Network Device Rank Selection via HARQ Feedback
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Solution Overview
Problem
5G wireless systems face significant performance degradation due to errors and biases in rank estimation for uplink and downlink transmissions, particularly with the increased number of layers supported, leading to suboptimal rank selection and potential overestimation or underestimation.
Innovation Solution
A method and network device for adjusting and selecting ranks based on successful transmission receipt, with mechanisms to increase or decrease ranks in predetermined steps, using Hybrid Automatic Repeat Request (HARQ) feedback and Signal to Interference plus Noise Ratio (SINR) thresholds to ensure optimal rank selection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the number of layers is increased to support higher data rates in 5G systems, then the throughput and data rate are improved, but the rank estimation accuracy deteriorates leading to performance degradation
Solution Approach 1:
The patent implements a feedback mechanism where the network device monitors transmission success/failure and adjusts the rank based on this feedback. The UE reports HARQ-ACK information indicating whether downlink transmissions were successfully received, and the network device uses this feedback to adjust the rank for subsequent transmissions, thereby improving rank estimation accuracy while maintaining high throughput
Solution Approach 2:
The patent applies preliminary action by adjusting the rank before transmission based on predicted SINR conditions and historical performance. The network device determines a target rank based on estimated SINR and adjusts it proactively before actual transmission occurs, preventing rank estimation errors before they impact throughput
2Productivity
If the rank is increased to improve data rate, then the throughput is improved, but the transmission reliability deteriorates due to rank estimation errors
Solution Approach 1:
The network device uses HARQ-ACK feedback from the UE to monitor transmission reliability. When transmission failures occur, the network device adjusts the rank downward to improve reliability. This feedback loop ensures that the system maintains optimal balance between data rate and transmission reliability by adapting rank based on actual transmission outcomes
Solution Approach 2:
The patent implements dynamic rank adjustment where the rank is not fixed but changes based on current channel conditions and transmission performance. The network device continuously adapts the rank parameter in response to changing SINR conditions and HARQ-ACK feedback, making the system dynamically balance data rate and reliability requirements
3Reliability
If the rank is adjusted frequently to adapt to changing SINR conditions, then the transmission reliability is improved, but the system complexity increases
Solution Approach 1:
The patent changes the rank parameter based on SINR thresholds and feedback conditions rather than continuously adjusting all transmission parameters. By focusing adjustments on the rank parameter specifically triggered by SINR changes and HARQ-ACK feedback, the system maintains reliability while avoiding the complexity of comprehensive parameter reconfiguration
4Reliability
If the rank estimation is made more conservative to reduce overestimation errors, then the transmission reliability is improved, but the throughput decreases due to underutilization of channel capacity
Solution Approach 1:
The feedback mechanism allows the system to start with conservative rank estimates and progressively increase the rank as successful transmissions confirm the channel can support higher rates. The HARQ-ACK feedback provides positive reinforcement when higher ranks succeed, enabling the system to aggressively exploit channel capacity while maintaining reliability through incremental adaptation
Data Source
AI summary
The present disclosure provides a method in a network device for rank selection. The method includes: adjusting a rank for a transmission to or from a terminal device; and selecting a rank to be used for the transmission based on whether the transmission using the adjusted rank has been successfully received.