Adaptive Segmentation Limit for RLC Protocol Overhead Reduction
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Solution Overview
Problem
The existing UTRAN protocol stack's fixed RLC PDU size leads to excessive overhead and inefficiencies in segmenting and concatenating Service Data Units (SDUs), particularly for large IP packets and small signaling messages, due to limited flexibility in PDU sizes and re-transmission inefficiencies during poor link quality.
Innovation Solution
Implementing an adaptive segmentation limit in the higher protocol layer that dynamically adjusts based on indications from the lower protocol layer, allowing for flexible PDU sizes that match available transport block sizes and link quality, thereby reducing overhead and improving re-transmission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If fixed RLC PDU size is used, then protocol structure is simple and stable, but overhead increases and efficiency decreases due to excessive segmentation and concatenation
Solution Approach 1:
The patent introduces dynamic PDU size adaptation where the RLC layer can adjust PDU sizes based on transport block sizes indicated by lower layers. This allows the system to transition from fixed to variable PDU sizes, optimizing data transfer efficiency while maintaining protocol stability through structured adaptation mechanisms.
Solution Approach 2:
The patent changes the parameter of PDU size from fixed to variable by introducing adaptation based on transport block sizes. The RLC layer receives indications of available transport block sizes and adjusts PDU sizes accordingly, reducing segmentation overhead and improving concatenation efficiency without fundamentally changing the protocol structure.
2Reliability
If small PDU sizes are used, then re-transmission efficiency improves, but overhead increases due to more frequent segmentation
Solution Approach 1:
The patent enables dynamic adjustment of PDU sizes based on transport block availability and link conditions. When link quality is poor, smaller PDU sizes can be used to improve re-transmission efficiency, while when conditions are good, larger PDU sizes reduce overhead. This dynamic adaptation resolves the contradiction between reliability and overhead.
Solution Approach 2:
The patent changes the PDU size parameter dynamically based on transport block size indications from lower layers. This allows the system to optimize the balance between re-transmission efficiency and protocol overhead by adjusting PDU sizes according to actual transmission conditions rather than using fixed sizes.
3Loss of substance
If large PDU sizes are used, then overhead is reduced, but reliability decreases under poor link quality due to re-transmission inefficiency
Solution Approach 1:
The patent introduces dynamic PDU size adaptation where the system can switch between large and small PDU sizes based on link quality and transport block availability. Under poor link conditions, smaller PDUs improve reliability through more efficient re-transmissions, while under good conditions, larger PDUs reduce overhead, resolving the contradiction between these two parameters.
Solution Approach 2:
The patent enables parameter changes in PDU size based on feedback from lower layers about transport block sizes and link conditions. This allows the system to adapt PDU sizes to match actual transmission capabilities, reducing overhead when possible while maintaining reliability when link conditions deteriorate.
4Productivity
If adaptive segmentation is implemented, then efficiency and flexibility improve, but device complexity increases
Solution Approach 1:
The patent uses transport block size indications from lower layers as an intermediary to drive adaptive segmentation decisions. Rather than implementing complex link quality monitoring and PDU size optimization logic in the RLC layer itself, the system uses indications from lower layers as intermediaries to guide segmentation, reducing implementation complexity while maintaining efficiency gains.
5Ease of manufacture
If padding is used to fill fixed PDU sizes, then transport format matching is simplified, but data efficiency decreases
Solution Approach 1:
The patent eliminates the need for padding by making PDU sizes dynamic and adaptable to actual data sizes and transport block availabilities. Instead of filling fixed PDU sizes with padding, the system adjusts PDU sizes to match data and transport block boundaries, simplifying transport format matching while improving data efficiency by eliminating wasted padding bytes.
Data Source
Figure 1~2b
Figure 3
Figure 4a~4b
AI summary
A method and nodes for providing adaptive segmentation in a higher protocol layer interacting with a lower protocol layer. An adaptable segmentation limit (200,204), defining a threshold of a largest Protocol Data Unit (PDU) that is to be submitted to a lower protocol layer, is deployed at a higher protocol layer interacting with the lower protocol layer. For each Service Data Unit (SDU;201,203) arriving at the higher protocol layer, it is determined if the respective SDU can fit into the segmentation limit or not. Each SDU that do not fit into the segmentation limit is segmented into PDUs (205,206) which are smaller than or equal to the segmentation limit, while no segmentation is performed on SDUs that fit into the segmentation limit.