Maritime University of Szczecin
Akademia Morska w Szczecinie
2014, 38(110) pp. 57–61 2014, 38(110) s. 57–61
ISSN 1733-8670
A model of Radiocommunication Events Management System
Andrzej Lisaj, Piotr Majzner
Maritime University of Szczecin70-500 Szczecin, ul. Wały Chrobrego 1–2, e-mail: {a.lisaj; p.majzner}@am.szczecin.pl
Key words: model of radiocommunication, SOLAS Convetion, REMS Abstract
Presenting a model of radiocommunication events management system, we have described its structure and flow of input and output data streams. Besides, we have pointed out the need for developing a system of radiocommunication events management, and possible applications of the developed model.
Introduction
The SOLAS Convention (Safety of Life at Sea) [1] has been initiated by the International Maritime Organisation. It is aimed at preventing accidents, and rescuing personnel and property at sea. Subse-quent amendments and revisions of the Convention with cooperation International Telecommunication Union, resulted in the GMDSS – Global Maritime Distress and Safety System.
The system,
com-posed of 10 subsystems, has been
in force since 1 February 1999.
The SOLAS Convention radio equipment provi-sions are binding for cargo ships with a gross ca-pacity of over 300 tonnes, engaged in international trade, and for passenger vessels. The Convention does not cover warships, fishing vessels and yachts not engaged in trade, and wooden hull ships of simple construction, commonly referred to as non- -SOLAS vessels.
The basic aim of functional requirements of the GMDSS is to enable ships in distress to send im-mediate signals to shore-based radio stations and marine search and rescue centres [1, 2]. Distress alert can be transmitted by a digital selective calling (DSC) unit in VHF and MF/HF wavebands, a tem of emergency radiobeacons and Inmarsat sys-tem terminals.
One of the priority tasks of the GMDSS is to disseminate distress and safety related messages, informing system users about possible dangers and
risks. A ship can receive this information via a number of subsystems: Navtex, EGC, radiotelex, so called MSI-NBDP, DSC or VHF and MF radio-telephony.
A large amount of data received through a radiocommunication device necessitates its verifi-cation. A GMDSS operator has to monitor continu-ously the stream of information and follow proce-dures set forth in the Radio Regulations. Many false alarms and a substantial amount of maritime safety information, combined with complex procedures lead to difficulties in making decisions by GMDSS operators, make them unnecessarily engaged in handling such information, and distract from con-centrating on current navigational functions.
The research problem
GMDSS operators should have qualifications endorsed by a proper document, for instance GOC – General Operator Certificate, entitling the holder to handle equipment as provided by the Radio Regulations [3].
The introduction of the GMDSS system has in-creased the effectiveness of rescue operations and enhanced the dissemination of safety information. The radio equipment and systems continue to be developed, for instance recent modernizations of the COSPAS-SARSAT and INMARSAT systems.
System availability, need to verify plenty of da-ta, complex procedures, improper handling of the
devices by operators are frequent factors making the overall GMDSS system inefficient, ineffective and unusable.
An analysis of the mentioned phenomena lead to a conclusion that to date no system has been de-vised in marine radiocommunication that would properly:
control obtained radio data;
archive a large amount of data from many ship-board and external sources;
propose possible solutions and support the GMDSS operators’ in decision making process; analyze radiocommunication procedures at the
stage of formulating amendments to the Radio Regulations;
analyze operational radiocommunication proce-dures followed by radio stations and SAR ser-vices;
verify procedures in force through a statistical analysis of radiocommunication events;
develop guidelines for the construction of simu-lators and training simusimu-lators for radio opera-tors;
develop guidelines for the construction of simu-lators for autonomous and non-autonomous re-search into marine radiocommunications. The scope of operation of our model of Radio-communication Events Management System includes:
duplex distress comunication; coordinating SAR communication; On-scene Coordinator communication; location of distaster position;
analysis of information related to the assurance of the safety of navigation;
communications between many vessels in a pre-emergency and pre-emergency situations;
general communications.
The developed system addresses GMDSS sub-systems, and may co-operate with such systems as AIS, LRIT, IRIDIUM, GLOBALTAR, THURAYA [4].
A Scheme of a Radiocommunication Events Management System (REMS)
REMS is intended to manage information and control radiocommunication events. Based on the theory of systems [5, 6], we denote the system a set of elements Ω, while relations between them are denoted as R, presented in figure 1. The structure of REMS can be written as:
Fig. 1. REMS system (own study based on [5, 6])
Z , S" , S' , Γ" , Γ' , A , A R M A, Ω R Ω; REMS TX RX (1) where: A – of radiocommunication systems;
M – subsystem of radiocommunication events management;
ARX – stream of incoming (received)
radiocom-munication events;
ATX – stream of outgoing (transmitted)
radiocom-munication events;
' – stream of decisions controlling radiocom-munication devices;
" – stream of radiocommunication events di-rected to a control subsystem;
S' – stream of events implicating radiocom-munication events;
S" – stream of events developed on the basis of radiocommunication events and a stream of assessment measures of REMS functioning; Z – stream of disturbances.
