Space-Time Cochannel Interference Cancellation in MIMO Systems
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Solution Overview
Problem
Traditional cochannel interference cancellation techniques in wireless communication systems, such as those based on IEEE 802.16 standards, are limited by their reliance on spatial correlations alone, failing to effectively address complex MIMO interferences like Alamouti space-time coded cochannel interference, which requires additional antennas for cancellation.
Innovation Solution
The implementation of a space-time cochannel interference cancellation (ST CIC) technique that exploits both spatial and time correlation properties of interference signals, allowing for joint space-time optimization of transmit and receive beamformer weights to cancel space-time coded interferences without the need for additional antennas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional space-only CIC techniques are used, then the system is simpler to implement, but it cannot effectively cancel space-time coded interference without additional antennas
Solution Approach 1:
The patent transitions from traditional spatial-only interference cancellation to joint space-time interference cancellation by incorporating the time dimension. The receiver processes signals across multiple time slots and utilizes temporal correlation properties of interference signals, enabling effective cancellation of space-time coded interference without requiring additional antenna elements beyond what is needed for basic MIMO operation.
Solution Approach 2:
The patent changes the processing parameters by exploiting temporal correlation characteristics of interference signals. By analyzing signal correlations across different time slots and incorporating time-domain processing alongside spatial processing, the system achieves enhanced interference cancellation capability while maintaining the same hardware configuration.
2Reliability
If additional antennas are added to cancel space-time coded interference, then interference cancellation performance improves, but system complexity and cost increase
Solution Approach 1:
The patent resolves this contradiction by utilizing the time dimension for interference cancellation. Instead of adding spatial resources (antennas), the system processes signals across multiple time slots and exploits temporal correlation properties, achieving effective space-time interference cancellation with the existing antenna configuration.
Solution Approach 2:
The patent uses received signal copies from multiple time slots to perform interference cancellation. By maintaining and processing copies of signals across different time instances, the system can estimate and subtract interference components without requiring additional physical antenna elements.
3Productivity
If space-time correlation properties are exploited, then spectral efficiency improves, but signal processing complexity increases
Solution Approach 1:
The patent changes the processing approach by incorporating temporal correlation analysis alongside spatial processing. The receiver estimates interference characteristics using signals from multiple time slots and applies joint space-time filtering, improving spectral efficiency through better interference suppression while managing complexity through efficient algorithm design.
Solution Approach 2:
The patent implements iterative interference cancellation where the receiver estimates interference based on temporal correlations, subtracts it from received signals, and refines estimates in subsequent processing stages. This feedback-based approach improves spectral efficiency by progressively reducing interference while organizing complexity into manageable iterative steps.
Data Source
AI summary
An apparatus, system, and method for space-time cochannel interference cancellation are described. The apparatus may include a time stacking module to stack consecutive subcarrier signals for a period of time equal to several symbols and a space-time subcarrier beamformer module to perform space-time subcarrier beamforming by applying space-time beamformer weights to stacked symbols on one or more subcarriers. The space-time beamformer weights may be calculated based on spatial and time correlation properties of one or more interference signals. Other embodiments are described and claimed.