MIMO Rank Control for MU-MIMO Retransmission Bottlenecks
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Solution Overview
Problem
In wireless communication systems, the limited number of MIMO layers allocated to each UE in a MU-MIMO group restricts the number of UEs that can be included, leading to potential throughput issues, especially in heavily loaded scenarios where additional spectrum is costly to acquire.
Innovation Solution
The base station selectively reduces the MIMO rank of UEs with high data retransmission rates, allowing them to be served on fewer MIMO layers, which can increase their effective data rate and enable more UEs to be included in a MU-MIMO group, thereby enhancing spectral efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the number of MIMO layers allocated to each UE is increased to improve throughput, then the data rate for individual UEs is improved, but the number of UEs that can be included in the MU-MIMO group is reduced, leading to lower spectral efficiency
Solution Approach 1:
The patent dynamically adjusts the MIMO rank parameter for different UEs based on their channel conditions and retransmission rates. By changing the MIMO layer allocation parameter, the system optimizes the balance between individual UE throughput and overall group capacity, allowing more UEs to be served simultaneously while maintaining acceptable performance levels.
Solution Approach 2:
The patent applies different MIMO layer allocations to different UEs within the MU-MIMO group based on their specific characteristics. UEs with good channel conditions and low retransmission rates receive higher MIMO ranks, while UEs with poor conditions receive lower ranks, optimizing resource distribution locally for each UE rather than applying a uniform allocation.
2Quantity of substance
If the MIMO rank of UEs with high retransmission rates is reduced to enable more UEs in the MU-MIMO group, then spectral efficiency is improved, but the throughput of individual UEs may be reduced
Solution Approach 1:
The patent implements a feedback mechanism that monitors the retransmission rates of UEs in real-time. Based on this feedback, the base station dynamically adjusts the MIMO rank allocation for each UE. This closed-loop control ensures that UEs with high retransmission rates receive adjusted allocations that improve overall spectral efficiency while the system continuously monitors to prevent excessive throughput degradation.
Solution Approach 2:
The patent converts the harmful effect of high retransmission rates into a beneficial control signal. Instead of treating high retransmission rates purely as performance degradation, the system uses them as indicators to adjust MIMO rank allocations, thereby improving overall spectral efficiency by identifying UEs that would benefit from reduced layer allocations.
3Productivity
If additional spectrum is acquired to support more UEs with higher data rates, then throughput and capacity are improved, but the cost increases
Solution Approach 1:
The patent implements dynamic MIMO rank adjustment that adapts to changing channel conditions and traffic demands in real-time. This dynamic allocation allows the system to maximize the utilization of existing spectrum resources by optimizing the number of MIMO layers allocated to each UE based on current conditions, thereby improving data rates without requiring additional spectrum acquisition.
Data Source
AI summary
When a base station has reason to increase the extent of MU-MIMO service that it can provide or in other contexts, the base station could select at least one of the base station's served UEs to have its MIMO rank reduced, with the selecting being based at least on a determination that the selected UE has had a threshold high rate of data retransmissions such as a threshold high rate of HARQ retransmissions for instance.