HARQ Process Handling at TTI Length Switch
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Solution Overview
Problem
Existing systems face challenges in efficiently handling retransmissions during changes in Transmission Time Interval (TTI) length, leading to data loss and delays due to the loss of HARQ processes, which are not addressable after a TTI length switch, especially when switching between different numbers of HARQ processes.
Innovation Solution
The method involves stopping the HARQ process associated with data to be retransmitted and using a different procedure, such as switching to the Radio Link Control (RLC) layer for retransmission, by communicating a local negative acknowledgement (NACK) from the Medium Access Control (MAC) layer to the RLC layer, allowing for efficient retransmission on the new TTI length and number of HARQ processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If HARQ processes are used for retransmission handling in legacy LTE, then retransmission reliability is improved, but data loss and delays occur when TTI length changes cause HARQ processes to become unaddressable
Solution Approach 1:
The patent introduces an intermediary mechanism between MAC layer HARQ processes and RLC layer retransmissions. When TTI length changes cause HARQ processes to become unaddressable, the system uses RLC as an intermediary to handle retransmissions, bridging the gap between the stopped HARQ process and the new TTI configuration.
Solution Approach 2:
The patent segments the retransmission handling into two distinct paths: continuing to use stopped HARQ processes for some retransmissions and introducing RLC layer retransmissions for others. This segmentation allows the system to manage the transition during TTI length changes without complete data loss.
2Adaptability or versatility
If HARQ processes are stopped during TTI length switch, then adaptation to new TTI length is achieved, but retransmission delays increase due to loss of active HARQ processes
Solution Approach 1:
The patent performs preliminary actions by flushing HARQ buffers and stopping HARQ processes before the TTI length switch is complete. This preparation ensures that the system is ready for the new TTI length, and retransmissions can be handled efficiently using RLC layer mechanisms without causing additional delays.
Solution Approach 2:
The patent implements feedback mechanisms where the MAC layer communicates with the RLC layer about stopped HARQ processes and their associated data. This feedback loop enables the RLC layer to take over retransmission responsibilities and maintain timely data delivery during the transition.
3Productivity
If multiple HARQ processes are supported for short TTIs, then retransmission capacity is increased, but system complexity increases due to management of multiple processes during TTI length changes
Solution Approach 1:
The patent extracts the complexity management from the MAC layer HARQ process management and transfers it to the RLC layer. By taking out the retransmission handling responsibility from the stopped HARQ processes, the system simplifies the overall management during TTI length changes while maintaining high retransmission capacity.
Data Source
AI summary
A network node, a wireless device for communication with a network node and corresponding methods are provided. The network node includes processing circuitry configured to stop a hybrid automatic repeat request (HARQ) process associated with data to be retransmitted and retransmit the data using a procedure that is different from the stopped HARQ process.