Non-GBR Bearer Fallback for Faster IMS Voice Call Setup
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Solution Overview
Problem
Voice calls in cellular networks often fail or drop due to the inability to set up an IMS dedicated bearer in time, degrading user experience.
Innovation Solution
Implementing a system that allows voice and video calls to proceed over a non-guaranteed bit rate (non-GBR) default bearer when the wireless network is unable to set up a guaranteed bit rate (non-GBR) data pipe (non-GBR) data pipe (non-GBR) data pipe (non-GBR) bearer when a guaranteed bit rate (GBR) dedicated bearer cannot be set up in time, using a proxy node to switch to a proxy node to set up a voice session using an existing non-GBR data pipe.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the system attempts to set up a GBR dedicated bearer for voice calls, then call quality is improved, but call setup time increases and calls may fail if not completed in time
Solution Approach 1:
The system performs preliminary actions by attempting to set up the GBR dedicated bearer before the voice call actually begins. The proxy node initiates the bearer setup process in advance, and if successful, the call proceeds with high quality. This preliminary action allows the system to secure the quality improvement while managing the time constraint by having the setup process start before the call is needed.
Solution Approach 2:
The proxy node acts as an intermediary between the UE and the network core, managing the bearer setup process. It coordinates the GBR bearer establishment, monitors timeout conditions, and makes the decision to switch to non-GBR bearer if the GBR setup fails. This intermediary role allows the system to pursue high-quality GBR calls while having a fallback mechanism to prevent call failures.
2Reliability
If the system waits for GBR bearer setup completion before allowing voice calls, then call quality is maintained, but call setup delay increases
Solution Approach 1:
The system performs the GBR bearer setup as a preliminary action before the voice call is fully established. The proxy node initiates the bearer setup process in advance, allowing the call to proceed on a non-GBR bearer immediately if the GBR setup is not completed in time. This approach maintains the opportunity for high quality calls while avoiding setup delays by not blocking the call initiation.
Solution Approach 2:
The system dynamically adjusts the bearer type based on setup success. Initially, the system attempts to use GBR bearer for high quality, but if the setup fails within the timeout period, it dynamically switches to non-GBR bearer to allow the call to proceed. This dynamic adaptation resolves the contradiction by pursuing quality when possible while accepting lower quality when time constraints prevent GBR setup.
3Loss of time
If the system uses non-GBR default bearer for voice calls, then call setup time is reduced, but call quality deteriorates
Solution Approach 1:
The system performs a preliminary attempt to set up the higher-quality GBR bearer before falling back to the non-GBR default bearer. The proxy node initiates the GBR bearer setup in advance, and only if this preliminary action fails within the timeout period does the system proceed with the non-GBR bearer. This preliminary action allows the system to minimize call setup time while still pursuing better quality when possible.
Solution Approach 2:
The system uses the non-GBR default bearer as a temporary, disposable solution when the GBR bearer setup fails. Instead of persisting with the failed GBR setup or rejecting the call entirely, the system accepts the lower-quality non-GBR bearer as a acceptable fallback that allows the call to proceed. This approach prioritizes getting the call established quickly over maintaining the highest possible quality.
Data Source
AI summary
Solutions for providing best effort service for voice calls (including video calls) using a non-guaranteed bit rate (GBR) bearer include: receiving, at a proxy node (e.g., a proxy-call session control function (P-CSCF)), a request to set up a voice session for a UE; requesting, by the proxy node, a policy node (e.g., a policy and charging rules function (PCRF) or a policy control function (PCF)) to set up a GBR data pipe (e.g., a dedicated bearer, a quality of service (QOS) class identifier (QCI) 1 bearer, or a fifth generation (5G) QoS identifier (5QI) 1 bearer); based at least on an error condition (e.g., a timeout or error message), instructing, by the proxy node, the UE to set up the voice session using an existing non-GBR data pipe (e.g., a default bearer, a QCI-5 bearer, or a 5QI-5 bearer).