RLF Handling in Inter-eNB Carrier Aggregation
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Solution Overview
Problem
In dual connectivity mode of wireless networks with inter-eNB carrier aggregation, existing methods for handling Radio Link Failures (RLFs) on Secondary Cells (SCells) are inefficient, leading to service interruptions and increased battery power consumption due to legacy RRC connection re-establishment procedures, especially when RLFs occur on SCells served by different eNBs.
Innovation Solution
A method and system that allows User Equipment (UE) to autonomously initiate random access procedures on Secondary eNBs (SeNBs) during addition or replacement of Secondary Cells and handle RLFs by detecting issues on SCells, reporting them to the Master eNB, and reconfiguring data radio bearers without triggering unnecessary RRC connection re-establishment, thereby minimizing service interruptions and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE follows legacy RRC connection re-establishment procedure upon detecting RLF on SCell, then the RLF is handled according to standard protocol, but service interruptions occur and battery power consumption increases
Solution Approach 1:
The patent segments the RLF handling procedure into two distinct paths: one for PCell failures (legacy RRC re-establishment) and another for SCell failures (MAC layer recovery only). This segmentation allows the UE to avoid unnecessary RRC connection re-establishment when only SCell experiences RLF, thereby reducing service interruptions while maintaining reliable handling of actual connection issues.
Solution Approach 2:
The patent applies local quality by making the RLF handling approach dependent on the specific cell type affected. When RLF is detected on SCell, only MAC layer recovery procedures are triggered locally without affecting the overall RRC connection. This localized response ensures that service interruptions are minimized while still addressing the specific failure condition appropriately.
2Reliability
If the UE triggers RRC connection re-establishment upon RLF on SCell, then protocol compliance is maintained, but battery power consumption increases
Solution Approach 1:
The patent segments the error handling responsibilities between MAC layer and RRC layer based on the affected cell type. For SCell RLF, only MAC layer procedures are activated, avoiding the energy-intensive RRC connection re-establishment process while still maintaining protocol compliance through appropriate MAC layer error handling and recovery mechanisms.
Solution Approach 2:
The patent applies partial action by implementing only the necessary MAC layer recovery procedures for SCell RLF without triggering the full RRC connection re-establishment sequence. This partial response is sufficient to handle SCell failures while conserving battery power, and would be escalated to full RRC re-establishment only if PCell failure occurs.
3Speed
If independent random access procedure is implemented on SeNB, then uplink synchronization is achieved efficiently, but procedure complexity increases
Solution Approach 1:
The patent enables the UE to autonomously initiate random access procedures on SeNB without requiring network coordination or additional signaling overhead. The UE independently determines when random access is needed for uplink synchronization on SCell and executes the procedure directly, achieving fast synchronization while avoiding the complexity of coordinated network-controlled random access mechanisms.
Data Source
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AI summary
A method and system for performing a Random Access procedure by a User Equipment in a wireless network, including: performing a random access procedure on a Primary Cell of a first base station; receiving, from the first BS, a Radio Resource Control connection reconfiguration message for addition or modification of a second BS; transmitting, to the first BS, a response message corresponding to the RRC connection reconfiguration message; performing the RA procedure on a Secondary Cell of the second BS, including transmitting a RA preamble on a Physical Random Access Channel, receiving, from the second BS, a random access response RAR message, and setting a first cell radio network temporary identifier C-RNTI to a value of a temporary C-RNTI included the RAR message; and transmitting uplink data to the SCell, wherein the first C-RNTI and a second C-RNTI allocated by the first BS are independently allocated to the UE.