MCS Feedback Mapping for Reliable Downlink Transmission
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Solution Overview
Problem
In LTE systems, ensuring high data transmission reliability is challenging due to the lack of knowledge about channel quality before sending downlink data, particularly in 5G scenarios requiring ultra-reliable and low latency communications (URLLC) with stringent block error rate requirements.
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 deteriorates
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 action provides the network device with channel quality information in time, enabling it to determine appropriate modulation and coding schemes, thereby improving data transmission reliability without adding complex real-time feedback mechanisms
Solution Approach 2:
The reference CQI index serves as an intermediary that conveys channel quality information from the terminal device to the network device. Instead of directly transmitting complex channel state information, the system uses this standardized index as a mediator, simplifying the feedback mechanism while ensuring the network device can make informed decisions about modulation and coding schemes
2Adaptability or versatility
If the network device uses fixed modulation and coding schemes, then the system complexity is low, but adaptability to varying channel conditions deteriorates
Solution Approach 1:
The system implements a feedback mechanism where the terminal device sends the reference CQI index to the network device, which then adapts its modulation and coding scheme selection accordingly. This feedback loop enables the network device to adjust transmission parameters based on actual channel conditions, improving adaptability while maintaining manageable system complexity through standardized feedback procedures
Solution Approach 2:
The network device dynamically selects modulation and coding schemes based on the received reference CQI index and current network resource status. Instead of using fixed schemes, the system allows dynamic adaptation of transmission parameters, enabling the network device to optimize performance for varying channel conditions while following standardized selection procedures
3Measurement precision
If the terminal device feeds back detailed channel quality information, then the network device can make precise decisions, but the amount of feedback data increases
Solution Approach 1:
The system extracts only the essential channel quality information needed for modulation and coding scheme selection by using the reference CQI index. Instead of transmitting complete and detailed channel state information, the terminal device selects and feeds back this specific index that captures the most critical aspects of channel quality, reducing feedback overhead while maintaining sufficient precision for accurate transmission parameter selection
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.