Open-Loop Precoder for MIMO Spatial Multiplexing
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Solution Overview
Problem
MIMO systems face performance degradation due to channel correlation in open-loop systems like broadcast and mobile communication systems, where feedback information from the receiver is not available, limiting the application of conventional precoding techniques.
Innovation Solution
An open-loop precoding method using a precoding matrix with a rotational and phase rotation matrix is applied, determining optimal parameters to minimize pairwise error probability (PEP) by assuming a worst channel state, allowing for effective transmission without receiver feedback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If open-loop precoding is used in MIMO systems without feedback information, then system complexity is reduced and broadcast applications become feasible, but receive signal performance degrades due to channel correlation
Solution Approach 1:
The patent applies preliminary action by pre-determining optimal precoding matrix parameters (α and β) before transmission based on assumed channel correlation characteristics. The transmitter selects precoding parameters in advance without waiting for feedback, thereby reducing system complexity while maintaining acceptable performance through proactive optimization.
Solution Approach 2:
The patent employs parameter changes by dynamically adjusting the precoding matrix parameters α and β based on channel correlation conditions. By varying these parameters, the system adapts to different channel environments without requiring feedback, thus improving receive signal performance while maintaining the open-loop simplicity.
2Ease of operation
If conventional precoding techniques are applied without feedback, then implementation becomes feasible for broadcast systems, but pairwise error probability increases due to lack of channel state information
Solution Approach 1:
The patent applies self-service by enabling the transmitter to independently determine optimal precoding parameters without external feedback. The system uses pre-defined parameter selection based on channel correlation assumptions, making implementation feasible for broadcast systems while maintaining reliability through autonomous optimization.
3Productivity
If spatial multiplexing is employed to increase data transmission capacity, then transmission efficiency improves, but receive performance degrades due to channel correlation between transmit antennas
Solution Approach 1:
The patent uses parameter changes by adjusting the precoding matrix parameters α and β to mitigate channel correlation effects. This allows spatial multiplexing to maintain high data transmission capacity while the modified parameters reduce the harmful correlation between signals from different transmit antennas, preserving receive performance.
Data Source
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AI summary
Disclosed is an open-loop precoder and an open-loop precoding method of a multiple-input multiple-output (MIMO) spatial multiplexing system having a transmitter that is provided with at least two transmit antennas and transmits spatially multiplexed transmit signals and a receiver that is provided with at least two receive antennas and receives the spatially multiplexed transmit signals from the transmitter. The open-loop precoder comprises: a signal decomposition and modulation unit configured to decompose a signal to be transmitted to match the number of the transmit antennas and modulate the decomposed signals; an orthogonal complex matrix condition search unit having a precoding matrix for the number of the transmit antennas; an error minimization parameter determination unit configured to determine an optimum parameter of the precoding matrix such that an error is minimized by assuming a worst channel state; a precoding application unit configured to apply the precoding matrix having the determined parameter to the decomposed and modulated transmit signals output from the signal decomposition and modulation unit; and a transmit unit configured to transmit each of the transmit signals subjected to the precoding matrix via the corresponding transmit antennas. According to the present invention, since the decomposed transmit signals are precoded using the precoders obtained by assuming the transmit correlation coefficient of the worst case and considering the worst channel state capable of preventing performance degradation of the average receive signals, it is possible to prevent performance degradation of the receive signals in the channel without feedback information from the receiver and accordingly reduce the pairwise error probability (PEP).