978-1-4244-4657-5/09/$25.00 ©2009 IEEE ICICS 2009
HATS:A Handover Optimized Routing Algorithm for
the Low Earth Orbit (LEO) Satellite Network
Feng Shen, Hongfang Yu, Xiaoning Zhang
Key Lab of Broadband Optical Fiber Transmission and Communication Networks
University of Electronic Science and Technology of China
Chengdu, China
{shenfeng, yuhf, xnzhang}@uestc.edu.cn
Abstract—In this paper, we analyze several issues involved in
developing effective routing schemes for the LEO satellite
network. It is observed that the relative movement of the
satellites in the constellation has a significant impact on the ISL
connectivity. Motivated by this observation, we develop a new
effective algorithm called handover aware topology-slice (HATS)
routing algorithm for LEO the satellite network. The algorithm
focuses on reducing the delay jitter induced by changes of the ISL
connectivity. It is shown that the proposed algorithm results in
providing better performance in terms of the delay jitter when
compared with the previously proposed routing algorithm.
Keywords-routing algorithm; delay jitter; LEO satellite network
I. INTRODUCTION
Recently, the rapid development and globalization of
Internet promote the new telecommunication systems such as
NGN and 4G, which are designed to enhance the multimedia
service and the ability to access into the Internet anywhere.
While the satellite network, which is born to have the
advantage of large geographic coverage, is able to provide the
ubiquitous access service wherever the user terminals are. As a
result, the satellite network plays an important role to extend
the internetwork such as the television broadcast and Internet
connection to the place where cable and terrestrial radio cannot
economically or technically be installed and maintained [1].
Communication over the satellite commences with the
launch of the individual satellite on the Geostationary Earth
Orbit (GEO). In spite of the merit of the stationary to the
terrene and large coverage area, because of the high altitude of
the GEO satellites, it will leads to high propagation delay
which is unsuitable for some applications (especially for the
real-time and multimedia service). Therefore, attention is paid
to the LEO systems that locate at comparatively near to the
user terminals on the earth and require less antenna power. In
these systems, the satellites are connected to each other via the
inter satellite link (ISL). With the help of these ISLs, the
communication among the satellites will be independent with
the terrestrial network. Consequently, we will focus on the
LEO system in this paper.
The LEO satellite constellation consists of the several low
earth orbits satellites, the altitude of which is between 500 and
2000 kilometers, and the velocity of the rotation is about 20000
kilometers per hour. It will cost the satellite less than 2 hours to
cycle round the earth [2]. Because of the particular features of
the LEO satellite network, such as consisting of abundant
satellites, dynamic topology and frequent handover, etc, new
routing approach should be proposed. In this paper, we
introduce the handover aware topology-slice routing algorithm
that is aim to decrease the delay jitter caused by the changes of
the ISL connectivity.
The remainder of the paper is organized as follows: the
section 2 is mainly about the related work of LEO satellite
constellation and its routing scheme. In the section 3, our
system model is introduced. Then in section 4, we describe our
new routing scheme for the LEO satellite network. Section 5
illustrates our simulation platform and the result of the
algorithm performing. Conclusion will be summarized in the
last section 6.
II. B
ACKGROUND INFORMATION AND RELATED WORK
In order to construct a LEO satellite network, the
parameters of the satellite constellation should be confirmed
firstly. A conventional satellite constellation consists of a
number of orbits at certain altitude, a number of satellites per
orbit (also called plane), and possibly ISLs between some
satellite pairs. Through identifying whether the orbits traverse
the polar region, we can divide the LEO system into two
categories: polar constellation and non-polar constellation. The
Delta constellation designed by Walker is more commonly
used non-polar constellation presently [3]. This kind of
constellation is adopting the circle orbit, whose altitude and
obliquity are all equal, ascending nodes uniformly distribute in
the reference plane, satellites are spacing equally in the orbit
and its initial phase is proportional to the ascending angle of
the orbit. Satellites in the constellation are locating relatively
steady. The constellation is designed with good connectivity
without seam and suitable to deploy global coverage. The
typical examples of Delta constellation are the Globalstar and
Celestri system.
In the LEO satellite constellation, there may be the ISLs
between the satellites. Because of the high relatively velocity
and tracking control problem, at most 4 ISLs can be set up
from the present satellite to the adjacent ones in the common
situation. Presently, the ISL is usually implemented by the
space laser that achieves as much bandwidth as the radio way
This work is supported by Doctoral Fund for New Scholar of Ministry of
Education of China under Grant No. 200806141004.