Communication Coverage Awareness forSelf-aligning Wireless Communication in Disaster

OperationsThomas Pfeiffenberger and Peter Dorfinger and Ferdinand von Tullenburg

Salzburg Research Forschungsgesellschaft mbHAdvanced Networking Center

Jakob Haringer Str. 5 / III, 5020 Salzburg, Austriafirstname.lastname@salzburgresearch.at

Abstract—Broad band communication in international disasterresponse actions is becoming more and more important. Theinformation exchange between field commanders and tacticalcommanders lead to a better situational awareness on all layers ofdisaster management. After large scale disasters the communica-tion infrastructure is often destroyed. Setting up a communicationinfrastructure is essential in todays disaster response actions. Asorganizations in disaster response actions are not consisting ofIT experts, the setup and installation has to be easy. For example[1] presents such a system. Furthermore the knowledge where todeploy wireless communication gateways and wireless relay nodesis essential. Consequently the positions of field commanders cannot only be based on tactical needs but also on communicationneeds. In this paper we present a simulation based visualizationtool which helps to evaluate deployment locations for communi-cation equipment to achieve adequate communication coveragewith respect to specific disaster related information. This allowsan optimal positioning of relay nodes and field commanders in thefield to ensure broad band communication in disaster responseactions and thus faster help for the people.

Index Terms—communication infrastructure, first respondersupport,terrain analysis, simulation

I. INTRODUCTION

Both data and voice communication between first respon-ders of the same emergency organization or across differentorganizations, is crucial for an effective cooperation duringdisaster management. Especially data communication offersthe possibility to exchange relevant information across orga-nizational and national borders, making the help more targetedand faster, thus saving more people. One of the major problemsright now is that after a large scale disaster the existingbroad band network is often partially destroyed or overloaded.As the communication network is essential for a better andmore efficient collaboration between first responders there isa critical need for setting up an alternative communicationinfrastructure. In such a case, another issue arises: first respon-der organizations are not experts in setting up communicationequipment, thus these systems have to be designed such thatthey are easy to setup. The wireless communication systemproposed in this paper is part of the work done within theIDIRA (Interoperability of data and procedures in large-scale

multinational disaster response actions) [2] European FP-7research project. IDIRA’s main aim is to improve cooperationacross responding organizations by enabling interoperabilitybetween different information systems that can mutually actas data sources or data consumers, and with connected devicesused in the field. This leads to more efficient multi-nationaland multi-organizational disaster response actions.

In large scale disasters often satellite communication isused, which offers a good possibility to bring communicationon scene (used as uplink technology). Different technologiesand systems such as Broadband Global Area Network (BGAN)[3], Global Very Small Aperture Terminal Forum [4] orEmergency.lu [5] are used by the first responders. For on scenecommunication between different commanders in the fieldsatellite communication is too expensive and in the case ofBGAN has only a very limited bandwidth. For on scene com-munication a different system is needed which establishes locallinks. Bringing independent communication equipment such asWIMAX [6] or UMTS/LTE [7] equipment on scene has thedrawback that licenses to operate the system are needed. A sys-tem specifically targeted towards broad band communicationfor PPDR (public protection and disaster relief) organizationsis HiMoNN [8]. HiMoNN uses the frequency band 5150-5250MHz with a transmission power of up to 8W according tothe ECC Recommendation [9]. It is capable of transmitting28MBit/s over several kilometres. Unfortunately the systemsusage is only allowed in a few countries and thus is notusable for an interoperable communication infrastructure ininternational disaster relief. Within IDIRA we have decidedto use IEEE 802.11 [10] based systems which can be used allover the world without needing specific licenses.

A promising approach for an easy-to-deploy 802.11 basedsystem is described in [1]. The system consists of so calledWireless Gateways (WGW) which consist of three self-aligning directional antennas which establish communicationlinks between each other. The Wireless Gateways providelocal communication for end-devices and building up a mesh-network using the directional antennas. The self-alignmentprocess allows setting up a communication node by non ITtrained field staff. But even more important is the actual plan-c©2015 IEEE http://ieeexplore.ieee.org

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ning of the communication network itself. Here it is crucial toanswer the questions where to place the Wireless Gateways,where to place relay nodes, and where communication for thefield commanders is possible.

As described in [11] each field commander will be equippedwith a Wireless Gateway and a Communication Field Relayto ensure on-site communication. But in a disaster situation afield commander needs to know where exactly in the disasterarea the WGW should be placed to ensure interaction withother operational areas and with the tactical layer. To findintuitively an appropriate place for the wireless gateway orthe communication relay node within an operational area forthe first responders team is not possible. Field commandersneed to be supported by a system which allows them toposition themselves together with the Wireless Gateway basedon tactical needs as well as based on communication needs.

