Precoding Matrix Phase Shifter Optimization for Inter-User Interference
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Solution Overview
Problem
In wireless communication systems, existing precoding methods for multiuser MIMO do not adequately mitigate inter-user interference, leading to unequal power consumption across power amplifiers and increased energy expenditure due to the lack of a constant modulus property in precoding matrices.
Innovation Solution
A method for determining a precoding matrix with phase shifter elements that adjust phase angles to minimize interference strength, ensuring equal power consumption across transmit antennas by optimizing the precoding matrix to have a constant modulus property, thereby reducing power consumption and inter-user interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If conventional precoding methods (e.g., ZF based on CVQ) are used, then inter-user interference can be mitigated, but the precoding matrix lacks constant modulus property leading to unequal power consumption across power amplifiers
Solution Approach 1:
The patent changes the parameters of the precoding matrix elements from complex values with varying magnitudes to phase shifters with constant modulus (unit magnitude). By restricting each element to the form e^(jθ) where θ is a phase angle, the precoding matrix achieves constant modulus property, ensuring equal power consumption across all power amplifiers while maintaining interference mitigation capability through optimized phase angle selection.
Solution Approach 2:
The patent combines the interference mitigation capability of Zero Forcing (ZF) precoding with the constant modulus property of phase shifters to create a hybrid precoding approach. This composite solution integrates the advantages of both concepts: ZF provides interference cancellation through nulling, while phase shifters ensure constant power amplification, resolving the contradiction between interference mitigation and power efficiency.
2Object-generated harmful factors
If precoding methods without constant modulus property are used, then interference mitigation is achieved, but device complexity increases due to unequal power loading requirements
Solution Approach 1:
By changing the parameter representation of precoding matrix elements to pure phase angles (constant modulus form), the patent simplifies the power amplifier operation. All power amplifiers operate at identical power levels, eliminating the need for complex power loading control circuits and unequal power distribution mechanisms, thus reducing device complexity while maintaining interference mitigation performance.
3Use of energy by moving object
If phase angles are optimized to achieve constant modulus property, then power efficiency improves, but calculation complexity increases for determining optimal phase angles
Solution Approach 1:
The patent segments the precoding matrix into individual phase shifter elements, each controlled by an independent phase angle. This segmentation allows the optimization problem to be decomposed into determining phase angles for each element separately, reducing the overall calculation complexity compared to optimizing the entire complex precoding matrix simultaneously, while still achieving constant modulus property and power efficiency.
Data Source
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AI summary
A method for determining a precoding matrix (PCM) for precoding symbols (s) to be transmitted to a plurality of wireless devices by a node of a wireless communication system is described. The precoding matrix (PCM, P) comprises a precoding vector (pk) for each wireless device of a plurality of wireless devices and each precoding vector (pk) comprises a precoding element (ejθi,k) for each transmit antenna of a plurality of transmit antennas of the node. Further, each precoding element (ejθi,k) represents a phase shifter being able to shift a phase of a symbol to be transmitted through the corresponding transmit antenna to the corresponding wireless device by a phase angle. The method comprises calculating a plurality of interference strength indicators for different phase angles (θ). The different phase angles are applied successively to a precoding element (ejθi,k) of a precoding vector (pk) for the calculation of the interference strength indicators. An interference strength indicator is calculated based on a precoding matrix (P), comprising the precoding element (ejθi,k) considering the respective different phase angle (θ). Further, the method comprises selecting for the precoding element (ejθi,k) of the precoding vector (pk) a phase angle (θ) corresponding to a calculated interference strength indicator fulfilling a predefined interference strength criterion.