Multicast Feedback via Negative Acknowledgment and Resource Overlap
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Solution Overview
Problem
In wireless communications, supporting feedback for multicast transmissions is challenging due to concurrent feedback transmission from multiple UEs, leading to collisions and increased system overhead, and the lack of repeated transmissions for decoding reliability.
Innovation Solution
A method where UEs receive multicast information with a DL grant indicating UL resources for negative acknowledgment feedback, allowing them to transmit NACK feedback if decoding fails, and the base station monitors these resources to determine retransmissions, using overlapping UL resources and beam sweeping procedures to improve decoding reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If feedback is supported for multicast transmissions, then decoding reliability is improved, but system overhead increases due to concurrent feedback transmission from multiple UEs
Solution Approach 1:
The patent extracts only the necessary feedback information (NACK for unsuccessful decoding) and transmits it using uplink resources already allocated for other purposes. This selective extraction of feedback requirements reduces overall system overhead while maintaining decoding reliability through targeted retransmission triggers.
Solution Approach 2:
The patent makes uplink resources serve multiple functions: they are used both for regular uplink transmissions and for feedback transmission regarding multicast decoding status. This multi-functionality reduces the need for dedicated feedback resources, thereby lowering system overhead while maintaining reliability.
2Reliability
If feedback is supported for multicast transmissions, then decoding reliability is improved, but resource collisions occur due to concurrent feedback transmission from multiple UEs
Solution Approach 1:
The patent merges feedback transmission with existing uplink resource allocations. Instead of creating separate feedback channels that could collide, the feedback is combined with regular uplink transmissions, utilizing the same time-frequency resources already assigned to UEs for their scheduled uplink data or control information.
Solution Approach 2:
The patent uses copies of existing uplink resource allocations for feedback purposes. The same uplink resources that are copied from the original resource allocation scheme are reused for feedback transmission, ensuring that feedback does not create new collision scenarios but rather utilizes established resource patterns.
3Reliability
If repeated transmissions are implemented for multicast, then decoding reliability is improved, but productivity decreases due to additional transmissions
Solution Approach 1:
The patent implements a feedback mechanism where UEs indicate unsuccessful decoding status. This feedback enables the base station to perform targeted retransmissions only when and where needed, rather than implementing universal repeated transmissions for all multicast data. This selective retransmission approach maintains decoding reliability while preserving transmission efficiency.
Solution Approach 2:
The patent applies partial action by implementing retransmissions only for the specific cases where decoding failure is detected through feedback, rather than applying repeated transmissions universally to all multicast data. This partial application of retransmission maintains reliability for failed decodes while avoiding unnecessary transmissions that would reduce productivity.
Data Source
AI summary
Methods, systems, and devices for wireless communications are described that support feedback for multicast communications. A user equipment (UE) in a group of UEs may receive multicast information from a base station in a downlink (DL) transmission scheduled by a DL grant. The DL grant may also indicate a set of uplink resources for the group of UEs to use to transmit feedback. The UE may attempt to decode a message containing the multicast information in the DL transmission. If the UE determines the message was successfully decoded, the UE may send no feedback to the base station. If the UE determines the message was not successfully decoded, the UE may transmit a feedback message to the base station to indicate the message was unsuccessfully decoded. The base station may monitor for the feedback message and determine to retransmit the multicast information if the feedback message is received.