RLC PDU Size Adaptation for UMTS E-DCH Overhead Reduction
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Solution Overview
Problem
The existing RLC entities in UMTS networks are either radio unaware, leading to excessive overhead and error rates due to segmentation and HARQ residual errors, or radio aware, which can be processing-intensive and inefficient in adapting to changing radio conditions.
Innovation Solution
A method and apparatus for generating RLC PDUs that match the selected E-TFC size, ensuring they are within the minimum and maximum configured sizes, thereby reducing RLC overhead and HARQ residual error rates by making the RLC entity aware of current channel conditions during the E-DCH transport format combination selection procedure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a fixed RLC PDU size is used, then the RLC entity operation is simple, but large L2 overhead results when a small fixed RLC PDU size is used
Solution Approach 1:
The patent implements dynamic RLC PDU size adjustment by making the RLC entity aware of current radio conditions and available data. The RLC PDU size is dynamically adapted based on the minimum of available data and available transmission resources, replacing fixed-size schemes with a flexible, condition-based sizing mechanism that optimizes overhead efficiency.
2Loss of substance
If a large fixed RLC PDU size is used, then overhead is reduced, but large error rates result from residual HARQ errors when MAC segmentation is used
Solution Approach 1:
The patent dynamically adjusts RLC PDU size based on available transmission resources and data, preventing the use of excessively large PDUs that would require MAC segmentation. By adapting PDU size to current conditions, the system reduces segmentation operations and thereby lowers residual HARQ error rates while maintaining overhead efficiency.
Solution Approach 2:
The patent introduces feedback mechanisms where the RLC entity monitors radio conditions and transmission resource availability, using this information to adjust PDU size dynamically. This feedback loop enables the system to avoid conditions that lead to high error rates while optimizing overhead, creating a self-regulating mechanism for reliable transmission.
3Productivity
If the RLC entity is radio unaware, then the RLC entity generates RLC PDUs of a maximum size, but more than one PDU per TTI may be generated resulting in segmentation
Solution Approach 1:
The patent transforms the RLC entity from radio-unaware to radio-aware by implementing feedback mechanisms that monitor radio conditions and transmission resources. This feedback enables the RLC entity to generate appropriately sized PDUs that match available resources, preventing the need for segmentation and reducing harmful errors while maintaining high productivity.
Solution Approach 2:
The patent implements dynamic adaptation of RLC PDU generation by making the entity aware of current radio conditions. The PDU generation process dynamically adjusts size based on real-time resource availability and data amount, replacing the static maximum-size approach with a flexible mechanism that prevents segmentation while maintaining efficient transmission rates.
4Adaptability or versatility
If the RLC entity is radio aware, then RLC PDU size can be determined based on instantaneous available data rate, but processing power requirements increase
Solution Approach 1:
The patent implements a balanced approach to radio awareness by providing just enough information to the RLC entity to make effective sizing decisions. Rather than full radio awareness with all possible parameters, the system uses key metrics (available data, available resources) to achieve effective adaptation with minimal processing overhead, applying partial action to balance adaptability and complexity.
Data Source
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AI summary
A method and apparatus are used to generate radio link control (RLC) protocol data units (PDUs). A data request for a logical channel is received as part of an enhanced dedicated channel (E-DCH) transport format combination (E-TFC) selection procedure in a medium access control (MAC). Upon determining the data field size, an RLC PDU is generated such that it matches the requested data from the E-TFC selection. The size of the RLC PDU generated can be greater than or equal to the minimum configured RLC PDU size (if data is available) and less than or equal to the maximum RLC PDU size. The data is then transmitted in the RLC PDU in a current transmission time interval (TTI).