Download ASMS(02)

TECHNOLOGY TRENDS AND MAKET DRIVERS FOR
BROADBAND MOBILE VIA SATELLITE:
INMARSAT BGAN
Antonio Franchi, Jay Sengupta
Inmarsat, 99 City Road, London, EC1Y 1AX, United Kingdom
Email: [email protected]
1. Abstract
Inmarsat’s Broadband Global Area Network (BGAN) system is scheduled to enter service in 2004. The network
infrastructure will consist of a constellation of new geostationary satellites (I4 satellites) and an optimised ground
network which will interconnect with a variety of terrestrial networks at local ‘points of presence’. The system will
employ bandwidth efficient modulation and coding techniques, capable of supporting variable bit-rate services and
quality of service depending on the needs of the application.
A range of terminals will be supported, ranging from small personal devices linking up with handheld and notebook
PCs, aeronautical and maritime vehicular installations linking up with on-board entertainment and communications
systems, to remote base stations linking up with local area networks. Depending on the terminal type, user data rates up
to 432 kbit/s will be supported.
The BGAN system is positioned as the satellite component of IMT-2000 (specifically the UMTS standard). The system
will provide a near-global coverage overlay for the terrestrial networks, giving users service availability beyond the
reach of terrestrial IMT-2000 networks.
2. Background
Inmarsat currently operates a global satellite system comprised of its second and third generation satellites. The
current system supports voice and data communications to more than 200,000 mobile user terminals serving
maritime, aeronautical and land mobile market segments. With the recent launch of the GAN (Global Area
Network) system, ISDN and IP services are accessible at data rates up to 64 kbit/s.
Inmarsat is now developing the BGAN (Broadband Global Area Network) system, aimed at delivering multimedia services to personal, mobile and portable terminal users. The BGAN system will be compatible with
terrestrial 3rd Generation UMTS/IMT-2000 services, enabling users equipped with BGAN terminals to access
these services over the near-global coverage provided by the BGAN system.
The paper deals with the major aspects of the BGAN system, namely:



The technology: the key features of the satellite technology for the latest I4 satellites are presented, as well as
network architecture and convergence with terrestrial 3G mobile infrastructure. The section also introduces the
optimised user terminal technology utilised for the new product family planned for BGAN;
The services: a full range of broadband multimedia services is planned. The service offering and its fit with user
needs emerging from the latest market researches is presented, along with the satellite coverage areas and the
phasing strategy for the introduction of BGAN services;
The Markets: the BGAN system will be compared with alternative terrestrial networks and other planned satellite
systems, resulting in a clear market positioning for the BGAN system.
3. The Technology
The new technology being implemented for the BGAN system comprises the new ‘Inmarsat-4’ space segment
plus new ground infrastructure to provide the terrestrial network interconnect. These elements are described in
the following sections.
3.1
New Powerful Satellites
The new, more powerful Inmarsat-4 satellites will enable Inmarsat to develop smaller user terminals (UT’s) with
higher data rates than currently available via the Inmarsat system. In addition, it will be possible to develop
further enhancements to Inmarsat’s current range of services.
The Inmarsat-4 satellites will use the geostationary orbit, which simplifies the network control and operations,
enables the use of simpler user terminal technology for high speed data communications, and avoids the risk of
data loss during satellite-to-satellite handovers that are necessary for non-geo constellations. The satellites will
use the L-band spectrum for the mobile link services to ensure backward compatibility with currently
operational Inmarsat systems.
Each satellite coverage area will be serviced by two types of spot beams:
 around 200 narrow spot beams will be provided covering a significant area of continental land
masses within the satellite field of view. These narrow spot beams will allow the new BGAN
multimedia services to be accessed via new BGAN UT’s at user data rates up to 432 kbps.
 19 wide spot beams will also be provided giving coverage over the entire satellite field of view for
existing Inmarsat services. These spot beams have higher performance than currently provided on
the Inmarsat-3 satellites, enabling higher data rates to be delivered to evolved version of the current
range of user terminals.
The I-4 satellites are being built by the European aerospace company Astrium. Three complete satellites are
being procured; at present, two of these are planned to be deployed at Inmarsat’s existing IOR (65 0 East
longitude) and AOR-West (540 West longitude) orbit locations, with the third being developed as a ground spare.
