IAB UE Buffer Overflow Mitigation via Dynamic RTT Scaling
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Solution Overview
Problem
In integrated access and backhaul (IAB) networks, user equipment (UE) experiences buffer overflows due to higher effective round trip times (RTTs) compared to non-IAB arrangements, leading to packet drops even under good radio conditions.
Innovation Solution
The UE is configured to report information to the network for reducing the maximum data rate in specific IAB topologies, and IAB-nodes perform reordering operations to mitigate buffer overflows.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the UE uses a standard RLC RTT buffer size for reordering data, then the device complexity is reduced and ease of manufacture is improved, but buffer overflows occur in IAB networks causing packet drops
Solution Approach 1:
The patent changes the RTT parameter from standard RLC RTT to an extended RTT that accounts for multiple backhaul links in IAB networks. The extended RTT is calculated as the sum of RTTs for each backhaul link traversed, allowing the buffer size to be appropriately scaled for multi-hop scenarios while maintaining the same buffer management mechanism
Solution Approach 2:
The patent introduces dynamic buffer size adjustment based on the number of backhaul links. The UE determines the extended RTT dynamically by counting the number of IAB nodes in the data path and scaling the buffer size accordingly, allowing the buffer to adapt to different network topologies without requiring fundamentally different buffer designs
2Productivity
If the maximum data rate is maintained at high levels, then the productivity and data transmission speed are improved, but buffer overflows occur more frequently in IAB networks with extended RTT
Solution Approach 1:
The patent changes the data rate parameter by introducing a scaling factor that reduces the maximum data rate proportionally to the number of backhaul links. The scaled maximum data rate ensures that the product of data rate and extended RTT remains within the buffer capacity, preventing overflows while maintaining optimal throughput for each specific network configuration
3Reliability
If the UE buffer size is increased to accommodate extended RTT in IAB networks, then packet delivery reliability is improved, but the device complexity and manufacturing cost increase
Solution Approach 1:
The patent implements dynamic buffer size determination based on the extended RTT calculation. Rather than using a fixed large buffer for all scenarios, the UE calculates the required buffer size as the product of the scaled maximum data rate and the extended RTT, which dynamically adapts to the specific number of backhaul links in the current network topology
Solution Approach 2:
The patent changes the buffer size parameter from a fixed standard value to a calculated value based on extended RTT. The buffer size is determined as Extended RTT × Scaled Maximum Data Rate, where the extended RTT accounts for multiple backhaul links, allowing the buffer to be appropriately sized for each specific IAB scenario without requiring excessive buffer capacity in all cases
Data Source
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AI summary
A user equipment (UE) is configured to access a first base station in a network via an access link, wherein the first base station is an integrated access and backhaul (IAB) node in a first IAB network topology connected to a second base station via one or more backhaul links, wherein the second base station is an IAB-donor for the first base station, report, to the first base station, information for reducing a maximum data rate for the UE when the UE is deployed in one or more IAB network topologies and receive data packages with a reduced maximum data rate based on the reported information