Australia will be introducing a dedicated Mobile Satellite Communications System following the launch of the AUSSAT-B satellites late in 1991. The Mobile Satellite System, MOBILESAT, will provide circuit switched voice/data services and packet-switched data services for land, aeronautical and maritime users. Here, an overview is given of the development program being undertaken within Australia to enable a fully commercial service to be introduced in 1992

Wagg, Michael

English

NASA Technical Reports Server

N92-24072
MOBILESAT, Australia's Own
Michael Wagg
MOBILE COMMUNICATIONS BUSINESS
AUSSAT PTY LTD
GPO Box 1512
Sydney Australia
Ph: 61-2-238 7800
Fax: 61-2-238 7803
ABSTRACT/INTRODUCTION MARKET
Australia will be introducing a dedicated
Mobile Satellite Communications System
following the launch of the AUSSAT-B satellites
in late 1991. The Mobile Satellite System,
MOBILESAT, will provide circuit switched
voice/data services and packet-switched data
services for land, aeronautical and maritime
users. This paper overviews the development
program being undertaken within Australia to
enable a fully commercial service to be
introduced in 1992.
SYSTEM
The two AUSSAT-B satellites are HS-601
spacecraft being built by Hughes and due for
launch on the Chinese Long March rockets. The
primary purpose of the AUSSAT-B satellites is to
provide replacement Ku-Band capacity for the
current AUSSAT-A satellites with the major
secondary function of providing L-Band capacity
for mobile services. Each satellite will have a
single 14 MHz L-Band transponder with
associated Ku-Band back-haul providing 48 dBW
of usable EIRP into a single beam covering the
whole of Australia and its surrounding waters.
The ground infrastructure will consist of a
network management system, to be provided in a
redundant configuration from two locations,
gateway stations to provide access to the public
switched network and base stations for
connection to private networks as well as the
customer mobile terminals. Figure 1
schematically represents the system.
The market for MOBILESAT services within
Australia is targetted primarily at servicing the
rural and remote areas of the country in a
complementary nature to urban services such as
cellular telephony and UHF/VHF private mobile
radio systems. Australia is a vast country
(- 7.6 million square kilometres) with a small
population (16 million) which is concentrated in
less than ten major urban areas centres. Despite
the population concentration in the urban areas
the Australian export economy revolves around
industries such as agriculture (sheep/wool,
cattle/beef, wheat, etc), mining (coal, iron ore,
etc) and tourism which, in general, are located in
the remote regions of the country where the
telecommunications infrastructure (both fixed
and mobile) is quite often rudimentary or in some
cases non-existent.
The urban population has rapidly adopted the
mobile services provided by the cellular mobile
telephone system with currently an 8% growth
rate per month. The services was introduced in
1987 with, as of March 1990, over 10 users per
thousand population, representing one of the
most rapid take-ups of the technology throughout
the world. The system is targetted at covering
around 80% of the population during the next few
years (currently 70% coverage) but this only
represents around 1% coverage of the area of the
country.
Market surveys have found that users in the
rural and remote regions of the country also
desire and have a need (it could be argued that the
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need is greater than that of their urban cousins)
for a quality mobile communications service with
features equivalent to that available to urban
dwellers. As well as showing a definite
requirement for a satellite based mobile
communications system, the market surveys
identified a variation with the potential markets in
the US and Europe where the long distance
transport market dominated the user population.
The trucking user does not dominate the
Australian market but rather a range of service
industries requiring a mix of public access and
private network telephony applications
dominated the usage requirements. Figure 2
shows the predicted mobile voice terminal market
whilst table 1 summarises the usage breakdown.
Sector Percentage
Sales
Trades
Agriculture
Construction
Pastoral
Road Transport
Mining
Others
19.7%
18.1%
13.0%
9.8%
8.2%
7.2%
6.2%
17.8%
Table 1
MOBILESAT Telephony Market
Segmentation
The market within Australia has indicated a
need for data only services but significantly at a
terminal price around 50 - 60% of a voice
terminal. As well a strong desire for a combined
