HARQ Retransmission Timer for Narrowband Uplink Reliability
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Solution Overview
Problem
Narrow-band communications, such as NB-IoT and eMTC, face challenges in ensuring reliable data transmission due to limited frequency bandwidth and increased chances of transmission failures in challenging locations, necessitating repeated transmissions and support for narrow-band TDD frame structures.
Innovation Solution
Implementing a hybrid automatic repeat request (HARQ) retransmission timer that manages uplink data transmission and random access procedures in narrow-band communication systems, allowing for controlled retransmissions and reduced uncertainty in HARQ feedback, thereby enhancing transmission reliability and reducing RACH load on base stations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If narrow-band communications are used to reduce device complexity and extend battery life, then device complexity and energy consumption are improved, but transmission reliability deteriorates due to limited frequency bandwidth and increased chances of transmission failures
Solution Approach 1:
The system performs preliminary actions by implementing repeated transmissions before attempting new data sends. The HARQ retransmission timer is configured to allow a predetermined number of retransmission attempts before considering the channel unavailable, thereby proactively addressing potential transmission failures before they result in data loss or extended delays.
Solution Approach 2:
The system implements feedback mechanisms through HARQ acknowledgments and the configuration of retransmission timers. The base station provides feedback on transmission success or failure, and the UE uses this feedback along with the timer configuration to determine whether to retransmit or initiate random access procedures, creating a closed-loop control system that adapts to channel conditions.
2Reliability
If repeated transmissions are implemented to increase transmission success rate, then transmission reliability is improved, but transmission delay increases
Solution Approach 1:
The system dynamically adjusts transmission behavior based on the HARQ retransmission timer configuration and current transmission attempts. The UE can adaptively decide whether to proceed with random access or wait for retransmission opportunities based on real-time channel conditions and timer status, optimizing the balance between reliability and delay.
Solution Approach 2:
The system changes parameters by configuring different HARQ retransmission timer values and maximum retransmission counts based on channel conditions and service requirements. These parameter adjustments allow the system to optimize performance for different scenarios, reducing unnecessary delays when channels are good while maintaining reliability when channels are poor.
3Adaptability or versatility
If random access procedures are frequently initiated to obtain uplink grants, then access flexibility is improved, but base station load increases
Solution Approach 1:
The system applies preliminary anti-action by preventing unnecessary random access procedures through the HARQ retransmission timer mechanism. When the timer is configured and active, the UE suppresses random access attempts during the timer duration, anticipating that retransmission opportunities will be available, thereby reducing RACH load while maintaining access flexibility when truly needed.
Data Source
AI summary
There is a need to support HARQ retransmission for narrow-band communications. The present disclosure provides a solution by supporting a HARQ retransmission timer for narrow-band communications. In an aspect of the disclosure, a method, a computer-readable medium, and an apparatus are provided. The method for wireless communication at a user equipment may include receiving, by a user equipment (UE), a hybrid automatic repeat request (HARQ) retransmission timer, the HARQ retransmission timer indicates a time interval, identifying, by the (UE), data for uplink transmission, and starting, by the UE and after expiration of the HARQ retransmission timer, a random access procedure to obtain an uplink grant for the data.