UE BWP Fallback and Random Access Alignment
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Solution Overview
Problem
Current wireless communication systems face limitations in flexibility and efficiency, particularly in managing bandwidth parts (BWPs) for downlink and uplink transmissions, which affects the alignment of UL BWP usage during fallback procedures and initial configuration in scenarios like EN-DC.
Innovation Solution
Configuring a special UL BWP with PRACH resources and corresponding common search space in DL BWP for UE in connected mode, allowing fallback and enabling proper alignment between UE and gNB for fallback procedures, and independently configuring initial DL/LTL BWPs and default BWPs for EN-DC.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If UE autonomously falls back to UL BWP with PRACH resources when current active UL BWP does not have configured PRACH resources, then random access capability is maintained, but alignment between gNB and UE on which UL BWP to use becomes problematic
Solution Approach 1:
The gNB provides feedback through downlink control information indicating the active UL BWP index, enabling the UE to correctly identify which UL BWP should be used for random access procedures, resolving the alignment problem between gNB and UE
Solution Approach 2:
The network pre-configures multiple UL BWPs with different PRACH resource configurations before the UE needs to perform random access, allowing the UE to fall back to an appropriate UL BWP while maintaining alignment with gNB expectations
2Adaptability or versatility
If network configures special UL BWP with PRACH resources for connected mode UE fallback, then flexibility in BWP management is improved, but device complexity increases
Solution Approach 1:
The special UL BWP configuration serves multiple functions: it provides PRACH resources for random access, enables fallback procedures for both initial access and connected mode, and maintains compatibility with existing BWP management mechanisms, thereby reducing overall system complexity
3Adaptability or versatility
If initial DL/LTL BWPs and default BWPs are independently configured for EN-DC, then configuration flexibility is improved, but complexity of BWP alignment procedures increases
Solution Approach 1:
The BWP configuration is segmented into distinct components (initial DL BWP, initial UL BWP, default BWP) with independent configuration parameters, allowing flexible setup for EN-DC while providing clear reference points for alignment procedures
Data Source
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AI summary
A user equipment (UE) is described. Receiving circuitry is configured to receive a radio resource control (RRC) message including first information used for indicating an index of a downlink bandwidth part (DL BWP) in a primary cell. Transmitting circuitry is configured to perform, based on an initiation of a random access procedure, the random access procedure. In a case that physical random access channel (PRACH) resources are not configured for an active UL BWP in the primary cell, the random access procedure is performed on a DL BWP in the primary cell and an UL BWP in the primary cell. An index of the DL BWP being defined as "0", and an index of the UL BWP being defined as "0".