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Hybrid SIC Aided Hybrid NOMA: A New Approach For Improving Energy Efficiency

Yanshi Sun, Wei Cao, Ning Wang, Momiao Zhou, Zhiguo Ding

TL;DR

This work tackles energy efficiency in uplink hybrid NOMA by introducing a simple add-on: HSIC-aided hybrid NOMA built on top of a legacy TDMA network. By allowing opportunistic users to share legacy slots with a controllable power reduction $\beta$, and by dynamically selecting SIC ordering via a threshold $τ_m$, the scheme yields closed-form expressions and high-SNR insights for the probability $\tilde{P}_n$ that HSIC fails to outperform OMA. The analysis shows that HSIC relaxes the conditions needed for energy-efficient superiority relative to FSIC and that $\tilde{P}_n$ decays exponentially with the number of users (rate index $n$) in many regimes, with strong numerical validation. The results demonstrate practical guidelines for HSIC-aided hybrid NOMA design, including the importance of $β$, legacy rate $R_m$, and user pairing, highlighting significant energy-efficiency gains for real-world legacy networks.

Abstract

Hybrid non-orthogonal multiple access (NOMA), which organically combines pure NOMA and conventional OMA, has recently received significant attention to be a promising multiple access framework for future wireless communication networks. However, most of the literatures on hybrid NOMA only consider fixed order of successive interference cancellation (SIC), namely FSIC, for the NOMA transmission phase of hybrid NOMA, resulting in limited performance. Differently, this paper aims to reveal the potential of applying hybrid SIC (HSIC) to improve the energy efficiency of hybrid NOMA. Specifically, a HSIC aided hybrid NOMA scheme is proposed, which can be treated as a simple add-on to the legacy orthogonal multiple access (OMA) based network. The proposed scheme offers some users (termed ``opportunistic users'') to have more chances to transmit by transparently sharing legacy users' time slots. For a fair comparison, a power reducing coefficient $β$ is introduced to ensure that the energy consumption of the proposed scheme is less than conventional OMA. Given $β$, the probability for the event that the achievable rate of the proposed HSIC aided hybrid NOMA scheme cannot outperform its OMA counterpart is obtained in closed-form, by considering impact of user pairing. Furthermore, asymptotic analysis shows that the aforementioned probability can approach zero under some given conditions in the SNR regime, indicating that the energy efficiency of the proposed scheme is almost surely higher than that of OMA for these given conditions. Numerical results are presented to verify the analysis and also demonstrate the benefit of applying HSIC compared to FSIC.

Hybrid SIC Aided Hybrid NOMA: A New Approach For Improving Energy Efficiency

TL;DR

This work tackles energy efficiency in uplink hybrid NOMA by introducing a simple add-on: HSIC-aided hybrid NOMA built on top of a legacy TDMA network. By allowing opportunistic users to share legacy slots with a controllable power reduction , and by dynamically selecting SIC ordering via a threshold , the scheme yields closed-form expressions and high-SNR insights for the probability that HSIC fails to outperform OMA. The analysis shows that HSIC relaxes the conditions needed for energy-efficient superiority relative to FSIC and that decays exponentially with the number of users (rate index ) in many regimes, with strong numerical validation. The results demonstrate practical guidelines for HSIC-aided hybrid NOMA design, including the importance of , legacy rate , and user pairing, highlighting significant energy-efficiency gains for real-world legacy networks.

Abstract

Hybrid non-orthogonal multiple access (NOMA), which organically combines pure NOMA and conventional OMA, has recently received significant attention to be a promising multiple access framework for future wireless communication networks. However, most of the literatures on hybrid NOMA only consider fixed order of successive interference cancellation (SIC), namely FSIC, for the NOMA transmission phase of hybrid NOMA, resulting in limited performance. Differently, this paper aims to reveal the potential of applying hybrid SIC (HSIC) to improve the energy efficiency of hybrid NOMA. Specifically, a HSIC aided hybrid NOMA scheme is proposed, which can be treated as a simple add-on to the legacy orthogonal multiple access (OMA) based network. The proposed scheme offers some users (termed ``opportunistic users'') to have more chances to transmit by transparently sharing legacy users' time slots. For a fair comparison, a power reducing coefficient is introduced to ensure that the energy consumption of the proposed scheme is less than conventional OMA. Given , the probability for the event that the achievable rate of the proposed HSIC aided hybrid NOMA scheme cannot outperform its OMA counterpart is obtained in closed-form, by considering impact of user pairing. Furthermore, asymptotic analysis shows that the aforementioned probability can approach zero under some given conditions in the SNR regime, indicating that the energy efficiency of the proposed scheme is almost surely higher than that of OMA for these given conditions. Numerical results are presented to verify the analysis and also demonstrate the benefit of applying HSIC compared to FSIC.
Paper Structure (16 sections, 8 theorems, 85 equations, 6 figures, 4 tables)

This paper contains 16 sections, 8 theorems, 85 equations, 6 figures, 4 tables.

Table of Contents

  1. Introduction
  2. System model
  3. NOMA transmission in the $m$-th time slot
  4. FSIC Scheme for NOMA transmission
  5. HSIC Scheme for NOMA transmission
  6. OMA transmission in the $n$-th time slot
  7. Performance analysis for HSIC aided hybrid NOMA scheme
  8. Analytical results for $m< n$
  9. Analytical results $m>n$
  10. Numerical Results
  11. Conclusion
  12. Proof for Lemma 1
  13. Proof for Theorem 1 ($m<n$)
  14. Proof for Corollary $1$ ($m<n$)
  15. Proof for Theorem 2 ($m>n$)
  16. ...and 1 more sections

Key Result

Theorem 1

When $m<n$, $\tilde{P}_n$ can be expressed as where the expressions for $P_1$, $P_{2,1}$ and $P_{2,2}$ under the case where $\epsilon_m>\frac{\beta}{1-\beta}$ and the case where $\epsilon_m\le\frac{\beta}{1-\beta}$ are summarized by table I and table II, respectively. In Tables I and II, the expressions for the variables are given as follows: where $c_{mn}\!=\!\frac{M!}{(m-1)!(n-m-1)!(M-n)!}$, $

Figures (6)

  • Figure 1: $\tilde{P}_n$ versus SNR for $m>n$ and $m<n$. $R_m=0.2$ bits per channel use (BPCU), $M=5$, and $\beta=\frac{1}{3}$.
  • Figure 2: $\tilde{P}_n$ with varying $m$ and fixed $n$. $M=5$ and $\beta=\frac{1}{3}$.
  • Figure 3: Comparisons of HSIC and FSIC aided hybrid NOMA schemes in terms of $\tilde{P}_n$ and $\bar{P}_n$. $M=5$, $\beta=\frac{1}{3}$.
  • Figure 4: Comparisons of HSIC and FSIC aided hybrid NOMA schemes in terms of $\tilde{P}_n$ and $\bar{P}_n$. $\frac{\rho_n}{\rho_m}=5$, and $M=5$.
  • Figure 5: $\tilde{P}_n$ versus $\beta$. $R_m=1$, $n=5$, $\frac{\rho_n}{\rho_m}=6$, SNR=$15$ dB.
  • ...and 1 more figures

Theorems & Definitions (12)

  • Theorem 1
  • Corollary 1
  • Remark 1
  • Remark 2
  • Corollary 2
  • Corollary 3
  • Theorem 2
  • Corollary 4
  • Remark 3
  • Remark 4
  • ...and 2 more