Adaptive UE Capability Message Compaction for CA Transmission Failures
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Solution Overview
Problem
The increasing size of UE capability messages due to the growing number of supported CA combinations poses a risk of unsuccessful transmission to the base station, leading to repeated setup-and-release scenarios and potential barring of the UE from connecting, especially in problematic cells with poor UL conditions or base station configuration limitations.
Innovation Solution
A UE employs adaptive UE capability message compaction by iteratively transmitting successively smaller subsets of CA combinations, using a PC list and network maximum CC list to determine compacted messages, until successful receipt by the base station or a threshold of attempts is reached, thereby avoiding the need to default to a lower-performance RAT.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the UE transmits complete capability messages representing all supported CA combinations, then the base station can be configured for optimal performance, but the message size increases to tens of kilobytes causing transmission failures
Solution Approach 1:
The UE capability message is segmented into two parts: a compact indicator field that signals support for extended CA combinations, and the actual capability information that is only fully transmitted when needed. This segmentation allows the initial message to remain small while still conveying essential capability information.
Solution Approach 2:
The base station performs preliminary configuration using a compact capability message that includes an indicator of extended CA support. Based on this preliminary information, the base station can decide whether to request full capability details or proceed with configuration using the indicated capabilities, avoiding unnecessary large message transmissions.
2Loss of information
If the UE transmits large capability messages to represent all CA combinations, then complete capability information is provided, but transmission time exceeds the allotted 5 milliseconds under poor uplink conditions
Solution Approach 1:
Capability information is segmented into essential indicators transmitted within the 5ms window, with detailed CA combination lists available on-demand or in subsequent transmissions. This ensures critical information is conveyed within time constraints while preserving complete capability data.
Solution Approach 2:
The UE transmits a partial capability message containing key indicators of CA support during the initial 5ms window. The base station uses this partial information to determine if full capability details are necessary, potentially avoiding the need for complete transmission and thus saving time.
3Reliability
If the base station releases the UE after failed capability message reception, then the system can retry the connection setup, but repeated failures lead to UE barring and fallback to legacy RAT
Solution Approach 1:
The UE and base station perform preliminary capability exchange using compact messages before full connection setup. This preliminary action provides enough information to proceed with configuration or identify incompatibilities early, reducing the likelihood of repeated setup-and-release cycles.
Solution Approach 2:
The base station provides feedback based on the compact capability indicators received, indicating whether full capability information is needed or if the indicated capabilities are sufficient. This feedback mechanism prevents unnecessary repeated transmissions and guides the connection establishment process efficiently.
Data Source
AI summary
A UE performs up to a threshold number of attempts to transmit a default capability message to a base station, the default capability message representing a default set of CA combinations supported by the UE. If transmission is unsuccessful, the UE switches to a compact capability mode in which the UE attempts to transmit compacted UE capability messages representing successively smaller subsets of the default set of CA combinations until either a capability message is successfully received by the base station or a second threshold number of unsuccessful transmission attempts is performed. To facilitate configuration of an initial compacted capability message, the UE maintains a PC list that lists one or more cells that have been identified previously as incapable of receiving default-sized capability messages and that further identifies a representation of a limited subset of CA combinations to include in capability messages sent to a corresponding listed cell.