MCS Feedback Mapping for Reliable URLLC Downlink Transmission
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Solution Overview
Problem
In LTE systems, the lack of knowledge about channel quality before sending downlink data hinders the achievement of high data transmission reliability, particularly in 5G ultra-reliable and low latency communications (URLLC) scenarios, where a block error rate less than 1e-9 is required.
Innovation Solution
A data sending method where a terminal device measures channel quality, selects a reference CQI index from a prestored mapping table, and feeds it back to the network device, allowing the network device to determine the appropriate modulation order, code rate, and coding scheme for improved data transmission reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the base station sends downlink data without knowing channel quality, then the system operation is simple, but data transmission reliability is poor
Solution Approach 1:
The terminal device performs preliminary channel quality measurement and selects a reference CQI index before the network device sends downlink data. This advance preparation allows the network device to use the fed back CQI index for reliable modulation and coding scheme selection, improving transmission reliability without adding complex real-time monitoring systems.
Solution Approach 2:
The CQI index acts as an intermediary that bridges the terminal device's channel quality measurement and the network device's modulation and coding scheme selection. The terminal feeds back the CQI index, which the network device uses to determine appropriate transmission parameters, enabling reliable communication without direct real-time channel quality knowledge at the base station.
2Reliability
If the terminal device feeds back CQI index, then data transmission reliability is improved, but uplink signaling overhead increases
Solution Approach 1:
The solution extracts only the essential CQI index from the full channel quality information for feedback. Instead of transmitting complete channel quality data, the terminal device selects and feeds back only the relevant CQI index, which is then used by the network device to determine modulation and coding schemes, reducing signaling overhead while maintaining reliability.
Solution Approach 2:
The channel quality information is transformed into a discrete CQI index parameter for feedback. This parameter transformation converts continuous channel quality measurements into standardized index values that can be efficiently transmitted, reducing the amount of signaling required while preserving the essential information needed for reliable transmission.
3Adaptability or versatility
If multiple mapping tables are used for different reliability requirements, then adaptability to different scenarios is improved, but device complexity increases
Solution Approach 1:
The system dynamically selects appropriate mapping tables based on the required reliability level. Different mapping tables are prepared for different target block error rates (e.g., 10%, 1%, 0.1%, 1e-9), and the terminal device and network device coordinate to use the appropriate mapping table for the current service requirements, enabling flexible adaptation without permanently storing all possible configurations.
Solution Approach 2:
Multiple mapping tables are prepared in advance for different reliability requirements. The terminal device and network device prestore these mapping tables with different target block error rates, allowing them to quickly select the appropriate table based on service requirements without performing complex real-time calculations, thus reducing processing complexity while maintaining high adaptability.
Data Source
AI summary
This application provides a method for communicating a modulation and coding scheme (MCS). A terminal device obtains a modulation order, a code rate, or a spectral efficiency, determines an index of a reference MCS from a mapping table based on the obtained modulation order, code rate, or spectral efficiency, and reports the index of the reference MCS to a network device. The mapping table includes one or more mapping relationships between an MCS index and a modulation order, a code rate, or a spectral efficiency. The terminal device may process uplink or downlink data based on the determined MCS, thereby improving data transmission reliability.