MMSE Precoding with Eigenmode Selection Feedback
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Solution Overview
Problem
Current multiuser wireless communication systems face challenges in achieving efficient signaling between access points and user terminals, particularly in managing bandwidth and reducing inter-user interference in SDMA systems, which affects data throughput and error rates.
Innovation Solution
The method involves sending a predefined training sequence to user terminals to estimate channels, perform singular value decomposition, select reliable eigenmodes, and feed back quantized eigenvectors and eigenvalues to the access point, allowing for the generation of a precoding matrix that reduces inter-user interference and increases transmission capacity using MMSE techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If SDMA techniques are used to allow multiple user terminals to share the same channel, then data throughput is improved, but inter-user interference increases
Solution Approach 1:
The patent segments the communication channel into multiple orthogonal spatial streams using eigenmode decomposition. Each user terminal is assigned a specific eigenmode (spatial channel) that is orthogonal to others, allowing simultaneous transmission without interference. This segmentation of the channel into independent spatial paths resolves the contradiction by enabling multiple users to share the channel while maintaining orthogonality and eliminating inter-user interference.
Solution Approach 2:
The patent introduces precoding matrices as an intermediary mechanism between the data source and the wireless channel. These precoding matrices, generated based on channel state information and eigenmode selection, pre-process the transmitted signals to ensure that each user receives only their intended signal without interference from other users. This intermediary processing resolves the interference issue while maintaining high throughput.
2Measurement precision
If quantized eigenvectors and eigenvalues are fed back from user terminals to the access point, then precoding accuracy is improved, but feedback overhead increases
Solution Approach 1:
The patent extracts only the essential channel information (quantized eigenvectors and eigenvalues) needed for precoding, rather than feeding back the complete channel state information matrix. By selecting and transmitting only the dominant eigenmodes and their corresponding parameters, the system achieves accurate precoding while significantly reducing the amount of feedback data required, thus resolving the contradiction between precision and overhead.
Solution Approach 2:
The patent transforms the continuous channel state information into discrete quantized parameters (eigenvectors and eigenvalues) that can be efficiently represented and transmitted with limited bits. This parameter transformation allows the system to maintain sufficient precoding accuracy while reducing feedback overhead, as the quantized parameters capture the essential channel characteristics without requiring full-precision channel matrices.
3Productivity
If multiple spatial streams are transmitted simultaneously to different user terminals, then transmission capacity is improved, but device complexity increases
Solution Approach 1:
The patent performs preliminary channel estimation and eigenmode decomposition at the user terminals before transmission. Each terminal pre-processes the received training sequences to extract channel state information, compute eigenvalues and eigenvectors, and select the dominant eigenmodes. This preliminary action at the terminals reduces the processing burden at the access point and enables efficient multi-stream transmission by pre-identifying the optimal spatial channels for each user.
Solution Approach 2:
The patent implements dynamic eigenmode selection where the number of active spatial streams and the specific eigenmodes used are adapted based on current channel conditions. The system dynamically adjusts the precoding configuration by selecting the top N eigenmodes with the largest eigenvalues for each user, allowing the transmission capacity and processing complexity to be optimized in real-time according to channel quality, thus resolving the contradiction between capacity and complexity.
Data Source
AI summary
Different methods of signaling between an access point and user terminals in a multiuser wireless system for performing a minimum mean square error (MMSE) precoding at the access point preceded with eigenmode selection are provided. For one embodiment of the present disclosure, a compact feedback may be utilized between a plurality of user terminals and the access point. For another embodiment of the present disclosure, a hybrid feedback may be utilized between the plurality of user terminals and the access point. For yet another embodiment of the present disclosure, a full feedback may be utilized between the plurality of user terminals and the access point.