Rate Splitting for Interference Cancellation in MU-MIMO
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In wireless cellular communication networks, especially in massive MU-MIMO systems, interference limits capacity growth due to limited feedback information, non-ideal beamforming, and interference from sidelobes, reflections, and neighboring cells, making it difficult to separate signals effectively.
Innovation Solution
A new air interface is proposed that uses subbands as basic scheduling units for codeword-level interference cancellation (CWIC), with novel resource element mapping and code rate assignment with rate splitting, along with assistance information exchange between base stations and user equipment to facilitate interference cancellation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If non-orthogonal transmission is used to allow multiple users to share the same resource elements, then multiuser system capacity is improved, but interference between users increases
Solution Approach 1:
The transmission is segmented into multiple layers within each beam, allowing non-orthogonal multiplexing of multiple users on the same resource elements. The segmentation of code blocks into different groups with different code rates enables selective interference cancellation at the receiver
Solution Approach 2:
Different code rates are assigned to different code block groups within the same transport block. The first code block group uses a lower code rate to enable interference cancellation, while the second group uses a higher code rate to maximize spectral efficiency. This parameter differentiation allows the system to simultaneously achieve high capacity and manageable interference
2Productivity
If code rate is increased to improve spectral efficiency, then data transmission rate is improved, but decoding reliability at cell edge decreases
Solution Approach 1:
Different code rates are applied to different code block groups within the same transport block based on local requirements. The first code block group uses a lower code rate optimized for cell edge users with poor channel conditions, while the second code block group uses a higher code rate optimized for cell center users with good channel conditions. This local differentiation of code rate quality enables both high spectral efficiency and reliable decoding at the cell edge
3Productivity
If interference cancellation is implemented to improve capacity region, then system capacity is improved, but receiver complexity increases
Solution Approach 1:
The transmitter performs preliminary actions by differentiating code block groups with different code rates before transmission. This pre-structuring of the transmitted signal enables the receiver to perform interference cancellation more efficiently by knowing which code blocks are intended for which users and at what code rates, reducing the complexity of blind interference cancellation attempts
Data Source
AI summary
A new air interface that is interference cancellation friendly is proposed. In one novel aspect, a novel code rate assignment with rate splitting is proposed. In one embodiment, a base station decomposes a codeword {x1} into two codewords {x1a} and {x1b}. The two codewords are applied with different code rates and/or modulation orders. More specifically, the code rate or modulation order of codeword {x1a} is set appropriately so that a victim UE can decode and cancel {x1a} under the channel quality of the victim UE. Typically, the channel quality of a victim UE is poorer than the channel quality of the intended UE. As a result, the MCS for {x1a} can be lower than the MCS for {x1b} such that the victim UE is able to apply CWIC to decode and cancel {x1a}.