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Switch-DFT: Adaptive Waveform and MIMO Switching for Energy-Efficient Base Stations

Jaebum Park, Chan-Byoung Chae, Robert W. Heath

Abstract

Energy efficiency has emerged as a critical challenge in modern base stations (BSs), as the power amplifier (PA) consumes a substantial portion of the total power due to its limited efficiency. We investigate waveform and mode adaptation to enhance the energy efficiency of BSs. We propose Switch-DFT, an adaptive switching framework that selects between cyclic prefix orthogonal frequency division multiplexing (CP-OFDM) and discrete Fourier transform-spread-OFDM (DFT-s-OFDM) waveforms, as well as between single-input multiple-output (SIMO) and multiple-input multiple-output (MIMO) modes. Switch-DFT improves efficiency by reducing PA backoff with DFT-s-OFDM and achieves the target rate at lower power by leveraging higher MIMO throughput. This results in superior energy efficiency over a wide range of the spectral efficiencies compared with static configurations.

Switch-DFT: Adaptive Waveform and MIMO Switching for Energy-Efficient Base Stations

Abstract

Energy efficiency has emerged as a critical challenge in modern base stations (BSs), as the power amplifier (PA) consumes a substantial portion of the total power due to its limited efficiency. We investigate waveform and mode adaptation to enhance the energy efficiency of BSs. We propose Switch-DFT, an adaptive switching framework that selects between cyclic prefix orthogonal frequency division multiplexing (CP-OFDM) and discrete Fourier transform-spread-OFDM (DFT-s-OFDM) waveforms, as well as between single-input multiple-output (SIMO) and multiple-input multiple-output (MIMO) modes. Switch-DFT improves efficiency by reducing PA backoff with DFT-s-OFDM and achieves the target rate at lower power by leveraging higher MIMO throughput. This results in superior energy efficiency over a wide range of the spectral efficiencies compared with static configurations.

Paper Structure

This paper contains 13 sections, 25 equations, 5 figures, 1 table, 1 algorithm.

Table of Contents

  1. Introduction
  2. System model with PA analysis
  3. Energy-efficient and power consumption analysis of radio unit
  4. Transmit power and spectral efficiency in SIMO and MIMO
  5. RU power consumption and crossover point analysis with DFT-s-OFDM
  6. Energy-efficiency optimization problem
  7. Single-ratio fractional programming optimization
  8. Equivalent quadratic transform
  9. Subproblem in $p$
  10. Iterative algorithm and global convergence
  11. Energy efficiency and power consumption results
  12. Conclusion
  13. Acknowledgment

Figures (5)

  • Figure 1: 64QAM constellations of CP-OFDM (left) and DFT-s-OFDM (right) with PA nonlinearity (TDL-C channel, PA backoff $=5$ dB). Compared with CP-OFDM, the lower PAPR yields more compact received signal constellation clusters and about 3 dB EVM improvement.
  • Figure 2: EVM versus PA backoff for CP-OFDM and DFT-s-OFDM. DFT-s-OFDM requires less backoff to satisfy a given EVM constraint (-28 dB), enabling higher transmit power and improved PA efficiency.
  • Figure 3: Total RU power consumption versus spectral efficiency for SIMO (CP-OFDM or DFT-s-OFDM) and MIMO (CP-OFDM). Using DFT-s-OFDM for SIMO transmission reduces power consumption and extends the spectral efficiency range where SIMO remains preferable.
  • Figure 4: Total RU power consumption versus spectral efficiency for different transmission modes. The proposed Switch-DFT strategy achieves the lowest power consumption across the entire range and outperforms the baseline.
  • Figure 5: Energy efficiency (EE) versus spectral efficiency for SIMO and MIMO with CP-OFDM and DFT-s-OFDM. The proposed Switch-DFT achieves higher EE across both low and high spectral efficiency regions, outperforming the baseline.