MU-MIMO Beam Feedback for Interference-Aware Scheduling
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Solution Overview
Problem
Current MU-MIMO in LTE systems suffer from poor performance due to coarse CSI feedback, scheduling loss, and link adaptation losses, particularly because of limited information on mutual inter-user interference and the inability to effectively manage beam selection and interference.
Innovation Solution
Communication devices provide first and second information to a coordinating device, identifying preferred beams and regions of high spatial correlation or interference, allowing the coordinator to schedule communications that minimize interference by preferentially assigning preferred beams and avoiding highly interfering ones.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If coarse CSI feedback is used in LTE MU-MIMO, then feedback overhead is reduced, but scheduling loss and link adaptation loss increase due to insufficient interference information
Solution Approach 1:
The patent segments the CSI feedback into two distinct parts: first feedback information (quantized CSI for link adaptation) and second feedback information (interference measurement for scheduling). This segmentation allows each part to serve its specific function optimally without compromising the other, resolving the contradiction between feedback precision and overhead.
Solution Approach 2:
The patent introduces an intermediary mechanism where the UE measures interference on candidate beams and reports this information to the network. This intermediary interference measurement process enables the network to make informed scheduling decisions without requiring the UE to feedback complete CSI for all possible beams, thus reducing overhead while improving scheduling accuracy.
2Reliability
If more CSI quantization bits are allowed, then link adaptation performance improves, but feedback overhead increases
Solution Approach 1:
The patent divides the feedback into two segments: first feedback information containing quantized CSI for link adaptation (using standard CQI bits), and second feedback information containing interference measurements for scheduling decisions. This segmentation allows efficient use of limited feedback resources for the specific purpose of link adaptation while separately capturing interference information needed for scheduling.
Solution Approach 2:
The patent applies local quality by tailoring different feedback requirements to different purposes: high precision quantized CSI is provided for link adaptation where it is most critical, while interference measurements are provided with appropriate granularity for scheduling decisions. This localized optimization ensures that feedback overhead is not wasted on precision where it is not needed.
3Object-affected harmful factors
If beam selection is optimized considering spatial correlation, then inter-user interference is reduced, but device complexity increases due to additional processing
Solution Approach 1:
The patent applies preliminary action by having the UE pre-measure interference levels on candidate beams and pre-identify spatially correlated beams before the actual scheduling decision is made. The UE computes interference measurements and identifies beams with high spatial correlation in advance, so that when scheduling occurs, the network can quickly make informed decisions without performing complex real-time analysis.
Solution Approach 2:
The patent uses feedback mechanisms where the UE reports measured interference information and spatial correlation characteristics back to the network. This feedback enables the network to adjust scheduling decisions based on actual measured conditions rather than relying on complex predictions or exhaustive searches, reducing the computational burden while maintaining interference optimization.
Data Source
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AI summary
The application relates, inter alia, to a communication device [e.g., UE] (204, 252- 254) for communicating with one or more other communication devices using a multiple-input-multiple-output, MIMO, communication, wherein the communication device [e.g., UE] (204, 252-254) is configured to: (102) select [e.g., from Ω] one or more preferred beams [e.g., b,] (302); and (104) find one or more other beams (301b, 305, 305b) [e.g., those such that INRk(Cl)>ε1] which have a comparatively high spatial correlation with the one or more preferred beams (302) or which have a comparatively high probability of interference with the one or more preferred beams (302) [e.g., if INRk(Cl)>ε1], wherein the communication device [e.g., UE] (204, 252-254) is configured to provide, to a coordinating communication device [e.g., BS, gNB] (204, 251): first information (210) [e.g., Fk,1] identifying the one or more preferred beams (302) [e.g., Fk,1 is made of columns identifying the preferred beams]; and second information (212) [e.g., rk,i,1, rk,i,2] identifying the one or more found other beams (301b) or a region [e.g., shape] in a map of beams (300) comprising the one or more found other beams (301b).