ACK Transmission Reliability in Limited Link Budget Wireless Systems
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Solution Overview
Problem
Wireless communication systems face challenges in efficiently transmitting control information, particularly in scenarios with limited link budgets, where acknowledgement (ACK) information needs to be repeated across multiple subframes, and channel quality information (CQI) is jointly coded with ACK, potentially leading to unreliable error rates.
Innovation Solution
The method involves identifying ACK information to be transmitted in a common subframe with CQI, determining if ACK is configured for repeat transmission, and either dropping CQI or adjusting the coding rate to ensure reliable ACK transmission by transmitting only ACK information in subframes where ACK is repeated, thereby maintaining a desired error rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ACK information is repeated across multiple subframes to improve reliability in limited link budget scenarios, then the reliability of ACK transmission is improved, but the transmission efficiency and throughput are reduced due to repeated transmissions occupying multiple subframes
Solution Approach 1:
The patent segments control information into different types (ACK/NACK and CQI) and applies different transmission strategies to each type. ACK/NACK information is repeated across multiple subframes for high reliability, while CQI is transmitted only in the first subframe to avoid redundant transmissions. This segmentation allows the system to optimize reliability for critical ACK transmissions while maintaining efficiency for less critical CQI transmissions.
2Productivity
If both ACK information and CQI are jointly coded and transmitted in the same subframe, then the resource utilization is improved, but the error rate increases and reliability decreases when ACK repetition is required
Solution Approach 1:
The patent extracts CQI transmission from the repeated ACK transmission sequence. When ACK repetition is configured, the system transmits ACK/NACK information across multiple subframes but removes (drops) CQI transmission in subframes after the first one. This extraction ensures that ACK information maintains its required reliability through repetition while CQI is transmitted efficiently without compromising ACK performance.
3Loss of information
If CQI is transmitted in every subframe where ACK is repeated, then the channel quality information availability is improved, but the overall system performance deteriorates due to increased interference and reduced ACK reliability
Solution Approach 1:
The patent applies preliminary action by transmitting CQI information in the first subframe before the ACK repetition sequence begins. This preliminary CQI transmission provides the base station with channel quality information in advance, allowing it to prepare appropriate reception parameters for the subsequent ACK repeated transmissions. This approach ensures CQI availability while avoiding interference with the critical ACK repetition process.
Data Source
AI summary
Systems and methodologies are described that facilitate arrangement and transmission of control information in a wireless communication system. As described herein, a scheduled transmission of acknowledgement (ACK) signaling and channel quality information (CQI) signaling in a common subframe can be adapted for network implementations with limited link budget wherein ACK signaling is configured for repetition over multiple subframes to ensure a desired error rate level for the ACK signaling. To these ends, various aspects described herein facilitate modification of a coding rate applied to ACK signaling to be transmitted with data based on a repetition factor of the ACK signaling. Additionally and/or alternatively, various aspects described herein facilitate dropping of CQI signaling and transmission of only ACK signaling on subframes where CQI and ACK signaling are to be transmitted substantially simultaneously and ACK transmission is configured for repetition over multiple subframes.