Base Station-Driven PAPR Reduction Method Utilizing Null Space for MIMO-OFDM Systems With Amplify-and-Forward Relaying

• Published in: IEEE access Vol. 12; p. 1
• Main Authors: Kakehashi, Asuka, Hara, Takanori, Higuchi, Kenichi
• Format: Journal Article
• Language: English
• Published: Piscataway IEEE 01.01.2024; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Amplify-and-forward; Antennas; Beamforming; Channel capacity; Computer simulation; Fading channels; Frequency selective surfaces; frequency-selective fading channel; MIMO communication; multiple-input multiple-output (MIMO); non-linear power amplifier; Nonlinear systems; Null space; OFDM; Orthogonal Frequency Division Multiplexing; orthogonal frequency division multiplexing (OFDM); Peak to average power ratio; peak-to-average power ratio (PAPR); Power amplifiers; Reduction; Relay stations; Relaying; Relays; Signal processing; Transmitting antennas
• ISSN: 2169-3536; 2169-3536
• DOI: 10.1109/ACCESS.2024.3365702

This paper proposes a peak-to-average power ratio (PAPR) reduction method that utilizes the null space in a multiple-input multiple-output (MIMO) channel for downlink MIMO-orthogonal frequency division multiplexing (OFDM) signals with multiple-antenna amplify-and-forward (AF)-type relaying. In order to achieve sufficient coverage enhancement using beamforming with multiple antennas and relaying, the PAPR not only at the base station (BS) but also at the relay station (RS) should be reduced to suppress the amount of input backoff (IBO) in the non-linear power amplifier. However, performing complex signal processing for PAPR reduction at the AF-type RS is impractical and leads to the concern that the channel capacity (throughput) will be reduced due to processing delay. In the proposed method, the BS alternately repeats the signal processing for generating the signal to reduce the PAPR at the BS and the signal to reduce the PAPR at the RS, where the RS does not require any signal processing for PAPR reduction. The generated PAPR reduction signals are projected onto the null space of the integrated MIMO channel of the entire system for each frequency block. Computer simulation results using the non-linear power amplifier model show that the proposed method achieves higher throughput compared to the clipping and filtering (CF) method for the BS by reducing the PAPR at the RS utilizing the null space of the channel.