Joint Space-Time Filter Switching for Co-Channel Interference
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Solution Overview
Problem
Current Global System for Mobile (GSM) cellular systems face challenges in addressing co-channel interference (CCI) on the mobile station side while meeting the requirements of Downlink Advanced Receiver Performance (DARP) standards, particularly in estimating channel impulse responses and designing filters to maximize signal-to-interference ratios.
Innovation Solution
A Joint Space-Time Optimum Filter (JSTOF) based receiver is introduced, which includes a multi-channel, space-time filter circuit that jointly estimates space-time filter weights and channel impulse responses, and a multi-channel matched filter circuit that uses these estimates to reduce interference, with an auto-switching mechanism to adapt between different filtering modes based on interference levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If single channel space-time filters or pre-filters are used to cancel interference, then co-channel interference cancellation is improved, but the system cannot meet DARP requirements and lacks robustness against various interference scenarios
Solution Approach 1:
The patent implements dynamic switching between different filter types (single-channel and multi-channel) based on the detected interference scenario. The system adapts its filtering approach in real-time, selecting the appropriate filter configuration to match the current channel conditions, thereby achieving both interference cancellation and robustness across varying scenarios
Solution Approach 2:
The system changes filter parameters (channel count, filter type) based on the interference environment. By detecting the number of active channels and interference characteristics, the system adjusts its filtering parameters to optimize performance for the specific scenario, enabling it to meet DARP requirements while maintaining robustness
2Object-affected harmful factors
If maximization of signal-to-interference is used to design space-time filter, then interference cancellation is improved, but channel impulse response estimation accuracy deteriorates
Solution Approach 1:
The patent segments the filtering process into distinct stages: first estimating the channel impulse response using training sequences, then designing the space-time filter based on this estimation. This segmentation allows independent optimization of each function, preventing the degradation of estimation accuracy that would result from joint optimization focused solely on interference cancellation
3Reliability
If multi-channel space-time filtering is implemented to meet DARP requirements, then receiver performance is improved, but computational complexity increases
Solution Approach 1:
The system dynamically selects between single-channel and multi-channel filtering based on the detected number of active channels and interference levels. By switching to single-channel filtering when appropriate, the system maintains DARP compliance while significantly reducing computational complexity in scenarios that do not require full multi-channel processing
4Device complexity
If single antenna is used on mobile station, then device simplicity is maintained, but virtual antenna array capability is lost
Solution Approach 1:
The patent introduces a signal processing intermediary that creates virtual antenna array capabilities through mathematical transformation of the single antenna's received signal. By processing the single antenna output to generate multiple virtual channels, the system achieves diversity branching without adding physical antennas, maintaining device simplicity while enabling advanced interference cancellation
Data Source
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AI summary
A filter for reducing co-channel interference within a communications receiver may include a multi-channel, space-time filter circuit that filters n signal parts that have been split from a communications signal by jointly estimating space-time filter weights and multi-channel impulse responses (CIRs). The filter may further include a multi-channel, matched filter circuit that receives multi-channel signals from the multi-channel, space-time filter circuit and has a filter response that is provided by a channel impulse response estimation from the space-time filter circuit.