Multi-TRP Uplink Power Control with Per-TRP TPC Signaling
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Solution Overview
Problem
Existing power control mechanisms in NR are cumbersome and inflexible for uplink transmissions to multiple Transmission Reception Points (TRPs, particularly in FR2, where beam management and pathloss estimation need to account for beamforming gains, leading to inefficient power control.
Innovation Solution
Implementing methods for power control that include multiple TPC commands in DCI for PUCCH and PUSCH transmissions to multiple TRPs, with joint indexing of closed loops and PHR reporting for accurate power control across different TRPs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If existing power control mechanisms are used for uplink transmissions to multiple TRPs, then the system maintains backward compatibility, but the power control becomes cumbersome and inflexible
Solution Approach 1:
The power control mechanism is segmented by introducing separate TPC commands for each TRP (first TPC command for first TRP, second TPC command for second TRP). Each TPC command independently controls the uplink transmission power towards a specific TRP, allowing flexible and independent power adjustment for each transmission point without affecting others.
Solution Approach 2:
The power control is extended from a single-dimension (single TRP) to multi-dimension (multiple TRPs) by introducing TRP-specific TPC commands. The DCI structure is enhanced to include multiple TPC command fields, each associated with a specific TRP through spatial relation information, enabling independent power control in the TRP dimension.
2Measurement precision
If multiple TPC commands are included in DCI for multiple TRPs, then power control accuracy improves, but DCI structure and signaling overhead increase
Solution Approach 1:
The DCI structure is designed with universal applicability for both single-TRP and multi-TRP scenarios. The TPC command fields are configured based on the number of TRPs, allowing the same DCI framework to handle different numbers of TRPs flexibly. The spatial relation information universally links TPC commands to specific TRPs regardless of the total number of TRPs.
Solution Approach 2:
The DCI structure dynamically adapts to the number of TRPs involved in uplink transmission. When multiple TRPs are used, multiple TPC command fields are activated; when a single TRP is used, only one TPC command field is active. This dynamic configuration optimizes the DCI size and reduces signaling overhead based on actual transmission requirements.
3Reliability
If beamforming gains are accounted for in pathloss estimation, then signal reception quality improves, but power control calculation complexity increases
Solution Approach 1:
The network node pre-calculates and provides pathloss compensation values that already incorporate beamforming gains for each TRP. These pre-computed values are used by the UE in uplink power control calculations, eliminating the need for the UE to perform complex beamforming gain computations and simplifying the power control process while maintaining accurate signal reception quality.
Data Source
AI summary
Systems and methods for enabling power control of multiple Transmission Reception Points (TRPs) are provided. In some embodiments, the wireless device performs at least one of: receiving in a Downlink Control Information (DCI) a first Transmit Power Control (TPC) command and a second TPC command and an indication of a first transmission of the physical channel to a first TRP associated with a first closed-loop and a second transmission of the physical channel to a second TRP associated with a second closed-loop; determining a first and a second transmit power based on the first and the second TPC commands, respectively; and applying the first and the second transmit power to the first UL transmission and the second UL transmission, respectively. In this way, some embodiments herein enable more accurate per TRP power control with a simple signaling for multiple UL transmissions towards different TRPs scheduled by a single DCI.