Communication Device HARQ Mode Switching for Power Savings

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Solution Overview

Problem

In LTE downlink traffic scenarios, user equipment (UE) inefficiently consumes power by waking up every transmission time interval to check the physical downlink control channel for a downlink grant, even though the Evolved Node B does not schedule downlink data on the physical downlink shared channel for most of the time, leading to unnecessary power consumption.

Innovation Solution

A communication device is configured to toggle between a robust mode and a power-efficient mode, skipping PDSCH decoding only when the network supports hybrid automatic repeat request (HARQ) retransmissions, by triggering a HARQ NACK after receiving a PDSCH grant during the random access channel setup procedure and switching to a power-efficient mode if a retransmission is detected.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the UE wakes up every TTI to check PDCCH for downlink grant, then the UE can detect scheduled downlink data, but the UE consumes excessive power due to frequent wake-ups even when no data is scheduled

Engineering Contradiction:

Improvedownlink data detection reliabilityVSAvoidUE power consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The UE dynamically switches between two operating modes: in the first mode, the UE wakes up every TTI to decode PDCCH and reliably detect downlink grants; in the second mode, the UE skips PDSCH decoding when HARQ retransmissions are supported. This dynamic adaptation allows the system to optimize power consumption based on network conditions while maintaining reliable data reception when needed.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes the decoding parameter state by toggling between decoding and skipping decoding based on HARQ retransmission support. When the network supports HARQ retransmissions, the UE changes its behavior to skip PDSCH decoding, effectively changing the operational parameter from active decoding to passive reception, thereby reducing power consumption while maintaining reliability through retransmission mechanisms.

Inventive Principle:

Principle #35Parameter changes

2Use of energy by moving object

If the UE skips PDSCH decoding to save power, then power consumption is reduced, but the UE cannot reliably receive downlink data when HARQ retransmissions are not supported

Engineering Contradiction:

ImproveUE power consumptionVSAvoiddownlink data reception reliability

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The UE dynamically adjusts its decoding behavior based on network capabilities. When HARQ retransmissions are supported, the UE operates in power-saving mode by skipping PDSCH decoding. When HARQ retransmissions are not supported, the UE automatically switches to robust mode and performs full PDSCH decoding to ensure reliable data reception. This dynamic switching resolves the contradiction by adapting the decoding strategy to the specific network environment.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system uses feedback from the network about HARQ retransmission support to determine the appropriate decoding strategy. The UE receives feedback indicating whether the network supports retransmissions and adjusts its PDSCH decoding behavior accordingly. This feedback mechanism ensures that power-saving measures are only applied when they will not compromise reception reliability.

Inventive Principle:

Principle #23Feedback

3Reliability

If the UE always decodes PDSCH, then downlink data is reliably received, but power is wasted when no data is scheduled by the eNodeB

Engineering Contradiction:

Improvedownlink data reception reliabilityVSAvoidunnecessary power consumption

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

Instead of always performing full PDSCH decoding, the UE applies partial action by selectively skipping decoding in specific conditions. When the network supports HARQ retransmissions, the UE performs only partial reception without full decoding, relying on the retransmission mechanism to ensure data integrity. This partial action approach eliminates unnecessary power consumption while maintaining reliability through the hybrid ARQ process.

Inventive Principle:

Principle #16Partial or excessive action

Solution Approach 2:

The UE dynamically adjusts its decoding effort based on whether data is actually scheduled and whether HARQ retransmissions are supported. Rather than maintaining constant high-power decoding operation, the system transitions between active decoding and passive reception states, optimizing power usage while ensuring that reliable reception occurs when needed through the combination of selective decoding and HARQ retransmissions.

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS10728886B2Communication device and method for decoding data from a network

Publication Date: 2020.07.28 APPLE INC

AI summary

A communication device and method adapted for network data decoding and connection modes switching in a mobile communication system consisting of connecting to a network in a first mode comprising decoding data received from the network; receiving a message from the network; transmitting a negative acknowledgement (NACK) for the message to the network; identifying a retransmission of the message from the network; and switching to a second mode comprising skipping data decoding based on the identified retransmission of the message from the network.