Downlink Link Adaptation via Uplink Path Gain Statistics
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Solution Overview
Problem
Current downlink link adaptation in communication systems is inefficient during initial UE setup, particularly for bursty traffic patterns, due to the need for robust and non-optimal modulation and coding schemes, leading to slow initialization and increased resource usage.
Innovation Solution
Estimating the initial downlink SINR for new UEs by utilizing uplink path gain statistics from active users in the cell, allowing for faster link adaptation and reducing the size of initial messages, which can be refined with subsequent CQI reports.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If robust MCS is used for initial downlink transmissions to new UEs, then reliability of message delivery is improved, but transmission efficiency deteriorates due to increased resource usage and slower initialization
Solution Approach 1:
The system performs preliminary actions by collecting uplink path gain measurements from multiple UEs and pre-calculating statistical measures (mean, standard deviation) before new UEs need downlink transmissions. This preliminary preparation enables faster, more accurate initial SINR estimation when new UEs arrive, avoiding the need to use overly robust MCS while maintaining reliability.
Solution Approach 2:
The patent replaces the traditional mechanical approach of using fixed robust MCS tables with a statistical estimation system. By substituting the mechanical MCS selection process with statistical SINR estimation based on uplink path gain correlations, the system achieves both reliability and efficiency simultaneously.
2Reliability
If very robust MCS is used for initial transmissions until CQI is received, then communication reliability is improved, but initialization speed deteriorates
Solution Approach 1:
The system performs preliminary actions by continuously collecting and storing uplink path gain measurements from active UEs before they are needed. Statistical measures are pre-calculated and maintained in the network node, enabling immediate SINR estimation when new UEs arrive, thus reducing initialization time while maintaining reliability.
Solution Approach 2:
The system uses feedback from uplink path gain measurements to continuously update statistical measures. This feedback mechanism allows the system to learn from ongoing transmissions and improve the accuracy of initial SINR estimates for new UEs, reducing both initialization time and the need for overly robust MCS.
3Reliability
If robust encoding is used for PDCCH messages in initial setup, then message delivery reliability is improved, but resource consumption increases
Solution Approach 1:
The patent changes the parameter used for MCS selection from conservative fixed values to dynamically estimated SINR values. By changing the basis of MCS selection from static robust values to adaptive statistical estimates, the system reduces PDCCH CCE consumption while maintaining message delivery reliability.
Data Source
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AI summary
In a method for downlink link adaptation in a network node in a communication system, the network node serving a cell and active user equipment within the cell, performing the steps of obtaining (S10) uplink path gain and downlink SINR for at least a subset of active user equipment in the cell, estimating (S50) an initial downlink SINR for new user equipment in the cell, based on an estimated uplink path gain together with a determined statistical measure for the obtained uplink path gain and downlink SINR for the at least a subset of active user equipment in the cell, and utilizing (S60) the estimated initial downlink SINR for downlink link adaptation for a subsequent transmission to the new user equipment.