MU-MIMO Precoding Weights for Interference-Limited Downlinks
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Solution Overview
Problem
In multi-user MIMO communication systems, the disparity in resources between user terminals and base stations limits the effectiveness of signal processing, leading to interference and reduced channel capacity due to the inability to satisfy the condition of equal or greater receive antennas at user terminals compared to transmit antennas.
Innovation Solution
The method involves determining pre-coding signal weights based on channel state information to provide proportional power allocation and separate signals, with the base station performing inter-user separation and user terminals performing MIMO layer separation and decoding, effectively splitting interference cancellation between the transmitter and receiver sides.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If receiver-based interference cancellation is used in conventional systems, then implementation simplicity is maintained, but channel capacity and signal processing effectiveness are limited due to resource constraints at user terminals
Solution Approach 1:
The patent inverts the conventional approach by moving interference cancellation from the receiver side to the transmitter side. The base station performs pre-coding operations using spatial coding matrices based on channel state information, pre-canceling interference before transmission. This allows user terminals with limited resources to receive signals with reduced interference without requiring complex receiver-based cancellation algorithms.
Solution Approach 2:
The system performs preliminary interference cancellation at the transmitter before signals are transmitted to users. By calculating pre-coding weights and applying spatial coding matrices in advance based on channel state information, the interference is eliminated before the signals reach the resource-constrained user terminals, improving channel capacity without burdening the receivers with complex processing.
2Adaptability or versatility
If user terminals have fewer antennas than base stations, then wireless communication practicality is improved, but the constraint of equal or greater receive antennas versus transmit antennas cannot be satisfied
Solution Approach 1:
The patent changes the fundamental parameter relationship by enabling effective MIMO operation where the number of receive antennas at user terminals is fewer than the number of transmit antennas at the base station. This is achieved by using pre-coding techniques that transform the signal space, allowing the system to overcome the traditional constraint that requires N_receive ≥ N_transmit for reliable signal separation and interference cancellation.
3Productivity
If proportional power allocation is applied through pre-coding signal weights, then channel performance is enhanced, but computational complexity at the transmitter increases
Solution Approach 1:
The system uses channel state information fed back from user terminals to automatically determine the pre-coding weights and spatial coding matrices. The base station leverages this information to self-adjust its transmission parameters, optimizing power allocation and interference cancellation without requiring external control or manual configuration. This self-service approach enhances transmission efficiency while managing computational complexity through algorithmic optimization.
Data Source
AI summary
Systems and methods of optimizing communication channels in multi-user communication systems are provided. Coding weights are determined based on communication channel state information for communication channels between a transmitter and multiple receivers. The coding weights are applied to communication signals to be transmitted from the transmitter to the receivers. Each receiver decodes received signals using inverses of the coding weights. Embodiments of the invention support multi-user MIMO (Multiple Input Multiple Output) where each receiver has fewer antennas than the transmitter, and enhance system performance if the total number of antennas at all of the receivers exceeds the number of antennas at the transmitter.