Cross-Polarized MIMO Precoding for Non-Ideal XPD
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Solution Overview
Problem
In MIMO systems with a cross-polarized antenna structure, ideal Cross Polarization Discrimination (XPD) is often not achieved, leading to interference between different polarized waves and a deterioration in precoding performance.
Innovation Solution
A wireless communication system and method that uses a precoding matrix of projection matrices to orthogonalize channel response matrices for different polarized waves, even when ideal XPD is not satisfied, by applying a first precoding matrix for forming transmission beams and a second precoding matrix, such as a unitary matrix, to minimize interference between polarized waves.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a code book using a section diagonal matrix is used for precoding operation in a cross-polarized MIMO system, then precoding can be performed under ideal XPD conditions, but precoding performance deteriorates when ideal XPD conditions are not satisfied
Solution Approach 1:
The invention applies dynamic precoding matrices that can adapt to varying channel conditions. Instead of using fixed section diagonal matrices that assume ideal XPD, the system employs precoding matrices that dynamically adjust based on actual channel state information, allowing optimal performance under both ideal and non-ideal XPD conditions
Solution Approach 2:
The invention changes the parameters of the precoding matrices to accommodate non-ideal XPD conditions. By modifying the structure and characteristics of the precoding matrices to match actual channel conditions rather than ideal assumptions, the system maintains high precoding performance across varying environmental conditions
2Productivity
If cross-polarized antennas are used to increase the number of transmission antennas in a MIMO system, then spatial multiplexing capability is improved, but interference between different polarized waves occurs when ideal XPD is not achieved
Solution Approach 1:
The invention extracts and separately processes different polarized wave components through dedicated precoding matrices. By treating each polarized wave component independently with its own optimized precoding matrix, the system can maintain spatial multiplexing capability while minimizing interference between polarized waves
Solution Approach 2:
The precoding matrices act as intermediaries between the cross-polarized antennas and the channel. These matrices process and condition the signals from different polarized waves before transmission, reducing direct interference while preserving the spatial multiplexing benefits of cross-polarized antenna structures
Data Source
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AI summary
In a MIMO system using a cross-polarized antenna structure, even if no ideal XPD can be obtained, the interference between different polarized waves can be reduced to allow an effective precoding to be executed. When a MIMO communication is performed between a transmitter (250) and a receiver (260) each using a cross-polarized antenna structure, a channel estimating and precoding selection section (214) of the receiver (260) performs a channel estimation of MIMO channels from the transmitter to the receiver, decides a precoding matrix (P) of a projection matrix for mutually orthogonalizing or substantially orthogonalizing the channel response matrixes for respective different polarized waves, and feeds the determined precoding matrix (P) back to the transmitter (250). In the transmitter (250), a precoding processing section (208) applies the precoding matrix (P) to the spatial stream corresponding to one of the polarized waves to perform a precoding, thereby allowing the transmitter (250) to transmit the polarized waves with the orthogonality therebetween maintained.