Performance Analysis of NOMA-Assisted Optical OFDM ISAC Systems with Clipping Distortion

TL;DR

This paper evaluates the performance of NOMA-assisted optical OFDM ISAC systems with clipping distortion, proposing a new transmitter architecture to mitigate distortion effects and analyzing impacts on communication and sensing metrics.

Contribution

It introduces a novel transmitter design that performs clipping before NOMA coding and analyzes its effects on system performance considering power allocation and distortion.

Findings

Allocating more power to the strong user improves sum rate and sensing accuracy.

Balanced power allocation degrades BER and sensing performance.

Simulation confirms the effectiveness of the proposed architecture.

Abstract

This paper studies the performance of optical orthogonal frequency-division multiplexing (OFDM)-based multi-user integrated sensing and communication (ISAC) systems employing non-orthogonal multiple access (NOMA). Due to their inherent high peak-to-average power ratio (PAPR), OFDM waveforms are clipped to fit the limited dynamic range of the optical transmitters (e.g., light-emitting diodes (LEDs)), resulting in clipping distortion. To alleviate the impact of the distortion, we propose a novel transmitter architecture where the clipping processes are performed before NOMA superposition coding. We then analyze the performance of the proposed optical ISAC systems considering the effects of power allocation and clipping distortion. For the communication subsystem, we analyze the effect of NOMA on the achievable sum rate and bit error rate (BER). For the sensing subsystem, the root mean square error (RMSE) and Cram\'er-Rao bound (CRB) of estimating the transmission distance accuracy are obtained. Simulation results reveal that allocating more power to the strong user yields a higher sum rate, lower BER, and better sensing performance, whereas a more balanced power allocation among users results in degraded BER and sensing performance.