MIMO Secondary Transmitter Null-Space Interference Management
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Solution Overview
Problem
Multiple-input multiple-output (MIMO) wireless communication systems face interference issues due to overlapping transmission systems, leading to reduced spectral efficiency, receiver sensitivity, and total throughput.
Innovation Solution
A method is introduced where a secondary transmitter learns the null-space of the interference channel with an unintended receiver by transmitting learning signals, determining interference values, and adjusting its transmissions to minimize interference, using rotation matrices and cyclic Jacobi methods, without requiring explicit information exchange or cooperation with the primary transmitter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple transmission systems operate simultaneously in MIMO systems, then system capacity and throughput increase, but interference between systems increases reducing spectral efficiency and receiver sensitivity
Solution Approach 1:
The patent converts the harmful interference from secondary transmitter to primary receiver into useful information by having the primary receiver feed back interference measurements. These measurements are then used to compute null-space precoding vectors that eliminate interference, transforming the harmful interference problem into a beneficial interference management mechanism that enables spatial multiplexing.
Solution Approach 2:
The patent changes the spatial parameters of transmission by computing null-space precoding vectors that constrain the transmitted signal to lie in the null-space of the interference channel. This parameter transformation allows the secondary transmitter to maintain high throughput while eliminating interference to the primary receiver by adjusting the spatial direction of transmission.
2Device complexity
If null-space learning is implemented without explicit information exchange, then system complexity and synchronization requirements are reduced, but the ability to accurately determine interference channels may be compromised
Solution Approach 1:
The patent implements self-service by having the primary receiver autonomously measure and feed back interference levels from secondary transmissions, and having the secondary transmitter autonomously compute null-space precoding vectors based on this feedback. This eliminates the need for complex centralized coordination while maintaining accurate interference channel estimation through distributed self-organization.
Solution Approach 2:
The patent establishes a feedback loop where the primary receiver measures interference caused by secondary transmissions and feeds back these measurements to the secondary transmitter. This feedback mechanism enables accurate interference channel estimation without explicit information exchange, allowing the secondary transmitter to adapt its precoding vectors to eliminate interference while maintaining low system complexity.
3Measurement precision
If learning signals are transmitted to determine null-space, then interference mitigation accuracy improves, but transmission time and energy consumption increase
Solution Approach 1:
The patent applies partial action by transmitting a limited set of learning signals rather than exhaustive channel probing. The secondary transmitter transmits learning signals only in the directions that potentially cause interference to the primary receiver, rather than sweeping all possible transmission directions. This partial exploration achieves sufficient null-space determination accuracy while minimizing time and energy overhead.
Data Source
AI summary
Methods and apparatuses, including computer program products, are provided for determining the null-space for a channel between a transmitter and an unintended receiver. In one aspect there is provided a method. The method may include transmitting, by a secondary transmitter, a plurality of learning signals, determining, for each of the plurality of learning signals, a value representative of an interference caused by the transmitting to an unintended receiver, determining, based on the determined values, a null-space for a channel between the secondary transmitter and the unintended receiver and transmitting, by the secondary transmitter, a signal in accordance with the determined null-space.