The satellites will incorporate a feeder link using C-band spectrum to ensure compatibility with existing
Inmarsat ground infrastructure. The satellite transponders will provide exceptional flexibility as well as
increased RF power, enabling spot beam coverage and channelisation to be reconfigured in-orbit. The satellite
payload is also highly efficient in terms of spectrum utilisation, achieving more than 20 times frequency reuse at
L-Band.
The communications payload requires a powerful satellite platform capable of providing the required DC power
(10 to 12 KW) and other resources. The new Astrium Eurostar 3000 platform is planned to be used, which is a
development of the Eurostar 1000 and 2000 series platforms used for many spacecraft missions. The resulting
spacecraft will have an overall launch mass which allows the spacecraft to be compatible with a range of current
and planned launch vehicles.
In addition to the Forward (C to L band ) and Return (L to C band) transponders, the Inmarsat-4 satellites also
incorporate transponders for Mobile to Mobile links, C to C links and also a Navigation transponder providing
positioning information compatible with the GPS Navigation satellite system.
Inmarsat-2
No. of satellites
Coverage
Mobile link EIRP
Channelisation
Satellite dry mass
Solar array span
Inmarsat-3
Inmarsat-4
4
4 + 1 spare
3 (inc. 1 spare)
Global beam
7 wide spots
+ global beam
200 narrow spots + 19
wide spots +global beam
39dBW
49dBW
67dBW
4 channels
between 4.5 &
7.3MHz bandwidth
46 channels
between 0.9 &
2.2MHz bandwidth
630 channels at
200KHz
700kg
1000kg
3000kg
14.5
20.7m
48.0 m
Table 1: Comparison of Inmarsat satellites main parameters
Figure 1: The Inmarsat-4 Satellite
3.2 Advanced Multimedia Network
Inmarsat’s existing voice and low speed data services will continue to be offered via the current ground network
comprising Land Earth Stations (LESs) and service providers. The new ground network infrastructure will be
optimised to deliver, utilising the existing ground facilities as appropriate, the new multimedia data services
efficiently. Two new satellite access stations (SASs) are planned to be developed for each new satellite coverage
region to enable interconnect to the terrestrial networks and to provide redundancy backup in case of failure of
either SAS.
A major driver in the determination of the network architecture and technology is Inmarsat’s strategy of
alignment of BGAN with terrestrial 3G mobile networks. There are obvious benefits in such compatibility, such
as lower development and production costs for user terminal and ground network infrastructure, as well as
service commonality and roaming with 3G terrestrial networks. The BGAN service is positioned as the satellite
component of UMTS, providing the global area coverage overlay to terrestrial UMTS networks. As a result,
users would be able to roam between terrestrial and satellite networks using a common subscription and service
provision relationship.
A schematic of the AMN is given in Figure 2. The four SAS’s (two per satellite region) are interconnected by a
Data Communication Network (DCN). The DCN will be procured as a managed bandwidth service from global
network operators. The BGAN network interconnects with terrestrial networks at several Point of Presence
(PoPs). With the majority of the intelligence concentrated at the SAS, the PoP is intended to be merely a
switching and multiplexing node implemented to the appropriate interconnect specification. The Business
Support System (BSS) is a modular system comprising a wholesale billing system, along with customer
activation, customer care, fraud management modules and other functions. The BSS is fully integrated with the
AMN, in order to provide a superior service, while also allowing Service Providers to differentiate their retail
service offering as desired.
Inmarsat from the Network Operation Centre (NOC) exercises the overall network control and management,
while the satellites will be controlled from the Satellite Control Centre (SCC). These two systems require a
sophisticated integration, especially due to the need to dynamically reconfigure and allocate channel resources to
the spot beams as a function of network traffic and geographic traffic distribution.
The SAS itself can logically be divided in two parts: the Radio Switching Subsystem (RSS) and the Network
Switching Subsystem (NSS). The RSS maps into the UMTS RAN (Radio Access Network), since it implements
the necessary air interface for reliable communications over the satellite, as well as the radio frequency
components of the station. Advanced modulation and coding schemes are employed in order to achieve high
spectrum efficiency, while at the same time implementing an effective power efficient scheme. Turbo coding FEC
and 16 QAM modulation scheme have been adopted, building on the experience gained with the GAN system.
