Spatial Spreading Matrix for Equal Power MIMO Output
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Solution Overview
Problem
In wireless MIMO communication systems, the use of a single spatial spreading matrix for all tones or combinations of tones leads to unequal power distribution across transmission antennas when data streams are correlated, causing power amplifiers to operate outside their linear range, resulting in signal distortion and high data error rates.
Innovation Solution
A spatial spreading matrix is designed to satisfy specific constraints, ensuring equal power output across all transmission antennas by having equal row and column dimensions, with constraints that include equal sum of squared norms for rows and columns, and proportional power distribution based on power amplifier operating regions, to maintain linear operation and prevent distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single spatial spreading matrix is used for all tones or combinations of tones, then device complexity is reduced, but power distribution becomes unequal across transmission antennas causing signal distortion
Solution Approach 1:
The patent applies dynamics by making the spatial spreading matrix adaptive rather than static. The system dynamically selects different spatial spreading matrices based on channel conditions, tone combinations, and correlation characteristics of data streams. This allows the matrix to adapt to varying transmission requirements, ensuring equal power distribution across antennas while maintaining low complexity through a finite set of pre-defined matrices.
Solution Approach 2:
The patent changes parameters of the spatial spreading matrix based on transmission conditions. Different matrices are designed with specific properties (such as orthogonal vs. non-orthogonal columns) to match different data stream correlation characteristics. The system selects appropriate matrices by monitoring parameters like correlation coefficients and power distribution, thereby optimizing transmission reliability without requiring a single complex adaptive matrix.
2Ease of manufacture
If conventional spatial spreading matrices are used without constraints, then ease of manufacture is improved, but power amplifiers operate outside linear range causing distortion
Solution Approach 1:
The patent applies preliminary action by pre-designing spatial spreading matrices with specific constraints that guarantee equal power distribution across transmission antennas. These matrices are designed in advance with properties such as equal column norms and orthogonal columns, ensuring that power amplifiers operate within their linear ranges before transmission begins. This eliminates the need for real-time power adjustment while preventing distortion.
Solution Approach 2:
The patent changes the parameters of the spatial spreading matrix by imposing specific mathematical constraints on matrix elements. The matrices are designed with equal column norms and orthogonal columns, which fundamentally alters the power distribution characteristics. This ensures that each antenna receives equal power regardless of data stream correlation, keeping power amplifiers in their linear operating region and eliminating distortion.
3Reliability
If spatial spreading matrices with orthogonal columns are used, then power distribution is equalized, but adaptability to different data stream correlations is reduced
Solution Approach 1:
The patent applies segmentation by dividing the single spatial spreading matrix into multiple specialized matrices, each optimized for specific data stream correlation characteristics. Some matrices have orthogonal columns for uncorrelated streams, while others have non-orthogonal columns for correlated streams. The system segments the transmission task by selecting the appropriate matrix type based on measured correlation coefficients, thereby achieving both power equality and adaptability.
Solution Approach 2:
The patent changes parameters of the spatial spreading matrix by designing multiple variants with different mathematical properties. Some matrices have orthogonal columns with equal norms, while others have non-orthogonal columns with specific correlation properties. The system selects the matrix with appropriate parameters based on data stream correlation characteristics, enabling adaptability while maintaining equal power distribution through constrained matrix design.
Data Source
AI summary
A transceiver utilizes a spatial spreading matrix to distribute two or more encoded spatial data streams to multiple antennas. The spatial spreading matrix satisfies one or more of the following two constraints: (a) the ratio of squared norms of the sum of the components of a row, for different rows of the spatial spreading matrix, is equal to a first constant sequence, and (b) the ratio of squared norms of the sum of a symbol S1 to be transmitted, when the symbol S1 is equal to 1 or −1, multiplied by each of the components of a row, for different rows of the spatial spreading matrix, is equal to a second constant sequence.