Non-GBR Bearer Fallback for Voice Calls During GBR Setup Delays
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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 fail-over mechanism where a proxy node instructs the UE to use a non-guaranteed bit rate (non-GBR) data pipe for voice sessions when a guaranteed bit rate (GBR) data pipe cannot be set up within a specified time, using existing non-GBR data pipes such as default bearers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the system waits for a GBR data pipe to be set up before allowing voice calls, then call quality is improved, but call setup time increases and calls may fail or drop
Solution Approach 1:
The system performs preliminary actions by attempting to set up the GBR data pipe in advance before the voice call actually begins. The proxy node initiates the GBR setup process as soon as a voice call request is received, and simultaneously prepares a non-GBR data pipe as a backup. This preliminary preparation allows the system to have both quality assurance (through GBR) and time efficiency (through ready non-GBR fallback).
Solution Approach 2:
The system implements beforehand cushioning by pre-configuring a non-GBR data pipe as a backup before it is actually needed. When the GBR data pipe setup fails or takes too long, the pre-prepared non-GBR pipe is immediately activated without causing call failure or delay. This cushioning mechanism protects against the harmful effect of setup delays while maintaining call quality when possible.
2Reliability
If the system uses a GBR data pipe for voice calls, then call quality is improved, but system complexity increases due to setup failures and fallback mechanisms
Solution Approach 1:
The proxy node acts as an intermediary between the voice call request and the data pipe setup process. It receives the voice call request, coordinates the GBR data pipe setup with the policy node, monitors the setup status, and automatically switches to the non-GBR data pipe if needed. This intermediary simplifies the overall system architecture by centralizing the complexity in one component rather than distributing it across multiple elements.
Solution Approach 2:
The non-GBR data pipe is designed with multi-functionality, serving both as a general data bearer and as a backup voice call bearer. Instead of creating separate dedicated structures for fallback scenarios, the system uses the existing non-GBR pipe for dual purposes: normal data transmission and emergency voice call transmission. This universality reduces system complexity by eliminating the need for separate fallback infrastructure.
3Reliability
If the system attempts to set up a GBR data pipe for every voice call, then call quality is improved, but productivity decreases due to setup delays
Solution Approach 1:
The system applies partial action by attempting GBR data pipe setup only when necessary for voice calls, while using non-GBR pipes for other data transmissions. For voice calls specifically, the system performs the GBR setup attempt but is willing to accept partial achievement (non-GBR fallback) rather than insisting on complete GBR setup, thereby improving overall call setup efficiency while maintaining quality when possible.
Solution Approach 2:
The system implements dynamics by making the data pipe selection flexible and adaptive rather than static. The proxy node dynamically determines whether to use GBR or non-GBR data pipes based on real-time setup success and timing conditions. This dynamic approach allows the system to optimize call setup efficiency for each individual call while maintaining quality assurance, rather than following a rigid one-size-fits-all GBR setup policy.
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).