Wideband CSI-RS Subband Selection for Interference Reduction
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Solution Overview
Problem
In densely deployed wireless communication environments, such as factories, base stations and user equipment face interference, reflection, and blocking issues due to numerous objects, which reduce signal quality and require effective channel state information (CSI) for flexible resource scheduling across a wide frequency range.
Innovation Solution
A two-stage procedure is implemented where base stations broadcast wideband CSI-RS signals covering multiple subbands, and user equipment selects preferred subbands by transmitting narrowband SRS signals to indicate channel conditions, allowing the base station to schedule traffic efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If wideband CSI-RS is broadcast across all subbands to obtain accurate channel state information, then measurement precision is improved, but loss of information increases due to interference and blocking in densely deployed environments
Solution Approach 1:
The wideband frequency spectrum is divided into multiple subbands, and the CSI-RS broadcast is segmented to occur only in selected subbands rather than all subbands. This segmentation allows the system to maintain measurement precision in critical frequency regions while reducing overall information loss by avoiding transmission in heavily interfered subbands.
Solution Approach 2:
The system applies local quality by selectively broadcasting CSI-RS in specific subbands based on channel conditions, interference levels, and blocking characteristics. Rather than uniform transmission across all frequencies, the broadcast quality and presence are optimized locally for each subband, improving measurement accuracy where needed while minimizing information loss in problematic regions.
2Adaptability or versatility
If CSI-RS is broadcast across a wide frequency range to enable flexible resource scheduling, then adaptability is improved, but device complexity increases due to the two-stage procedure
Solution Approach 1:
The system performs preliminary action by first identifying and selecting suitable subbands for CSI-RS broadcasting before actually transmitting the reference signals. This preliminary subband selection step simplifies the overall procedure by pre-determining which frequency regions will be used, thereby reducing the complexity of the two-stage process while maintaining wideband adaptability for resource scheduling.
Solution Approach 2:
The system applies dynamics by making the CSI-RS broadcast configuration adaptive and changeable based on channel conditions, traffic demands, and interference patterns. The set of subbands used for broadcasting is not fixed but can be dynamically adjusted, allowing the system to maintain adaptability for resource scheduling while managing device complexity through flexible, condition-based configuration.
3Loss of energy
If narrowband SRS is transmitted only in selected subbands to indicate channel conditions, then loss of energy is reduced, but measurement precision decreases compared to wideband transmission
Solution Approach 1:
The system applies the taking out principle by extracting and isolating the most critical subbands for SRS transmission from the entire wideband spectrum. Instead of transmitting SRS across all frequencies, the system identifies and extracts only the subbands that provide the most valuable channel state information, thereby reducing transmission energy while maintaining measurement precision in the selected regions.
Solution Approach 2:
The system uses partial action by transmitting SRS in only a subset of subbands rather than all subbands. This partial transmission approach reduces energy consumption while still providing sufficient measurement precision for resource scheduling decisions, as the SRS feedback from selected subbands is adequate to characterize the overall channel conditions without requiring exhaustive wideband measurement.
Data Source
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AI summary
Techniques for obtaining wideband channel state information (CSI) for a plurality of subbands is described. A two-stage procedure may be used to obtain the wideband CSI. At a first stage, a base station may broadcast a wideband channel state information reference signal (CSI-RS) that includes a plurality of subbands. The wideband CSI-RS may be received by any user equipment (UE) within range of the base station. The UE may select one or more subbands in the wideband CSI-RS for communication with the base station. To indicate which subbands were selected, at a second stage, the UE may transmit a narrowband sounding reference signal (SRS) in each of the selected subbands. The base station may schedule traffic for the wireless communications system based on the narrowband SRSs.