Precoder Partial Null Steering for Multi-User MIMO Diversity Gain
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Solution Overview
Problem
The Block Diagonalization (BD) method for multi-user MIMO systems limits the degree of freedom in beam formation, making it difficult to improve transmission diversity gain, especially in environments with a larger number of terminals, which restricts the enhancement of the received signal-to-noise power ratio (SNR).
Innovation Solution
A transmitting apparatus that performs precoding to direct beams to multiple receiving apparatuses, ensuring that the received power in unintended terminals is equal to or less than a threshold, thereby allowing for the formation of multiple beams and improving transmission diversity gain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If block diagonalization method is applied to eliminate inter-user interference, then received power in unintended terminals is reduced to zero, but degree of freedom in beam formation is lost and transmission diversity gain cannot be improved
Solution Approach 1:
The patent applies partial null steering by directing nulls only to specific interfering terminals rather than all other terminals. The precoder forms beams with selective null directions, allowing some flexibility in beam formation while still suppressing interference from dominant interferers. This partial application of null steering maintains transmission diversity gain compared to complete BD method.
2Object-affected harmful factors
If block diagonalization method is applied to cancel multiuser interference, then interference cancellation is achieved, but received signal-to-noise power ratio cannot be improved due to loss of beam formation freedom
Solution Approach 1:
The patent applies different precoding strategies to different spatial directions. Beams are formed with specific null directions targeted at interfering terminals, while other directions maintain transmission diversity. This local differentiation allows interference cancellation toward specific users while preserving SNR improvement in other directions through diverse beam forming.
3Object-affected harmful factors
If null steering is performed for all other terminals in BD method, then complete interference cancellation is achieved, but transmission diversity gain cannot be improved especially in environments with larger number of terminals
Solution Approach 1:
The patent extracts and targets only the dominant interfering terminals for null steering rather than treating all other terminals equally. By identifying and directing nulls specifically toward the most significant interferers, the system maintains transmission diversity gain while achieving practical interference cancellation. This selective extraction approach is particularly beneficial in environments with many terminals where complete BD becomes overly restrictive.
Data Source
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AI summary
A transmitting apparatus (1) according to the present invention includes transmission antennas (15-1 to 15-T) capable of forming a plurality of beams respectively directed to a plurality of terminals and a precoder unit (12) that performs precoding on signals transmitted from the transmission antennas (15-1 to 15-T) such that received power in the terminals excluding a desired terminal serving as a transmission destination of a transmission signal and two or more IUI terminals, which are the terminals other than the desired terminal, is equal to or smaller than a threshold.