Multi-Hop RLC Buffer Control Using PDCP Acknowledgments
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Solution Overview
Problem
Current approaches to radio link control (RLC) data forwarding in multi-hop backhauling lack proper buffer management, leading to issues such as premature deletion of transmitted PDCP PDUs, inefficient resource usage, and increased latency, which can result in data loss and unnecessary retransmissions.
Innovation Solution
Implementing PDCP acknowledgment mechanisms, including new triggering conditions and flow control options, to avoid premature deletion of PDCP PDUs and manage buffer sizes effectively, with end-to-end and hop-by-hop acknowledgement procedures to ensure timely data availability and efficient resource utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If PDCP PDU is deleted from buffer after transmission in multi-hop backhauling, then buffer memory is freed for new data, but premature deletion occurs causing data loss and retransmissions
Solution Approach 1:
The patent implements feedback mechanisms where intermediary nodes send acknowledgments back to the source transmitter about PDCP PDU reception status. This feedback loop allows the transmitter to determine whether to delete buffered PDUs based on actual delivery confirmation, preventing premature deletion while efficiently managing buffer resources.
Solution Approach 2:
Intermediary nodes act as mediators in the multi-hop backhauling system, receiving PDCP PDUs from upstream nodes and forwarding them downstream. These intermediaries provide visibility into the transmission path, enabling the source transmitter to make informed decisions about buffer management based on acknowledgment feedback from intermediaries about PDU delivery status.
2Reliability
If PDCP PDU is kept in buffer until end-to-end acknowledgement, then data delivery reliability is ensured, but latency increases due to prolonged buffering
Solution Approach 1:
The patent implements partial acknowledgment mechanisms where intermediaries can provide partial feedback about PDU reception status. This allows the source transmitter to delete acknowledged PDUs from the buffer while maintaining others, achieving a balance between reliability and latency by not requiring complete end-to-end confirmation for all PDUs.
Solution Approach 2:
The acknowledgment process is segmented into hop-by-hop acknowledgments rather than requiring a single end-to-end acknowledgment. This segmentation allows the source transmitter to receive and act on partial acknowledgment feedback from intermediaries, reducing the time PDUs remain in the buffer while maintaining delivery reliability through cumulative acknowledgment tracking.
3Measurement precision
If hop-by-hop acknowledgement is implemented, then buffer management accuracy is improved, but protocol complexity increases
Solution Approach 1:
The patent implements a universal acknowledgment mechanism that can operate in multiple modes (hop-by-hop, end-to-end, or hybrid) depending on network conditions and configuration. This multi-functional approach allows the same basic protocol structure to provide precise buffer management when needed while simplifying operation when lower complexity is sufficient, reducing overall protocol complexity.
4Reliability
If buffer size is increased to prevent premature deletion, then data loss is reduced, but resource usage efficiency decreases
Solution Approach 1:
The patent implements dynamic buffer management where the effective buffer size and retention policies are adjusted based on real-time acknowledgment feedback from intermediary nodes. This dynamic approach allows the system to maintain high reliability by keeping PDUs in buffer only as long as necessary, while efficiently releasing buffer resources once delivery is confirmed, optimizing the balance between reliability and resource efficiency.
Data Source
AI summary
Current approaches to radio link control (RLC) data forwarding with no end-to-end RLC entities between a given UE and IAB donor node lack proper buffer management. In various examples, the premature deletion of transmitted PDCP PDUs is avoided. Various embodiments also address buffer size control, for example end-to-end flow control, hot-by-hop flow control, explicit and implicit flow control options are described. Content of flow control messages, transmitter actions at the reception of flow control, and triggers for flow controls are also described herein.