267

1 INTRODUCTION

The improved GMDSS network through the Global

Mobile Satellite Communication (GMSC) systems has

to provide more reliable communication solutions for

alerting and Search and Rescue (SAR) operations of

oceangoing ships in emergency and distress

situations, which have to ensure more automated

alerting and SAR operations of ships and aircraft in

distress at sea. Recent developments and

advancements in maritime mobile satellite technology

and technique have made it vitally important for

commercial and safety satellite communication

systems and for the integration of other GMSC

networks into GMDSS infrastructures.

In order to integrate various maritime satellite

communication networks into their safety and

commercial systems, access to satellite networks and

data needs to be improved. The already developed

Inmarsat GEO, Iridium Big Earth Orbit (LEO), and

Orbcomm Little LEO satellite systems are very

important for GMDSS network because they are

providing large areas of coverage, making them

reliable and cost-effective for distress, safety and

businesses solutions everywhere. They also provide

many benefits to private companies and public

networks, including being a subsegment of the

integration in the future modernization of the GMDSS

network.

Alternative Maritime Satellite Solutions for Enhanced

GMDSS Network

.S. Ilcev

University o

f Johannesburg (UJ), Johannesburg, South Africa

ABSTRACT: In this paper are introduced alternative architectures for the novel development of the enhanced

Global Maritime Distress and Safety System (GMDSS) satellite communication network and equipment within

the Gostationary Erath Orbits (GEO and Non-

GEO satellite constellations. Since its founding in 1959, the

International Maritime Organization (IMO) and its member states, in close co-operation with the International

Telecommunication Union (ITU) and other international organizations, notably the World Meteorological

Organization (WMO), the International Hydrographic Organization (IHO), the International Mobile Satellite

Organization (IMSO) and Cospas-Sarsat partners, have striven to improve maritime distress and safety radio

and satellite communications, as well as general communications for operational and personal purposes. This

paper also reviews the principal concept of the GMDSS network, an overview of existing LRIT and maritime

Integrated Radio-Automatic Identification System (R-AIS) and Satellite-AIS (S-AIS) networks. In addition, new

proposed by author networks of the Satellite Data Link (SDL), Maritime GNSS Augmentation Satellite Data

Link (GASDL), Maritime Global Ship Tracking (GST), and Maritime Satellite Automatic Dependent

Surveillance-Broadcast (SADS-B) are also described in this paper.

http://www.transnav.eu

the

International Journal

on Marine Navigation

and Safety of Sea Transportation

Volume 16

Number 2

June 2022

DOI: 10.12716/1001.16.0

2.09

268

2 MARITIME SATELLITE LONG RANGE

IDENTIFICATION AND TRACKING (LRIT)

The current LRIT maritime satellite system is not a

mandatory part of GMDSS communication

requirements, but is mandatory for ships on

international voyages and all ships of 300 GRT must

comply with IMO regulations. Initially, LRIT used the

existing devices, such as Inmarsat-C or mini-C

satellite equipment, and recently began using Iridium

satellite devices to report the ship identities, locations,

dates and times that are regularly sent to the owner’s

headquarters or flag authorities.

The satellite LRIT network was subject to the new

SOLAS regulations contained in its Chapter V which

apply to ships constructed after 31 December 2008

with a gradual period of application for existing ships.

Vessels trading exclusively in the A1 sea area and

having R-AIS are exempt from the LRIT requirement.

Thus, LRIT equipment onboard ships must be directly

interfaced to the ship’s Global Navigation satellite

Systems (GNSS) equipment or have internal US GPS

or Russian GLONASS receivers for positioning

capability.

Figure 1. Maritime LRIT Network – Source: Ilcev

In Figure 1 is illustrated LRIT satellite network

containing GNSS satellite constellation of GPS and

GLONASS satellites, which provides GNSS signals to

oceangoing or coastal going ships sent via GEO/LEO

satellite systems. The LRIT network is also containing

GEO/LEIO satellite systems for transmitting position

and other messages. Ships sailing in a certain area are

sending LRIT messages to the National LRIT Control

Centre (NLCC) and then messages are forwarded to

the Global LRIT Control Centre (GLCC) for

processing and delivering to potential users

worldwide.