voice and packet-data capability led to the
development of packet-data services using the
voice signalling channels.
MARKET EXPECTATIONS
The market expectations for equipment pricing
and service charges have generally been of
pricing which is a little greater than that available
from the urban cellular telephone system. This is
due, in the main, to the perceived high
technology nature of the service and, more
importantly, to the added functionality, in
particular the ubiquitous coverage capability of a
satellite system. The expectations for a service to
be introduced in 1992 are as follows:
Mobile Telephony Terminal
A$5000 (US$3750)
Mobile Radio Terminal
A$5000 (US$3750)
Mobile Data Terminal
A$2500 (US$1875)
Voice, Per minute air-time charge
+ Monthly Access Fee
A$1.20 (US$0.90) + AS0.0 to A$0.80 (US$0.60)
+ A$50 (US$37.50)
Data, Monthly Fee
A$30 - A$50 (US$22.50 - US$37.50)
These figures compare to ~A$1000 for a car
mounted cellular telephone, ~A$3000 for a
hand-held cellular telephone, -A$3000 for a HF
radio and A$35 per month plus A$0.70 per
minute for long distance cellular charges in
Australia.
The current knowledge of the system costs and
perceived terminal prices suggests that the
terminal prices should be achievable if not a little
bit high at the commencement of service. As
well, the usage charges, owing to the efficiencies
of the digital voice implementation, are readily
achievable and offer scope to be competitive with
long distance cellular services.
TECHNICAL FEATURES
The MOBILESAT system developed for
Australia shares many of the features of the
systems being developed elsewhere as well as
those of terrestrial mobile communication
systems. However a number of key technical
features have been adopted to address the market
requirements and to utilise the full potential of
the available technology.
A common signalling channel architecture has
been adopted to accommodate developments in
modulation and processing technologies and
allow for a variety of communication standards.
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International Mobile Satellite Conference, Ottawa, 1990
Indeed the fast release of the system specification
has adopted both analog ACSSB and digital
voice modulation as schemes being permitted to
operate over MOBILESAT. Further, the features
and the reserve capacity of the signalling system
have been used to implement a packet-data
communications service operating in conjunction
with the circuit-switched voice service. This
feature will provide for services such as position
location in association with a voice service and
will allow for a range of enhanced capabilities to
be added to the voice services. This capability
will also allow low cost stand alone packet-data
terminals to provide for messaging and telemetry
style applications.
The channel plan is based on 2.5 kHz channel
spacing in a non-paired channel format, and will
initially support up to 1,500 circuits using digital
voice modulation with 5 kHz channels, at a
threshold C/No of less than 45 dBHz. An
additional 3 dB fade margin will be used to
provide a high quality, robust voice service that
will operate under severely shadowed satellite
links.
The MOBILESAT system has adopted a three
try (two repeat) strategy in the call initialisation
procedure to accommodate for potential
shadowing in the communications link. The
three try strategy has been demonstrated to be the
optimum scheme to provide a highly reliable
signalling channel in the propagation
environment of the mobile satellite service.
The voice modulation will be based on a
nominal 4800 bps encoding algorithm. At the
time of writing (March 1990), Australia's
TELECOM Research Laboratories were
undertaking an evaluation program, for
Australia's MOBILESAT system and for
INMARSAT's-M system, to determine the most
approporiate digital encoding algorithm. The
joint MOBILESAT/INMARSAT evaluation is
aimed at achieving a common standard.
The MOBILESAT system will support a
digital facsimile service based on the
INMARSAT-M specifications, but operating at
up to 4.8 kbps and incorporating an ARQ
protocol to ensure error free transmission. The
system design allows for an easy transition to a
Store and Forward facsimile service in the future.
The public access gateway stations will
directly interconnect with the ISDN network and
provide an advanced, high capacity link into the
PSTN, whilst low capacity minor base stations
will support customised private networks.
IMPLEMENTATION
The MOBILESAT program is focussed on
providing services using the AUSSAT-B
satellites from mid 1992. However, the user
community has an immediate need for the
