Iterative Interference Cancellation for Co-Channel Wireless Systems
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Solution Overview
Problem
Co-channel interference between multi-carrier and narrowband wireless communication systems leads to performance degradation during the transition from 3G to 4G wireless communication systems, as these systems share the same spectrum, causing interference that existing technologies struggle to efficiently mitigate.
Innovation Solution
A method that treats co-channel signals as desired signals and iteratively demodulates and regenerates both wideband and narrowband signals based on symbol decisions and a predetermined channel impulse response, allowing for interference cancellation by subtracting the estimated interfering signal from the aggregate signal, effectively improving performance in a few iterations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multi-carrier and narrowband systems share the same spectrum during transition from 3G to 4G, then spectrum utilization efficiency is improved, but co-channel interference causes performance degradation in both systems
Solution Approach 1:
The patent converts the harmful co-channel interference into a beneficial signal by treating the interfering signal as a desired signal for demodulation. The interference signal is extracted, demodulated, and regenerated, then subtracted from the aggregate signal to cancel its harmful effect, thereby improving performance while maintaining spectrum sharing
Solution Approach 2:
The patent introduces an intermediary processing chain that separates the aggregate signal into desired and interfering components. By using channel impulse response and symbol decisions as intermediaries, the system can estimate and subtract the interfering signal, resolving the contradiction between spectrum utilization and performance
2Measurement precision
If iterative interference cancellation is performed to mitigate co-channel interference, then symbol error rate performance is improved, but computational complexity increases
Solution Approach 1:
The patent applies partial action by performing interference cancellation for only the dominant interfering signal rather than all possible interferers. The method processes signals iteratively with a limited number of steps, achieving significant performance improvement without the full computational burden of exhaustive interference cancellation
Solution Approach 2:
The patent uses preliminary channel impulse response estimation and initial symbol decisions to prepare for interference cancellation. By pre-processing the signal with channel compensation and making initial demodulation decisions, the system reduces the computational complexity of subsequent iterative cancellation steps
Data Source
AI summary
In a co-channel deployment of narrowband and multi-carrier technologies (e.g., a femtocell and a macrocell), a method provides cancelling of interference which treats the co-channel signals as desired signals and enhances each of them iteratively. At each iteration, each signal is demodulated and regenerated based on symbol decisions already made and a predetermined channel impulse response. To estimate the other (interfering) co-channel signal, the regenerated signal is subtracted from the aggregate signal. Simulations have shown that a method of the present invention can provide fundamental improvement in the performances of both interfering systems in as few as two iterations. The fundamental performance gain that can be obtained outweigh the required computational burden.