Regulations require that, by default, LRIT reports

should be transmitted every six hours to the LRIT

centres with frequency of transmission to be

controlled remotely, allowing for reports to increase

as security levels change up to a rate of one report

every 15 minutes. The SOLAS regulation on LRIT

establishes a multilateral agreement for sharing LRIT

information between SOLAS contracting governments

for security and SAR purposes. It maintains the right

of flag states to protect information about the ships

entitled to fly their flag, where appropriate, while

allowing coastal states access to information about

ships navigating off their coasts [01, 02, 03, 04].

3 MARITIME INTEGRATED R-AIS AND S-AIS

The existing VHF Radio-AIS (R-AIS) is the most

attractive system for short-range tracking and

detecting of ships in coastal navigation, sea passages

and approaching to anchorages. Due to the limited R-

AIS communication range that recently uses VHF

bands, long-range satellite AIS (S-AIS) is proposed for

global coverage via Inmarsat GEO, Iridium Big LEO

and Orbcomm Litlle LEO satellite communication

networks, whose integrated R-AIS and S-AIS Systems

for Enhanced GMDSS Network are shown in Figure 2.

The IMO Convention requires R-AIS to be fitted

aboard oceangoing ships of 300 GRT or more, and all

passenger ships regardless of size. The scenario is

similar to the previous network, namely coastal

sailing ships automatically broadcast information,

such as their position, course, speed, rate of turn and

navigational status at regular intervals via VHF

transponder for enhanced Ship Traffic Control (STC)

and Ship Traffic Management (STM).

Figure 2. Integration of Maritime R-AIS and S-AIS Systems

for Enhanced GMDSS Network – Source: Ilcev

Thus, the information originates from the ship’s

navigational sensors, typically its GNSS (GPS or

GLONASS) receiver and gyrocompass, while other R-

AIS information, such as MMSI, vessel name and call

sign, are programmed during equipment installation

and are also regularly transmitted. The signals are

received by R-AIS transponders fitted onboard other

ships and on the land R-AIS Base Station (BS),

connected to the R-AIS Control Centre (ACC) and the

Vessel Traffic Service (VTS). The received information

can be displayed on radar or chart plotter, showing

the positions of other vessels and their call sign

information, in order to increase these systems and

improve navigation safety. Other R-AIS data can be

added to radar and chart plotting systems, making

these critical systems much more efficient.

Thus, R-AIS provides coverage in the VHF band

over short distances, so it can be integrated with

Satellite AIS (S-AIS) to extend coverage, which

onboard installed unit can send AIS data via GEO or

LEO satellites to CES, STC and STM for processing. In

this way, S-AIS messages detected by GEO or LEO

satellites have become a very reliable method for

detecting, tracking and collision avoidance solutions

globally [01, 05, 06, 07].

269

4 MARITIME SATELLITE DATA LINK (SDL)

The proposed ships SDL network is similar to the

VHF Data Link (VDL) radio network, the system

configuration of which is illustrated in Figure 3.

Namely, the SDL transponder for determination and

traffic management can be installed onboard

oceangoing ships sailing on the high seas outside of

radio VHF coverage. Otherwise, the SDL transponder

installed onboard ships is integrated with a GNSS

receiver able to receive navigation signals from GPS

or GLONASS satellites and resend them via CES to

STC and STM stations.

Figure 3. Maritime SDL System for Enhanced GMDSS

Network – Source: Ilcev

All received Position, Velocity and Time (PVT)

data from ships within SDL coverage will be

processed and displayed on the radar like VDL

display unit. In vise versa direction, a ship traffic

controller can send PVT via GEO or LEO satellites to

all ships outside seaports and manage their

determinations and movements in a safer manner

with enhanced collision avoidance. In such a way,

captain of the ships can navigate more safely even in

extreme bad weather conditions with zero visibility.

