Mixed Rank Downlink Interference Alignment Scheme
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Solution Overview
Problem
Existing interference alignment schemes in wireless communication systems require perfect global channel knowledge and are sensitive to channel estimation and quantization errors, antenna configuration, and mobility, leading to significant feedback overhead and coordination challenges.
Innovation Solution
A mixed rank downlink compound multi-user interference alignment scheme that operates with local channel knowledge, using linearly independent vectors to project cross-channel interference into a predetermined subspace, allowing each transmitter to precode signals and align interference without requiring global channel information, suitable for both cases where the number of receiver antennas is greater than or equal to the number of transmitter antennas and vice versa.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If perfect global channel knowledge is used for interference alignment, then interference alignment performance is improved, but feedback overhead and coordination complexity increase significantly
Solution Approach 1:
The patent divides the network into local cells, where each cell performs interference alignment using only local channel knowledge. This segmentation eliminates the need for global channel knowledge across the entire network, reducing feedback overhead while maintaining interference alignment performance within each cell boundary.
Solution Approach 2:
The patent implements interference alignment with local channel knowledge specific to each cell rather than requiring global channel knowledge. Each cell uses its own channel characteristics to perform interference alignment, which reduces the complexity of feedback and coordination while achieving reliable interference management locally.
2Device complexity
If traditional orthogonalization-based schemes are used to manage interference, then coordination complexity is reduced, but throughput performance deteriorates due to limited degrees of freedom
Solution Approach 1:
The patent employs interference alignment techniques that utilize spatial dimensions more efficiently by aligning interference signals into specific subspaces rather than orthogonalizing channels. This dimensional approach allows multiple users to share the same time-frequency resources while maintaining throughput performance, overcoming the limitations of traditional orthogonalization methods.
Data Source
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AI summary
A method, system and device are provided to enable one or more users to receive mixed-rank data from two transmitters by using an indexed list of linearly independent, predetermined vectors {V1 ref,..,VM ref} and channel knowledge H1, H2 from first and second transmitters to compute equivalent channel matrix information Hi eq based on the assigned or determined rank of the receiver. With this information, each transmitter selects Li receivers and constructs a transmitted signal by applying a selected precoding matrix to the mixed rank data, thereby eliminating interference to the rest of the receivers in the network so that a receiver can receive transmitted signals from both transmitters.