RedCap UE Self-Identification via RACH Resources
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Solution Overview
Problem
Reduced capability (RedCap) user equipments (UEs) face performance degradation due to complexity reduction features, and existing technologies lack effective mechanisms for early identification, leading to inadequate compensation for link budget losses during communications.
Innovation Solution
The method involves a RedCap UE determining, based on criteria such as the number of receive branches and reference signal received power, whether to indicate its reduced capability status during or after a random access procedure, allowing for early identification and enabling coverage recovery techniques by the gNB.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If RedCap UEs use complexity reduction features (fewer receive branches, reduced bandwidth), then device cost and power consumption are reduced, but communication performance and link budget are degraded
Solution Approach 1:
The UE performs preliminary self-identification as RedCap before completing the random access procedure by selecting specific RACH resources (preamble, occasion, or both) that indicate its RedCap status to the gNB. This early identification enables the gNB to apply coverage recovery techniques in advance, compensating for the link budget loss caused by complexity reduction features before actual data transmission begins.
2Reliability
If RedCap UEs indicate their status during the random access procedure, then early identification and coverage recovery are enabled, but signaling overhead and procedure complexity increase
Solution Approach 1:
The patent uses existing RACH resources (preamble sequences, time-frequency occasions) as intermediaries to convey RedCap UE status information. Instead of introducing new dedicated signaling messages, the UE's selection of specific RACH resources serves as an implicit indication of its RedCap capability, allowing the gNB to identify RedCap UEs through standard random access procedures without additional signaling overhead.
3Device complexity
If RedCap UEs use fewer receive branches or reduced bandwidth, then device cost is reduced, but link budget loss occurs leading to inadequate coverage
Solution Approach 1:
The gNB changes transmission parameters based on the identified RedCap UE status, applying coverage recovery techniques such as adjusting transmit power, modifying modulation and coding schemes, or using repetition schemes. These parameter adjustments compensate for the link budget loss caused by the UE's reduced receive branches or bandwidth, ensuring adequate coverage despite the UE's simplified hardware configuration.
Data Source
AI summary
A user equipment (UE) may determine, based on a criterion, whether to indicate, to a gNB, that it is a reduced capability (RedCap) UE during or after a random access (RA) procedure, and indicate that it is the RedCap UE during or after the RA procedure according to a determination result. The RedCap UE has a reduced quantity of receive branches or a reduce bandwidth than a non-RedCap UE. The gNB may determine whether a first message received during the RA procedure indicates that the UE is the RedCap UE. When the first message indicates the UE as the RedCap UE, the gNB sends a second message to the UE during the RA procedure using a coverage recovery technique. When the first message does not indicate the UE as the RedCap UE, the gNB determines whether the UE is the RedCap UE after the RA procedure is completed.