Multi-Element Antenna Interference Cancellation Without Capacity Loss
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Modern wireless systems face challenges in reducing dynamic and unpredictable interference at wireless stations, particularly in fixed wireless access networks, which can affect data capacity and reliability.
Innovation Solution
A method involving a multi-element antenna array that forms a wanted signal beam, generates linear combinations of sub-carriers with known modulation, and creates orthogonal beams to cancel interference by applying weights to interference signals, using channel estimates and linear prediction techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If time and/or frequency resource is provided in which the wanted signal is absent to form beams for interference reduction, then interference reduction capability is improved, but data capacity is reduced
Solution Approach 1:
The patent performs preliminary channel estimation and interference covariance matrix calculation during periods when the wanted signal is present, using linear combinations of sub-carriers to separate interference components. This preliminary action enables subsequent interference cancellation without requiring dedicated interference measurement periods, thus maintaining data capacity while achieving interference reduction.
Solution Approach 2:
The patent introduces linear combinations of sub-carriers as an intermediary mechanism to extract interference characteristics in the presence of the wanted signal. By creating weighted combinations that cancel the wanted signal component, the system can measure interference without sacrificing data transmission resources, resolving the contradiction between interference reduction and data capacity.
2Ease of operation
If direct measurement of interference is performed on the first subcarrier position, then interference measurement is simplified, but the first subcarrier cannot be energised for data transmission
Solution Approach 1:
The patent uses linear combinations of multiple sub-carriers as an intermediary to indirectly measure interference on the first subcarrier position. Instead of directly measuring interference on the first subcarrier (which would require it to be unenergized), the system creates a composite signal from multiple sub-carriers that cancels the wanted signal component, allowing interference measurement while the first subcarrier remains energised for data transmission.
Solution Approach 2:
The patent replaces the direct physical measurement approach (which requires the subcarrier to be unenergized) with a signal processing substitution. By using linear combinations and mathematical operations on energized sub-carriers, the system achieves interference measurement without the mechanical constraint of leaving the first subcarrier unenergized, thus maintaining data capacity.
3Measurement precision
If weights are generated from a small number of symbols to reduce interference that changes from symbol to symbol, then interference cancellation accuracy is improved, but processing complexity increases
Solution Approach 1:
The patent performs preliminary calculation of the interference covariance matrix and weight generation using linear combinations of sub-carriers from a small number of symbols. This preliminary action captures the current interference characteristics before they change, enabling accurate interference cancellation for each symbol without requiring extensive processing over multiple symbols, thus balancing accuracy and complexity.
Solution Approach 2:
The patent changes the parameter of weight generation from using a large number of historical symbols to using a small number of recent symbols. This parameter change allows the system to track dynamic interference that changes from symbol to symbol, improving cancellation accuracy for current conditions while reducing processing complexity compared to using extensive historical data.
Data Source
AI summary
A first wanted signal beam is formed at a multi-element antenna array to receive a first wanted signal having a first and second sub-carrier, each having known transmitted modulation, and the subcarriers are combined using a first linear relationship determined to reduce a component of the wanted signal. A first orthogonal beam is formed that is orthogonal to the first wanted signal beam, and a first subcarrier received in the first orthogonal beam corresponding in frequency to the first subcarrier of the first wanted signal is combined, using the first linear relationship, with a second subcarrier received in the first orthogonal beam corresponding in frequency to the second subcarrier of the first wanted signal. The linear combinations are processed to generate weights, which are applied to interference received in the first orthogonal beam to produce weighted interference which is combined with the received first wanted signal to reduce interference.