MIMO Wireless System Inter-Stream Interference Cancellation
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Solution Overview
Problem
Current wireless communication systems with multiple transmit and receive antennas face challenges in efficiently transmitting independent symbol streams due to interference between streams, and require significant channel state information feedback, which can lead to performance losses and increased delay in time-varying channels.
Innovation Solution
A wireless communication system where multiple transmit antennas transform independent symbol streams using a linear basis transformation matrix selected by the receiver from a finite set, with the identification of the selected basis and its parameters fed back to the transmitter, allowing for adaptive interference cancellation and improved data rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple transmit antennas transmit independent symbol streams, then data rate is improved, but inter-stream interference increases
Solution Approach 1:
The patent converts the harmful inter-stream interference into a useful signal by treating it as additional information that can be cancelled at the receiver. The receiver uses knowledge of the basis transformation matrix and channel state information to calculate and subtract the interference component from the received signal, thereby recovering the original transmitted symbols with improved accuracy.
Solution Approach 2:
The system implements feedback by having the receiver determine the basis transformation matrix from received signals and feed back identification information about the selected basis to the transmitter. This feedback loop enables the transmitter to adapt its transmission strategy and allows the receiver to accurately model and cancel inter-stream interference.
2Measurement precision
If extensive channel state information feedback is used, then transmission accuracy is improved, but feedback overhead and delay increase
Solution Approach 1:
The patent extracts only the essential information needed for interference cancellation - specifically the basis transformation matrix identification - rather than feeding back complete channel state information. This selective extraction significantly reduces feedback overhead while maintaining sufficient accuracy for effective interference cancellation and adaptive transmission.
Solution Approach 2:
The system changes the parameter being fed back from complete channel state information to a compact basis identification parameter. This parameter transformation reduces the amount of feedback data required while preserving the critical information needed for signal processing and interference cancellation.
3Reliability
If complete channel state information is fed back, then system performance is improved, but complexity of the system increases
Solution Approach 1:
The patent extracts and processes only the critical basis identification information rather than complete channel state information. This reduces the computational complexity of feedback processing at both transmitter and receiver while maintaining the reliability needed for effective interference cancellation and adaptive modulation.
Data Source
AI summary
A wireless receiver (74) for receiving signals from a transmitter (72). The transmitter comprises a plurality of transmit antennas (TAT1′, TAT2′) for transmitting the signals, which comprise respective independent streams of symbols. Additionally, interference occurs between the respective streams. The receiver comprises a plurality of receive antennas (RAT1′, RAT2′) for receiving the signals as influenced by a channel effect between the receiver and the transmitter. The receiver also comprises circuitry (80) for multiplying the signals times a conjugate transpose of an estimate of the channel effect and times a conjugate transpose of a linear basis transformation matrix. The receiver also comprises circuitry (84) for selecting the linear basis transformation matrix from a finite set of linear basis transformation matrices. Lastly, the receiver comprises circuitry (88) for removing the interference between the respective streams.