Dynamic RLP Mode Switching for Wireless Queue Stall Prevention
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Solution Overview
Problem
In high data rate wireless communication systems, such as CDMA 1XEV-DV, the transmit buffer can fill up due to incorrectly received frames, leading to queue stalls and transmission delays, as the reliable transport protocol like RLP/RLC re-transmits frames, causing a drop in data rate.
Innovation Solution
A method and apparatus that dynamically switch the Radio Link Protocol (RLP) mode based on air interface quality, switching to a transparent mode when conditions are good to minimize error correction overhead and to a non-transparent mode when conditions are poor to ensure reliable re-transmissions, thereby preventing queue stalls.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a reliable transport protocol (RLP/RLC) is used to re-transmit incorrectly received frames, then transmission reliability is improved, but the transmit buffer fills up due to queue stalls, causing transmission delays and data rate drop
Solution Approach 1:
The patent implements dynamic switching between two RLP modes (transparent mode and non-transparent mode with re-transmission) based on buffer status and air interface conditions. The system transitions from a static protocol configuration to a dynamic one that adapts to changing network conditions, allowing the data rate to be maintained by switching to transparent mode when the buffer is nearly full, thus preventing queue stalls while preserving transmission reliability when conditions permit.
2Reliability
If the transmit buffer size is increased to accommodate re-transmissions, then transmission reliability is improved, but the buffer fill time increases, leading to more frequent queue stalls
Solution Approach 1:
The patent changes the operational parameters of the RLP protocol dynamically by switching between transparent mode (no re-transmission, faster buffer clearance) and non-transparent mode (with re-transmission, higher reliability). This parameter change allows the system to adjust the effective buffer utilization based on current conditions, preventing the buffer fill time from becoming excessive while maintaining adequate transmission reliability.
3Reliability
If error correction and re-transmission are always performed, then transmission reliability is improved, but error correction overhead increases, reducing effective data throughput
Solution Approach 1:
The patent applies partial error correction action by switching between full error correction mode (non-transparent RLP with re-transmission) and no error correction mode (transparent RLP). Instead of always performing error correction, the system applies it only when necessary based on buffer status and air interface quality, thus reducing the error correction overhead while maintaining adequate transmission reliability for the portion of data that requires it.
Data Source
AI summary
A communication device minimizes an opportunity for a queue stall during a communication session employing a reliable transport protocol by setting a current mode of operation for a Radio Link Protocol (RLP) and, based on a quality of an air interface, switching to an RLP mode of operation different from the current mode during the communication session.