The NSS part of the SAS is essentially driven by terrestrial mobile technologies. This is analogous to the UMTS
CN (Core Network) part of the network, where off-the-shelf UMTS switching nodes can be integrated into the
network.
A careful selection of open standard interfaces provides a completely modular network approach, as well as the
intrinsic ability to upgrade the network in line with ongoing developments in mobile communications systems.
INM-4 F1
INM-4 F2
Network
Management
Satellite
Region 1
Satellite
Region 2
Inter-site
VPN
SAS
SAS
SAS
SAS
Service
Provider
PoP
PSTN
Internet
Access link
GPRS/
UMTS
Figure 2: Advanced Multimedia Network
3.3 User Terminal Product Portfolio
Inmarsat mobile product portfolio can effectively be classified into three main classes:
1. Existing products for Maritime, Aero and Land Mobile markets: these products will continue to be
supported over the I-4 global and wide spot beams, as well as over the I-3 satellites;
2. Evolved products for maritime, Aero and Land Mobile markets: dual mode terminals will be developed,
supporting enhanced services within I-4 coverage, as well as existing services within I-3 coverage, thus
providing full global coverage for these services; both Existing and Evolved services will be offered via the
current network of LESs;
3. New BGAN products, which would be capable of operation only over I-4 narrow spot beams covering
land, major aero and coastal maritime routes. Figure 3 and 4 show the two currently planned versions of
the BGAN units: the notebook (A4 size) and the pocket (A5 size). These units will effectively represent
plug and play satellite modems typically for PC laptops or PDA (Personal Digital Assistant) with the need
of satellite communications. Table 2 shows the main terminal characteristics. The BGAN user terminals
will be compatible with standard IT/PC communications software, and also have integrated position
determination capability using the GPS system. Their alignment with global mobile telecommunications
industry allows roaming to/from terrestrial data networks by means of a standard USIM card.
Figure 4: Pocket Terminal Concept
BG
Figure 3: Notebook Terminal Concept
Characteristics
Size & Dimensions
Mass (incl batteries)
Operating Time
Interfaces
Location Determination
Data Transmission Rate
BGAN Notebook
~ A4 (21x30x3cm)
~ 1.0 kg
1 hr transmit, 36 hr standby
USB, Bluetooth, WLAN
GPS receiver
144(U)/432(D) kbit/s
BGAN Pocket
~ A5 (15x21x3 cm)
~ 0.75 kg
1 hr transmit, 36 hr standby
USB, Bluetooth, RS-232
GPS receiver
64(U)/216(D) kbit/s
Table 2: BGAN User Terminals
4. The Services
The user will probably already be equipped with a commodity general-purpose PC, most
probably a laptop computer. In order to make use of the BGAN services he will obtain a
subscription, a smart (SIM) card, and a BGAN communications unit (CU) which would allow his
existing PC to send and receive data directly via satellite.
4.1
Bearer Services
Fundamentally, the BGAN system offers a variable bandwidth service on a per session basis to
the BGAN CU. The variable bandwidth session has 2 basic attributes as described below :
 Committed Information Rate (CIR), which is the guaranteed minimum data rate
which is committed for the duration of the session;
 Maximum Information Rate (MIR), which is potential maximum data rate which
could be made available to the session, on the basis of available spare capacity.
For each individual session, a particular CIR and MIR value would be negotiated between the
BGAN CU and the SAS, based on the QOS requirements of the PC user application. The system
can support multiple simultaneous communications sessions to a given BGAN CU.
The variable bandwidth protocols are thus capable of supporting both circuit-mode (constant bit
rate) and packet-mode (variable bit rate) type services, multiplexed over common bearer
channels. Hence, a single channel BGAN CU is able to support multiple simultaneous calls, both
CBR and VBR. This is a key feature of the BGAN system.
4.2
Communications Services
The CU interfaces to the PC and appears to the computer as a multi-function device providing a
range of communication devices. All these ‘devices’ are actually implemented upon an underlying
variable-bandwidth transport service. It is intended to provide some or all of the following
communications services for use by PC applications:
 data modem
 fax modem
 voice modem
 ISDN modem
Support for these communications services will be achieved by extending the corresponding
terrestrial network service, over the air interface to the PC in a manner transparent to the PC
operating system and application software. The BGAN communication services will be presented
to the PC as a set of virtual communication devices that are indistinguishable from their real
counterparts, although in some cases the performance characteristics may differ. Thus the BGAN
system is able to support a range of different networking protocols and serve numerous
communications applications, with no additional development for the PC user.
