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BER Analysis and Optimization for Continuous RIS-Enabled NOMA

Mahmoud AlaaEldin, Amy S. Inwood, Peter J. Smith, Michail Matthaiou

Abstract

This letter investigates a novel uplink (UL) system that integrates power-domain non-orthogonal multiple access (PD-NOMA) with a continuous reconfigurable intelligent surface (CRIS). We analyze the effective CRIS-assisted channels under spatially correlated fading to accurately approximate the characteristic function of the cascaded channel. This allows the derivation of an expression for the bit error rate (BER), a key performance metric for UL PD-NOMA. We further utilize the derived BER expressions to introduce a joint optimization framework that minimizes the average BER via UL power allocation and dynamic RIS partitioning among the users. The analytical results are validated by simulations, and show that the proposed optimization scheme eliminates the BER floors that are associated with UL NOMA. The results also confirm the superiority of the optimized CRIS-NOMA scheme over conventional orthogonal multiple access (OMA) and non-optimized UL NOMA schemes.

BER Analysis and Optimization for Continuous RIS-Enabled NOMA

Abstract

This letter investigates a novel uplink (UL) system that integrates power-domain non-orthogonal multiple access (PD-NOMA) with a continuous reconfigurable intelligent surface (CRIS). We analyze the effective CRIS-assisted channels under spatially correlated fading to accurately approximate the characteristic function of the cascaded channel. This allows the derivation of an expression for the bit error rate (BER), a key performance metric for UL PD-NOMA. We further utilize the derived BER expressions to introduce a joint optimization framework that minimizes the average BER via UL power allocation and dynamic RIS partitioning among the users. The analytical results are validated by simulations, and show that the proposed optimization scheme eliminates the BER floors that are associated with UL NOMA. The results also confirm the superiority of the optimized CRIS-NOMA scheme over conventional orthogonal multiple access (OMA) and non-optimized UL NOMA schemes.
Paper Structure (8 sections, 1 theorem, 26 equations, 3 figures)

This paper contains 8 sections, 1 theorem, 26 equations, 3 figures.

Table of Contents

  1. Introduction
  2. System Model
  3. Analysis of the RIS effective channels
  4. First moments
  5. Second moments
  6. PA and RIS area splitting-based optimization scheme for CRIS-NOMA
  7. Simulation Results
  8. Conclusions

Key Result

Proposition 1

Assuming isotropic correlation, $\mathbb{E}\left[\gamma_{kk}^2\right] = \Omega(k)$ and $\mathbb{E}\left[|\gamma_{ki}|^2\right] = \Omega(i)$, with $\Omega(x)$ given in eq:Omegax and with $r_k{=}\sqrt{\!(\!x_k\!{-}x_k')^2{+}(y_k\!{-}y_k')^2\!}$ and $r_{\!i}{=}\sqrt{\!(\!x_i{-}x_i')^2{+}(y_i{-}y_i')^2\!}$.

Figures (3)

  • Figure 1: A CRIS-enabled UL NOMA system.
  • Figure 2: for two-user systems: (a) $U_1$, (b) $U_2$.
  • Figure 3: for three-user systems: (a) $U_1$, (b) $U_2$, (c) $U_3$.

Theorems & Definitions (2)

  • Proposition 1
  • proof