Closed Loop Power Control for Multicast Feedback
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Solution Overview
Problem
Current wireless communication systems face challenges in efficiently managing acknowledgment feedback for multicast transmissions, particularly in setting appropriate transmit power control commands for multiple user equipment (UEs) receiving the same multicast, as a single TPC command may not be suitable for all UEs, leading to suboptimal power control and potential retransmissions.
Innovation Solution
The proposed solution involves a user equipment (UE) configured to receive a control message scheduling a multicast transmission, where it identifies a closed loop power control parameter for acknowledgment feedback by monitoring a group-TPC DCI message, which can include a separate set of consecutive bits indicating the power control parameter, allowing for specific power control for each UE, and adjusts transmit power based on reception of retransmission DCI within a time window.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a single TPC command is used for all UEs receiving multicast transmissions, then the system complexity is reduced and ease of operation is improved, but the power control precision deteriorates leading to suboptimal power control and potential retransmissions
Solution Approach 1:
The patent segments the power control mechanism by separating the TPC command into two parts: a group-common TPC command transmitted via group-common PDCCH for all UEs, and UE-specific TPC commands transmitted via UE-specific PDCCH for individual power adjustment. This segmentation allows the system to maintain simple group-level power control while adding precise UE-specific power control when needed, resolving the contradiction between ease of operation and power control precision.
2Manufacturing precision
If UE-specific power control parameters are implemented for each UE, then the power control precision is improved, but the device complexity and signaling overhead increase
Solution Approach 1:
The patent implements a dynamic power control mechanism where the system can switch between group-common TPC commands and UE-specific TPC commands based on channel conditions and UE requirements. The UE monitors both group-common PDCCH and UE-specific PDCCH, and applies the appropriate TPC command dynamically. This dynamic approach allows the system to maintain high power control precision while avoiding unnecessary complexity when group-level control suffices.
3Reliability
If separate TPC commands are transmitted to each UE, then the reliability of feedback transmission is improved, but the signaling overhead and loss of time increase
Solution Approach 1:
The patent merges the TPC command transmission by allowing the same TPC command to serve multiple purposes: it can be transmitted via group-common PDCCH for all UEs, and simultaneously referenced by UE-specific PDCCH for individual UEs. This merging reduces redundant signaling overhead and time consumption while maintaining the ability to provide UE-specific power control adjustments, thus improving reliability without excessive time loss.
Data Source
AI summary
Methods, systems, and devices for wireless communications are described. A user equipment (UE) may be configured to receive a control message scheduling a multicast transmission, where the UE may identify a closed loop power control parameter for transmitting acknowledgment feedback responsive to the multicast transmission based on the multicast transmission transmitted to multiple UEs. The closed loop power control parameter may be indicated by a base station in a separate message than a downlink control information (DCI) scheduling the multicast transmission. For example, the base station may transmit the indication of the closed loop power control parameter in a group-transmit power control DCI or in a configuration for transmitting sounding reference signals. Additionally, the UE may adjust a transmit power for the acknowledgment feedback based on whether or not a DCI scheduling a retransmission is received in a time window after transmitting the acknowledgment feedback.