The subsystem of radiocommunication systems A is a set of models of radiocommunication sys-tems limited to their functionalities. The simplest case represents 10 models of a GMDSS subsystem. The control subsystem M manages the operation of the entire REMS. A GMDSS operator, holding one of required types of cerificates, is its indispensable element. A stream of incoming radiocommuni-cation events ARX, and a stream of outgoing
radio-communication events ATX, are, respectively, radio
Radiocommunication subsystems Management subsystem REMS M A ' " S' S" ARX ATX Z
messages received and transmitted by shipboard devices. The stream " is a stream of received mes-sages ARX processed by radio subsystems models
and then directed to the control subsystem. It also contains a stream of events generated from radio devices themselves. The stream ' is a set of all possible commands controlling radiocommuni-cation devices. The stream S' includes all possible events implicating a decision to be made by the control subsystem, whilst S" is the stream of all events managed by the subsystem M not relating directly to radiocommunications devices. S" also contains a set of assessment measures of the system REMS functioning. Z is a stream of radio, meteoro-logical and other disturbances defined at the model-ling stage [7].
The above model can be referred to a single ship on a micro-scale, while a macro-scale approach applies to a set of interrelated radio stations. In the latter case, a set of assessment measures will domi-nate in the stream S".
A Subsystem of Radiocommunication Systems
Radiocommunication systems A comprise mod-els of specific radiocommunication subsystems. GMDSS has 10 subsystems. At the stage of identi-fication, we define the degree of detail of a subsys-tem model.
Radiocommunication subsystems making up GMDSS are shown in figure 2.
Fig. 2. GMDSS subsystems (owa study based on [2, 8])
Subsystems A are characterized by a set of con-stant value measures and random variables. The state K of the subsystem of radiocommunication systems can be described as:
n i m j j i k K 1 1 , (2) where:K – variable describing a state of the
radio-communication systems subsystem;
i – subsystem number;
j – subsystem-describing measure number; n – number of subsystems;
m – number of measures describing a given i-th
subsystem.
Each change in values of measures describing the system state is a radiocommunication event. The time interval Ti between i-th event and another
one can be described by a random variable with a function fi of probability density. The mean
inten-sity of radiocommunication event occurrence iav is:
i i i i iav t f t dt (3)where ti is a realization of random variable Ti, that
is the actual time length of i-th radiocommunication event.
Radiocommunication events may be external and internal. Examples of external events are: reception of a message by a receiving device; transmission of a message by a transmitting
device;
finishing of message (information) transmission by a transmitting device;
lack of reception of an expected message (in-formation) within a specific time interval. Examples of internal radiocommunication events are as follows:
start-up of a radiocommunication device; switching off a radiocommunication device; change of settings of radiocommunication
de-vices;
performing equipment test.
The Management Subsystem
Figure 3 illustrates the structure of the subsys-tem of a radiocomunication events management.
These streams flow into the radiocommunication events management subsystem:
stream of random non-radiocommunication internal events, for example damage to a ship that leads to sending a distress message, crew
VHF Radio- -telephony MF/HF Radio- -telephony VHF DSC INMARSAT NAVTEX NBDP MF/HF COSPAS SARSAT EGC EPIRBs SART GMDSS MF/HF DSC
Fig. 3. The structure of management subsystem (own study)
members’ lives are at risk, power supply failure (blackout), ship’s operational problems or other necessitating a decision to use radio equipment; stream of random non-radiocommunication
external events, for instance sighting a vessel or people in distress, sighting an iceberg, drifting container nor reported in any safety message re-ceived, observation of dangerous phenomena in an area, location of a ship on opposite course; stream of radiocommunication external events
verified by a model of radiocommunication sys-tems ', for example received alarms and other radio messages; this stream does not include messages received by a system and not trans-ferred to the management system, e.g. VHF dis-tress call, in a situation where a receiver was set at improper frequency or noise reduction level was too high;
stream of radiocommunication internal events verified by a model of radiocommunication sub-systems, e.g. a message from radio devices on a failure to perform a correct test, inability to tune in an antenna in the MF/HF radio station, failure to log in an Inmarsat C terminal.
These streams flow out of the radiocommuni-cation events management subsystem:
stream of random non-radiocommunication internal events, such as operational decisions re-lating to the ship;
stream of random non-radiocommunication external events, for instance navigational deci-sions, decisions on manoeuvre performance; stream of radiocommunication external events,
for example transmitted messages;
stream of radiocommunication internal events, such as changes in settings of radiocommuni-cation devices;
stream of REMS assessment measures.
The set of assessment measures is extensive. The selection of measures is subject to the superior objective of the tests performed by REMS. Exam-ple measures may be as follows:
operational measures – time of occupancy of each system, particularly frequency occupancy within each system,
safety measures – defined by the probability of events relating to safety.
The model of management subsystem develops decisions in three stages:
1. safety; 2. threat; 3. distress.
Subsystem models make decisions on giving an order generating a radiocommunication event in compliance with [8]:
legal instruments such as the Radio Regulations, SOLAS Convention, IMO resolutions, local navigation regulations,
principles of good sea practice.
Conclusions
This article describes a structure of a model of Radiocommunication Events Management System (REMS) that may be used for:
testing radiocommunication procedures, e.g. through simulation tests;
developing a training simulator for radio opera-tors;
developing a system of shipboard radio operator decision support.
The model may contribute to the enhancement of safety at sea, as a complement to currently de-veloped navigational decision support systems.
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