IEEE - Aerospace and Electronic Systems - April 2023 - 11

Chaudhry et al.
Figure 4.
First shortest path between New York and Istanbul over the FSOSN at 5016 km LISL. Note that the highest LISL range of 5016 km causes
long LISLs and only three hops on this path. The propagation delay, node delay, and the latency of this path are 30.57, 3, and 33.57 ms,
respectively.
For a specific LISL range, we notice that the longer
the intercontinental distance between cities, the greater
the improvement in average latency. For example, for
New York-London, New York-Istanbul, and New York-
Sydney intercontinental connections, the improvement in
FSOSN's average latency at 5016 km LISL range over
2500 km LISL range is 1.28, 2.14, and 4.77 ms, respectively.
Note that the distance between GSs at New York
and London, New York and Istanbul, and New and Sydney
along the surface of the Earth is 5579, 8076, and
16,005 km, respectively. Ignoring 659.5 km LISL range
due to its unfeasibility and thereby the improvement in
average latency from 659.5 km LISL range to 1319 km
LISL range, the improvement in average network latency
from 2500 km LISL range to 5016 km LISL range in the
three intercontinental connection scenarios is also the biggest
improvement in average latency between any two
consecutive LISL ranges in any scenario.
It is interesting to note from Table 4 that average propagation
delay or dprop is the dominant part ofaverage latency
at all LISL ranges in all three scenarios. The average node
delay or dnode is directly proportional to nhop and is equal to
nhop times node delay per hop/satellite. In this work, we consider
a node delay per satellite of1 ms. For a higher value of
node delay per satellite, dnode can become the dominant factor
in average network latency especially in longer intercontinental
connections at lower LISL ranges where the
average number ofhops tends to be higher.
CONCLUSIONS AND FUTURE CHALLENGES
Figure 5.
Plot of LISL range (km) versus average network latency or dtotal
(ms). The solid blue line with square markers, the solid red line
with circle markers, and the solid black line with diamond markers
correspond to New York-London, New York-Istanbul, and New
York-Sydney intercontinental connections, respectively. Note that
the average network latency decreases with increase in LISL range
in all three intercontinental connection scenarios.
APRIL 2023
We studied the effect of varying the LISL range of satellites
on network latency within an FSOSN in this work.
Six different LISL ranges and three different scenarios for
long-distance intercontinental data communications were
examined to investigate this effect. We observe that the
satellite connectivity and thereby the network connectivity
improves with increase in LISL range. More and farther
satellites are available within the LISL range of a satellite
as the LISL range increases. Longer LISLs with farther
neighbors at higher LISL ranges lead to better shortest
paths with fewer LISLs and hops, lower propagation and
node delays, and lower average network latency.
IEEE A&E SYSTEMS MAGAZINE
11

IEEE - Aerospace and Electronic Systems - April 2023

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