HARQ Retransmission Across Multiple TTIs for Cell-Edge Uplinks

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Solution Overview

Problem

In mobile telecommunications networks, power-limited mobile terminals face challenges with transmission power limitations and high retransmission delays due to Hybrid Automatic Repeat reQuest (HARQ) processes, which can lead to unacceptable packet loss rates, especially at cell edges.

Innovation Solution

Implementing a method that uses multiple transmission time intervals (TTIs) for a single HARQ process, where retransmissions occur independently of feedback, allowing for increased transmission power and reduced overhead, and configuring the number of TTIs through RRC signaling or MAC scheduling to manage retransmissions efficiently.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If multiple retransmissions are performed using traditional HARQ process, then transmission reliability is improved, but transmission delay increases proportionally

Engineering Contradiction:

Improvetransmission reliabilityVSAvoidtransmission delay

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The patent segments the transmission resource by introducing a separate grant-free retransmission resource pool, distinct from the original HARQ process resources. This segmentation allows initial transmissions to use traditional HARQ with feedback, while retransmissions utilize the dedicated grant-free resources, thereby reducing the overall transmission delay while maintaining reliability through diversified resource usage.

Inventive Principle:

Principle #1Segmentation

2Reliability

If multiple HARQ retransmissions are performed, then transmission reliability is improved, but packet loss rate increases due to feedback errors

Engineering Contradiction:

Improvetransmission reliabilityVSAvoidpacket loss rate

Core Design Contradiction:

ReliabilityVSLoss of information

Solution Approach 1:

The patent introduces an intermediary grant-free retransmission mechanism that operates independently of the traditional HARQ feedback loop. By using pre-configured uplink grants for retransmissions, the system bypasses the error-prone feedback channel, thereby reducing packet loss caused by NACK-ACK errors while maintaining transmission reliability through the additional retransmission opportunity.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If traditional HARQ process is used, then transmission reliability is improved, but system complexity increases due to feedback management

Engineering Contradiction:

Improvetransmission reliabilityVSAvoidsystem complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent extracts the feedback-dependent retransmission function from the traditional HARQ process and places it into a separate grant-free resource pool. This extraction simplifies the overall system by removing the complex feedback management for retransmissions, while maintaining reliability through the dedicated retransmission resources that operate independently of the feedback loop.

Inventive Principle:

Principle #2Taking out (Extraction)

Data Source

PatentUS8370696B2Method and arrangement for retransmission using HARQ

Publication Date: 2013.02.05 OPTIS WIRELESS TECHNOLOGY LLC

AI summary

The present invention relates to a method and device for enhancing coverage of a power-limited mobile terminal by sending information relating to a single Hybrid Automatic Repeat Request (HARQ) process from the mobile terminal to a base station using several transmission time intervals.