via a Data Collection Coordination Function (DCCF) to manage PDU session establishment requests during congestion, allowing the Session Management Function (SMF) to access stored signal data and continue processing without waiting for the backoff timer expiration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the expiration time of the backoff timer is extended to reduce network load during congestion, then the load on the network side decreases, but the usability decreases due to extended non-availability time
Solution Approach 1:
The network node stores signal data of PDU session establishment requests in advance before congestion occurs. When congestion is detected, the SMF can directly access pre-stored signal data from the DCCF without waiting for backoff timer expiration, thereby reducing non-availability time while maintaining network load control
Solution Approach 2:
The DCCF acts as an intermediary storage function between the terminal and the SMF. It stores signal data of PDU session establishment requests and allows the SMF to retrieve this data during congestion periods, enabling continued processing without direct terminal interaction and thus reducing both network load and non-availability time
2Loss of time
If the expiration time of the backoff timer is shortened to improve usability, then the non-availability time decreases, but the load on the network side increases
Solution Approach 1:
Signal data is preliminarily stored in the DCCF before congestion occurs. During congestion, the SMF accesses this pre-stored data directly, allowing rapid resumption of service (short non-availability time) without generating new signaling traffic that would increase network load
Solution Approach 2:
The system uses its own stored resources (signal data in DCCF) to serve itself during congestion. The SMF can independently retrieve and process stored signal data without requiring new signaling exchanges with the terminal, thereby improving responsiveness while avoiding additional network load
Data Source
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AI summary
A network node includes: a reception unit configured to receive a PDU (Protocol Data Unit) session establishment request related to a certain terminal from an AMF (Access and Mobility Management Function); a transmission unit configured to transmit a rejection signal including an indication of using a DCCF (Data Collection Coordination Function) to the AMF; and a control unit configured to access the DCCF and obtain signal data of the PDU session establishment request related to the certain terminal, in accordance with a congestion state of a DNN (Data Network Name).