Transmit Precoding for Out-of-Cluster Interference Alignment
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Solution Overview
Problem
Existing interference alignment techniques in wireless communication systems are ineffective in real-world cellular networks due to out-of-cluster interference, which limits their performance gains and spectral efficiency.
Innovation Solution
The proposed solution involves a precoding technique that accounts for both in-cluster and out-of-cluster interference by using information from transmitters within and outside the coordinated cluster, allowing each transmitter to design its precoding to align signals with the direction of maximum interference at undesired receivers while improving the desired signal's strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If interference alignment is performed using only in-cluster transmitters, then coordination complexity is reduced, but out-of-cluster interference degrades performance
Solution Approach 1:
The patent segments the interference management into two levels: intra-cluster coordination for signal alignment and inter-cluster coordination for interference suppression. This segmentation allows the system to manage complexity by handling different interference sources through different coordination mechanisms, resolving the contradiction between reduced coordination complexity and maintained performance.
2Productivity
If coordinated cluster size is increased to improve interference alignment, then spectral efficiency improves, but feedback requirements and system complexity increase
Solution Approach 1:
The patent extracts and processes interference covariance information separately from channel state information. By taking out the interference characterization as a distinct feedback element, the system can achieve improved spectral efficiency through better interference alignment while keeping feedback requirements manageable through focused information exchange.
3Measurement precision
If perfect channel state information is assumed for interference alignment, then theoretical performance is maximized, but practical implementation becomes infeasible
Solution Approach 1:
The patent performs preliminary estimation of interference covariance matrices before actual precoding operations. This preliminary action allows the system to work with statistically characterized interference rather than requiring perfect instantaneous channel state information, making the implementation practically feasible while maintaining good performance.
Solution Approach 2:
The patent implements feedback mechanisms where receivers provide interference covariance information to transmitters. This feedback loop enables practical channel state information acquisition, resolving the contradiction between theoretical perfect knowledge assumptions and practical implementation constraints.
Data Source
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AI summary
Embodiments relate to a concept for precoding a transmit signal (si) in a wireless communication system (200), the wireless communication system comprising a transmitter cluster (210) comprising a first transmitter (212-i) and at least a second transmitter (212-j), wherein the first transmitter (212-i) communicates with a first receiver (214-i) and the second transmitter (212-j) communicates with a second receiver (214-j). It is determined a first transmit precoding information (253) based on interference experienced at the second receiver (214-j) due to interfering signal transmissions from at least the first transmitter (212-i) of the transmitter cluster (210) and from transmitters (216) of the wireless communication system (200) outside the transmitter cluster (210). It is further determined a second transmit precoding information (255) based on a cross-channel state information of a wireless communications channel between the second receiver (214-j) and the first transmitter (212-i). A signal (si) transmitted from the first transmitter (212-i) to the first receiver (214-i) is precoded based on the determined first and second transmit precoding information (253; 255).