Single-DCI PT-RS Mapping for Multi-TRP Phase Tracking
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Solution Overview
Problem
The existing NR R15 PT-RS mapping scheme for multi-TRP transmission in URLLC is inadequate as it fails to ensure that each TRP has the correct density of phase-tracking reference signals (PT-RS), particularly in single-DCI based URLLC schemes, due to differing RF chains of different TRPs.
Innovation Solution
A method for PT-RS mapping in single-DCI based URLLC schemes that ensures each TRP receives the correct density of PT-RS by frequency or time division multiplexing, using DCI to indicate TCI states and adjusting frequency or time density based on resource block or symbol allocations, ensuring proper phase noise estimation and compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single PT-RS mapping scheme is used for multi-TRP transmission, then the system complexity is reduced, but the phase noise estimation accuracy for each TRP deteriorates
Solution Approach 1:
The patent divides the PT-RS resources into separate sets for different TRPs (first PT-RS set for first TRP, second PT-RS set for second TRP). Each TRP has its own dedicated PT-RS resources with independent frequency and time density configurations, allowing accurate phase noise estimation for each TRP while maintaining manageable system complexity through structured resource allocation.
Solution Approach 2:
The patent applies different PT-RS density configurations locally to different TRPs based on their specific channel conditions and requirements. Each TRP can have customized frequency density (KPT-RS) and time density (LPT-RS) parameters, enabling optimized phase tracking performance for each TRP rather than using a uniform configuration across all TRPs.
2Measurement precision
If PT-RS density is increased for better phase tracking, then the phase noise estimation accuracy is improved, but the uplink resource overhead increases
Solution Approach 1:
The patent enables dynamic adjustment of PT-RS density parameters (frequency density KPT-RS and time density LPT-RS) for each TRP based on channel conditions, modulation scheme, and phase noise characteristics. This allows the system to use higher PT-RS density only when and where needed for accurate phase tracking, while reducing density in conditions where it is not necessary, thereby optimizing the trade-off between estimation accuracy and resource overhead.
Solution Approach 2:
The patent changes the PT-RS density parameters independently for different TRPs and different transmission conditions. By adjusting frequency density (subcarrier spacing) and time density (symbol interval) parameters, the system can adapt the PT-RS resource allocation to match the actual phase noise characteristics of each TRP, achieving accurate phase tracking with minimal resource consumption.
3Measurement precision
If separate PT-RS resources are allocated for each TRP, then the phase noise estimation accuracy for each TRP is improved, but the resource allocation complexity increases
Solution Approach 1:
The patent implements a universal resource allocation framework that handles multiple TRPs with a consistent methodology. The same DCI format and resource allocation rules apply to all TRPs, with each TRP identified by its TCI state. This universal approach simplifies the allocation process despite serving multiple TRPs with different requirements, as the system uses a standardized procedure that can be extended to any number of TRPs.
Solution Approach 2:
The patent uses TCI (Transmission Configuration Indication) states as intermediaries to manage the mapping between TRPs and PT-RS resources. The TCI states serve as a mapping layer that connects the physical TRPs to the logical PT-RS resource sets, simplifying the allocation process by providing a standardized interface for resource assignment rather than directly managing complex one-to-one mappings between TRPs and resources.
4Measurement precision
If PT-RS frequency density is increased, then the phase tracking precision is improved, but the frequency resources consumed increase
Solution Approach 1:
The patent determines the optimal PT-RS frequency density in advance based on the configured frequency hopping pattern and the total number of resource blocks allocated to each TRP. By pre-calculating the frequency density parameter KPT-RS according to the formula that considers the hopping pattern and resource block count, the system ensures adequate phase tracking precision while efficiently utilizing the available frequency resources without excessive overhead.
Data Source
AI summary
Embodiments of the present disclosure are directed to methods and apparatuses for PT-RS mapping. In an embodiment of the present disclosure, the method includes transmitting a first set of phase-tracking reference signals in a first plurality of subcarriers within a first resource block set associated with a first TCI state with a first frequency density; transmitting a second set of phase-tracking reference signals in a second plurality of subcarriers within a second resource block set associated with a second TCI state with a second frequency density, where the first resource block set and the second resource block set are frequency division multiplexed in a time interval and a third resource block set composed of the first resource block set and the second resource block set is scheduled by a DCI.