Downlink Covariance Matrix Estimation via Angular Power Spectrum
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Solution Overview
Problem
Conventional methods for estimating the downlink channel spatial covariance matrix in massive MIMO FDD systems face challenges due to high feedback overhead and require a training phase, which reduces spectral efficiency.
Innovation Solution
A device and method that estimate the downlink covariance matrix from the uplink covariance matrix using the frequency invariance property of the angular power spectrum, computed through a feasibility problem in a Hilbert space, eliminating the need for a training phase and achieving performance comparable to best conventional approaches with training.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional approaches use DL pilot sequences to obtain DL covariance matrix information at UE and feed back to BS, then DL CSI acquisition is feasible, but feedback overhead becomes excessively large in massive MIMO systems
Solution Approach 1:
The patent inverts the conventional approach by estimating the DL covariance matrix at the BS using UL covariance matrix information instead of having the UE obtain and feed back DL covariance information. This inversion eliminates the need for large feedback overhead while maintaining DL CSI acquisition feasibility through channel reciprocity principles adapted for FDD systems.
Solution Approach 2:
The patent introduces the UL covariance matrix as an intermediary to obtain DL covariance information. By using UL pilot sequences and measuring UL channel responses, the BS can infer DL channel characteristics through the relationship between UL and DL covariance matrices, thereby avoiding direct feedback of DL covariance information from the UE.
2Measurement precision
If conventional approaches use training phase to acquire training set of samples for estimating DL covariance matrix, then estimation performance improves, but spectral efficiency is significantly reduced
Solution Approach 1:
The patent performs preliminary actions by pre-computing and storing the relationship between UL and DL covariance matrices based on channel reciprocity principles. This allows the BS to directly estimate DL covariance matrices from UL measurements without requiring a time-consuming training phase, thereby maintaining high spectral efficiency while achieving accurate estimation.
Solution Approach 2:
The patent enables continuous estimation of DL covariance matrices from UL measurements throughout the operational period without interrupting for training phases. The useful action of covariance matrix estimation continues uninterrupted, improving spectral efficiency while maintaining measurement precision through ongoing UL channel response analysis.
Data Source
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AI summary
The present invention provides a device, a base station device, and a method for respectively obtaining an estimate of a DL covariance matrix from an UL covariance matrix. The devices and method are particularly suitable for massive MIMO scenarios, and are particularly applicable to FDD systems. The device comprises a processor configured to compute an APS of an antenna array, in particular in the continuous angular domain, based on the UL covariance matrix of a communication channel and an UL response of the antenna array. Further, the processor is configured to compute the DL covariance matrix of the channel based on the APS and a DL response of the antenna array. The base station device includes the device and the antenna array.