Delayed HARQ Retransmissions for Low Bandwidth Power Saving
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Solution Overview
Problem
In 4G LTE networks, Hybrid Automatic Repeat Request (HARQ) scheduling leads to unnecessary power consumption in user equipment (UE) due to prolonged active periods for HARQ retransmissions, especially during low-bandwidth applications like VoLTE communications, which compromises power-saving modes like C-DRX and SPS.
Innovation Solution
A network base station monitors HARQ information and delays retransmissions until the UE is in an active state, bundles HARQ retransmissions with new downlink transmissions, and adjusts modulation and coding schemes based on SINR conditions to minimize power consumption, allowing the UE to remain in sleep mode during unnecessary periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If HARQ retransmissions are performed according to standard LTE scheduling, then reliable data transmission is achieved, but UE power consumption increases due to prolonged active periods
Solution Approach 1:
The base station delays HARQ retransmissions until the next ON duration of C-DRX cycle, performing the retransmission action in advance of when the UE would naturally wake up. This allows the UE to remain in sleep mode during OFF durations while ensuring retransmissions occur when the UE is active, resolving the contradiction between reliable transmission and power consumption
Solution Approach 2:
The invention aligns HARQ retransmissions with the periodic C-DRX ON/OFF cycles of the UE. By scheduling retransmissions only during ON durations rather than using continuous or frequent retransmission attempts, the system maintains reliability while reducing power consumption by matching transmission activity to the periodic wake-sleep pattern of the UE
2Reliability
If HARQ retransmissions are performed frequently to ensure reliable delivery, then transmission reliability improves, but the UE cannot enter sleep mode during low-bandwidth applications
Solution Approach 1:
The base station performs preliminary scheduling of HARQ retransmissions to occur only during ON durations of the C-DRX cycle. By planning ahead and delaying retransmissions until the UE is guaranteed to be active, the system ensures reliable delivery without forcing the UE to extend its active period, allowing the UE to enter sleep mode during OFF durations even for low-bandwidth applications
3Reliability
If the UE remains awake to handle HARQ retransmissions, then transmission reliability is maintained, but power-saving modes like C-DRX and SPS are compromised
Solution Approach 1:
The base station performs preliminary scheduling of HARQ retransmissions to coincide with UE ON durations. By planning retransmissions in advance and aligning them with periods when the UE is naturally active, the system maintains reliable HARQ acknowledgments without requiring the UE to extend its active period, thus preserving power-saving modes and reducing overall system power consumption
Data Source
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AI summary
Apparatus and methods are disclosed for performing delayed hybrid automatic repeat request (HARQ) communications in the downlink (DL) to reduce power consumption for a user equipment (UE) during a connected mode discontinuous reception (C-DRX) cycle. An enhanced NodeB can be configured to monitor a physical uplink control channel (PUCCH) for DL HARQ information to determine when the PUCCH contains a negative acknowledgement (NACK) message, and in response to determining that the PUCCH contains a NACK message, the eNodeB can wait until a next C DRX ON duration to transmit a HARQ DL retransmission. The eNodeB can also determine whether or not to bundle the HARQ DL retransmission in consecutive transmission time intervals, based on a signal to interference plus noise ratio (SINR) associated with the UE.