Availability, outage, and capacity of spatially correlated, Australasian free-space optical networks

TL;DR

This paper develops a comprehensive framework combining satellite cloud data, probabilistic modeling, and heuristic optimization to assess and enhance the capacity and reliability of free-space optical networks in Australasia.

Contribution

It introduces novel methods for evaluating ground station availability and correlation, and proposes optimization strategies for FSOC network design in the Australasian region.

Findings

Australasian region has 69% average site availability.

Low spatial cloud cover correlations enhance network diversity.

Optimized networks can achieve tens of terabits per day capacity.

Abstract

Network capacity and reliability for free space optical communication (FSOC) is strongly driven by ground station availability, dominated by local cloud cover causing an outage, and how availability relations between stations produce network diversity. We combine remote sensing data and novel methods to provide a generalised framework for assessing and optimising optical ground station networks. This work is guided by an example network of eight Australian and New Zealand optical communication ground stations which would span approximately $60^\circ$ in longitude and $20^\circ$ in latitude. Utilising time-dependent cloud cover data from five satellites, we present a detailed analysis determining the availability and diversity of the network, finding the Australasian region is well-suited for an optical network with a 69% average site availability and low spatial cloud cover correlations. Employing methods from computational neuroscience, we provide a Monte Carlo method for sampling the joint probability distribution of site availabilities for an arbitrarily sized and point-wise correlated network of ground stations. Furthermore, we develop a general heuristic for site selection under availability and correlation optimisations, and combine this with orbital propagation simulations to compare the data capacity between optimised networks and the example network. We show that the example network may be capable of providing tens of terabits per day to a LEO satellite, and up to 99.97% reliability to GEO satellites. We therefore use the Australasian region to demonstrate novel, generalised tools for assessing and optimising FSOC ground station networks, and additionally, the suitability of the region for hosting such a network.