The networking protocols and applications available as part of the MS Windows product or from
third-party software vendors will work with the BGAN virtual devices just as they do with real
devices of the same class. Consequently, it is expected that any commodity PC communications
application will function over the relevant BGAN communications service exactly as it does when
connected directly to the terrestrial service.
Example applications intended to be used in conjunction with one or more of the BGAN
communications services are:
 Internet/Intranet applications (email, FTP, Web browsing, etc.)
 Telefax
 Voice telephony including voice mail
 Dial-up access to on-line services
 Video conferencing
4.3 Service Deployment and Phasing Strategy
The two I-4 satellites will be located at 65E (IOR) and 54W (AORW). The satellite coverage
areas are shaded in Figure 5. The other two contours represent the coverage of two of the I-3
satellites. Global coverage would be provided by the combination of the I-4 and I-3 satellites. The
I-4 satellites are expected to be launched by end 2003 and be in operation in 2004. The third I-4
satellite is a ground spare, which may be launched either to replace a previous launch failure or
to extend the coverage area to global, based on business and operational considerations.
Before the launch of the the I-4s, Inmarsat is currently planning to launch BGAN services by end 2002,
operating over leased satellite capacity from regional satellite operators. The sevice is currently
denominated BGAN-R, which stands for BGAN-Regional. The type of terminals will be similar to the
BGAN terminals, but the offered data rates will be limited to 144 kbit/s and the coverage area restricted
to Europe, North Africa and Asia.
Inmarsat BGAN-R is made up of five main elements located at three sites:
1. Inmarsat NOC, developed by Inmarsat, in London
2. Business Support System (BSS) in London
3. Satellite Access Station (SAS), located at Fucino, Italy
4. Modifications to the regional satellite operator AOC
5.
Data Communication Network (DCN), interconnecting the various elements of the system.
Although the upper layers of the air interface are virtually unchanged from the GPRS standard, several
modifications are implemented for the lower layers, namely RLC/MAC, to optimise its use for satellite.
AORW AORE
IOR
POR
Figure 5: I-3 and I-4 Combined Coverage.
5. The Satellite Broadband Multimedia Market
5.1 Competitor Analysis and BGAN positioning
The trend toward wider bandwidths to support multimedia applications over mobile networks is
evident in the growing number of personal computer (PC) users both in the household and in the
business sector as well as in the growth in use PC modem cards.
The market is moving to networks that can offer high levels of mobility, functionality, and
reliability at a price capable of sustaining a mass market. This trend has resulted in an increase
in the number of players in the mobile satellite communications business, all trying to get their
share of the market.
Existing and future players in the mobile multimedia market can be classified as follows:
1.
2.
3.
4.
5.
Global Handheld LEO/MEOs (narrowband): narrowband systems for global voice and
low speed data services.
Regional Handhelds (narrowband): narrowband similar to those of the Global
Handhelds but on a regional basis.
Ka-band Regional/Global LEO/MEO/GEOs (Broadband): These systems will supply fixed
(at least initially), broadband multimedia services to mass markets.
C-band and Ku-band non global systems (VSATs and USATs). Lareger size terminals (60
cm to 2.4 m) used mostly for communications between fixed sites and areas lacking
terrestrial communications infrastructure.
GSM and third generation mobile UMTS.
Figure 6 shows the positioning of the various classes in a diagram where the axis are mobility and
data rate. It appears that the traditional areas covered by Inmarsat, typically the mobile, low
rate, is targeted by the satellite hand-held systems, while terrestrial UMTS is going to cover the
higher rates for mobile users (where there is terrestrial coverage).
data rate
3. Ka-band
broadband
HIGH
5.
5.
UMTS
4. VSAT
Inmarsat
GPRS
GSM
LOW
1.2. handhelds
FIXED
MOBILE
Mobility
Figure 6: Competitive Positioning
From the above analysis, it appears that no other systems are pursuing directly comparable
offering to the BGAN service. Hand-held satellite systems are initially targeting the provision of
voice and lower data speeds; broadband and VSAT systems provide high speed data capability
but offer very restricted mobility and portability; planned 2G/3G terrestrial mobile systems
provide high mobility and data capability but will have very limited coverage. The BGAN
service, on the other hand, will offer high speed data, mobility and coverage of key land mass
areas.
