Performance Analysis of M-ary Optical Communication over Log-Normal Fading Channels for CubeSat Platforms

Abstract

A CubeSat platform has become a popular choice due to inexpensive commercial off-the-shelf (COTS) components and low launch cost. However, it requires more power-efficient and higher-data rate downlink capability for space applications related to remote sensing. In addition, the platform is limited by the size, weight and power (SWaP) constraints as well as the regulatory issue of licensing the radio frequency (RF) spectrum. The requirements and limitations have put optical communications on promising alternatives to RF communications for a CubeSat platform, owing to the power efficiency and high data rate as well as the license free spectrum. In this study, we analyzed the performance of optical downlink communications compatible with CubeSat platforms in terms of data rate, bit error rate (BER) and outage probability. Mathematical models of BER and outage probability were derived based on not only the log-normal model of atmospheric turbulence but also a transmitter with a finite extinction ratio. Given the fixed slot width, the optimal guard time and modulation orders were chosen to achieve the target data rate. And the two performance metrics, BER and outage data rate, were analyzed and discussed with respect to beam divergence angle, scintillation index and zenith angle.

Evaluation of a Laser Altimeter using the Pseudo-Random Noise Modulation Technique for Apophis Mission

“…Unlike pulsed TOF altimeters, PRN altimeters allow low power CW diode lasers which are commercially available and can increase an average power using a master oscillator fiber amplifier (MOFA). The CW diode lasers with the MOFA architecture has been demonstrated in most CubeSat optical communications owing to the compact and robust architecture and a high peak-to-average-power ratio (Lim et al 2020). Thus, the PRN altimeter can be designed in a fast and cost-effective way with reducing SWaP requirements.…”