Group HARQ Transmission Synchronization Using UE Checksums
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Solution Overview
Problem
In group transmission using Device-to-Device (D2D) communications, maintaining synchronization of Hybrid Automatic Repeat Request (HARQ) buffers among UEs is crucial for enhancing Signal-to-Interference-plus-Noise-Ratio (SINR) and throughput, but unsynchronized transmissions can lead to interference and degraded performance, especially as group size increases.
Innovation Solution
A method involving checksum calculations and notifications among UEs to ensure synchronized HARQ buffer transmissions, where UEs stop transmitting when checksums differ, and a coordinator UE manages synchronization by computing and distributing checksums to maintain buffer synchronization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If group transmission is used to increase SINR and throughput, then coverage and user bit rate are improved, but interference and performance degradation occur when UEs are unsynchronized
Solution Approach 1:
The patent implements feedback mechanisms where UEs report their synchronization status and buffer states to the network node. The network node receives feedback information about which UEs are synchronized and which are not, allowing it to dynamically adjust transmission parameters or request re-synchronization to maintain high SINR while minimizing interference from unsynchronized UEs.
Solution Approach 2:
The system dynamically adjusts the group transmission configuration based on real-time synchronization status. When UEs become unsynchronized, the network can modify resource allocation, change modulation and coding schemes, or reconfigure the group to maintain optimal performance. This dynamic adaptation allows the system to exploit group diversity when synchronized while preventing interference when desynchronization occurs.
2Productivity
If all UEs transmit simultaneously to increase SINR, then throughput is improved, but interference increases when UEs have different data in their HARQ buffers
Solution Approach 1:
UEs provide feedback information about their HARQ buffer content and synchronization status to the network node. This feedback enables the network to identify which UEs have matching data and can transmit simultaneously, and which UEs have divergent data that would cause interference. The network can then selectively enable or disable simultaneous transmission based on this feedback.
Solution Approach 2:
The patent segments the group transmission into multiple subsets or layers based on synchronization status. Synchronized UEs with identical HARQ buffer content are grouped together for simultaneous transmission to achieve diversity gain, while unsynchronized UEs are separated or transmitted on different resources. This segmentation allows the system to maximize throughput from synchronized UEs while preventing interference from unsynchronized ones.
3Device complexity
If the network treats the group as a single UE to simplify signaling, then device complexity is reduced, but it becomes difficult to detect and manage unsynchronized transmissions
Solution Approach 1:
The patent introduces an intermediary coordination mechanism where one UE in the group (or a designated coordinator) acts as a reference for synchronization. This intermediary UE's transmission serves as the timing and data reference for other group members. The network node monitors this intermediary's transmissions and uses them as a baseline to detect whether other UEs are synchronized, simplifying the detection process while maintaining group management efficiency.
Solution Approach 2:
The system uses distinguishable signaling indicators (analogous to color changes) to mark the synchronization status of different UEs. Synchronized UEs transmit with specific signaling characteristics that indicate their buffer content matches the group reference, while unsynchronized UEs use different indicators. This allows the network node to easily detect and identify unsynchronized UEs without complex analysis, maintaining simplicity while enabling effective monitoring.
Data Source
AI summary
The embodiments herein relate to a first user equipment (UE), a second UE and methods thereof for reliable group transmissions. The group includes multiple UEs transmitting the same Hybrid Automatic Repeat request (HARQ), buffer data packets to a network node. The method in the first UE includes receiving a predetermined number of Non ACKnowledgments (NACKs), performing a checksum calculation on the HARQ buffer, receiving a computed checksum from a second UE acting as a coordinator of the group; comparing the calculated checksum with the received computed checksum and stopping/refraining from further transmission of the HARQ buffer data to the network node when the calculated checksum and the received computed checksum differ.