The SDL network can be a part of an overall maritime

satellite communication solution via Inmarsat or

Iridium satellite networks for the following services:

1. SDL Tracking Messages Service – The concept of

this service in similar way to VDS will be able to

provide a satellite broadcast link supporting

navigation and surveillance functions. Its

transmission can be realized via Short Burst

Messages (SBM) between SES terminals and CES

connected to STC and STM. Vessels may be fitted

with satellite transponders or satellite tracking

devices integrated with a GNSS receiver (GPS or

GLONASS), which may have autonomous SDL

communication within the coverage of a particular

CES or may operate with any compatible CES

worldwide via the GEO satellite constellation. The

SDL transponder can also support similar services

via the Iridium network and well be able to

provide real global coverage including both Poles.

The SDL transponder allows ship captains and

STC operators to ”display” vessels traffic in ocean

or coastal navigation outside VDL coverage with

the greatest possible position accuracy, which can

improve safety and security at sea. Thus, different

CES terminals can operate within Inmarsat,

Globalstar, Iridium or Orbcomm networks around

the world, respectively. However, CES terminals

and an interfaced terrestrial network will provide

increased functionality and capability for wide

area coverage of advanced CTC and STM. The

functionality of CES terminals is tailored to system

specific service applications by its software

configuration.

2. SDL Communication Service – Every seagoing

vessel carries SDL transponders or satellite

communication devices will be able to send and

receive Short Burst Data (SBD) or High Speed Data

(HSD) messages for Communication, Navigation

and Surveillance (CNS) purposes. As part of

overall maritime communications solutions, the

new SDL technology can provide customers with a

global secure and accurate messaging service. The

ship's captain can use two-way messaging,

navigation data, text and graphics waether

bulletins (WX), navigation warnings (NX) and

route planning with just a few applications

provided by Inmarsat and Iridium satellite

operators around the world. Both operators also

provide valuable redundancy to satellite services,

while at the same time requiring minimal equipage

or upgrade reliability, creating a cost-effective,

safety and vital communications service for ships.

This service will also provide real-time

information on sailing, destinations, Estimated

Time of Arrival (ETA), movement times, engine

parameters, delays, positioning, maintenance, etc

[08, 09, 10, 11].

5 MARITIME GNSS AUGMENTATION SATELLITE

DATA LINK (GASDL)

The Regional Satellite Augmentation System (RSAS)

networks of GNSS infrastructures are a combination

of ground monitoring and satellite communications

systems dedicated for providing augmentation of

standard GPS or GLONASS signals, which GASDL

diagram for enhanced GMDSS Network is illustrated

in Figure 4. The major functions being provided by

RSAS are as follows: 1. Differential corrections are

determined to improve the accuracy of GNSS signals;

2. Integrity monitoring is predisposed to ensure that

errors are within tolerable limits with a very high

probability and thus ensures safety; and 3. Ranging is

proposed to improve availability.

Figure 4. Maritime GASDL System for Enhanced GMDSS

Network – Source: Ilcev

The numbers of Reference Stations or Ground

Monitoring Stations (GMS) are receiving not

augmented signals of GPS or GLONASS satellites,

270

and then processing and forwarding this data to

Master Station or Ground Control Stations (GCS).

Thus, GCS terminals provide processing of GNSS data

to determine the differential corrections and bounds

on the residual errors for each monitored satellite.

They are also providing determination of the clock,

ephemeris and ionospheric errors (ionospheric

corrections are broadcast for a selected area) affected

during propagation. The corrections and integrity

information from the GCS terminal are then sent to

each RSAS CES and uplinked to the GEO Satellites.

These separate differential corrections are

broadcast by RSAS CES through GEO SDL via GNSS

transponder on the same frequency used by the not

augmented GPS receiver. The augmented GPS

receiver (Rx) receives augmented signals of GPS

satellite and determines the more accurate position of

ships. The not-augmented GPS Rx can also receive

augmented signals if the appropriate software or

hardware is provided. The most important stage in

this network is to provide a technical solution so that

the augmented position of ships can be automatically

sent via SDL or voice to CES and STC centre. These

positioning signals can be processed by a special

processor and displayed on look like radar display,

whish the traffic controller uses for STC and STM

enhanced ship traffic control and improved collision

avoidance in certain monitoring sea area, (09.12,13).

