User Equipment HARQ Buffer Management for Battery Reduction
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Solution Overview
Problem
The existing UE implementation in LTE systems leads to higher battery consumption due to the HARQ mechanism operating at the physical layer but being controlled by the MAC layer, resulting in inefficient retransmissions and unnecessary battery usage during discontinuous reception.
Innovation Solution
A method that activates an inactivity timer during uplink data transmission, measures the maximum HARQ retransmission time, and compares it with the remaining DRX cycle time to determine the link state, switching the UE to a sleep mode and removing data from the HARQ buffer when the retransmission time is less than the cycle time and link state is below a threshold, thereby reducing battery consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE continuously monitors PDCCH and stores data in HARQ buffer during DRX cycle, then the reliability of retransmission is improved, but the battery consumption increases
Solution Approach 1:
The patent applies preliminary action by measuring the maximum HARQ retransmission time in advance and comparing it with the remaining DRX cycle time before entering sleep mode. This pre-calculation allows the UE to determine whether to flush the HARQ buffer or wait for potential retransmissions, avoiding unnecessary battery consumption while ensuring reliable retransmission when needed.
Solution Approach 2:
The patent changes the parameter of HARQ buffer management by introducing a threshold-based decision mechanism. When the measured maximum retransmission time is less than the remaining DRX cycle time and link state is below a threshold, the UE flushes the buffer and enters sleep mode. This parameter change optimizes the balance between reliability and energy consumption.
2Reliability
If the UE waits for ACK/NACK before flushing HARQ buffer, then the data transmission reliability is improved, but the processing time increases
Solution Approach 1:
The patent applies preliminary action by pre-measuring the maximum HARQ retransmission time and comparing it with the remaining DRX cycle time before making the flush decision. This eliminates the need to wait for actual ACK/NACK signals, significantly reducing processing time while maintaining reliability through the threshold-based decision mechanism.
Solution Approach 2:
The patent uses feedback from link state measurements and timer comparisons to make intelligent decisions about buffer flushing. The link state threshold provides feedback about channel conditions, allowing the UE to flush the buffer confidently when retransmission is unlikely, thus reducing waiting time without sacrificing reliability.
3Reliability
If the UE stores uplink data in HARQ buffer for extended period, then the retransmission capability is improved, but the memory utilization efficiency decreases
Solution Approach 1:
The patent applies discarding and recovering by selectively flushing the HARQ buffer when the measured maximum retransmission time is less than the remaining DRX cycle time and link state is below the threshold. This discards data that is unlikely to be needed, improving memory utilization efficiency while maintaining retransmission capability for data that requires it.
Solution Approach 2:
The patent uses preliminary measurement of maximum retransmission time to make informed decisions about buffer management. By comparing this pre-measured value with the remaining DRX cycle time, the UE can proactively flush the buffer when it is safe to do so, optimizing memory utilization without compromising retransmission capability.
Data Source
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AI summary
Disclosed is a method and system to reduce user equipment (UE) battery consumption and efficiently utilize uplink hybrid automatic repeat request (HARQ) memory, including sending uplink data to a base station and saving a backup copy of the uplink data in an uplink HARQ buffer, receiving an acknowledgement from the base station indicating that the uplink data has been received, measuring a HARQ retransmission time required to retransmit the uplink data to the base station after receiving the acknowledgement, comparing the measured HARQ retransmission time to a remaining discontinuous reception cycle, and removing the uplink data from the uplink HARQ buffer after expiration of an inactivity timer and switching the UE to a sleep mode based on the comparison.