MAC CE TRP Indicator for PUSCH Pathloss Reference Updates
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Solution Overview
Problem
In New Radio (NR) networks, there is an ambiguity in updating the Pathloss Reference RS ID for PUSCH transmission to multiple Transmission and Reception Points (TRPs), as existing Medium Access Control (MAC) Control Elements (CE) do not clearly indicate which TRP the update refers to, leading to difficulties in power control for PUSCH repetitions.
Innovation Solution
A new MAC CE is proposed with additional fields to explicitly indicate which TRP a pathloss reference update refers to, allowing for separate power control settings for each TRP by including new fields in the MAC CE to distinguish between SRS resource sets and update SRI ID mappings accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If existing MAC CE is used for pathloss reference RS ID update, then the signaling structure remains simple, but the ambiguity arises in identifying which TRP the update refers to when transmitting to multiple TRPs
Solution Approach 1:
The patent divides the pathloss reference RS ID update into separate TRP-specific updates by introducing a TRP indicator field in the MAC CE. This segmentation allows the system to maintain simple overall structure while eliminating ambiguity through explicit TRP identification, resolving the contradiction between structural simplicity and information completeness.
Solution Approach 2:
The patent introduces a TRP indicator field as an intermediary element within the MAC CE that mediates between the pathloss reference RS ID update and the TRP identification requirement. This intermediary field provides the necessary TRP information without significantly complicating the overall signaling structure.
2Device complexity
If pathloss reference RS ID is updated without TRP indication, then the MAC CE structure remains simple, but power control accuracy for PUSCH repetitions to multiple TRPs deteriorates
Solution Approach 1:
The patent segments the power control parameters into TRP-specific sets by introducing TRP indicator field in MAC CE. This segmentation enables accurate power control for each TRP independently, resolving the contradiction between structural simplicity and measurement precision by adding minimal overhead for TRP identification.
Solution Approach 2:
The patent applies local quality by making the TRP indicator field specific to each MAC CE instance, allowing different TRPs to have their own pathloss reference RS ID updates and power control parameters. This localized approach maintains overall structural simplicity while achieving TRP-specific power control accuracy.
3Measurement precision
If separate power control settings are implemented for each TRP, then power control accuracy improves, but the complexity of power control mechanism increases
Solution Approach 1:
The patent implements universality by using a standardized MAC CE structure with an optional TRP indicator field that can work for single TRP or multi-TRP scenarios. This multi-functional design enables TRP-specific power control without requiring completely separate mechanisms, thus improving accuracy while limiting complexity increase.
Solution Approach 2:
The patent applies dynamics by making the TRP indicator field optional and configurable, allowing the power control mechanism to adapt between simple (single TRP) and complex (multi-TRP) modes. This dynamic configuration enables TRP-specific power control when needed while maintaining simplicity when TRP differentiation is not required.
Data Source
AI summary
Systems and methods for signaling Pathloss Reference RS are provided. In some embodiments, a method performed by a wireless device for identifying which Transmission and Reception Point (TRP) an update refers to includes: receiving a configuration of a first and second Sounding Reference Signal (SRS) resource sets associated to a first and second TRP; receiving a control message indicating a Physical Uplink Shared Channel (PUSCH) pathloss reference update; where the control message comprises an indication of which TRP the update refers to. In some embodiments: the control message comprises a Medium Access Control (MAC) Control Element (CE); the pathloss reference update comprises a PUSCH Pathloss Reference Signal (RS) ID field; the pathloss reference update comprises one or more SRS Resource Indicator (SRI) ID fields. In this way, pathloss can be updated for SRIs associated with different SRS resource sets for per TRP power control in PUSCH repetition to multiple TRP.