Uplink Control Information Mapping for Wireless Latency Reduction
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Solution Overview
Problem
Current wireless communication systems face challenges in reducing latency, particularly in uplink transmission operations involving multiple transmission time intervals, subcarrier spacing, and processing times, as well as in mapping and reporting of control information across multiple channels.
Innovation Solution
A method and apparatus that map uplink control information, including HARQ-ACK, RI, CQI, and PMI, to radio resources within transmission time intervals of two or three symbols, with specific mapping rules to optimize transmission efficiency, such as mapping HARQ-ACK to the first symbol and RI to the other symbol in descending order of frequency index, and limiting the number of coded symbols based on subcarriers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If multiple transmission time intervals and subcarrier spacings are supported to reduce latency, then transmission speed and responsiveness are improved, but system complexity and difficulty of resource mapping increase
Solution Approach 1:
The patent segments uplink control information into different types (HARQ-ACK, RI, CQI/PMI) and assigns each type to specific symbols within the TTI based on their priority and timing requirements. This segmentation allows the system to handle multiple TTIs and subcarrier spacings by treating each control information type independently, thereby reducing the overall complexity of resource mapping while maintaining high transmission speed.
Solution Approach 2:
The patent implements dynamic resource mapping where the allocation of symbols for different control information types varies depending on the TTI length and subcarrier spacing configuration. For example, in shorter TTIs, HARQ-ACK is mapped to earlier symbols while in longer TTIs, more flexible mapping is allowed. This dynamic adaptation enables the system to support multiple TTIs and subcarrier spacings without requiring a completely separate mapping scheme for each configuration, thus reducing system complexity.
2Reliability
If control information is mapped to multiple symbols to improve reliability, then transmission reliability is improved, but processing time and latency increase
Solution Approach 1:
The patent performs preliminary mapping of high-priority control information (HARQ-ACK) to the first available symbol in the TTI, ensuring that critical acknowledgments are transmitted as early as possible. Lower-priority information (RI, CQI/PMI) is then mapped to subsequent symbols. This preliminary action for critical information ensures reliability for time-sensitive data without requiring all control information to wait for later symbols, thereby reducing overall processing time while maintaining reliability.
Solution Approach 2:
The patent applies different mapping strategies to different control information types based on their local requirements. HARQ-ACK, which requires high reliability and low latency, is mapped to the first symbol with highest frequency indices. RI and CQI/PMI, which can tolerate more processing time, are mapped to subsequent symbols. This local quality differentiation allows the system to optimize reliability for critical information while minimizing processing time for less critical information.
3Productivity
If resource elements are allocated densely to improve spectral efficiency, then data transmission capacity is improved, but error rate and reliability worsen
Solution Approach 1:
The patent employs asymmetric mapping where HARQ-ACK is allocated to the first symbol with the highest frequency indices, while RI and CQI/PMI are mapped to subsequent symbols with lower frequency indices. This asymmetric allocation ensures that the most critical information (HARQ-ACK) receives the most robust resource elements first, improving reliability for time-sensitive data. The remaining resources are then densely packed for less critical information, maintaining spectral efficiency without compromising the reliability of critical control information.
Data Source
AI summary
A method of transmitting uplink (UL) control information for a user equipment (UE) for supporting a plurality of TTI lengths, a plurality of subcarrier spacing, or a plurality of processing times in a wireless communication system is performed by the UE and includes mapping the UL control information to a radio resource in a TTI including two or three symbols, the UL control information including HARQ-ACK, a rank indicator (RI), a channel quality indicator (CQI), or a precoding matrix indicator (PMI), and transmitting the UL control information to a base station, wherein, when there is no symbol to which a DMRS is mapped in the TTI, HARQ-ACK is mapped to a first symbol in the TTI in descending order from a highest frequency index resource element (RE) and the RI is mapped to the other symbol in the TTI in descending order from a highest frequency index RE.