Linear Precoding for MIMO Capacity and Diversity
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Solution Overview
Problem
Existing MIMO systems face limitations in spectral efficiency, decoding complexity, and failure to exploit maximum spatial diversity and capacity, particularly in BLAST and V-BLAST techniques, which also struggle with correlated channels.
Innovation Solution
A method employing linear precoding with a block precoding matrix, such as a unitary or Hadamard matrix, to transmit symbols across multiple antennas, allowing for maximum capacity and diversity exploitation without requiring space-time codes, and using low-complexity decoding techniques like Cholesky decomposition for reception.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If BLAST spatial multiplexing technique is used to increase transmission capacity, then system capacity increases linearly with number of antennas, but decoding complexity becomes excessively high
Solution Approach 1:
The patent segments the transmitted signal into multiple layers, where each layer is processed independently through the MIMO channel. This layering approach allows the receiver to separately decode each layer, reducing overall decoding complexity while maintaining high transmission capacity through spatial multiplexing
Solution Approach 2:
The patent applies preliminary spatial precoding at the transmitter before signal transmission through the MIMO channel. This pre-processing of signals across multiple antennas creates orthogonal or near-orthogonal channels that simplify the receiver's decoding task, effectively reducing decoding complexity while preserving capacity benefits
2Device complexity
If V-BLAST architecture is used to simplify the system, then decoding is simplified with zero forcing criterion, but maximum spatial diversity is not exploited
Solution Approach 1:
The patent dynamically adapts the precoding strategy based on channel conditions, transitioning between different transmission modes. When channel conditions permit, it exploits spatial diversity through appropriate precoding; when capacity is prioritized, it uses spatial multiplexing configurations, thus achieving both simplicity and diversity exploitation
3Reliability
If space-time codes are combined with V-BLAST to improve performance, then system performance is enhanced, but maximum system capacity is not exploited
Solution Approach 1:
The patent changes the fundamental parameter of signal processing by abandoning traditional space-time coding in favor of spatial precoding with layered transmission. This parameter change enables the system to achieve both improved performance through better noise robustness and maximum capacity exploitation through efficient spatial multiplexing
4Reliability
If maximum likelihood receiver is used to achieve full diversity and full rate, then both diversity and capacity are maximized, but implementation complexity becomes prohibitive and limits precoding matrix size
Solution Approach 1:
The patent extracts the complexity from the receiver by moving signal processing functions to the transmitter through spatial precoding. The precoder pre-processes signals to create favorable channel conditions, allowing the receiver to use simpler decoding algorithms while still achieving full diversity and supporting large precoding matrices
Data Source
AI summary
An embodiment of invention relates to a method for the transmission of a signal formed by vectors, each vector comprising N source symbols to be transmitted, using M transmission antennas, wherein M is greater than or equal to 2. The method comprises the following steps: linearly precoding the signal using a matrix product of a source matrix formed by vectors that are organized in successive lines by a linear precoding matrix, delivering a precoded matrix; and successively transmitting precoded vectors corresponding to columns of said precoded matrix, the M symbols of each precoded vector being distributed to the M antennas.