Frequency Domain Correlation Feedback for Partial Reciprocity
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Solution Overview
Problem
Existing wireless communication systems face challenges in achieving full frequency domain reciprocity, especially in TDD systems where UEs may not be capable of transmitting SRS on all component carriers, leading to partial reciprocity. This limits the accuracy of downlink beamforming and increases RF retuning requirements.
Innovation Solution
The method involves a UE transmitting a sounding reference signal (SRS) on a first set of sub-bands and reporting channel state information (CSI) associated with a second set of sub-bands. The CSI includes information on frequency domain correlations between the first and second sets of sub-bands, allowing for enhanced frequency domain partial reciprocity downlink.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a UE transmits SRS on all component carriers to achieve full frequency domain reciprocity, then downlink beamforming accuracy is improved, but device complexity and power consumption increase significantly
Solution Approach 1:
The patent applies partial action by having the UE transmit SRS only on a subset of component carriers rather than all carriers. The network device uses the reported frequency domain correlation information to infer channel state information for the remaining carriers, thereby achieving acceptable downlink beamforming accuracy while significantly reducing UE transmission complexity and power consumption.
Solution Approach 2:
The patent introduces frequency domain correlation information as an intermediary. Instead of directly measuring channel state information on all component carriers, the UE measures correlation between sub-bands and transmits this compact representation. The network device then uses this intermediary information to derive the full channel state, reducing the direct measurement burden on the UE.
2Measurement precision
If a UE transmits SRS on all component carriers to achieve full frequency domain reciprocity, then downlink beamforming accuracy is improved, but power consumption increases
Solution Approach 1:
The patent applies partial action by having the UE transmit SRS only on a subset of component carriers rather than all carriers. The network device uses the reported frequency domain correlation information to infer channel state information for the remaining carriers, thereby achieving acceptable downlink beamforming accuracy while significantly reducing UE transmission complexity and power consumption.
3Measurement precision
If frequency domain correlation information is reported for all sub-bands, then channel state information accuracy is improved, but uplink overhead increases
Solution Approach 1:
The patent applies local quality by having the UE report frequency domain correlation information selectively for specific sub-bands where it is most beneficial, rather than uniformly for all sub-bands. The network device uses this targeted information combined with other available measurements to reconstruct accurate channel state information across the full bandwidth, reducing uplink overhead while maintaining necessary accuracy.
Solution Approach 2:
The patent applies partial action by reporting correlation information for only a subset of sub-bands rather than all sub-bands. This partial reporting, when combined with network-side inference and other measurements, provides sufficient channel state information accuracy while significantly reducing the quantity of uplink feedback required.
4Measurement precision
If SRS carrier switching is performed frequently to cover all component carriers, then frequency domain reciprocity is improved, but time consumption and resource usage increase
Solution Approach 1:
The patent applies preliminary action by having the UE pre-calculate and report frequency domain correlation information between sub-bands before the network device needs to perform downlink beamforming. This advance preparation allows the network device to infer channel state information for unsounded component carriers without requiring the UE to perform additional SRS transmissions, thereby eliminating the need for time-consuming carrier switching while maintaining frequency domain reciprocity.
Solution Approach 2:
The patent applies copying by having the UE measure and report correlation patterns that represent the relationship between different sub-bands. The network device then uses these correlation copies to infer channel state information for component carriers where direct SRS measurements were not performed, avoiding the need for actual SRS carrier switching while maintaining measurement accuracy.
Data Source
AI summary
Various aspects of the present disclosure generally relate to wireless communication. In some aspects, a user equipment (UE) may transmit a sounding reference signal (SRS) on a first set of sub-bands (305). The UE may report channel state information (CSI) associated with a second set of sub-bands (310). The first set of sub-bands may be different from the second set of sub-bands. The CSI may include information that identifies one or more frequency domain correlations among the first set of sub-bands and the second set of sub-bands. Numerous other aspects are described.