Rel-16 CSI Feedback Compression Using Segmented Codebook
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Solution Overview
Problem
In the New Radio (NR) system, the high overhead of channel state information (CSI) feedback due to the large difference in codebook overhead between rank 1 and rank 2 codebooks in Rel-15 leads to inefficiencies in CSI decoding, particularly when there are many sub-bands, and there is no corresponding sending or receiving mechanism for the CSI in the Rel-16 codebook structure.
Innovation Solution
A method for sending and receiving CSI using a codebook structure in Rel-16, where a terminal device determines a compressed base vector in a precoding matrix and sends base vector indication information to a network device, allowing the network device to construct the precoding matrix and parse the CSI, thereby reducing overhead by compressing coefficients of each sub-band.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If Type II codebook in Rel-15 is used for CSI feedback, then the codebook supports rank 1 and rank 2 codebooks with linear combining for orthogonal beams, but the overhead is high when Rank Indication takes different values due to large difference in codebook coefficients quantity
Solution Approach 1:
The codebook is segmented into a first codebook part and a second codebook part. The first codebook part contains base vectors that are common to both rank 1 and rank 2 codebooks, while the second codebook part contains rank-specific information. This segmentation allows the terminal device to feedback only the necessary rank-specific information, significantly reducing feedback overhead while maintaining support for both rank 1 and rank 2 codebooks.
Solution Approach 2:
The invention extracts the common base vectors into a separate first codebook part that is shared across different ranks. Only the differential or rank-specific components are included in the second codebook part for feedback. This extraction eliminates redundant feedback of common information, resolving the contradiction between codebook versatility and feedback overhead.
2Reliability
If two-part structure is adopted for reporting Type II CSI in Rel-15, then overhead fuzziness is avoided, but feedback overhead is high when there are many sub-bands due to including both phase coefficient and amplitude coefficient for each sub-band
Solution Approach 1:
The invention extracts and separates the base vector information into a dedicated first codebook part, allowing the second codebook part to focus only on sub-band specific information. This separation enables more efficient encoding of sub-band information and reduces the total feedback overhead while maintaining the two-part structure's ability to avoid overhead fuzziness.
Solution Approach 2:
The invention changes the parameter representation by using a unified base vector set for both rank 1 and rank 2 codebooks. This parameter change allows the system to represent different ranks using the same base vectors with different weighting coefficients, reducing the feedback overhead associated with transmitting separate base vector information for each rank.
3Quantity of substance
If Type II codebook with low overhead is provided in Rel-16 based on coefficient compression of sub-bands, then feedback overhead is reduced, but there is no corresponding sending or receiving mechanism for the CSI
Solution Approach 1:
The invention segments the CSI feedback into two distinct parts: base vector indication information in the first codebook part and compressed sub-band coefficients in the second codebook part. This segmentation provides a complete sending and receiving mechanism for the Rel-16 codebook structure, ensuring that both the base vectors and compressed coefficients are properly transmitted and decoded, thereby maintaining ease of operation while achieving low overhead.
Data Source
AI summary
Disclosed in the present application are methods for sending and receiving channel state information (CSI), a terminal device and a network device, which are used to provide a CSI sending method or receiving method on the basis of a Rel-16 codebook structure. The method for sending CSI includes determining a compressed basis vector in a precoding matrix, the compressed basis vector belonging to a set of candidate basis vectors, and the compressed basis vector weighted by coefficients of the precoding matrix is used to construct frequency domain characteristics of the precoding matrix; and sending the CSI to a network device, and the CSI includes basis vector indication information, and the basis vector indication information is used to indicate the compressed basis vector.