Adaptive HARQ Feedback for Multicast Reliability in NR
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Solution Overview
Problem
Current wireless communication networks, such as LTE and NR, lack a mechanism to enhance the reliability of multicast transmissions based on UL (Uplink) transmissions, leading to inadequate reliability in various use cases and applications.
Innovation Solution
The implementation of specific methods for HARQ (Hybrid Automatic Repeat Request) feedback in multicast transmissions, including determining a HARQ feedback mode based on DCI (Downlink Control Information) and RRC (Radio Resource Control) messages, and selectively transmitting HARQ feedback to the network node.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If HARQ feedback mechanism is implemented for multicast transmissions, then reliability of multicast transmissions is improved, but device complexity and signaling overhead increase
Solution Approach 1:
The patent segments the multicast group into different feedback modes: UEs can be configured to send HARQ feedback (ACK/NACK) or not send feedback at all, depending on their reception conditions. This segmentation allows the system to apply HARQ selectively to only those UEs that need it, rather than requiring all UEs to participate in HARQ feedback, thereby improving reliability for vulnerable UEs while limiting the overall complexity increase.
Solution Approach 2:
The patent implements partial HARQ action by allowing the network to configure certain UEs to send HARQ feedback while others do not. The network can selectively enable HARQ feedback for specific UEs based on their channel conditions, distance from the base station, or service requirements. This partial implementation improves reliability for the subset of UEs that need it, while avoiding the full complexity burden of universal HARQ feedback.
2Reliability
If HARQ feedback is selectively transmitted based on decoding success, then reliability is improved, but loss of time due to feedback processing increases
Solution Approach 1:
The patent implements periodic HARQ feedback where UEs transmit ACK or NACK at predetermined time intervals after receiving multicast data. The network configures specific time resources for HARQ feedback transmission, creating a periodic rhythm of feedback exchange. This periodic structure allows UEs to process decoded data systematically and transmit feedback at organized intervals, balancing reliability improvement with controlled processing time.
Solution Approach 2:
The patent applies preliminary action by having UEs perform decoding and determine feedback content before actually transmitting the HARQ feedback. The UE decodes the multicast data, determines whether to send ACK or NACK, and prepares the feedback message in advance. This preliminary processing allows the actual feedback transmission to be quick and efficient, reducing the perceived time loss while maintaining reliability.
3Adaptability or versatility
If adaptive HARQ feedback modes are configured based on DCI and RRC messages, then reliability and adaptability are improved, but device complexity and signaling overhead increase
Solution Approach 1:
The patent implements a hierarchical feedback configuration mechanism where the network sends RRC messages to configure general HARQ feedback mode parameters, and then uses DCI messages to provide adaptive adjustments. The UE receives and processes both types of feedback configurations, allowing the system to adapt HARQ behavior dynamically while maintaining a structured configuration approach. This feedback mechanism enables reliability improvement through adaptive configuration without requiring complete reconfiguration from scratch.
Solution Approach 2:
The patent creates a universal HARQ feedback configuration framework that can handle multiple feedback modes (ACK-only, NACK-only, or no feedback) through a single configurable system. The same RRC and DCI messaging structures are used regardless of which feedback mode is active, making the system multi-functional and adaptable. This universality allows the network to switch between different HARQ behaviors using the same configuration infrastructure, improving adaptability while limiting the need for separate complex configuration systems for each mode.
Data Source
AI summary
Embodiments include methods performed by a user equipment (UE) for hybrid ARQ (HARQ) feedback in relation to multicast transmissions from a network node in a radio access network (RAN). Such methods include receiving, from the network node, first downlink control information (DCI) scheduling a first multicast transmission and determining a HARQ feedback mode for the first multicast transmission based on the first DCI and/or and a radio resource control message received from the network node before the first DCI. Such methods include, based on the first DCI, attempting to decode the first multicast transmission and, based on the determined HARQ feedback mode and on whether the attempt to decode is successful or unsuccessful, selectively transmitting HARQ feedback related to the first multicast transmission to the network node. Other embodiments include complementary methods for a network node, as well as UEs and network nodes configured to perform such methods.