Ship Science & Technology - Vol. 14 - n.° 27 - (75-92) July 2020 - Cartagena (Colombia)

DOI: https://doi.org/10.25043/19098642.207

A Preliminary Study of Routing Protocols in a Tactical Data Link Ad Hoc Network in Colombian Maritime Scenario

Estudio Preliminar de Protocolos de Enrutamiento en una Red Ad-Hoc de Enlace de Datos Tácticos en un Escenario Marítimo Colombiano

Arturo Arenas Castro 1

Geovanny D. Sánchez Marín 2

Guefry L. Agredo Méndez 3

Camilo E. Segovia Forero 4

1 Facultad de Ingeniería Electrónica y Telecomunicaciones. Universidad del Cauca. Popayán, Colombia. Email: arturoarenas@unicauca.edu.co

2 Facultad de Ingeniería Electrónica y Telecomunicaciones. Universidad del Cauca. Popayán, Colombia. Email: geosanmarin@gmail.com

3 Facultad de Ingeniería Electrónica y Telecomunicaciones. Universidad del Cauca. Popayán, Colombia. Email: gagredo@unicauca.edu.co

4 Facultad de Ingenieria Naval. Escuela Naval Almirante Padilla. Cartagena, Colombia. Email: camilo.segovia@armada.mil.co

Date Received: June 7th 2020 - Fecha de recepción: Junio 7 de 2020

Date Accepted: July 5th 2020 - Fecha de aceptación: Julio 5 de 2020

Abstract

Tactical Data Link (TDL) systems are a kind of Mobile Ad Hoc NETwork (MANET) used in diverse maritime operational environments such as natural disasters, surveillance, maritime search, and rescue. A TDL network is usually composed of nodes or units representing surface ships, submarines, and aircrafts able to participate in maritime operations. A routing protocol is required to establish communication between nodes, which guarantees the route from the source node to the destination node. A TDL has been developed in the Colombian Caribbean Sea (CTDL). However, no efficient routing protocol has been implemented. This works to perform a preliminary study to implement an appropriate routing protocol for the CTDL.

Local environment constraints, in addition to the chosen protocols' performance analysis, will provide preliminary alternatives for a routing protocol with acceptable efficiency. This article provides a background of ad-hoc networks routing protocols, a description of the Colombian Caribbean maritime operational environment, a comparative analysis of routing protocols, and a discussion of conclusions and future developments regarding CTDL.

Key words: Routing, MANET, Table Driven, tactical data link.

Resumen

El sistema de enlaces tácticos de datos (Tactical Data Link, TDL) es una especie de red móvil Ad-hoc (Mobile Ad-Hoc Network, MANET) utilizada en diversos entornos operativos marítimos como desastres naturales, vigilancia, búsqueda y rescate en el mar, entre otros. Por lo general, una red TDL se compone de nodos o unidades que representan buques de superficie, submarinos y aeronaves capaces de participar en operaciones marítimas. Los protocolos de enrutamiento son necesarios para establecer la comunicación entre los nodos que garantiza el establecimiento de la ruta desde el nodo de origen al nodo de destino. Se ha desarrollado un TDL en el mar Caribe Colombiano (CTDL); sin embargo, no se ha implementado ningún protocolo de enrutamiento eficiente. Por lo tanto, el objetivo de este trabajo es realizar un estudio preliminar para implementar un protocolo de ruteo apropiado al CTDL.

Las restricciones de entorno local, además del análisis de rendimiento de los protocolos elegidos, proporcionarán candidatos preliminares para un protocolo de enrutamiento con una eficiencia aceptable. El artículo proporciona antecedentes de protocolos de enrutamiento en redes Ad-Hoc, una descripción del entorno operativo marítimo del caribe Colombiano, un análisis comparativo de los protocolos de enrutamiento y unas conclusiones y desarrollos futuros con respecto a CTDL.

Palabras claves: Protocolos de Enrutamiento, MANET, Enlace de datos tácticos.

Introduction

A TDL is an ad-hoc [1] network with a specific task, characterized for having two or more units (nodes) equipped with wireless communications with network integration ability establishing a direct or indirect (through relay nodes) contact. TDL features are self-organized and adaptative. Even when data is underway, the path from the source to the destination node requires no administration system. Ad-hoc networks could have different forms, such as mobile, standalone, or network of any other system.

Fig. 1 describes the functional elements of a TDL, which include a source node/unit willing to establish communication with another node called destination, directly or through relay nodes. Note that nodes have a Human Machine Interface (HMI), a processor module, and a transmission module that allows for information broadcasting.

