Massive MIMO Beamforming PAPR Reduction
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Solution Overview
Problem
Massive MIMO systems face challenges in reducing Peak to Average Power Ratio (PAPR) without introducing Error Vector Magnitude (EVM) and Adjacent Channel Leakage Ratio (ACLR), as current methods like clipping are inefficient and distort signals.
Innovation Solution
The solution involves reducing PAPR by applying phase shifts to each antenna element in a multi-antenna system, compensating for phase errors and power losses, and manipulating the spatial profile of the emitted signal to avoid distortion, thereby maintaining the spectral shape of the initial signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If clipping is used to reduce PAPR in massive MIMO systems, then the peak power is reduced, but signal distortion occurs leading to increased EVM and ACLR
Solution Approach 1:
The patent segments the signal processing task by dividing the PAPR reduction problem into two parts: (1) clipping the signal to reduce peaks, and (2) adding a correction signal to compensate for the distortion. This segmentation allows each part to address a specific aspect of the problem without compromising overall signal quality
Solution Approach 2:
The patent converts the harmful effect of clipping (signal distortion) into a beneficial outcome by generating a correction signal that specifically targets and compensates for the distortion introduced by clipping. The correction signal transforms the harmful distortion into an opportunity for precise compensation, thereby improving overall signal quality
2Reliability
If heavy Digital Pre Distortion (DPD) is applied to each amplifier in massive MIMO systems, then nonlinearity effects are minimized, but the system becomes expensive and energy consuming
Solution Approach 1:
The patent merges the PAPR reduction function with the distortion compensation function into a single signal processing stage. By combining these functions, the system achieves both peak power reduction and distortion compensation without requiring separate heavy DPD processing for each amplifier, thereby reducing overall energy consumption
Solution Approach 2:
The correction signal acts as an intermediary that mediates between the clipped signal and the final transmitted signal. This intermediary component provides the necessary distortion compensation without requiring direct heavy DPD processing in each amplifier path, reducing the energy burden on individual amplifiers
3Measurement precision
If the number of antenna elements is increased in massive MIMO systems, then spatial resolution and capacity are improved, but the complexity of PAPR management increases
Solution Approach 1:
The patent creates a correction signal that is a copy of the distortion introduced by clipping, but with opposite polarity. This copying approach allows the system to compensate for distortion in a scalable manner that does not increase proportionally with the number of antenna elements, as the same correction mechanism can be applied across multiple antennas
Data Source
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AI summary
Radio network node (110) and method (500) in a radio network node (110), for wireless communication with a user equipment (120) in a wireless communication system (100) in antenna streams, wherein the radio network node (110) comprises a plurality of antenna elements (210-1, 210-2, 210-n), forming a multiple antenna array (210) which is configured for massive MIMO transmission. The method (500) comprises beamforming (501) a signal to be transmitted to the user equipment (120) by splitting and phase shifting said signal; detecting (502) a peak of power of one beamformed (501) signal, exceeding a threshold value; manipulating (503) said signal until the peak of power of the signal is lower than said threshold value; and transmitting (504) said signal, to be received by the user equipment (120).