In our work we propose the simulation of possible de-ployment locations based on a radio wave propagation modeland terrain data. Here, we present an implementation of asimulation about the radio propagation based on SPLAT! [12].As mentioned above, in the case of desaster relief actions,the communication infrastructure must be easy to deploy.Thus, there is limit of weight and height of the poles foran independent radio communication network. The systemdescribed in [11] uses poles of 6m height. With such a heightforests and buildings getting essential obstacles. Consequently,accurate data on the digital surface is needed to retrieveappropriate simulation results for fast deployable networksafter disasters.

The radio propagation overview visualized together with theactual disaster situation helps the first responders in a largescale disaster to find adequate places and areas to establish abroadband wireless communication infrastructure. Based on amap and the radio propagation simulation the first respondersare able to install the wireless gateways and the communi-cation relay nodes. The setup of the communication channelswithin the wireless communication network is performed fullyautomatically by the wireless gateways.

In the following sections we describe i) the wireless gatewayto establish a secure and reliable communication infrastructureafter a large scale disaster destroyed the public communicationinfrastructure, ii) our approach to implement and extend theRF propagation simulation based on SPLAT! in a resolutionof 1/10 of an arc second, iii) the IDIRA Common operationalPicture application supporting the first responders and iv)we provide a validation scenario of the IDIRA system in areal world field trial after a large scale disaster with supportfor the first responders to setup a wireless communicationinfrastructure. Finally, we show some further steps and ideasto improve our proposed architecture.

II. WIRELESS GATEWAY

The motivation for the construction of the so called WirelessGateway (WGW) was the need that an independent communi-cation network should be established right after a disaster byfield personnel not consisting of IT experts. The core concept

Fig. 1: WGW Building Blocks [1]

behind the WGWs is a fully automated interlinking of direc-tional Wireless Local Area Network (WLAN) components.

A. Overview

Directional antennas are used as this allows increasingthe communication distance between two sites, compared toomnidirectional antennas. Due to the usage of directionalantennas the signal strength will be higher and the noiselevel will be lower. This increase in the signal to noise ratio(SNR) allows higher throughput at similar distances or longerdistances with similar throughput.

The different components, described later on, of the WGWare assembled into one case and can easily be installed ona pole to get better radio propagation. This is a prerequisitefor an easy installation in the operational area by the firstresponder teams. The WGW is able to align its antennasfully automated to other WGWs and provide a wireless cloudas well as a Local Area Network (LAN) connection to thespanned network.

In a large scale disaster the first responders need an easy touse and handy communication system where it is not necessaryto be an IT expert to deploy a communication system withinthe operational area. To setup a communication system basedon the WGW must be possible for non-trained users. This hasbeen a main requirement in the design and implementationphase of the wireless gateways. The WGW has two mainassets: easy setup/installation and extended coverage.

The main building blocks of the wireless gateway are shownin Figure 1.

B. Structure

The system is mounted in a housing which consists of fourlayers. The top three layers (also referred to as modules)are built up identically. Each one consists of a wirelessaccess point (which can also be configured as wireless client)connected to a directional antenna. Further a motor whichallows rotating each antenna individually by 360◦ is mountedin each of the top three layers. In the bottom layer the core

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parts of the systems are installed. A small embedded PC(router-board), with routing functionality, running OpenWRTfirmware together with a switch provides connectivity betweenthe WLAN stations and the rest of the system. The self-alignment algorithm is controlled by the router-board. Therouter-board is connected to a microcontroller which is respon-sible for the control of the rotation of the modules. It operatesthe motors and reads the sensor values controlling the rotationfrom the top three layers. The router-board is equipped withtwo WLAN modules one is configured to operate at 2.4 GHzand used for connecting end user terminals. The second oneis configured to operate in the 5 GHz range and is used forthe self-alignment algorithm of remote WGWs.

Additionally the Communication Field Relay (COFR) isconnected to the WGW and positioned at the foot of the poleon which the WGW is mounted. The COFR allows to connectwired end devices to the communication infrastructure andgives the possibility to provide internet uplink to the network(e. g. via WiMAX, Ethernet, satellite, 3G, etc.).

More details on the WGW and the COFR can be found in[1].

III. SIMULATION AND SUPPORT

The following section describes the possibilities of theReachability Optimized Positioning (ROP) subsystem ofIDIRA. By using a Web based interface the commandingpersonnel is able to get a map and an overview where to deployand install the WGW. ROP supports the early responder teamto identify the best suited place to setup a broadband wirelesscommunication infrastructure. To provide this information it isnecessary within ROP to calculate the radio signal propagationbased on the available digital surface model of the operationalarea. An IDIRA extension of the open source tool SPLAT![12] in the version 1.4 is used to calculate the radio signalpropagation for the operational area in a resolution 1/10 of anarc second.

