Joint Space-Time Optimum Filter 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 and meeting the requirements of Downlink Advanced Receiver Performance (DARP) standards, particularly in reducing interference and improving signal quality.
Innovation Solution
A multi-channel, space-time filter circuit is introduced that jointly estimates space-time filter weights and channel impulse responses, combining a MIMO-based Joint Space-Time Optimum Filter (JSTOF) with a MISO-based multi-channel matched filter to reduce interference and provide adaptive channel impulse response estimation, along with an auto-switching mechanism to optimize performance in varying interference conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If single channel space-time filters or conventional interference cancellation methods are used, then device complexity is reduced, but interference cancellation performance and signal-to-interference ratio deteriorate
Solution Approach 1:
The patent merges the space filter design and channel estimation into a joint space-time filter that simultaneously performs both functions. This integration allows the filter to achieve optimal interference cancellation by considering both spatial filtering and channel characteristics together, rather than separately as in conventional approaches.
Solution Approach 2:
The patent extends single-channel filtering to multi-channel space-time filtering by incorporating multiple antenna signals and time-delayed versions of these signals. This dimensional extension from single-channel to multi-channel processing enables more effective interference cancellation through spatial diversity and temporal processing.
2Measurement precision
If joint space-time filtering with multi-channel processing is implemented, then signal-to-interference ratio and bit error rate performance improve, but computational complexity increases
Solution Approach 1:
The patent segments the received signal into multiple time-delayed versions and processes each through separate space-time filter banks. This segmentation allows the complex joint estimation problem to be broken down into manageable filter design steps, reducing overall computational burden while maintaining performance.
Solution Approach 2:
The patent changes the filtering parameters by designing space-time filters with specific tap structures and coefficients that are optimized for the multi-channel environment. By carefully selecting filter parameters such as the number of taps and their weights, the system achieves high signal-to-interference ratio with controlled computational complexity.
3Measurement precision
If adaptive channel impulse response estimation is performed jointly with space-time filtering, then channel estimation accuracy improves, but processing complexity and time requirements increase
Solution Approach 1:
The patent performs preliminary channel estimation using the training sequence embedded in the received signal before final data detection. This preliminary action allows the system to establish initial channel impulse response estimates that are then refined through the joint space-time filtering process, reducing the time required for accurate estimation.
Solution Approach 2:
The patent maintains continuous channel estimation by utilizing the joint space-time filter structure that processes ongoing signal sequences. Rather than performing discrete estimation steps, the filter continuously refines channel impulse response estimates as new signal data arrives, improving accuracy without significant time penalty.
Data Source
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.