Dynamic TTI Bundle Scheduling for HARQ Process Collision Avoidance
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Solution Overview
Problem
The current LTE system faces challenges in efficiently managing dynamic TTI-bundle scheduling for multiple HARQ processes, leading to potential collisions and misinterpretation of PDCCH signals, which can result in radio link failures and protocol reset.
Innovation Solution
A method is introduced to dynamically schedule TTI bundles by adapting the timing of data transmission based on the state of the HARQ process, where a single grant applies to a bundle of TTIs, and the transmission is mapped cyclically onto subframes, with provisions for handling shifting grants and maintaining HARQ buffer continuity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If dynamic TTI-bundle scheduling is implemented for multiple HARQ processes, then scheduling flexibility and resource utilization are improved, but collisions and misinterpretation of PDCCH signals occur leading to radio link failures
Solution Approach 1:
The patent segments the TTI bundle transmission into multiple individual TTI transmissions, each handled by separate HARQ processes. This segmentation allows independent management of each TTI bundle, preventing collisions between multiple HARQ processes while maintaining scheduling flexibility through dynamic grant allocation for each segment.
Solution Approach 2:
The patent introduces an intermediary mechanism in the form of HARQ process state management and buffer continuity checks. This intermediary layer mediates between the dynamic scheduling grants and the actual TTI bundle transmissions, ensuring proper synchronization and preventing misinterpretation of PDCCH signals that would otherwise lead to radio link failures.
2Reliability
If TTI bundles are transmitted according to fixed timing, then synchronization is maintained, but scheduling efficiency and adaptability to varying channel conditions deteriorate
Solution Approach 1:
The patent implements dynamic TTI bundle scheduling where the timing and allocation of TTI bundles are adjusted based on current channel conditions and network requirements. Instead of fixed timing, the system dynamically grants resources for TTI bundle transmissions, allowing adaptation to varying conditions while maintaining synchronization through HARQ process management and buffer continuity mechanisms.
Solution Approach 2:
The patent changes the scheduling parameter from fixed timing to dynamic grant-based allocation. The timing offset, bundle size, and resource allocation are modified based on channel quality indicators and network traffic patterns, improving scheduling efficiency while synchronization is maintained through the HARQ protocol structure and buffer management rules.
3Productivity
If multiple HARQ processes are used for parallel transmissions, then throughput is improved, but complexity of managing timing and buffer continuity increases
Solution Approach 1:
The patent segments the overall transmission into multiple independent TTI bundles, each associated with a separate HARQ process. This segmentation allows parallel processing of multiple bundles while simplifying timing management within each segment. The segmentation approach reduces the complexity of managing buffer continuity by treating each segmented bundle as an independent unit with its own timing requirements.
Solution Approach 2:
The patent implements preliminary actions in the form of buffer continuity checks and timing offset calculations before TTI bundle transmissions. By performing these preparatory actions in advance, the system reduces the real-time complexity of managing multiple HARQ processes. The preliminary setup of buffer states and timing parameters simplifies the concurrent management of multiple parallel transmissions.
Data Source
AI summary
The present invention relates to transmitting data on a shared communication channel in a communication system supporting multiple hybrid automatic repeat request processes and configurable to apply a bundling of transmission time intervals. The data transmitting including mapping of TTIs of the HARQ processes cyclically onto subframes. In order to efficiently support dynamic bundle scheduling, when a grant is received during a bundle transmission, this grant becomes a shifting grant, according to which the bundle is transmitted and according to the location of which the timing of the grant reception and the data transmission is adapted. The transmission of the shifted bundle is performed in accordance with the state of its retransmission process, i.e. the bundle is either initially transmitted or retransmitted.