Fig. 2: IDIRA SPLAT! simulation result

A. Signal Propagation Calculation using SPLAT!

ROP supports the commanding personnel to deploy wirelesscommunication infrastructure. To find the appropriate placesand areas the commanding personnel setup and start a signalpropagation calculation for the operational area. The result ofthe calculation is a picture of the signal propagation simulationshown in Figure 2. The visualization of the ROP results canbe performed on a map of the operational area. Based on thesimulation and the map the commanding personnel will beguided where to establish the WGWs.

The calculation of the signal propagation is executed by theIDIRA extended SPLAT! tool. SPLAT!, as described, providesradio signal propagation and loss and terrain analysis toolsfor the electromagnetic spectrum between 20 MHz and 20GHz. The SPLAT! calculation is based on the Longley-RiceIrregular Terrain [13] as well as the new Irregular Terrain withObstructions (ITWOM v3.0) [14] model. Based on the antennaheight it is possible to establish line-of-sight communicationpaths and Fresnel Zone clearances absent of obstructions dueto terrain.

B. IDIRA SPLAT! Extension

Originally SPLAT! provides site engineering data to knowobstructions based on the U.S. Geological Survey and SpaceShuttle Radar Topography Mission [15] elevation data. Thisdata is available with a resolution of 1 arc second (for partsof the world) and with a resolution of 3 arc second for therest of the world. More detailed geographic data cannot behandled by SPLAT!. The IDIRA SPLAT! extension is ableto handle digital surface model in a resolution of 1/10 of anarc second which is in the middle of Europe approximately3 m. Based to the digital surface model of 1/10 of an arcsecond it gives the first responders an adequate simulationresult where to establish the WGW to have a guaranteedcommunication channel. It also provides further information toexperts where to put the WGW if the communication networkshould overstretch a bigger area.

C. Radio signal coverage

As described above Figure 2 shows the output of a radiopropagation simulation with the IDIRA extended SPLAT!based on the digital surface model. The white section in the cir-cle indicates an area where it is possible to deploy the WGWsand to establish a communication channel automatically. Thered or dark grey area indicates that it is not possible to establisha communication infrastructure due to obstacles between thedirectional antennas. In the middle of the circle the green orlight grey area gives the commander the information that it ispossible to support mobile equipment for communication inthe incident area.

D. Validation of the radio propagation simulation

Based on a simulation of an area in the north of Salzburg,shown in Figure 3, fourteen places were defined to validatethe possibility to establish a communication channel fullyautomatically (Point 1 – Point 14). In a real world field test

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the WGWs were deployed at the fourteen locations. Afterthe WGWs were deployed the system tries automaticallyto establish a communication channel. The results of theautomatic establishment were:

• WGWs placed on areas indicating a good signal noiserate, green and yellow areas (light grey), the communi-cation channel setup was successful: yellow points. (Point2,4,5,9,12,13)

• WGWs placed in red or grey areas the automaticcommunication channel setup fails: red points (Point1,3,6,7,8,10,11,14).

One of the main goals of the IDIRA ROP was a 100%support for the first responders to find the appropriate placeswhere they need no technical support to configure the com-munication infrastructure. This example field trial with 14locations shows that the simulation model provides correctestimations. Besides that, the simulation model has provento be correct during different field trials (trainings, smallexercises, large scale exercises) of the IDIRA Project.

IV. IDIRA COMMON OPERATIONAL PICTURE

The standalone simulation and visualization of ROP resultshas few benefits, as the decisions for the communicationnetwork are isolated from tactical disaster needs. Thus herewe introduce the IDIRA Common Operational Picture (COP)application integrated in the IDIRA Mobile Integrated Com-mand and Control Structure (MICS). The COP is the mainvisualization and human interaction interface of the MICS.It visualizes disaster related information and provides thepossibility to add incidents, assign tasks or post observations.The MICS is the main part of the IDIRA infrastructure in thecase of a large scale disaster. It supports the different earlyresponders with the exchange of related information about thedisaster. The MICS provides a whole range of interfaces toexchange information and works as an information hub for alldisaster related information and can be brought on site.

To have access to the MICS services it becomes moreimportant to offer broadband communication access to therelief forces in the operational area, allowing them to provide

Fig. 3: Simulation validation in the base area

information and access the COP to be better aware of theactual situation.

To exchange information within the commanders and dif-ferent relief forces in the operational area it is necessary toexpand the communication infrastructure to these areas. Besidethe disaster related information exchange, COP is able tosupport the commanding personnel and the relief forces on-scene to establish a secure, flexible and broadband wirelesscommunication infrastructure based on the WGWs by showingthe results of the ROP subsystem.

A vehement challenge to setup a broadband and securecommunication infrastructure is not only to design a technicalinfrastructure and hardware for communication but also toimprove the acceptance of the system by the first responders.Since the commanding personnel and relief forces are no ITor communication experts, special attention is paid on theusability aspects of the IDIRA systems design and the IDIRAsystem requirements.

