Direction-Controlled PAPR Reduction in 5G Base Stations
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Solution Overview
Problem
High peak-to-average-power ratio (PAPR) in OFDM signals for 5G wireless communication systems leads to self-interference and clipping noise, complicating power amplifier biasing and reducing transmission efficiency.
Innovation Solution
A direction-controlled PAPR reduction technique that selectively transmits a PAPR reduction signal into a subset of the channel null space, avoiding high-path-gain directions and concentrating the signal in low-path-gain directions to minimize self-interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a power amplifier is biased to achieve suitable output power competence, then the average power is at or close to saturation region, but the peak power portions of the OFDM signal are clipped
Solution Approach 1:
The patent introduces a PAPR reduction signal as an intermediary component that is added to the original OFDM signal. This PAPR reduction signal acts as a mediator to suppress the peak power portions of the OFDM signal, preventing clipping when the power amplifier operates near saturation. The PAPR reduction signal is designed to be transmitted in the null space of the MIMO channel matrix, ensuring it does not interfere with the original data transmission while effectively reducing the peak power excursions.
2Reliability
If PAPR reduction signal is transmitted into the null space of the MIMO channel matrix, then PAPR is reduced, but self-interference occurs in high-path-gain directions
Solution Approach 1:
The patent applies local quality by making the PAPR reduction signal's spatial characteristics non-uniform. Instead of transmitting the PAPR reduction signal equally in all null space directions, the system selectively enhances or suppresses the signal in specific spatial directions based on the channel's path gain characteristics. The PAPR reduction signal is concentrated in low-path-gain directions where it causes minimal self-interference, while its amplitude is reduced or eliminated in high-path-gain directions where it would cause significant self-interference. This directional control resolves the contradiction by making the PAPR reduction effect location-dependent.
3Reliability
If conventional null-space-based PAPR reduction is used, then PAPR is reduced, but the system lacks direction control and causes self-interference
Solution Approach 1:
The patent introduces dynamics by making the PAPR reduction signal transmission adaptive and variable in the spatial domain. The system dynamically adjusts the characteristics of the PAPR reduction signal based on real-time channel conditions and spatial direction information. By incorporating direction control mechanisms that respond to channel state information, the system can adaptively concentrate or suppress the PAPR reduction signal in different spatial directions, transforming a static null-space transmission into a dynamic, direction-aware transmission scheme.
Data Source
AI summary
A direction-controlled PAPR reduction is provided in which a base station transmits a PAPR reduction signal using a subset of antenna beams selected from a null space plurality of antenna beams. The subset of antenna beams is selected such that the PAPR reduction signal is not directed having a relatively-high path gain to a UE and/or so that the PAPR reduction signal power is concentrated in directions that have a relatively-lo path gain to the UE.