Multi-Element Antenna Array Interference Cancellation Using Orthogonal Beams
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Solution Overview
Problem
Wireless stations with multi-element antenna arrays face challenges in reducing dynamic and random interference, which can change from symbol to symbol, affecting signal reliability and capacity, especially in congested spectrum environments.
Innovation Solution
A method involving forming a wanted signal beam and orthogonal beams using linear combinations of subcarriers with known modulation, generating weights to cancel interference, and applying these weights to orthogonal beams to combine with the wanted signal, thereby reducing interference without requiring direct interference measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If time and/or frequency resource is provided in which the wanted signal is absent to measure interference, then interference measurement accuracy is improved, but data capacity is reduced
Solution Approach 1:
The patent uses linear combinations of received sub-carriers as an intermediary to extract interference information without requiring direct interference measurement resources. By forming linear combinations that cancel the wanted signal component, the interference can be estimated from resources that would otherwise be used for data transmission, thus avoiding the trade-off between measurement accuracy and data capacity
Solution Approach 2:
The received sub-carriers serve multiple functions: they carry data information for communication and simultaneously provide the basis for interference measurement through linear combination processing. This multi-functionality eliminates the need for dedicated interference measurement resources, resolving the contradiction between using resources for data capacity versus interference measurement
2Loss of information
If direct interference measurement is performed on sub-carriers, then interference information is obtained, but wanted signal component interferes with accurate interference detection
Solution Approach 1:
The patent extracts the wanted signal component from the received sub-carriers through linear combination processing, separating it from the interference component. By designing linear combinations that null the wanted signal, only the interference information remains, enabling accurate interference detection without contamination from the wanted signal
Solution Approach 2:
The patent creates copies of the received sub-carriers and processes them through linear combinations to generate estimates of the wanted signal component. These copies are then subtracted from the original signals to isolate the interference, effectively copying and removing the unwanted signal component while preserving interference information
3Reliability
If interference reduction methods are applied to dynamic and random interference, then interference cancellation capability is improved, but system complexity increases
Solution Approach 1:
The patent employs dynamic linear combination coefficients that can be adapted to changing interference conditions. By allowing the combination weights to vary based on current signal characteristics, the system can track and cancel dynamic and random interference effectively without requiring complex adaptive algorithms, thus improving reliability while controlling complexity
Data Source
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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 that is determined to reduce a component of the wanted signal. A first orthogonal beam is formed that is orthogonal is 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 one or more 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.