Asynchronous HARQ Buffer Management for Unlicensed Band Retransmissions
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Solution Overview
Problem
In wireless communication systems, particularly in LTE and LTE-Advanced networks, the unlicensed band poses challenges for hybrid automatic repeat request (HARQ) operations due to unpredictable channel availability and flushing of HARQ buffers, leading to failed retransmissions when the channel is busy.
Innovation Solution
Implementing an asynchronous HARQ operation in communication devices, which involves transmitting uplink data blocks and stopping the maintenance of counters for HARQ buffers, allowing retransmissions without flushing the buffer, even after maximum attempts, and using received DCI for scheduling instead of predetermined sequences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If synchronous HARQ operation with predetermined timing is used in unlicensed band, then channel access efficiency is improved, but retransmission reliability deteriorates due to channel busy conditions causing HARQ buffer flushing
Solution Approach 1:
The patent transitions from synchronous HARQ with fixed timing to asynchronous HARQ with dynamic timing adjustment. The UE and eNB negotiate and adapt transmission timing based on actual channel conditions, allowing flexible retransmission scheduling when channels are busy, thus preventing HARQ buffer flushing while maintaining access efficiency
Solution Approach 2:
The patent changes the timing parameter from predetermined fixed values to negotiable dynamic values. By allowing UE and eNB to agree on transmission timing through signaling exchange, the system adapts timing parameters to channel conditions, resolving the conflict between efficient channel access and reliable retransmission
2Device complexity
If HARQ buffer is flushed after maximum transmission attempts in synchronous HARQ, then resource cleanup is improved, but data transmission reliability deteriorates due to unpredictable channel availability in unlicensed band
Solution Approach 1:
The patent makes HARQ buffer management dynamic by allowing timing negotiation between UE and eNB. Instead of fixed flushing at maximum attempts, the system adapts buffer retention duration based on channel conditions and negotiated timing, ensuring data remains available for retransmission when channel becomes accessible
Solution Approach 2:
The patent introduces feedback mechanisms where UE and eNB exchange signaling to confirm transmission timing and HARQ buffer status. This feedback loop ensures both sides have consistent understanding of buffer contents, preventing premature flushing while maintaining manageable complexity through coordinated control
Data Source
AI summary
A communication device configured with an asynchronous hybrid automatic repeat request (HARQ) operation for a first cell of a network comprises a storage unit for storing instructions and a processing means coupled to the storage unit. The processing means is configured to execute the instructions stored in the storage unit. The instructions comprise transmitting a first plurality of uplink (UL) transmissions of a data block in a first HARQ buffer associated with a first HARQ process on the first cell to the network by using the asynchronous HARQ operation; and stopping maintaining a first counter for counting a number of the first plurality of UL transmissions, when using the asynchronous HARQ operation.