6 MARITIME GLOBAL SHIP TRACKING (GST)

Today, there are specific shipborne technologies that

were designed for purposes of vessels tracking and

monitoring of oceangoing vessels. For example, R-AIS

network is a good global general radio coverage of

maritime assets, but it is practically not what it was

built for. There are applications for ships in which R-

AIS is good for safety during navigation, but

sometimes it is a problem to get the position of a

cargo ship at night or during extremely bad weather

conditions and poor visibility, or ship navigation

devices are switched off etc. Namely, today

oceangoing ships need discrete and autonomous

systems with their own GNSS receiver that run highly

intelligent satellite tracking devices, such as the

proposed Global Ship Tracking (GST), whose diagram

is shown in Figure 5.

Figure 5. Maritime GST System for Enhanced GMDSS

Network – Source: Ilcev

To sum it up, R-AIS only onboard device improves

the safety of navigation by assisting the Officer of the

Watch (OOW) or whatever entity. It’s pretty easy to

install as well, as R-AIS is generally integrated with

ship bridge navigation systems of GPS and radar or

multifunctional display, but what can happen if

someone intentionally turns off the ship's GPS or

radar or those devices have failed to work

properly.The additional limitations of R-AIS include:

(1) Its information may not be accurate and it could

become overwhelmed; (2) The information could be

misinterpreted; (3) It is not compulsory on every

vessel and operators may deactivate their R-AIS

device; (4) Users must be aware that erroneous

information might be transmitted by the R-AIS from

another ship; The OOW could become over-reliant on

R-AIS service, and (6) The ships position received on

the R-AIS display might not be referenced to the

World Geodetic System (WGS) 84 datum, and also the

information could be misinterpreted.

The flow of R-AIS vessels positioning data is good

and which is also designed to prevent collisions and

identify nearby vessels and even aircraft for safety,

but its reception is unpredictable and unverifiable. In

addition, the R-AIS network is designed on a low

reliability and unknown coverage of land based

transponders and provide delayed reports if is used

satellite S-AIS relays. Thus, all of the above

disadvantages of the R-AIS network may be managed

by commercially controlled and predictable S-AIS

satellite receivers, but R-AIS is not designed or

installed around satellite transmission because the

ship's antenna is linearly polarized and not directed

toward the sky.

On the other hand, the current LRIT satellite

system as the first compulsory equipment onboard

ships designed by the IMO to collect and disseminate

vessel position information received from IMO

member states ships that are subject to the

International Convention for the SOLAS vessels. It is

also obvious that this system is not very successful for

vessel tracking worldwide, because the problem is not

due to ship’s LRIT devices inability, but because of

not at all the functional design of LRIT system and

network. However, the biggest disadvantage of LRIT

network is that it cannot as a GST system to transmit

in real time and space navigation data of adjacent

ships on request of any ship sailing in certain sea area

for collision avoidance, to provide polling of this data

and that LRIT is not able to provide tracking of

missing or captured ships by pirates.

However, the proposed GST solution is able to

provide all service as LRIT does including to provide

tracking of missing and hijacking ships. It is the best

solution for satellite tracking of ships in any real time

and space worldwide, to determine positions of all

ships sailing in vicinity to the ship requesting this

data for collision avoidance or operator can get this

data by polling from Tracking Control Station (TCS).

In fact, using satellite links of GEO or LEO satellites

any ship equipped with GST unit is able to send

automatically its PVT and other data, provided by

GPS and/or GLONASS spacecraft, separately via

Inmarsat, Iridium, Globalstar or Orbcomm satellites to

CES, Internet, TCS and Ships Operations (STC and

STM). In such a way, the TCS terminal can receive

271

PVT data from any ship, process and display on radar

like display.

Thus, whatever LRIT and S-AIS networks can

implement, the new proposed GST network will be

best to provide PVT data for the tracking,

identification, and monitoring of all ocean-going

vessels in a given marine area to improve collision

avoidance. In addition, GST satellite network, will be

only able to provide PVT data for immediate

detecting position of ship captured by pirates and it is

able to improve GMDSS network facilities. Integrated

with special RFID units, the GST satellite devices can

be used for only possible and reliable Global

Container Tracking (GCT).

