Distributed MIMO Timing Calibration Using Dual-Band CSI Feedback
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Solution Overview
Problem
In distributed MIMO systems, timing mis-match calibration is challenging due to the distribution of antenna panels across multiple locations, which complicates the calibration of RF receive/transmit antenna ports, limiting spectral efficiency and coherence in channel reciprocity.
Innovation Solution
A network entity receives uplink reference signals from user equipment, estimates channels, configures beamformed downlink reference signals, and determines timing mis-match between TRPs based on channel state information feedback to perform calibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If antenna panels are distributed across multiple locations in distributed MIMO systems, then coverage and capacity are improved, but timing mis-match calibration becomes challenging and channel reciprocity coherence is compromised
Solution Approach 1:
The patent introduces downlink reference signals as an intermediary mechanism to enable timing mis-match calibration between distributed TRPs. The gNB transmits DL RS from different frequency locations (upper and lower portions of BWP) which are received by the UE, and the UE's CSI feedback on these signals provides the gNB with information to determine and correct timing mis-matches between TRPs, thus maintaining channel reciprocity coherence across distributed locations
Solution Approach 2:
The patent changes the frequency parameter of downlink reference signals by transmitting them from different frequency locations (upper and lower portions of the bandwidth part). This frequency diversity approach allows the gNB to probe timing characteristics at different frequencies and determine timing mis-matches between TRPs, thereby calibrating the distributed MIMO system while maintaining coverage extension
2Productivity
If multiple TRPs are used for distributed MIMO transmission, then spectral efficiency is enhanced, but timing mis-match between TRPs degrades channel reciprocity
Solution Approach 1:
The patent implements a feedback mechanism where the UE measures downlink reference signals transmitted from multiple TRPs and sends CSI feedback to the gNB. The gNB uses this feedback, combined with UL channel estimates, to determine timing mis-matches between TRPs and apply corrections, thereby maintaining channel reciprocity coherence while enabling spectral efficiency gains from multiple TRPs
Solution Approach 2:
The patent performs timing mis-match calibration as a preliminary action before coherent joint transmission. The gNB determines timing mis-matches between TRPs using DL RS and CSI feedback, and applies corrections in advance to ensure that when distributed MIMO transmission occurs, the TRPs are properly synchronized for reliable channel reciprocity
Data Source
AI summary
A method of operating a network includes receiving an UL RS, estimating UL channels for a plurality of TRPS based on the UL RS, configuring first DL RS resources from an upper portion of a BWP, transmitting via the plurality of TRPs, a first beamformed DL RS from the upper portion of the BWP, and receiving via one or more of the plurality of TRPs, first CSI feedback based on the first DL RS. The method further includes configuring second DL RS resources from a lower portion of the BWP, transmitting via the plurality of TRPs, a second beamformed DL RS from the lower portion of the BWP, receiving via one or more of the plurality of TRPs, second CSI feedback based on the second DL RS, and determining a timing mis-match between the plurality of TRPs based on the first CSI feedback and the second CSI feedback.