HARQ Buffer Flushing for Contention-Based Random Access
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Solution Overview
Problem
In the LTE wireless communication system, ongoing retransmissions of Scheduled Transmission messages after a contention-based random access procedure can interfere with other user equipment's uplink transmissions and cause unnecessary power consumption, as the Hybrid Automatic Repeat Request (HARQ) process continues without clear resolution.
Innovation Solution
A method and apparatus that flushes the HARQ buffer associated with the Scheduled Transmission message once the contention result of the random access procedure is determined, whether successful or unsuccessful, to terminate retransmissions and prevent interference and power wastage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the HARQ process continues retransmitting the Scheduled Transmission message after contention resolution, then the transmission reliability is maintained, but interference with other user equipment's uplink transmissions occurs and power consumption increases
Solution Approach 1:
The patent applies preliminary action by flushing the HARQ buffer immediately upon determining the contention result (whether successful or unsuccessful), before any potential interference can occur. This proactive termination of the HARQ process prevents the harmful retransmissions from happening in the first place, rather than waiting for errors to manifest and then correcting them.
2Reliability
If the Contention Resolution Timer is monitored until expiration, then the contention resolution status is accurately determined, but the time duration for potential retransmission increases
Solution Approach 1:
The patent extracts the Scheduled Transmission message from the HARQ buffer upon determining the contention result, removing it from the retransmission queue. This extraction action effectively terminates the retransmission process early, preventing the time loss that would occur if the full Contention Resolution Timer duration were allowed to elapse with potential retransmissions.
3Productivity
If the HARQ buffer is not flushed after contention resolution, then the Hybrid Automatic Repeat Request mechanism functions completely, but unnecessary retransmissions occur causing resource waste
Solution Approach 1:
The patent implements feedback by using the contention resolution determination (successful or unsuccessful) as a trigger signal to flush the HARQ buffer. This feedback mechanism allows the system to adapt the HARQ process behavior based on the random access outcome, terminating unnecessary retransmissions when the contention result is known, thereby improving resource utilization and reducing power consumption.
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AI summary
A method for handling a contention-based random access procedure in a user equipment (UE) of a wireless communication system is disclosed. The method includes steps of sending a Scheduled Transmission message, the Scheduled Transmission message applying an HARQ (Hybrid Automatic Repeat request) process for transmission (402), starting a Contention Resolution Timer and monitoring a PDCCH (Physical Downlink Control Channel) (404), and flushing a buffer of the HARQ process used for transmission of the Scheduled Transmission message when a contention result of the random access procedure is determined (406).