Antijam Filter for Wireless Systems Using Training Sequence Segmentation
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Solution Overview
Problem
High data rate wireless communication systems face limitations due to interference and noise, leading to reduced signal fidelity and increased error rates, particularly in unlicensed bandwidths, where existing interference mitigation techniques are complex, require training sequences, or are not adaptable to various wireless technologies.
Innovation Solution
A modular, low-complexity multiple-antenna based antijam filter that de-correlates interference signals across receiver antennas without requiring a training sequence or concurrent feedback, allowing for improved signal-to-noise ratio and interference suppression in spatially multiplexed systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multi user detection (MUD) techniques are used to suppress interference, then the signal-to-noise ratio is increased, but the computational complexity increases significantly
Solution Approach 1:
The patent segments the interference suppression process into two distinct stages: (1) a training phase where a known training sequence is transmitted and used to estimate the channel and interference characteristics, and (2) a data phase where the estimated parameters are applied to suppress interference in the actual data transmission. This segmentation allows the computationally intensive estimation to be performed once during training, rather than continuously during data transmission, thereby reducing overall computational complexity while maintaining reliable interference suppression.
Solution Approach 2:
The patent performs preliminary action by transmitting a training sequence before the actual data transmission. During this training phase, the receiver estimates the channel impulse response and interference characteristics in advance. These pre-estimated parameters are then stored and reused during the data phase, eliminating the need for continuous complex computations during high-speed data transmission. This preliminary estimation action significantly reduces the computational burden during the critical data transmission phase.
2Reliability
If training sequences are used to mitigate interference through adaptive filter techniques, then interference suppression is improved, but the overall throughput of the system decreases
Solution Approach 1:
The patent applies partial action by using a training sequence that is sufficient for accurate parameter estimation but not excessively long. The training sequence duration is optimized to provide just enough information for reliable channel and interference estimation, rather than using overly long sequences that would unnecessarily reduce throughput. Additionally, the patent uses only the essential parameters estimated during training (channel impulse response and interference characteristics) rather than computing all possible filter parameters, achieving adequate interference suppression with minimal overhead.
Solution Approach 2:
The patent changes the approach from continuous adaptive filtering during data transmission to discrete parameter estimation during training. Instead of continuously adjusting filter coefficients based on incoming data (which would require long training sequences or complex recursive algorithms), the patent estimates fixed parameters during a brief training phase and applies them directly during data transmission. This parameter transformation from continuous adaptation to discrete application reduces the effective training overhead while maintaining interference suppression performance.
3Adaptability or versatility
If blind techniques are used when training sequences are not available, then adaptability is improved, but the computational expense increases and performance deteriorates
Solution Approach 1:
The patent introduces a training sequence as an intermediary element that mediates between the transmitter and receiver to establish reliable communication. This training sequence acts as a known reference that enables the receiver to estimate channel and interference parameters without requiring complex blind algorithms. The training sequence intermediary provides a simple, structured way to acquire necessary information that would otherwise require computationally expensive blind estimation techniques, thereby improving performance while maintaining reasonable computational requirements.
4Reliability
If antenna-based techniques with null steering are used to mitigate interference, then interference suppression is improved, but the system requires knowledge of interferer directionalities which increases complexity
Solution Approach 1:
The patent extracts the interference suppression function from the spatial domain (which would require directionality estimation and null steering) and transfers it to the time domain through channel impulse response estimation. Instead of analyzing the spatial characteristics of interferers and steering nulls in specific directions, the patent extracts the temporal characteristics of the channel and interference by correlating the received signal with the known training sequence. This extraction of interference suppression capability from spatial processing to temporal processing eliminates the need for complex directionality estimation while maintaining effective interference suppression.
Data Source
AI summary
An antijam filter and method for filtering interference signals from signals received from the desired user in spatially multiplexed wireless communication systems. The antijam filter estimates the interference from known and unknown sources, and uses that estimate to filter the interference from the received signals. The filtered desired user signals are rendered for further signal processing using existing methods. The antijam filter and method are modular, with applicability to a wide range of wireless communication systems employing multiple antennas at the receiver.