Spatial Uplink Precoding for PAPR Reduction in Cellular Networks
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Solution Overview
Problem
Peak-to-Average Power Ratio (PAPR) in cellular communication systems, particularly in multicarrier systems like LTE and 5G, leads to inefficiencies in power amplifier utilization and reduced coverage due to peak power limitations, and existing methods like tone reservation signals require additional frequency resources, reducing spectral efficiency.
Innovation Solution
Implementing separate precoders for user data and peak cancellation signals, allowing transmission of the peak cancellation signal in the spatial domain without additional spectrum, and selecting precoders that span the null space of the channel to minimize interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If tone reservation signals are used to reduce PAPR, then PAPR is reduced, but spectral efficiency deteriorates due to additional frequency resources required
Solution Approach 1:
The patent transitions the PAPR reduction approach from the frequency domain (tone reservation) to the spatial domain by utilizing multiple transmit antennas. Instead of reserving subcarriers in frequency, the system uses spatial precoding with multiple antennas to generate peak cancellation signals, thereby reducing PAPR without consuming additional spectral resources.
Solution Approach 2:
The patent enables the uplink transmission to serve dual purposes: transmitting user data while simultaneously reducing PAPR through peak cancellation signals. The same transmit antennas and time-frequency resources are used for both data transmission and PAPR reduction, making the system multi-functional without requiring separate dedicated resources.
2Force
If peak cancellation signal is transmitted using separate resources, then PAPR is reduced, but device complexity increases
Solution Approach 1:
The patent combines the data transmission and peak cancellation functions into a single unified transmission process. The peak cancellation signal is generated and transmitted simultaneously with the user data through the same transmit antennas, merging two previously separate operations into one integrated process that reduces complexity.
Solution Approach 2:
The patent segments the precoding process into two independent components: a first precoder for user data and second precoders for peak cancellation signals. This segmentation allows the system to independently optimize each component and select from multiple second precoder options without increasing overall system complexity.
3Force
If multiple second precoders are available for peak cancellation, then PAPR reduction effectiveness is improved, but selection complexity increases
Solution Approach 1:
The patent implements a feedback mechanism where the network node evaluates the effectiveness of different second precoders based on channel conditions and PAPR reduction performance. The network node provides feedback to the transmitting device about which second precoder to select, thereby managing the complexity of multiple precoder options through centralized intelligent selection rather than distributed trial-and-error.
Data Source
AI summary
According to an example aspect of the present invention, there is provided an apparatus comprising, means for determining a first precoder for an uplink transmission, wherein the uplink transmission comprises user data and/or an uplink reference signal, and at least one second precoder for a peak cancellation signal, means for deciding whether to transmit, along with the uplink transmission, the peak cancellation signal using one of the at least one second precoder and means for transmitting, depending on said decision, at least the uplink transmission to a wireless network node using the first precoder.