Dynamic Poll Retransmission Timer for LTE RLC
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing LTE RLC protocol's poll-retransmit timer duration is inadequate, leading to delayed reaction to unanswered polls, resulting in duplicated non-acknowledgements and wasteful use of radio resources, especially when radio conditions deteriorate, affecting quality of experience for critical data transmissions.
Innovation Solution
The duration of the poll-retransmit timer is adjusted based on predefined conditions related to the sequence number of the protocol data unit, such as X−N≥3 or X−N≥1, allowing for optimized timer settings that span multiple one-way RLC delays, thereby reducing unnecessary retransmissions and improving resource efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the poll-retransmit timer duration is set to a fixed value, then the protocol is simple to implement, but it leads to delayed reaction to unanswered polls and duplicated non-acknowledgements when radio conditions deteriorate
Solution Approach 1:
The poll-retransmit timer duration is changed from a fixed value to a dynamic value that adapts based on radio conditions and transmission history. The timer is adjusted according to whether acknowledgments are received, allowing the system to react to deteriorating radio conditions by extending the timer duration, thereby preventing premature retransmissions and duplicated non-acknowledgements while maintaining reliability.
Solution Approach 2:
The timer duration parameter is modified based on observed system behavior and radio conditions. When acknowledgments are not received within expected timeframes, the timer duration is extended, allowing the system to adapt to deteriorating conditions. This parameter change enables the protocol to maintain reliability without requiring complex implementation, as it only requires monitoring acknowledgment status and adjusting the timer accordingly.
2Reliability
If the poll-retransmit timer duration is extended to cover worst-case scenarios, then reliability is improved, but latency increases for normal operations
Solution Approach 1:
The timer duration is made dynamic rather than statically extended for all cases. For normal operations with good radio conditions, the timer uses a shorter duration, maintaining low latency. When worst-case scenarios occur (e.g., multiple lost acknowledgments or deteriorating conditions), the timer is extended to ensure reliability. This dynamic adjustment resolves the contradiction by adapting the timer duration to actual conditions rather than always using the maximum value.
Solution Approach 2:
The system prepares for worst-case scenarios by having a mechanism to extend the timer duration, but does not always use the extended duration. Instead, it starts with a shorter timer for normal operations and only extends it when necessary, based on observed acknowledgment patterns. This preliminary preparation allows the system to maintain low latency under normal conditions while being ready to improve reliability when needed.
3Reliability
If frequent polling is performed to detect lost data quickly, then responsiveness is improved, but radio resource usage increases due to duplicated retransmissions
Solution Approach 1:
The polling frequency and retransmission timing are made dynamic based on acknowledgment reception. Instead of frequent fixed-interval polling, the system adjusts the timing of subsequent polls and retransmissions based on whether acknowledgments are received. When acknowledgments are received normally, polling is spaced out to conserve resources. When acknowledgments are lost, the timer is extended and polling is adjusted to detect the loss without causing duplicated retransmissions, thus maintaining responsiveness while reducing radio resource usage.
Solution Approach 2:
The system uses feedback from received acknowledgments to control polling and retransmission behavior. When acknowledgments are received, the system knows data was successfully transmitted and can reduce polling frequency. When acknowledgments are not received, the feedback triggers timer extension and adjusted polling to detect lost data. This feedback mechanism ensures responsive detection of lost data while avoiding unnecessary frequent polling that would waste radio resources.
Data Source
AI summary
Systems, methods, apparatuses, and computer program products for expediting repetition of an unanswered poll for automatic repeat request (ARQ) feedback are provided. One method includes transmitting a poll to a peer protocol entity to trigger status reporting at the peer protocol entity, starting a timer with a duration that is set based on whether at least one predefined condition is met. The at least one predefined condition depends at least on a value of a sequence number (SN) of a protocol data unit (PDU) in which the poll is transmitted. The method may further include re-transmitting a poll when the timer expires.