Multicast Frame NACK Feedback for Selective Retransmission
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Solution Overview
Problem
In wireless communications systems, multicast transmissions often result in some user equipment (UEs) failing to receive data due to interference or errors, affecting reliability and efficiency, as these UEs cannot provide feedback to the base station for frames that are unsuccessfully decoded.
Innovation Solution
User equipment (UEs) are configured to transmit negative acknowledgment (NACK) feedback within allocated uplink resources when they fail to decode multicast frames, allowing the base station or network node to retransmit the missed frames, either directly or through a network node like a user plane function (UPF), thereby enhancing multicast transmission reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multicast transmissions are used to broadcast data to multiple UEs, then system resource efficiency is improved, but transmission reliability deteriorates because UEs cannot provide feedback for unsuccessfully decoded frames
Solution Approach 1:
The patent introduces a feedback mechanism where UEs transmit NACK (negative acknowledgment) signals to the base station when they fail to decode multicast frames successfully. This feedback enables the base station to identify which frames were not received correctly and trigger appropriate retransmission actions, thereby resolving the reliability issue while maintaining multicast efficiency
Solution Approach 2:
The patent introduces an intermediary feedback channel and control mechanism between the base station and UEs. The NACK feedback acts as an intermediary signal that carries information about decoding failures, enabling indirect communication of reliability issues back to the transmitter without requiring full bidirectional communication for each data frame
2Reliability
If NACK feedback is transmitted by UEs for unsuccessfully decoded frames, then transmission reliability is improved, but uplink resource allocation complexity increases
Solution Approach 1:
The patent extracts the feedback function from the main data transmission channel and implements it as a separate, dedicated NACK feedback mechanism. This separation allows the feedback functionality to be handled independently with simplified resource allocation, reducing the complexity burden on the overall uplink resource management system
Solution Approach 2:
The NACK feedback uses minimal, temporary uplink resources that are allocated only when needed for feedback transmission. These resources are short-lived and disposed of after the feedback is sent, avoiding the need for permanent, complex resource allocations and reducing overall system complexity
3Reliability
If retransmission of missed frames is implemented, then multicast service reliability is improved, but transmission time increases
Solution Approach 1:
The base station pre-buffers multicast frames before transmission and maintains them in a buffer for potential retransmission. This preliminary preparation allows the base station to quickly retransmit missed frames without needing to regenerate or re-acquire them, reducing the time penalty associated with retransmission
Solution Approach 2:
The patent implements selective retransmission where only the specific frames that were not successfully decoded are retransmitted, rather than retransmitting the entire multicast data set. This partial action approach minimizes the additional transmission time while still ensuring all necessary frames are received
Data Source
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AI summary
Methods, systems, and devices for wireless communications are described. A wireless communications system may support multicast transmissions from a base station to multiple user equipments (UEs). Each UE may have uplink resources allocated for providing feedback to the base station regarding multicast transmissions. For example, a UE may not successfully decode one or more frames of a multicast transmission. When a UE does not successfully decode the one or more frames, the UE may transmit negative acknowledgment (NACK) feedback indicating the one or more frames that were not successfully received. A serving base station may store frames within a buffer for a transmission window and retransmit each of the frames indicated within the NACK feedback from the stored frames. In some cases, the serving base station may not retransmit frames that were not indicated within the NACK feedback (e.g., frames that may have been received successfully by the UE).