Emergency Call Redirection via Access Class Barring Parameters
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Solution Overview
Problem
Current LTE network specifications do not provide a clear mechanism for user equipment (UE) to initiate emergency calls when access class barring is enabled, as they fail to specify an alternate system for UEs to search and originate emergency calls when the ac-BarringForEmergency parameter is set to True.
Innovation Solution
A redirection procedure is introduced, where a redirection parameter carried by System Information Block (SIB) Type 2 messages aids the UE in establishing emergency calls by indicating attributes such as frequency channel numbers, cell identifiers, and wireless node identifiers of candidate cells, allowing the UE to redirect itself to a different cell for emergency call initiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If access class barring is enabled to protect the LTE network from failure during congestion, then network reliability is improved, but the ability of UEs to initiate emergency calls deteriorates
Solution Approach 1:
The network pre-configures and broadcasts ACB parameters including emergency call exemptions and redirection information to UEs before congestion occurs. When congestion is detected, the network has already prepared the mechanisms for emergency calls to bypass barring or redirect to alternative cells, ensuring emergency services remain accessible while normal traffic is restricted.
Solution Approach 2:
The patent applies different access control rules to different types of traffic: normal traffic subjects to strict ACB restrictions while emergency traffic receives special treatment through exemption mechanisms or priority redirection. This local differentiation allows the network to protect itself from congestion while maintaining emergency service availability.
2Adaptability or versatility
If ACB parameters are broadcast to UEs, then network control over access is improved, but the complexity of the access control system deteriorates
Solution Approach 1:
The patent uses a universal ACB parameter structure that handles multiple functions: normal access control, emergency call exemption, and redirection guidance. By encoding multiple control functions within a standardized parameter framework broadcast through existing system information blocks, the network achieves versatile access control without requiring separate complex signaling mechanisms for each function.
3Productivity
If UEs are barred from accessing the network during congestion, then network load is reduced, but emergency communication capability deteriorates
Solution Approach 1:
The patent introduces redirection parameters as an intermediary mechanism. When ACB bars UEs from accessing congested cells, the redirection parameters guide UEs with emergency calls to alternative non-congested cells or frequency layers. This intermediary redirection system allows the network to offload emergency traffic to alternative paths while maintaining strict access control on congested resources.
Data Source
AI summary
A method, a device, and a non-transitory storage medium having instructions to store a first access class barring parameter and a second access class barring parameter pertaining to emergency calls via a cell on which a wireless device is camped; receive an indication that an emergency call is to be established; select one or more values of the second barring parameter in response to a determination that a value of the first barring parameter indicates that the emergency call cannot be established via the cell; select a first candidate cell based on the one or more values of the second barring parameter; and determine whether the emergency call can be established via the first candidate cell based on the one or more values of the second barring parameter and system information pertaining to the first candidate cell.