The focus of maritime communications and GMDSS
networks these days is concentrated towards satellite
communications and IP networking. Many things
have changed from even a few decades ago, when
radiotelegraphy and radio telex were main method of
ship to shore and vice versa radiocommunication
systems, so oceangoing ships are now effectively
expanding computer LAN over satellite networks.
However, VHF, HMF and HF radio communication
systems continue to provide huge support for
upgrading the GMDS network.
Of course, the driver for all these changes in
distress Search and Ressque (SAR) operations was the
establishment of the GMDSS network in the early
1990’s, which still uses VHF and HF Digital Selective
Calls (DSC), VHF radiocommunication systems and
NAVTEX transmissions. After the GMDSS operator
onboard ships sends an DSC alert, then it switches to
the radiotelephone distress and safety channels and
conducts onscene communications with other ships,
SAR forces and shore stations. The problem is that
these channels are often plagued by interference and
that some new and most reliable solutions should be
proposed. Here will be shortly introduced new VHF
and MF radio systems able to improve radio
Communication, Navigation and Surveillance (CNS)
requirements for the GMDSS network [01, 02, 03].
Alternative Maritime Radio Solutions for Enhanced
GMDSS Network
.S. Ilcev
University of Johannesburg (UJ)
, Johannesburg, South Africa
ABSTRACT: This paper introduces novel alternative maritime radio solutions for the improved Global
Maritime Distress and Safety System (GMDSS) network and equipment within the Very High Frequency (VHF),
Medium Frequency (MF) and High Frequency (HF) Ship Radio Station (SRS) terminals. Since its foundiing in
1959, 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 the Cospas-Sarsat partners, have striven to improve maritime distress
and safety radiocommunications, as well as general radiocommunications for operational and personal
purposes. This paper also reviews concept of the GMDSS network, an overview of new propsed by author
maritime VHF Data Link (VDL), maritime Radio Automatic Dependent Surveillance-Broadcast (RADS-B), an
maritime GNSS Augmentation VDL-Broadcast (GAVDL-B). In addition, the type of the current radio Maritime
VHF Data Exchange System (VDES), Maritime MF-band Navigational Telex (NAVTEX), and Maritime MF/HF-
band Navigation Data (NAVDAT) are also described in this paper.
International Journal
on Marine Navigation
and Safety of Sea Transportation
me 16
Number 2
June 2022
DOI: 10.12716/1001.16.02.08
The aim of this section is to present a new proposed
marine VHF Data Link (VDL) similar to aeronautical
VDL, which can be applied in the future for the CNS
service within the GMDSS network in the Sea Area
A1. The new VDL service has to improve GMDSS
solutions in coastal navigation, inland waters,
approaching to anchorage and inside of the harbors as
new solution with 3 main objectives:
1. To provide a more reliable and effective ships
communications system based on efficient and
higher rate digital transmission over VHF radio
including International Ship and Port Facility
Security Code (ISPS) system in harbors;
2. To improve R-AIS basic functions for ships
collision avoidance; and
3. To enhance GMDSS network, Ship Traffic Control
(STC) and Ship Traffic Management (STM)
through the VDL network, together with the
proposed RADS-B network.
Figure 1. Maritime VDL Radio System for Enhanced
GMDSS Network Source: Ilcev
The ship's VDL system will be similar to R-AIS
with the task of improving its capabilities and
functionality, the configuration of which is shown in
Figure 1. A major improvement of R-AIS requires the
installation of VDL transponders onboard ships for
improved STC and CTC in coastal waters,
approaching anchorages and seaports. In the same
way, similar VDL installations will be able to control
the movement of land vehicles and rails within
seaports. Both ships and vehicles transporters can be
integrated with GNSS receivers that can receive
navigation signals from GPS or GLONASS satellites
and resend them via VHF Coast Radio Stations (CRS)
terminals to STC and STM operational centres.
Received Position, Velocity and Time (PVT) data
from ships and vehicles within VHF coverage will be
processed and displayed on radar like a VDL display
unit. In the opposite direction, the ship traffic
controller may send PVT to all ships outside seaports
and in particular to all ships and land vehicles within
the seaport, and manage their movement in a safer
manner [04, 05, 06, 07, 08].
The Radio Automatic Dependent Surveillance-
Broadcast (RADS-B) communication mode has been
developed for aeronautical applications, but can also
be used for maritime applications, the configuration
of which is illustrated in Figure 2. This system can
uses radio transmissions from ships, approximately
once in a while, to provide PVT and other data that
have been detected and captured by onboard ships
sensors, such as not-augmented Global Navigation
Satellite System (GNSS) receiver (GPS or GLONASS),
Automatic Radar Plotting Aid (ARPA) or
The RADS-B VHF CRS terminal uses a non-
rotating omnidirectional radio antenna to receive VDL
messages transmitted from ships in a certain ocean
area. The maritime RADS-B network has been
proposed as a multiple use surveillance technique for
harbour terminals, approaching to anchorage, sea
passages and coastal waters in range of VHF CRS
terminals and is also applicable to STC, STM and
ship-to-ships data transmitting OUT and receiving IN
surveillance, known as an Internship RADS-B for
enhanced collision avoidance.
The RADS-B transmission is “line of sight” based
surveillance and requires CRS terminals to receive
data and transmit to STC and STM operational
centres. A single CRS can provide coverage out to
approximately 250 Nm for coastal enroute, terminals
and seaport area surface surveillance. This RADS-B
communication network can be integrated with
Ground Surveillance Radar (GSR) installations and
provide additional surveillance capabilities. In ordet
to improve ships surveillance and traffic control in the
seaport area, this new system will require a special
RADS-B transceivers integrated with GNSS receivers
installed onboard ships and land vehicles [02, 04, 09,
10, 11].
Figure 2. Maritime RADS-B System for Enhanced GMDSS
Network Source: Ilcev
The GNSS-1 network is integral part of all
applications where mobile CNS solutions play an
important role in the development of modern
configurations for enhanced STC and STM, and in
particular for improved GMDSS shipborne facilities.
In the GNSS-1 satellite network are integrated the US
GPS and the Russian GLONASS, while the Chinese
BeiDou or Compass and the European Galileo are
included in the GMSS-2 network. The GNSS network
provides standardized PVT information via VDL to
oceangoing ships for more precise navigation and
enhanced collision avoidance in global scene, which
scheme is shown in Figure 3. The VDL system in the