TECHNOLOGY TRENDS AND MAKET DRIVERS FOR
BROADBAND MOBILE VIA SATELLITE:
Antonio Franchi, Jay Sengupta
Inmarsat, 99 City Road, London, EC1Y 1AX, United Kingdom
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 (I-4 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.
Inmarsat currently operates a global satellite system comprised of its second and third generation satellites. At
December 2000, 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), mobile ISDN and mobile packet data 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 multi-media
rdservices to personal, mobile and portable terminal users. The BGAN system will be compatible with terrestrial 3
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. (is it still compatible? Legal always question this with me when I
The paper deals with the major aspects of the BGAN system, namely:
? The technology: the key features of the satellite technology for the latest I-4 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
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
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 thenetwork control and operations, enables the
use of simpler user terminal technology for high speed data communications, and avoid 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.
It is expected that 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 0 East longitude) and AOR-procured; at present, two of these are planned, to be deployed at Inmarsat’s existing IOR (650West (54 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, and is expected to achieve 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.
No. of satellites44 + 1 spare3 (inc. 1 spare)
CoverageGlobal beam7 wide spots200 narrow spots + 19 + global beam wide spots +global beam
Mobile link EIRP39dBW49dBW67dBW
Channelisation4 channels 46 channels 630 channels at between 4.5 & between 0.9 & 200KHz 7.3MHz bandwidth 2.2MHz bandwidth
Satellite dry mass700kg1000kg3000kg
Solar array span14.520.7m48.0 m
Table 1: Comparison of Inmarsat satellites main parameters
Figure 1: The Inmarsat-4 Satellite – Proposed Design
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. 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 to satellite networks using a common subscription and service provision relationship.
A schematic of the AMN is given in Figure 2. The 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 Points 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 F1INM-4 F2
Satellite Satellite Inter-siteRegion 1Region 2VPN
Figure 2: Advanced Multimedia Network – Proposed Design
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
virtual global coverage for these services; Existing and Evolved services will be offered via the current network of
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 PDAs (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 deternmination 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 3: Notebook Terminal Concept Figure 4: Pocket Terminal Concept BG
Characteristics BGAN Notebook BGAN Pocket Size & Dimensions ~ A4 (21x30x3cm) ~ A5 (15x21x3 cm) Mass (incl batteries) ~ 1.0 kg ~ 0.75 kg Operating Time 1 hr transmit, 36 hr standby 1 hr transmit, 36 hr standby Interfaces USB, Bluetooth, WLAN USB, Bluetooth, RS-232 Environmental Conditions Showerproof Showerproof Location Determination GPS receiver GPS receiver Data Transmission Rate 144(U)/432(D) kbit/s 64(U)/216(D) kbit/s
Table 2: BGAN User Terminals – Proposed Characteristics
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 is intended to offer 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.)
? Voice telephony including voice mail
? Dial-up access to on-line services
? Video conferencing
4.3 Service Deployment and Phasing Strategy
It is intended that 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. Virtual 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 two I-4s, Inmarsat is currently planning to launch BGAN services by end 2002, operating over leased satellite capacity from regional satellite operators. This project is currently denominated project 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 project BGAN-R is made up of five main elements located at three sites:
? Inmarsat NOC, developed by Inmarsat, in London ? Business Support System (BSS) in London ? Satellite Access Station (SAS), located at Fucino, Italy ? Modifications to the regional satellite operator AOC ? 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.
Figure 5: I-3 and I- Proposed 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
MOBILE 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. Global Handheld LEO/MEOs (narrowband): narrowband systems for global voice and low speed data
2. Regional Handhelds (narrowband): narrowband similar to those of the Global Handhelds but on a
3. Ka-band Regional/Global LEO/MEO/GEOs (Broadband): These systems will supply fixed (at least
initially), broadband multimedia services to mass markets.
4. C-band and Ku-band non global systems (VSATs and USATs). Larger size terminals (60 cm to 2.4 m)
used mostly for communications between fixed sites and areas lacking terrestrial communications
5. GSM and third generation mobile UMTS.
Figure 6 shows the likely positioning of the various classes in the 2004 time-frame; the axis in the diagram are mobility
and data rate. It appears that the traditional areas covered by Inmarsat, typically the mobile, low data 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
Figure 6: Competitive Positioning - 2004
From the above analysis, it appears that no other systems are pursuing directly comparable offers to the BGAN service.
Hand-held satellite systems appear initially to be 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 limited coverage. The BGAN service,
on the other hand, will offer high speed data, mobility and coverage of key land mass areas.
Inmarsat market research as well as Inmarsat’s knowledge of the mobile market, have indicated the identity of 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 for 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 seem to have emerged, which
support the BGAN service strategy and success. Let’s summarise them in this section, since they effectively represent
critical factors for BGAN:
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 aims to fully exploit this convergence, hopefully
resulting in optimised, cost effective terminals.
2. Data Rate .
Market research shows an increased demand for higher data rates. BGAN offers a clear answer, achieving 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.
3. Terminal Price and Air-time Tariff.
Price elasticity analysis shows that terminal price is a significant factor in the success of the system. BGAN is
being designed with the objective of reducing terminal price. This is being achieved in a number of ways:
- recurring engineering cost are naturally decreasing, due to cheaper availability of components and its
- volumes of terminals drives their price down;
- 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.
4. User terminal appealing and user-friendliness.
A number of factors are being considered, in order to build terminals that are attractive, while at the same time, 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. Moving from existing services towards BGAN, services offer higher data rates,
while improving integration with other systems; at the same time, thanks to the factors explained, both price and terminal
size get steadily educed.
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. project BGAN-R identifies the crossing point, where all CSF’s get properly considered in a synergistic way.
This combination should give Inmarsat an advantage into the high speed mobile multimedia market, while
allowing unprecedented user take up and market response. The coherent mix of CSF’s should allow Inmarsat to
get closer to the terrestrial cellular networks and, to reach for a much wider customer base.
Data RateData Rate
UT sizeUT sizeEXISTINGEXISTINGBGAN-RBGANBGAN-RBGANGANGAN
Figure 7: Inmarsat Services and Trends Grid. 6. Conclusions
Inmarsat planned BGAN and project BGAN-R services, together with the expected new I-4 satellites reflect Inmarsat
long-term commitment to the mobile business and to maintain a leadership profile in high speed broadband mobile data
services. The I-4 satellites are expected to provide a clear evolution path for the existing customer base, while at the same
time providing growth opportunity into new broadband markets. Smaller, less expensive products will be launched with
BGAN and project 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.