Multi-TRP Timing Advance Management via RACH Signaling
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Solution Overview
Problem
In new radio (NR) systems, maintaining timing alignment for uplink transmissions in multi-transmission and reception point (M-TRP) scenarios is challenging due to imperfect synchronization and varying propagation delays across different TRPs, leading to timing asynchronization and difficulties in determining the correct TRP associated with initial timing advance (TA) values.
Innovation Solution
The system supports acquisition and management of two different TA values for each TRP by using RACH signaling to obtain TA values from a base station, with explicit or implicit identification of TRPs through identifiers, and manages these values during M-TRP transmission, allowing for network-initiated or UE-initiated contention-based or contention-free RACH procedures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single TA value is used for a cell shared by two TRPs, then the system complexity is reduced, but timing asynchronization occurs on one TRP due to imperfect time synchronization and different propagation delays
Solution Approach 1:
The patent segments the timing advance management by introducing separate TA values for each TRP (first TA value for first TRP, second TA value for second TRP). This segmentation allows each TRP to have its own timing compensation mechanism, resolving the timing asynchronization issue while maintaining manageable complexity through structured separation of timing parameters.
Solution Approach 2:
The patent applies local quality by configuring different TA parameters (n-TimingAdvanceOffset values) for different TRPs based on their specific propagation characteristics. Each TRP receives customized timing advance parameters tailored to its local propagation conditions, ensuring optimal timing alignment for each TRP-UE link.
2Ease of operation
If UE-initiated RACH preamble transmission is used for initial TA acquisition, then the UE can obtain TA values, but the UE cannot determine which TRP is associated with the initial TA value in the RAR
Solution Approach 1:
The patent implements feedback mechanisms where the gNB provides not only TA values but also associated TRP identification information in the RAR message. This feedback loop enables the UE to correctly map received TA values to their corresponding TRPs, resolving the information loss issue while maintaining the simplicity of UE-initiated RACH procedures.
Solution Approach 2:
The patent introduces an intermediary mechanism through the use of downlink reference timing associations and TAG configurations that serve as mediators between the RACH procedure and TRP identification. These intermediaries carry the necessary mapping information from TA values to their corresponding TRPs without requiring changes to the fundamental RACH initiation process.
3Reliability
If two DL reference timings are supported for maintaining two TAs, then timing alignment for each TRP is improved, but the device complexity and configuration overhead increase
Solution Approach 1:
The patent applies universality by designing the downlink reference timing mechanism to serve multiple functions simultaneously: it provides timing reference for multiple TRPs, enables TRP identification, and supports both initial access and subsequent timing adjustments. This multi-functionality reduces the need for separate dedicated mechanisms for each function, thereby managing complexity while achieving reliable timing alignment.
4Measurement precision
If different n-TimingAdvanceOffset values are configured for different TRPs, then accurate timing compensation is achieved, but the signaling overhead and configuration complexity increase
Solution Approach 1:
The patent merges the configuration of multiple TRP-specific parameters into unified RACH procedure configurations and TAG-level settings. By combining the configuration of n-TimingAdvanceOffset values with existing RACH and TAG parameters, the system achieves precise timing compensation for multiple TRPs without requiring separate independent configuration procedures for each parameter.
Data Source
AI summary
A system and a method are provided in which a user equipment (UE) acquires, from a base station (BS), a first timing advance (TA) value for a first transmission and reception point (TRP) and a second TA value for a second TRP via random access channel (RACH) signaling based on an identifier. The UE manages the first TA value and the second TA value during multi-TRP transmission within a cell having the first TRP and the second TRP.