Adaptive Modulation Feedback for HARQ Latency Reduction

Solution Overview

Problem

In wireless communication systems like HSPA and LTE, non-adaptive modulation schemes during hybrid automatic repeat request (HARQ) retransmissions lead to increased latency and reduced data throughput due to the inability to change transport block size, modulation scheme, or channelization codes, especially in deteriorating channel conditions, affecting applications that require low latency such as voice services.

Innovation Solution

Implementing an explicit adaptive modulation and coding scheme selection method where a mobile device evaluates the quality of received transport blocks and suppresses acknowledgments or negative acknowledgments if below a threshold, allowing the network to switch to a more suitable modulation and coding scheme for retransmissions, thereby enabling dynamic adaptation to current channel conditions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If non-adaptive modulation scheme is used during HARQ retransmissions, then device complexity is reduced and ease of operation is improved, but latency increases and data throughput decreases in deteriorating channel conditions

Engineering Contradiction:

Improveease of operationVSAvoidlatency

Core Design Contradiction:

Ease of operationVSLoss of time

Solution Approach 1:

The patent implements dynamic modulation and coding scheme adaptation during HARQ retransmissions by introducing a multi-level feedback mechanism. The receiver evaluates channel conditions and sends feedback indicating whether to maintain the current MCS or switch to a more robust alternative, enabling the system to adapt transmission parameters dynamically based on actual channel quality rather than using fixed non-adaptive schemes.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the transmission parameters (modulation scheme and coding rate) during retransmission based on channel conditions. Instead of keeping MCS fixed, the system modifies these parameters by selecting from multiple predefined robust MCS configurations, allowing optimization of transmission reliability and latency performance according to actual radio conditions.

Inventive Principle:

Principle #35Parameter changes

2Device complexity

If non-adaptive modulation scheme is used during HARQ retransmissions, then device complexity is reduced, but data throughput decreases in deteriorating channel conditions

Engineering Contradiction:

Improvedevice complexityVSAvoiddata throughput

Core Design Contradiction:

Device complexityVSProductivity

Solution Approach 1:

The patent implements dynamic modulation and coding scheme adaptation during HARQ retransmissions by introducing a multi-level feedback mechanism. The receiver evaluates channel conditions and sends feedback indicating whether to maintain the current MCS or switch to a more robust alternative, enabling the system to adapt transmission parameters dynamically based on actual channel quality rather than using fixed non-adaptive schemes.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the transmission parameters (modulation scheme and coding rate) during retransmission based on channel conditions. Instead of keeping MCS fixed, the system modifies these parameters by selecting from multiple predefined robust MCS configurations, allowing optimization of transmission reliability and latency performance according to actual radio conditions.

Inventive Principle:

Principle #35Parameter changes

3Loss of time

If adaptive modulation and coding scheme selection is implemented, then latency is reduced and data throughput is increased, but device complexity increases due to multi-level feedback mechanism

Engineering Contradiction:

ImprovelatencyVSAvoiddevice complexity

Core Design Contradiction:

Loss of timeVSDevice complexity

Solution Approach 1:

The patent introduces a multi-level feedback mechanism where the receiver evaluates channel conditions and sends feedback to the transmitter. This feedback indicates whether the current modulation and coding scheme should be maintained or changed to a more robust alternative, enabling adaptive retransmission parameter selection that reduces latency and improves throughput despite the added complexity.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent changes the transmission parameters (modulation scheme and coding rate) during retransmission based on channel conditions. Instead of keeping MCS fixed, the system modifies these parameters by selecting from multiple predefined robust MCS configurations, allowing optimization of transmission reliability and latency performance according to actual radio conditions.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS9967055B2System and method to increase link adaptation performance with multi-level feedback

Publication Date: 2018.05.08 MALIKIE INNOVATIONS LTD

AI summary

A method and apparatus for explicit adaptive modulation and coding scheme selection, the method receiving, at a mobile device, a transport block targeted to the mobile device, and if a quality of the received transport block exceeds a threshold, providing an acknowledgment or negative acknowledgment to a network element; and if the quality of the received transport block is below the threshold, suppressing the acknowledgment or negative acknowledgement.