LAA Uplink HARQ Mode Switching for Retransmission
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Solution Overview
Problem
In licensed-assisted access (LAA) systems, the existing hybrid automatic repeat request (HARQ) mechanism for uplink transmission is limited by the maximum occupation duration on unlicensed carriers, preventing retransmissions and resulting in poor system performance and feasibility.
Innovation Solution
Configuring both synchronous and asynchronous HARQ modes for uplink transmission on unlicensed carriers, allowing user equipment to determine which mode to use based on available resources, and sending mode configuration indication information to enable flexible retransmissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If synchronous HARQ mode is used for uplink transmission on unlicensed carrier, then transmission timing is simplified and predictable, but retransmission cannot be performed when channel occupation duration is exceeded
Solution Approach 1:
The patent applies dynamics by enabling the system to switch between synchronous HARQ mode and asynchronous HARQ mode based on channel conditions and occupation duration. When the channel occupation duration is exceeded, the system dynamically transitions from synchronous to asynchronous mode, allowing retransmission flexibility while maintaining operational simplicity when conditions permit synchronous operation.
2Adaptability or versatility
If maximum occupation duration limit is enforced on unlicensed carrier, then channel access fairness is improved, but HARQ retransmission capability is lost
Solution Approach 1:
The patent segments the HARQ transmission process into two distinct modes: synchronous HARQ for initial transmissions within the occupation duration, and asynchronous HARQ for retransmissions when the duration limit is reached. This segmentation allows the system to maintain channel access fairness through LBT mechanisms while ensuring retransmission capability through mode switching.
Solution Approach 2:
The patent introduces mode configuration indication information as an intermediary mechanism that enables transitions between synchronous and asynchronous HARQ modes. This intermediary allows the system to maintain both channel access fairness (through LBT-compliant occupation limits) and retransmission capability (through asynchronous mode activation when needed).
3Productivity
If channel is released and re-contended for retransmission, then channel access control is maintained, but transmission delay increases and productivity decreases
Solution Approach 1:
The patent applies preliminary action by configuring both synchronous and asynchronous HARQ modes in advance through mode configuration indication information. This allows the system to immediately switch to asynchronous mode when occupation duration is exceeded, avoiding the time-consuming process of releasing and re-contending for the channel, thus reducing retransmission delay while maintaining channel access control.
Data Source
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AI summary
The present invention provides a method and an apparatus for transmitting uplink data in an LAA system. The method includes: receiving mode configuration indication information sent by a network device, where the mode configuration indication information is used to indicate that a synchronous HARQ mode and an asynchronous HARQ mode are configured for uplink transmission of user equipment on an unlicensed carrier; and performing uplink transmission on the unlicensed carrier by using the synchronous HARQ mode or the asynchronous HARQ mode and according to the mode configuration indication information. By means of the method for transmitting uplink data in an LAA system disclosed in the present invention, a prior-art problem that the UE cannot perform data retransmission because a time resource obtained by UE through contention on an unlicensed carrier is limited can be avoided.