Relay Network MCS Selection via CSI Feedback
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Solution Overview
Problem
Selecting an appropriate modulation and coding scheme (MCS) for cells with Type 2 relay nodes is challenging due to the lack of cell-specific reference signals, making it difficult for access nodes to determine the quality of the link between the relay node and user equipment (UE), which affects transmission efficiency and throughput.
Innovation Solution
The access node estimates the quality of the link between the relay node and the UE by using various methods, such as signal strength comparison and SINR estimation, to select an optimal MCS, considering factors like the number of relay nodes and service types like VoIP, and applies outer loop link adaptation to adjust MCS based on error rate statistics and retransmission statistics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If Type 2 relay nodes are deployed to extend coverage and enhance network capacity, then network coverage and throughput are improved, but the lack of cell-specific reference signals makes it difficult for access nodes to determine link quality between relay nodes and user equipment
Solution Approach 1:
The patent introduces CSI reference signals as an intermediary mechanism that enables the access node to indirectly measure link quality. The relay node transmits CSI reference signals to the user equipment, which then provides CSI feedback to the access node via the relay node. This intermediary signaling mechanism allows the access node to determine link quality without requiring direct cell-specific reference signals from the relay node, thus resolving the measurement precision problem while maintaining the coverage extension benefit of Type 2 relay nodes
Solution Approach 2:
The patent implements a feedback mechanism where the user equipment measures the quality of the relay link by receiving CSI reference signals from the relay node and sends Channel State Information (CSI) feedback to the access node through the relay node. This feedback loop enables the access node to adaptively select appropriate MCS based on actual link conditions, resolving the contradiction between deploying relay nodes for throughput improvement and maintaining accurate link quality measurement
2Reliability
If access nodes use traditional MCS selection methods without relay link quality information, then device complexity is reduced, but transmission reliability deteriorates due to inappropriate MCS selection
Solution Approach 1:
The patent enables the system to self-adjust MCS selection by automatically obtaining link quality information through the CSI feedback mechanism. The access node uses the CSI feedback from user equipment to automatically determine the appropriate MCS for relay link transmissions, eliminating the need for complex manual configuration or additional measurement procedures. This self-service approach improves transmission reliability through adaptive MCS selection while keeping device complexity manageable
Solution Approach 2:
The patent performs preliminary actions by having the relay node transmit CSI reference signals before actual data transmission. This allows the user equipment to pre-measure the link quality and provide CSI feedback in advance, enabling the access node to select appropriate MCS before data transmission begins. This preliminary measurement and feedback mechanism ensures reliable transmission without adding complexity to the actual data transmission process
Data Source
AI summary
A method for selecting an MCS for a cell in which one or more Type 2 relay nodes are present. The method includes the access node for the cell estimating the quality of the link between a relay node in the cell and a UA in the cell and using the estimate to select an MCS for the cell.