Two-Stage Feedback for Wireless Downlink Latency
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Solution Overview
Problem
Current wireless communication systems face challenges in reducing latency and improving reliability for multiple downlink transmissions due to limited feedback mechanisms, which hinder effective retransmission adaptations by base stations.
Innovation Solution
Implementing a two-stage feedback procedure that includes hybrid automatic repeat request (HARQ) feedback and channel state information (CSI) feedback for multiple physical downlink shared channels (PDSCHs), allowing user equipment (UE) to transmit both stages in a single or multiple physical uplink control channels (PUCCHs, based on transport block and transmission configuration indicator (TCI) states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional single-stage feedback mechanisms are used for multiple downlink transmissions, then the system complexity remains low, but latency increases and reliability deteriorates due to insufficient feedback information for effective retransmission adaptations
Solution Approach 1:
The feedback mechanism is segmented into two distinct stages: first-stage HARQ feedback for immediate acknowledgment and second-stage CSI feedback for channel quality information. This segmentation allows each stage to serve its specific function optimally, improving overall reliability without overwhelming system complexity with a single complex feedback mechanism.
Solution Approach 2:
The first-stage HARQ feedback is transmitted preliminarily before the second-stage CSI feedback. This preliminary action enables the base station to quickly determine whether retransmission is needed while awaiting more detailed channel state information, thereby improving reliability through faster initial response while maintaining manageable complexity through staged information gathering.
2Loss of time
If traditional single-stage feedback mechanisms are used for multiple downlink transmissions, then the feedback procedure remains simple, but latency increases due to insufficient information for optimized retransmissions
Solution Approach 1:
The feedback procedure is divided into two time-staged components: immediate HARQ acknowledgment and subsequent CSI reporting. This segmentation enables the system to make quick retransmission decisions based on HARQ feedback while incorporating refined channel state information later, thereby reducing latency without requiring a single overly complex feedback procedure.
Solution Approach 2:
HARQ feedback is transmitted as a preliminary action before CSI feedback. This allows the base station to initiate retransmission processes earlier based on acknowledgment information alone, then optimize subsequent transmissions using the more detailed CSI data, effectively reducing overall latency while maintaining procedural simplicity through clear stage separation.
3Adaptability or versatility
If basic HARQ feedback is transmitted without CSI feedback, then the feedback mechanism remains simple, but retransmission adaptation capability deteriorates
Solution Approach 1:
The feedback mechanism is segmented to separate acknowledgment function (HARQ) from channel state reporting function (CSI). This segmentation enables the system to maintain simple acknowledgment processing while adding adaptability through dedicated CSI feedback, allowing optimized retransmission decisions without complicating the core HARQ mechanism.
Solution Approach 2:
CSI feedback acts as an intermediary that bridges the gap between simple HARQ acknowledgment and sophisticated retransmission adaptation. By introducing this intermediate layer of channel state information, the system gains enhanced adaptability for optimizing retransmissions without requiring fundamental changes to the basic HARQ feedback structure, thus managing complexity effectively.
Data Source
AI summary
Methods, systems, and devices for wireless communications are described. Generally, the described techniques provide for reporting a first and second stage of feedback for multiple physical downlink shared channels (PDSCHs) to reduce latency and improve reliability. The first stage of feedback may include hybrid automatic repeat request (HARQ) feedback for all PDSCHs or each PDSCH, and the second stage of feedback may include channel state information (CSI) feedback for all PDSCHs or each PDSCH. A user equipment (UE) may transmit the first and second stages of feedback in a single physical uplink control channel (PUCCH) or multiple PUCCHs (e.g., a PUCCH corresponding to each PDSCH). In some cases, the UE may report the HARQ and CSI feedback based on whether the PDSCHs include the same or different transport blocks or whether the PDSCHs are transmitted with the same or different transmission configuration indicator (TCI) states.