5G NR Relay Flow Control Using Hop-by-Hop Buffer Feedback
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Solution Overview
Problem
There is a need for effective downlink hop-by-hop (HbH) flow control mechanisms in 3GPP 5G NR and NR-based relay networks to prevent congestion, particularly in integrated access and backhaul (IAB) networks, where existing end-to-end flow control mechanisms are insufficient.
Innovation Solution
A method for flow control involving a first node that identifies triggering events to generate and transmit downlink flow control feedback information, including available buffer size, through a backhaul adaptation protocol (BAP) layer message to a second node.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If end-to-end flow control mechanisms are used in IAB networks, then flow control coverage is provided, but congestion prevention is insufficient at intermediate hops
Solution Approach 1:
The patent divides end-to-end flow control into multiple hop-by-hop flow control segments. Each IAB node independently performs flow control with its parent node based on local buffer status, breaking the single end-to-end control into manageable per-hop segments that can respond to local congestion conditions.
Solution Approach 2:
The patent implements feedback mechanisms where each IAB node reports buffer status information to its parent node, and the parent node adjusts data transmission rates based on this feedback. This creates a closed-loop control system that adapts to changing network conditions at each hop.
2Reliability
If hop-by-hop flow control is implemented, then congestion prevention at intermediate nodes is improved, but signaling overhead increases
Solution Approach 1:
The patent combines flow control signaling with existing backhaul adaptation protocol (BAP) signaling structures. By integrating flow control information into existing BAP message formats rather than creating separate dedicated signaling channels, the patent reduces additional signaling overhead while still providing necessary hop-by-hop flow control functionality.
3Speed
If real-time buffer status feedback is transmitted, then flow control responsiveness is improved, but message transmission frequency and overhead increase
Solution Approach 1:
The patent implements periodic buffer status reporting where IAB nodes transmit flow control feedback messages at configured intervals or when buffer status changes exceed certain thresholds. This periodic action provides timely flow control responsiveness while avoiding excessive signaling during stable network conditions.
Data Source
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AI summary
A method performed by a first node for flow control in a wireless communication system is provided. The method includes identifying a triggering event for transmitting downlink flow control feedback information, generating the downlink flow control feedback information including an available buffer size based on the identified triggering event, and transmitting, to a second node, a backhaul adaptation protocol (BAP) layer message including the downlink flow control feedback information.