PTRS-to-DMRS Port Mapping for Multi-TRP Phase Tracking
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Solution Overview
Problem
The existing solutions for PTRS port association in multi-TRP operations in NR Release 16 do not effectively map PTRS ports to the strongest MIMO layers, leading to degraded phase tracking performance and increased block error rates.
Innovation Solution
The method involves associating a single PTRS port with the lowest indexed DMRS port within each TCI state for PDSCH transmission, ensuring improved phase tracking by aligning PTRS with the strongest MIMO layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If existing PTRS port association solutions are used in multi-TRP operations, then the system can support multiple transmission points, but phase tracking performance degrades and block error rates increase
Solution Approach 1:
The patent applies local quality by associating PTRS ports specifically with DMRS ports that correspond to the strongest MIMO layers. Instead of uniform PTRS association across all DMRS ports, the invention selectively links PTRS resources to specific DMRS ports based on channel quality metrics, ensuring that phase tracking is optimized for the most critical layers while maintaining multi-TRP operation capability
Solution Approach 2:
The patent changes the association parameter between PTRS and DMRS ports by introducing a mapping rule that connects PTRS ports to DMRS ports based on MIMO layer strength. This parameter change transforms the fixed association into a dynamic one that adapts to channel conditions, improving phase tracking reliability without sacrificing multi-TRP versatility
2Device complexity
If PTRS is associated with DMRS ports without considering MIMO layer strength, then the configuration is simple, but phase tracking performance deteriorates
Solution Approach 1:
The patent applies preliminary action by pre-establishing the mapping relationship between PTRS ports and DMRS ports based on MIMO layer strength indicators. The system determines which DMRS ports correspond to stronger layers in advance and configures PTRS association accordingly, so that when phase tracking is performed, the optimal PTRS-DMRS pairing is already in place without requiring real-time complex decisions
3Ease of operation
If a single PTRS port is associated with multiple DMRS ports across different TCI states, then resource allocation is simplified, but phase tracking accuracy decreases
Solution Approach 1:
The patent applies segmentation by dividing the PTRS resource allocation into separate associations for each TCI state. Instead of having a single PTRS port serve multiple DMRS ports across different TCI states, the invention segments the association so that each PTRS port is linked to specific DMRS ports within a particular TCI state context, maintaining resource efficiency while improving phase tracking precision for each transmission point
Data Source
AI summary
Systems and methods for Phase Tracking Reference Signal (PTRS) to Demodulation Reference Signal (DMRS) association when two or more Transmission Configuration Indication (TCI) states are indicated for a Physical Downlink Shared Channel (PDSCH) transmission in a cellular communications system are disclosed. In one embodiment, a method performed by a WCD comprises receiving a Physical Downlink Control Channel (PDCCH) comprising Downlink Control Information (DCI) that indicates two Transmission Configuration Indication (TCI) states for a PDSCH transmission to the WCD and DMRS ports within a single Code Division Multiplexing (CDM) group. The method further comprises determining a PTRS port to DMRS port association for the PDSCH transmission, wherein a single PTRS port is used for the PDSCH transmission and determining the PTRS port to DMRS port association comprises determining that the single PTRS port is associated with a lowest indexed DMRS port in the DMRS ports indicated in the DCI.