Inmarsat extensive market research as well as Inmarsat accurate knowledge of the mobile
market, have led to identify the BGAN primary users as corporate users, characterised by:
 the requirements for portable multimedia services (data transfer, video conferencing, voice,
etc.);
 the requirements for medium to high data rates (up to 432 kbit/s);
 the need for connectivity to standard PC devices (laptop, palmtop computers, PDA devices,
etc.);
 the requirements fo communications whilst roaming outside of coverage of terrestrial
alternatives such as 2G (GPRS), 3G (UMTS) terrestrial mobile networks.
5.2 Critical Success Factors
From the analysis carried out so far, a series of technology trends and commercial drivers have
emerged, which underpin the BGAN service strategy and success. Let’s summarise them in this
section, since they effectively represent critical success factors for BGAN:
1.
Convergence-Integration.
The convergence of four disciplines is critical to the success of future broadband mobile
satellite systems. Such disciplines are terrestrial cellular systems, satellite systems, PC
technologies and IP Internet technologies. The BGAN network infrastructure and mobile
terminal architecture fully exploits this convergence, resulting in optimised, cost effective
terminals.
2.
3.
4.
Data Rate .
Market research shows an increase demand for higher data rates. BGAN-R gives offers a
clear answer, achieving much higher rates with respect to the current systems. This can be
achieved thanks to a combination of more powerful satellites, together with the utilisation of
new spectrum efficient and power efficient coding and modulation schemes.
Terminal Price and Air-time Tariff.
Price elasticity analysis shows that terminal price is a critical factor to the success of the
system. BGAN has been designed with the clear objective of drastically reducing terminal
price. This has been achieved in a number of ways:
- recurring engineering cost are naturally decreasing, due to cheaper availability of
components and its miniaturisation;
- volumes of terminals drives their price dows;
- convergence with IP and PC technology allows to utilise ready available of the shelf
components;
- adoption of terrestrial standards (re-use of protocol stacks), further reduce non recurring
engineering costs.
User terminal appealing and user-friendliness.
A number of factors have been considered, in order to build terminals that are attractive,
while at the same tme, very easy to use, even for the non expert or occasional user. Factors
considered are: size of terminals, appealing industrial design, seamless use (e.g. support of
commonly used applications, already familiar to the user), roaming with terrestrial cellular
networks, variety of interface between user terminal and laptop/PC.
The CSF’s, the technology trends and commercial drivers can all be shown on the same chart,
together with a mapping of the Inmarsat systems. In Figure 7 each line represents one of these
trends. GAN, BGAN-R and BGAN are shown on the x-axis, together with existing services. For
each service, two symbols are used to represent the position of the service with respect to each
couple of lines. Existing services, for example, score low in integration and data rate, while at the
same time failing to achieve very competitive price and small terminal size. Quite the opposite is
true for BGAN.
The following considerations can be drawn from the figure:
1. a clear trend is revealed for Inmarsat systems and services: new services are following
the desired slopes, moving upwards on line 1 and 2 (higher integration and higher data
rate), while driving down user terminal price and size (line 3 and 4).
2. BGAN-R identifies the crossing point, where all CSF’s get properly considered in a
synergistic way. This combination should give Inmarsat a first mover advantage into the
high speed mobile multimedia market, while allowing unprecedented user take up and
market response. The coherent mix of CSF’s allows Inmarsat to shift gear and getting
closer to the terrestrial cellular networks, to reach for a much wider customer base, than
the traditionally one addressed with existing services.
 Integration



 Data Rate

 Price



 UT size
EXISTING
GAN
BGAN-R
BGAN
Figure 7: Inmarsat Services and Trends Grid.
6. Conclusions
Inmarsat planned BGAN and BGAN-R services, together with the new I-4 satellites reflect Inmarsat
long term commitment to the mobile business and to maintain leadership in high speed broadband
mobile data services. The I-4 satellites provide a clear evolution path for the existing customer base,
while at the same time providing significant growth potential into new broadband markets. Smaller, less
expensive products will be launched with BGAN and BGAN-R, that will align with mobile telecoms
standards. BGAN services will leverage the constantly increasing demand for Internet and e-business
applications across all markets.