SIB1 Broadcast Control in 5G NSA Networks
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Solution Overview
Problem
In 4G and 5G mobile networks, the continuous broadcasting of System Information Block 1 (SIB1) in Non-Standalone (NSA) mode leads to resource block wastage, as SIB1 is broadcasted even when not required, especially during transitions from Standalone (SA)+NSA to NSA mode, due to lack of control over SIB1 transmission by the Centralized Unit (CU) during Access and Mobility Function (AMF) disconnection.
Innovation Solution
The method involves configuring the gNB-CU-CP to request the gNB-DU to remove or broadcast a minimal version of SIB1 (AnrSIB1) or no SIB1 (NoSIB1) using the gNB-CU Configuration Update message, allowing the CU to control SIB1 transmission based on operational modes, thereby optimizing resource usage by stopping unnecessary SIB1 broadcasts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If SIB1 is continuously broadcasted in NSA mode, then cell information is available for UEs, but resource block wastage occurs
Solution Approach 1:
The patent implements dynamic SIB1 transmission control by introducing a flag parameter that can be set to 'removeSIB1' or 'minimalSIB1'. This allows the base station to adaptively adjust SIB1 broadcasting based on operational mode (SA/NSA) and gateway connection status, transmitting full SIB1 only when necessary for SA mode or initial access, and removing or minimizing it during NSA mode operation to conserve resource blocks
2Loss of energy
If SIB1 is removed in NSA mode, then resource block wastage is reduced, but ANR functionality may be impacted
Solution Approach 1:
The patent applies local quality by differentiating SIB1 transmission based on specific functional requirements. When ANR (Automatic Neighbor Relation) is needed, the system transmits a minimal version of SIB1 containing only essential information for neighbor cell identification, rather than removing it completely. This provides just enough information locally where needed for ANR while avoiding full SIB1 transmission waste
3Adaptability or versatility
If the base station handles both SA and NSA users, then service coverage is extended, but control complexity over SIB1 transmission increases
Solution Approach 1:
The patent implements a universal control mechanism through a single flag parameter that manages SIB1 transmission across multiple operational scenarios (SA mode, NSA mode, gateway connected, gateway disconnected). This multi-functional approach simplifies the control logic by using one unified parameter to handle all cases, rather than requiring separate complex control mechanisms for each mode
Data Source
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AI summary
Described are implementations of base station Control Plane (CU-CP) of a gNB-CU or an eNB-CU-CP configured to request a Distributed Unit (DU) to remove a System Information Block 1 (SIB1) or broadcast a minimal SIB1 for a network gateway - and Automatic Neighbor Relation (ANR) or a 4G Mobility Management Entity/Serving Gateway (MME/S-GW). At a disconnection of the network gateway, the CU Control Plane of the base station sends a request to the DU of the base station to remove the SIB1, or to broadcast a minimal transmission of the SIB1.