Massive MIMO Channel Measurement With Angle-Delay Feedback
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Solution Overview
Problem
The high feedback overheads associated with channel measurement in massive MIMO systems, particularly due to the need for terminal devices to feed back precoding matrices, lead to increased complexity and resource utilization.
Innovation Solution
A method where a network device precodes reference signals based on predetermined angles and delays, allowing terminal devices to feed back only weighting coefficients, reducing the need for feedback of space and frequency domain vectors, and enabling the construction of a precoding matrix through linear superposition of vectors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the terminal device feeds back precoding matrices using type II codebook feedback mode, then the precoding accuracy is improved, but the feedback overhead increases significantly
Solution Approach 1:
The patent extracts and feeds back only the essential components (weighting coefficients) of the precoding matrix rather than the complete matrix. The network device pre-configures angle vectors and delay vectors, and the terminal device only needs to feed back weighting coefficients for these pre-configured vectors, significantly reducing feedback overhead while maintaining precoding accuracy.
Solution Approach 2:
The network device performs preliminary action by pre-configuring angle vectors and delay vectors before the terminal device performs channel measurement. This pre-configuration allows the terminal device to focus feedback only on weighting coefficients rather than entire precoding matrices, reducing feedback overhead while preserving measurement precision.
2Measurement precision
If the terminal device performs complete channel measurement and feeds back space domain vectors and frequency domain vectors, then the channel measurement precision is improved, but the feedback overhead and calculation complexity increase
Solution Approach 1:
The patent extracts only the necessary weighting coefficients from the complete channel measurement process. By pre-configuring angle vectors and delay vectors at the network device, the terminal device only needs to calculate and feed back weighting coefficients for these pre-defined vectors, reducing calculation complexity while maintaining channel measurement precision.
Solution Approach 2:
The network device performs preliminary action by pre-configuring angle vectors and delay vectors before channel measurement. This allows the terminal device to skip complex calculations for space domain vectors and frequency domain vectors, as these are already determined by the pre-configured vectors, thereby reducing calculation complexity while preserving measurement precision.
3Adaptability or versatility
If multiple CSI-RS resources targeting different elevation angles are transmitted, then the channel measurement coverage is improved, but the pilot overhead increases
Solution Approach 1:
The patent makes angle vectors universal by pre-configuring a set of angle vectors that can cover multiple elevation angles. These pre-configured angle vectors serve multiple purposes: they enable channel measurement for different elevation angles without requiring separate CSI-RS resources for each angle, thus achieving multi-functionality and reducing pilot overhead while maintaining measurement coverage.
Data Source
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AI summary
This application provides a channel measurement method and a communications apparatus. The method includes: receiving, by a terminal device, a precoded reference signal, where the precoded reference signal is obtained by precoding a reference signal based on K angle vectors and L delay vectors; and generating and sending first indication information, where the first indication information is used to indicate P weighting coefficients corresponding to P angle-delay pairs; the P weighting coefficients are determined by using the precoded reference signal; the P angle-delay pairs and the P weighting coefficients corresponding to the P angle-delay pairs are used to determine a precoding matrix; and each angle-delay pair includes one of the K angle vectors and one of the L delay vectors. The K angle vectors and the L delay vectors are determined based on uplink channel measurement. Reciprocity between uplink and downlink channels is used, and a downlink reference signal is precoded based on an angle and a vector that are determined through uplink channel measurement, so that the terminal device can feed back only a weighting coefficient used to construct a precoding matrix, thereby reducing feedback overheads.