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Sleep or Transmit: Dual-Mode Energy-Efficient Design for NOMA-Enabled Backscatter Networks

Hajar El Hassani, Mikael Gidlund

TL;DR

This work addresses energy-efficient uplink Backscatter communication in a bistatic, NOMA-enabled IoT setting by jointly optimizing RF-source power, sleep/active time, and reflection coefficients. A Dinkelbach-based alternating-optimization algorithm with closed-form updates is developed, revealing two operating modes: HoT, where constant activity is possible with ample power, and HtT, requiring a sleep phase to harvest sufficient energy. The approach yields substantial EE gains over fixed-power and no-sleep baselines, and significant advantages over OMA across low to moderate power regimes, highlighting adaptive mode selection as key for scalable battery-free IoT deployments. The framework combines energy harvesting dynamics, SIC-based decoding, and fractional programming to deliver a practical, scalable solution for large-scale BackCom networks.

Abstract

The rapid growth of Internet-of-Things (IoT) devices demands communication systems that are both spectrally efficient and energy frugal. Backscatter communication (BackCom) is an attractive low-power paradigm, but its spectral efficiency declines in dense deployments. This paper presents an uplink BackCom design that integrates non-orthogonal multiple access (NOMA) and maximizes system energy efficiency (EE). In a bistatic network where multiple backscatter nodes (BNs) harvest RF energy and alternate between sleep and active modes, we formulate a fractional program with coupled time, power, and reflection variables and develop a Dinkelbach-based alternating optimization (AO) algorithm with closed-form updates. Analysis reveals two operating modes depending on power availability, circuit demands and propagation conditions. Simulations show the proposed design adapts the time allocation, achieving up to 8% higher EE than fixed-power and 68% than no-sleep baselines, and delivering up to 127% EE gains over orthogonal multiple access (OMA). These results establish NOMA-enabled BackCom as a scalable, energy efficient solution for large-scale IoT deployments.

Sleep or Transmit: Dual-Mode Energy-Efficient Design for NOMA-Enabled Backscatter Networks

TL;DR

This work addresses energy-efficient uplink Backscatter communication in a bistatic, NOMA-enabled IoT setting by jointly optimizing RF-source power, sleep/active time, and reflection coefficients. A Dinkelbach-based alternating-optimization algorithm with closed-form updates is developed, revealing two operating modes: HoT, where constant activity is possible with ample power, and HtT, requiring a sleep phase to harvest sufficient energy. The approach yields substantial EE gains over fixed-power and no-sleep baselines, and significant advantages over OMA across low to moderate power regimes, highlighting adaptive mode selection as key for scalable battery-free IoT deployments. The framework combines energy harvesting dynamics, SIC-based decoding, and fractional programming to deliver a practical, scalable solution for large-scale BackCom networks.

Abstract

The rapid growth of Internet-of-Things (IoT) devices demands communication systems that are both spectrally efficient and energy frugal. Backscatter communication (BackCom) is an attractive low-power paradigm, but its spectral efficiency declines in dense deployments. This paper presents an uplink BackCom design that integrates non-orthogonal multiple access (NOMA) and maximizes system energy efficiency (EE). In a bistatic network where multiple backscatter nodes (BNs) harvest RF energy and alternate between sleep and active modes, we formulate a fractional program with coupled time, power, and reflection variables and develop a Dinkelbach-based alternating optimization (AO) algorithm with closed-form updates. Analysis reveals two operating modes depending on power availability, circuit demands and propagation conditions. Simulations show the proposed design adapts the time allocation, achieving up to 8% higher EE than fixed-power and 68% than no-sleep baselines, and delivering up to 127% EE gains over orthogonal multiple access (OMA). These results establish NOMA-enabled BackCom as a scalable, energy efficient solution for large-scale IoT deployments.
Paper Structure (10 sections, 19 equations, 3 figures, 1 table, 1 algorithm)

This paper contains 10 sections, 19 equations, 3 figures, 1 table, 1 algorithm.

Table of Contents

  1. Introduction
  2. System model
  3. Energy-efficient resource allocation
  4. Problem formulation
  5. Dinkelbach-based AO approach
  6. Reflection coefficients optimization
  7. Joint time allocation and power optimization
  8. Convergence and complexity analysis
  9. Simulation results
  10. Conclusions

Figures (3)

  • Figure 1: Uplink bistatic BackCom system with NOMA multiplexing
  • Figure 2: Performance evaluation: (a) EE vs. RF source power for different numbers of BNs; (b) Time allocation vs. RF source power for different numbers of BNs; (c) Time allocation vs. path loss exponent for different numbers of BNs; (d) EE comparison between NOMA and OMA schemes.
  • Figure 3: Performance evaluation: (a) EE vs. BN circuit power for different numbers of BNs; (b) Time allocation vs. BN circuit power for different numbers of BNs; (c) EE comparison with different NOMA baselines.