PDU Segmentation in Wireless User Equipment
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Solution Overview
Problem
In wireless communications systems, particularly in 3G mobile telecommunications, the fixed length of Protocol Data Units (PDUs) from the Radio Link Control layer leads to inefficient bandwidth utilization and data processing, especially in high data rate applications like HSDPA and HSUPA, due to incorrect concatenation of PDU segments causing data errors.
Innovation Solution
A method and apparatus for delivering PDUs in user equipment that involves receiving reordering PDUs, determining segmentation using the Segmentation Indication field, and discarding previously stored PDU segments when all received PDUs are not segmented, ensuring correct concatenation and delivery to upper layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If fixed length PDUs are used from RLC layer, then implementation is simple, but bandwidth utilization and data processing efficiency are poor
Solution Approach 1:
The patent segments PDUs into variable length units at the MAC layer, dividing fixed length RLC PDUs into multiple MAC PDUs of different sizes based on transmission buffer status and channel conditions. This segmentation enables flexible bandwidth utilization while maintaining simple RLC layer implementation.
Solution Approach 2:
The patent introduces dynamic PDU segmentation and reassembly mechanisms in the MAC layer, where PDU sizes and transmission parameters are dynamically adjusted based on channel quality, buffer status, and QoS requirements. This dynamic approach improves bandwidth utilization without complicating the RLC layer.
2Adaptability or versatility
If PDU segments are stored for possible concatenation, then flexibility in reassembly is improved, but data errors occur due to incorrect concatenation
Solution Approach 1:
The patent performs preliminary actions by storing segmentation indication fields and sequence numbers with each PDU segment, enabling the receiver to correctly identify and concatenate segments in the proper order. This preliminary tagging prevents incorrect concatenation while maintaining reassembly flexibility.
Solution Approach 2:
The patent implements feedback mechanisms where the MAC layer monitors reassembly status and concatenation results, using this information to adjust segmentation strategies and prevent future concatenation errors. This feedback loop improves both reliability and reassembly flexibility.
3Productivity
If flexible RLC PDU sizes are adopted, then bandwidth utilization improves, but system complexity increases
Solution Approach 1:
The patent segments the protocol stack functionality, keeping the RLC layer simple with fixed length PDUs while implementing flexible segmentation and reassembly in the MAC layer. This segmentation of functionality achieves flexible PDU sizes without increasing RLC layer complexity.
Solution Approach 2:
The patent introduces the MAC layer as an intermediary between the RLC layer and the physical layer, where the MAC layer handles the complexity of flexible PDU sizing, segmentation, and reassembly. This intermediary approach enables bandwidth efficiency while isolating complexity from the RLC layer.
Data Source
AI summary
A method of delivering packet data units (PDUs) for a user equipment in a wireless communications system includes receiving a reordering PDU having at least one upper layer PDU from a protocol entity, determining whether the at least one upper layer PDU are segmented for reassembling with a previously stored segment of a upper layer PDU according to a segmentation indication message corresponding to the reordering PDU, and delivering the at least one PDU to an upper layer protocol entity and discarding the previously stored segment when the at least one upper layer PDU are all not segmented PDUs.