In conclusion, it can be stated that by using the

GST system on each vessel, all the shortcomings of the

LRIT, R-AiS and S-AIS networks can be avoided. The

new proposed GST network and ships installations

can provide the following services: (1) Autonomous

and discrete satellite tracking and detection system,

the installation of which is unknown to anyone

onboard ship; (2) Own power supply via ships

generator and rechargeable batteries; (3) Remotely

control of terminal parameters and Data Terminal

Equipment (DTE) installed on the bridge used as

small message terminal with keyboard and display;

(4) Communication with person in distress and

emergency (5) Command, control and different sensor

monitoring; (6) Terminal information, location,

firmware and device diagnostics; (7) Re-key or

encryption and authenticated negotiation; (8)

Geofencing or integration with GNSS or Radio

Frequency Identification (RFID) equipment and

hybrid network support; and (9) GPS quality and

jamming detection [08, 09, 14, 15].

Figure 6. Maritime SADS-B System for Enhanced GMDSS

Network – Source: Ilcev

7 MARITIME SATELLITE AUTOMATIC

DEPENDENT SURVEILLANCE-BROADCAST

(SADS-B)

The satellite SADS-B network is a new system

developed for airborne mission similar system to

radio RADS-B network with the only difference that it

operates via satellite instead of the VHF radio, and

which can be implemented for maritime applications,

shown in Figure 6.

Thus, each letter of the SADS-B means the

following explanation:

− Satellite indicated that it is used for transmission of

information and for RADS-B means that is using

VHF radio for data transmissions;

− Automatic means that SADS-B periodically

transmits information with no ship, vehicle or

aircraft operator input required, nor common or

specific interrogation;

− Dependent stands for sending position and

velocity vector derived from GNSS1 (GPS or

GLONASS) Receivers (Rx) terminals. In the future

can be used GNSS2 receivers, such as Chinese

BeiDou (Compass) and European Galileo systems;

− Surveillance is a method of determining the

position of ships, vehicles, aircraft or other mobile

assets; and

− Broadcast is transmitted information available to

anyone onboard mobile or at shore with the

appropriate receiving equipment.

The proposed SADS-B satellite network is a

modern shipborne satellite broadcasting system

proposed by author of this book, which is similar to

current airborne SADS-B in development phase. This

system will provide PVT and other data that have

been detected and computed by onboard ships

sensors, such as GNSS (GPS or GLONASS) receivers,

ground surveillance radar, gyrocompass and other

instruments. Typical SADS-B maritime system is

similar to the RADS-B with additional differences that

the SADS-B network is covering large distances and is

using service of GEO or LEO satellites to send OUT or

receive IN SADS-B information to STC and STM via

CES ground terminals, which configuration is shown

in Figure 7.13. A single CES terminal can provide

ships-to-ship, ship-to-shore and shore-to-ship

broadcasting in ocean areas for surveillance service to

ships sailing on the high seas, in critical straits

passages with an enhanced traffic, approaching to

anchorahes and even in large ports.

Therefore, an SADS-B system is a special

integrated satellite surveillance technology in which a

ship determines its position via satellite navigation

and periodically broadcasting via satellite own VPT

and other data important for safely and secure

navigation. The information can be received by STC as

a replacement for maritime ground radar system. It

can also be received by other ships to provide

situational awareness, allow safe sailing and enhanced

collision avoidance.

In addition to the good characteristics, the ADS

satellite network has not some features as GST does

such as:

1. This system is not discrete so that someone

uninvited, under force by pirates or purposly can

turn off the unit completely, part of the unit or just

GNSS receiver;

2. This system cannot work properly if it has not an

integrated GNSS (GPS or GLONASS) receiver; and

3. This system needs to be installed to some secret

place and although is powered by ship sources it

needs own charger and batteries [01, 09, 14, 15, 16].

272

8 CONCLUSION

The Iridium network is the largest commercial

satellite system in the world and the only network

that offers true global communication coverage of

totally 100% of our planet. Uniquely, new Iridium

NEXT satellites also cover the entire Earth, including

the poles, and provide voice, data and video services

via the new Certus terminals at sea, on land and in the

air. Importantly, the new Iridium Certus

communication system provides for the first time a

global broadband and Internet network via the NEKT

satellite constellation.

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