Cellular Modem IRAT Re-selection Latency Reduction
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Solution Overview
Problem
Existing wireless communication systems face challenges in reducing latency during Inter-Radio Access Technology (IRAT) re-selection, particularly in scenarios where race conditions occur between call setup and IRAT re-selection procedures.
Innovation Solution
The proposed solution involves a method where a cellular modem initiates an IRAT re-selection procedure and suspends processing of a call setup procedure until the re-selection is complete. This involves caching requests during the re-selection process and resuming call setup processing once the re-selection is finished.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the cellular modem processes call setup procedure concurrently with IRAT re-selection, then call setup speed is improved, but call setup failures increase due to race conditions
Solution Approach 1:
The patent applies preliminary action by completing the IRAT re-selection procedure before processing the call setup procedure. The cellular modem waits for the re-selection to finish (which may involve caching the call setup request and resuming processing only after re-selection completion) to ensure the network is in a stable state, thereby preventing race conditions and call setup failures while maintaining efficient call establishment.
2Reliability
If the cellular modem suspends call setup processing during IRAT re-selection, then call setup failures are reduced, but call setup latency increases
Solution Approach 1:
The patent uses preliminary action by suspending call setup processing until IRAT re-selection is complete, ensuring the network is in a stable state before proceeding. This prevents race conditions and call setup failures, while the suspension mechanism itself is optimized to minimize overall latency by resuming processing as soon as re-selection completes.
Solution Approach 2:
The patent introduces an intermediary mechanism where the cellular modem caches the call setup request during IRAT re-selection and resumes processing only after re-selection completion. This intermediary caching mechanism allows the system to maintain reliability by preventing race conditions while minimizing latency by quickly resuming call setup processing once the network is in a stable state.
3Speed
If the cellular modem completes IRAT re-selection quickly, then network switching speed is improved, but call setup stability deteriorates
Solution Approach 1:
The patent applies preliminary action by ensuring IRAT re-selection is completely finished before processing call setup. The cellular modem waits for re-selection completion (including successful cell switching or camping) to initiate call setup, thereby ensuring network stability and preventing call setup failures while maintaining efficient switching through optimized re-selection procedures.
Data Source
AI summary
Methods, apparatuses, and systems are disclosed for reducing latency during IRAT re-selection in the presence of race conditions. When a UE initiates an IRAT re-selection procedure, and concurrently initiates a call setup procedure, a race condition may result, in which the UE's NAS layer prioritizes the call setup procedure, while the RRC layer prioritizes the IRAT re-selection procedure. This may result in failure of the call setup procedure, which may lead to a user needing to re-initiate the call, resulting in poor user experience and significant latency. To prevent this, the UE may cache a message and/or other information relevant to the call setup procedure, until the IRAT re-selection procedure is complete. The UE may then proceed to complete the call setup procedure. The message may be cached, e.g., at the NAS layer or the RRC layer of the cellular modem, or by an application processor.