Multi-TRP PDCCH Diversity With Shared DMRS Under TRP Blocking
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Solution Overview
Problem
Existing methods for PDCCH transmission in NR networks using multiple TRPs face challenges when one TRP is blocked, leading to poor performance due to signal loss or increased code rate, particularly in Frequency Range 2 (FR2), where beams are narrow and require Line-of-Sight conditions.
Innovation Solution
Implementing Single Frequency Network (SFN) based PDCCH diversity by activating multiple TCI states for a CORESET, allowing PDCCH transmission across multiple TRPs in the same time and frequency resource, using a single DMRS associated with multiple TCI states, and applying different precoding across TRPs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PDCCH transmission uses multiple TRPs with separate DMRS, then diversity is improved, but resource overhead increases and performance degrades when one TRP is blocked
Solution Approach 1:
The patent merges the DMRS resources from multiple TRPs into a single shared DMRS. Instead of each TRP transmitting separate DMRS sequences, both TRPs use the same DMRS sequence and resource elements, allowing the UE to combine signals from multiple TRPs using a single DMRS for channel estimation, thereby reducing resource overhead while maintaining diversity benefits
Solution Approach 2:
The single DMRS serves multiple functions simultaneously: it provides channel estimation for multiple TRPs, enables SFN combining of PDCCH signals from different TRPs, and reduces overall resource consumption. This multi-functional approach allows one DMRS to support diversity transmission across multiple TRPs without the overhead of multiple separate DMRS sequences
2Quantity of substance
If PDCCH transmission uses single TRP, then resource overhead is reduced, but reliability deteriorates when the TRP is blocked
Solution Approach 1:
The system prepares for potential TRP blocking by pre-configuring multiple TCI states for the CORESET before transmission occurs. When a TRP is blocked, the UE can switch to or combine signals from alternative TRPs using the pre-configured TCI states, providing cushioning against reliability deterioration without requiring additional real-time resources
3Reliability
If PDCCH transmission uses multiple TRPs with different precoding, then diversity is improved, but standard complexity increases
Solution Approach 1:
The patent changes the parameter of DMRS configuration from multiple separate sequences to a single shared sequence across multiple TRPs. This parameter change simplifies the standard by reducing the number of DMRS configurations needed while still allowing different precoding applied by different TRPs to achieve diversity, as the UE combines signals based on the single DMRS and associated TCI states
Data Source
AI summary
Single Frequency Network (SFN) based Physical Downlink Control Channel (PDCCH) diversity over multiple Transmission/Reception Points (TRPs) is disclosed. More specifically, methods performed by a wireless device(s) and a base station(s) are provided. The methods disclosed herein make it possible for the wireless device(s) to receive PDCCH transmission from another one of the multiple TRPs, based on Control-Channel Elements (CCEs) transmitted from all of the multiple TRPs, when one of the multiple TRPs is blocked.