services that a mobile satellite system can offer
so a parallel program is underway to provide an
early entry MOBILESAT service. The close
parallels with the Canadians with their MDS and
the US with AMSC, Qualcomm and GEOSTAR
where services are being implemented prior to a
dedicated mobile satellite system, has been
recognised. The early entry MOBILESAT
service uses an unmodified INMARSAT-C
product and will operate via the hub station
provided in Perth, Australia by OTC Ltd,
Australia's international common carrier and
INMARSAT signatory.
The target market sectors for the early entry
product are the remote monitoring and control
industry, long distance transport and the remote
services sector. The following applications are
being implemented:
interface of the INMARSAT-C system into
a water resource management system
through development of an interface box
between the INMARSAT-C terminal and
remote monitoring and control devices and
modification of head office control software.
monitoring of valuable cargos using
INMARSAT-C interfaced to a position
location device (TRANSIT or GPS) in the
long distance transport and security
industries.
use of INMARSAT-C to provide the
communications link from a lap-top PC to a
head-office computer for applications such
International Mobile Satellite Conference. Ottawa, 1990
5
as records access for remote area medical
clinics provided by Australia's Royal Flying
Doctor Service.
The program for implementation of the
AUSSAT-B MOBILESAT service, at the time of
writing, is at the stage of evaluation of the ground
infrastructure components of the MOBILESAT
system. Formal responses have been received for
all components of the ground system, (Network
Management System, Gateway/Base Access
Stations and Mobile Terminals). The schedule
for the implementation program is; contracts for
infrastructure in mid 1990 with a service
introduction by June 1992.
As a large proportion of the MOBILESAT
market will be using a public-switched service, a
close technical relationship has developed
between AUSSAT, Australia's national satellite
service provider and TELECOM Australia,
Australia's monopoly PSTN and cellular service
provider (as of April 1990). The interface issues
between the terrestrial system and the mobile
satellite system have been resolved and a
mechanism for providing the ground
infrastructure has been developed which allows
for co-operation between the organisations in the
technical areas and competition in the provision
of services.
AUSTRALIAN INDUSTRY
The Australian decision to provide a Mobile
Satellite Service was relatively late when
compared to the deliberations and research and
development undertaken in various parts of the
world. However various sectors of industry
throughout Australia have learnt from the
international developments and will be in a
position to provide the ground infrastructure for
the MOBILESAT system (largely software
control) as well as compete in the provision of
MOBILESAT terminals, both within Australia
and worldwide. Indeed, the timing of the
MOBILESAT system being some twelve to
eighteen months in advance of the dedicated
North American systems has been recognised as
an opportunity by both the Australian and
international industry to utilise Australia as a
test bed for a range of technical and service
developments.
CONCLUSIONS
Mobile communications represents one of the
fastest growing areas of the telecommunications
industry within Australia. The MOBILESAT
system is a vital component within the mobile
telecommunications product range providing
services to the economically important rural and
remote areas of Australia. The activities within
the MOBILESAT program are at the forefront of
service developments throughout the world,
tailored to the Australian market, but also with an
eye to developments and opportunities
throughout the world.
The MOBILESAT development team
recognises that satellites will play an important
role in the development and provision of
ubiquitous mobile and personal communications
services and that the MOBILESAT program is
but one step in the evolution towards the now
'not-so-futuristic' "Dick Tracy" or "Star Trek"
communicators.
6
international Mobile Satellite Conference, Ottawa, 1990
Mobile Fixed Private
Closed User Base Station
Groups
Figure 1
MOBILESAT Configuration
I1,,.,
E
0
,,e,.i
0
60,000
50,000
40,000
30,000
20,000
10,000
B
II
0
1991/92 1992/93 1993/94 1994/95 1995/96 1996/97 1997/98 1998/99 1999/00
Private
Networks
Public
Networks
Figure 2
MOBILESAT Voice Terminal Market
International Mobile Satellite Conference, Ottawa, 1990
7


MOBILESAT: Australia's own

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