Fig. 1. Tactical Data Link.

Most TDLs are developed either by the North Atlantic Treaty Organization (NATO) or by private commercial companies. These developments are not open source, generic, or for general use. The customizing network is not available to the enduser, and the original equipment manufacturer is not allowed to release the network or system security parameters.

For the Caribbean Sea scenario, the mentioned TDLs do not fit all information requirements such as weather conditions, units positions, sea state, or the performance of the participating teams, among others.

Although there has only been one TDL implementation in Colombia [2], no evidence of routing protocols has been found in its systems. Therefore, introducing routing protocols is necessary to contribute to the efficient development of the Colombian Tactical Data Link (CTDL).

In the early 1970s, the first ad-hoc networks, packet radio systems, were implemented [3]. They used routing protocols for mobile networks and faced restrictions such as:

Currently, routing protocols have successfully overcome those constraints and have reached maturity to fulfill end user's needs.

This article provides an overview to recommend the appropriate TDL routing protocols to work in a specific maritime environment. To achieve these objectives, this paper provides a background on ad-hoc networks, followed by a description of the maritime operational environment in the Colombian Caribbean Sea and a discussion regarding routing protocols, including a comparative analysis among them and, finally, states the conclusions and expectations for future developments of the CTDL.

Background

Ad-hoc networks [4], [5] are wireless means to set up communications in different kinds of unexpected maritime environments, jungles, and deserts, where no established communications systems are available. Each node should detect other nodes or units present in the operational scenario to perform a handshake to guarantee an active link, communication, data, and network services, among them. Concerning these issues, ad-hoc networks do not solely need to detect other nodes, but they must also identify the types of neighboring node devices and their features. The intrinsic characteristics of the ad-hoc-network include its infrastructure-less configuration without a predetermined topology or centralized control. There is no fixed base radio station, router, wires, or fixed routes, whereby routed information will change as per network node mobility changes, which will be reflected in the link connectivity. Ad-hoc networks face many other constraints, such as different hardware brands (computers, mobile phones, communication equipment, etc.), and power consumption becomes critical due to the relay of information packets between nodes, which requires hardware to work permanently.

Some of the challenges and difficulties [1] that ad-hoc mobile networks face are:

For this study, the important constrain is item #5. As mentioned in the introduction, the CTDL lacks a routing protocol. Hence, the initial requirement is to know the operational environmental conditions where the CTDL will perform to determine the routing protocol. This will allow the designer to determine the CTDL features such as network size, node quantity, node mobility features, as well as environmental conditions such as oceanic status, wind, etc.

Maritime Operational Environment

The CTDL project [6] describes the Colombian Caribbean Sea environmental characteristics addressing end-user needs. Its scope is to enhance the operational direction performance, sensor integration, and information exchange in case of natural disasters, maritime domain awareness, and contributing to decision-making processes.

Usually, maritime operations are carried out in groups of units (nodes for ad-hoc networks), which can be surface vessels, aircraft, or submarines, according to each specific situation. Transmission of tactical information among them is fundamental to have a real-time scenario that enables operations coordination. The system must be secure and end user friendly, regarding the appropriate bandwidth use, and all the required software and hardware tools to visualize standard operation picture and information exchange among participant units.

The CTDL scenario composition is four vessels, one submarine, and two aircraft (one helicopter and one airplane). The analysis is performed considering each unit as a node having specific behaviors such as speed and altitude sensors and variables a ffecting the network like the line of sight and distance between nodes.

Weather conditions can influence a TDL design and its routing protocol. Therefore, factors such as humidity, air salinity, high temperatures, rainy and dry seasons, and all typical tropical conditions must be considered.

Now, certain features need to be considered for routing protocols to be able to perform in the maritime environment CTDL.

A. End-User Needs.

Need detaches from the essential CTDL requirement:

B Functions and management.

C. System.

D. Integration capacity.

These features determine the implementation design of the routing protocol. End-user-needs can show the network topology. Functions and management can rule the network's size and density. The system offers the electromagnetic spectrum and bandwidth usage. Finally, integration capability drives network node quantity.

A designed scenario is essential; the CTDL simulation model is composed of two surface vessel nodes, one submarine node, one helicopter node, and one airplane node, as described in Table 1. The design purpose is to establish a future simulated scenario capability. This model must have assumptions, i.e., all nodes must be in the line of sight range, and nodes should establish communications in the same frequency even if there are different hardware brands.

Table 1. CTDL Scenario Composition.

From Table 1, and the CTDL features, it is possible to infer that: