Null Space Generator for Multi-User Interference Elimination
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Solution Overview
Problem
Codebook-based Multiple Input Multiple Output (MIMO) systems experience performance degradation due to multi-user interference when serving multiple users, as existing techniques like Maximum Ratio Transmission (MRT) lack effective methods to reduce this interference.
Innovation Solution
The system employs a null space generator to create orthogonal null spaces for each user, and a projector to transmit beamformed user signals into these null spaces, preventing interference by selecting user combinations where beamforming vectors are orthogonal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If codebook-based MIMO systems serve multiple users, then system capacity and user coverage are improved, but multi-user interference causes performance degradation
Solution Approach 1:
The patent segments the signal transmission space by creating separate null spaces for different users. Each user's signal is transmitted in a dedicated null space that is orthogonal to other users' beamforming vectors, effectively dividing the shared MIMO channel into isolated user channels and eliminating multi-user interference.
Solution Approach 2:
The patent introduces a null space matrix as an intermediary between the beamformed user signals and the transmission channel. This null space matrix acts as a mediator that projects signals into interference-free subspaces, preventing direct interference between users while maintaining system capacity.
2Ease of manufacture
If beamforming vectors are selected from predefined codebooks, then implementation complexity is reduced, but orthogonality between users cannot be guaranteed
Solution Approach 1:
The patent performs preliminary action by pre-calculating and storing null space matrices corresponding to each beamforming vector in the codebook. When a beamforming vector is selected from the codebook, its corresponding null space matrix is readily available for immediate use, eliminating the need for real-time null space computation and maintaining low implementation complexity.
Solution Approach 2:
The patent transforms the beamforming problem by changing from directly selecting beamforming vectors to selecting pairs of beamforming vectors and their corresponding null space matrices. This parameter change ensures that orthogonality is inherently built into the system architecture rather than being a statistical outcome.
3Productivity
If the number of users increases, then system throughput is improved, but multi-user interference increases causing performance degradation
Solution Approach 1:
The patent moves the problem from the original signal space to a transformed null space dimension. By projecting user signals into null spaces that are orthogonal to other users' beamforming vectors, the system effectively adds a dimensional transformation that eliminates interference regardless of the number of users, allowing throughput to scale with user count.
Data Source
AI summary
Provided are an apparatus and method for eliminating multi-user interference in a codebook-based beamforming system. A transmitter for providing a service to multi-users in the codebook-based beamforming system includes a beamformer for generating beamformed user signals by multiplying transmit data of users, to whom the service is to be provided, by corresponding weighting factor vectors using feedback information; a null space generator for generating a null space matrix orthogonal to weighting factor vectors of other users; and a projector for projecting the beamformed user signals on the corresponding null space matrix and transmitting the resulting signals through a plurality of antennas. Because the multi-user signals can maintain orthogonality, the performance degradation caused by the multi-user interference can be prevented.