Uplink Channel Matrix Based Downlink MCS Determination
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Solution Overview
Problem
In LTE-TDD systems, the inaccurate downlink modulation and coding scheme (MCS) determined by user equipment (UE) due to assumed transmission modes and quantization errors leads to inefficiencies in data transmission, affecting system performance.
Innovation Solution
A method that involves acquiring an uplink channel matrix and determining the signal-to-interference-plus-noise ratio (SINR) for downlink transmission streams to accurately determine a second downlink MCS, thereby improving channel quality and transmission efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the UE determines downlink CQI according to assumed downlink transmission mode (transmit diversity or closed-loop spatial multiplexing), then the UE can provide feedback for downlink scheduling, but the CQI becomes inaccurate when the actual transmission mode is beamforming
Solution Approach 1:
The patent introduces an uplink channel matrix as an intermediary to estimate downlink channel quality. Instead of relying on UE's assumed transmission mode, the eNB obtains uplink channel information from SRS, performs channel estimation, and uses this as a basis for determining accurate downlink MCS, thereby resolving the mismatch between assumed and actual transmission modes
Solution Approach 2:
The patent inverts the traditional approach by having the eNB determine downlink channel quality based on uplink channel measurements rather than relying on UE's downlink CQI feedback. This inversion allows the eNB to accurately assess channel conditions without being constrained by UE's transmission mode assumptions
2Productivity
If the eNB determines downlink MCS according to quantized CQI feedback from UE, then the downlink scheduling can be performed, but quantization errors lead to inaccurate MCS determination
Solution Approach 1:
The patent performs channel estimation and MCS determination based on uplink channel measurements before downlink transmission. By preliminarily obtaining accurate channel state information through SRS-based estimation, the eNB can determine appropriate MCS without relying on quantized CQI feedback, thus avoiding quantization errors while maintaining scheduling efficiency
3Device complexity
If the UE assumes transmit diversity or closed-loop spatial multiplexing mode for CQI calculation, then the feedback process is simplified, but transmission efficiency is reduced when beamforming is actually used
Solution Approach 1:
The uplink channel matrix obtained from SRS serves as a mediator that provides accurate channel state information without requiring the UE to assume specific transmission modes. This intermediary approach maintains simple feedback processes while enabling efficient beamforming transmission, as the eNB uses the uplink-based channel estimate to determine appropriate downlink MCS
Data Source
AI summary
Embodiments of the present invention provide a data transmission method and apparatus, and UE. The method includes: receiving a downlink CQI fed back by first UE, and determining a first downlink MCS of the first UE according to the downlink CQI fed back by the first UE; allocating a transmission resource of a first cell to the first UE according to the first downlink MCS of the first UE; acquiring an uplink channel matrix of a sub-bandwidth SB level of each cell in a measurement set of the first UE; determining an SINR of a downlink transmission stream to be sent by each cell in a transmission set of the first UE; and determining a second downlink MCS of the first UE according to the SINR of the downlink transmission stream to be sent.