Laser Inter-Satellite Link Setup Delay: Quantification, Impact, and Tolerable Value

TL;DR

This paper quantifies the setup delay of laser inter-satellite links, analyzes its impact on satellite network latency, and provides design guidelines for tolerable delay values to enable dynamic LISLs for low-latency communications.

Contribution

It offers the first comprehensive quantification of LISL setup delay, evaluates its impact on satellite network latency, and proposes design guidelines for enabling dynamic LISLs in satellite constellations.

Findings

LISL setup delay is in the order of seconds.

Impact of LISL delay significantly affects end-to-end latency.

Maximum tolerable LISL setup delay is identified for low-latency applications.

Abstract

Dynamic laser inter-satellite links (LISLs) provide the flexibility of connecting a pair of satellites as required (dynamically) while static LISLs need to be active continuously between the energy-constrained satellites. However, due to the LISL establishment time (termed herein as LISL setup delay) being in the order of seconds, realizing dynamic LISLs is currently unfeasible. Towards the realization of dynamic LISLs, we first study the quantification of LISL setup delay; then we calculate the end-to-end latency of a free-space optical satellite network (FSOSN) with the LISL setup delay; subsequently, we analyze the impact of LISL setup delay on the end-to-end latency of the FSOSN. We also provide design guidelines for the laser communication terminal manufacturers in the form of maximum tolerable value of LISL setup delay for which the FSOSN based on Starlink's Phase I satellite constellation will be meaningful to use for low-latency long-distance inter-continental data communications.