The Reachability Optimized Positioning subsystem ofIDIRA allows to visualize radio propagation results as de-scribed in Section III. If the communication network coverageis visualized together with disaster related information withinthe COP this brings great benefits on the situational awarenessand the decision process for commanders in disaster manage-ment. As this would allow that the field commanders choosetheir optimal position based on operational needs as well asbased on communication needs as the common visualizationprovides details on both information categories. This knowl-edge mapped together allows an optimal positioning of fieldcommanders to be on the one hand able to provide informationto/from the MICS and being able to cope with the operationalneeds on site.

The propagation simulation visualization in COP togetherwith the WGWs ensures that positioning and installation ofa communication infrastructure by first responders is an easytask and does not block many resources of first responders.

V. IDIRA ROP VALIDATION

This section shows an on-scene (field trial) using the IDIRAMICS and COP together with the Reachability OptimizedPositioning (ROP) subsystem. It should show that the IDIRAframework supports the commanding personnel and the reliefforces to establish a communication infrastructure within theoperational area. The intention is to demonstrate that by visu-alizing ROP results together with disaster relevant informationwithin the COP it is possible to choose the position of fieldcommanders such that on the one hand the communicationneed can be fulfilled and on the other hand the operationalneeds in the disaster are fulfilled.

A. Validation scenario

The starting point in this validation scenario is a largescale disaster in a test area in the north of Salzburg. Thescenarios for the validation were debris flows and the dangerof landslides after extreme rain conditions. As a consequenceof the disaster the public communication infrastructure was

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destroyed and it was not able to receive or send informationabout the impact of the disaster using the public communica-tion infrastructure. Figure 4 shows the disaster area with fourdifferent incident areas (A-D). The IDIRA framework supportsthe first responders to establish a communication infrastructureby using the WGWs without knowledge about the topologyand the particular surrounding of the incident areas.

B. Usage of the IDIRA framework

Using the IDIRA framework the commanding personnelis able to gather the already available information about thedifferent incident areas. The information was added to the mapand the commander determines a location for the IDIRA MICSwhich is deployed somewhere on-site. After fixing a positionof the MICS which is mainly driven by tactical needs andbased on the information of the incident areas the commandingpersonnel start a first simulation of the radio propagationcoverage of the installed WGW at the MICS location. Figure5 shows the result of the radio propagation together with theincident areas. It shows that at specific parts of incident areaA it is possible to establish a direct communication channel.Consequently the WGW for incident area A is located at aspecific position which is reachable from the MICS and fulfillsthe tactical needs of the field commander on-site. A directcommunication channel from MICS to incident area B, C andD is not possible. As a WGW will be installed at the definedlocation within incident area A a simulation for this positionwill be performed. The results of the simulation at incidentarea A (Figure 6) shows that it is possible to establish aconnection to incident area B.

As areas C and D cannot be reached, the commanderdecides to install a relay WGW (R1) at the border of theautomatic alignment coverage and start a simulation for thislocation. The relay WGW R1 was able to span a wirelesscommunication channel to the incident area C as shown inFigure 7.

As a WGW will be installed at the defined location withinincident area C a simulation is started for this position. Theresult of the simulation at incident area C (Figure 8) shows

Fig. 4: Incident areas

that it is possible to establish a communication channel toincident area D via C.

This scenario has been used in real world training and hasshown the benefit of using ROP for deciding where to place thecommunication nodes for a disaster area. During the exercisethe simulation has been performed. The positions of the fieldcommanders have been chosen based on tactical needs and onthe simulation results. Further the network has been setup bythe first responders by installing the WGWs at the simulatedpositions and the links where established automatically. Thecommunication needs of the first responders at incident areasA,B,C and D could be fulfilled. The needed informationbetween the commanders at the incident areas and the tacticalcommanders at the MICS has been exchanged by the WGWnetwork.

C. Improvements

During several IDIRA meetings and field trials interviewswith the first responders organizations were realized. The maingoal of the interviews was to know how we can extend andenhance the simulation tool for a better support. Based onthe interviews we identify three main improvements: i) theduration of the simulation (which right now lasts about 40minutes), ii) support for different radio frequency range fordifferent radio technologies and iii) the system should proposethe areas where it is possible to setup a relay communicationnode.

VI. CONCLUSION AND OUTLOOK

This paper presents an accurate simulation model for sup-porting the setup of and independent communication networkfor first responders. The network itself is based on so calledWireless Gateways. The simulation model is based on a digitalelevation and a digital surface model with a resolution of1/10 of an arc second. The results of the model are presentedtogether with tactical information in one GIS system calledCommon Operational Picture. Showing the coverage of thecommunication network together with tactical informationallows more appropriate decisions to be taken by the com-manders.

An evaluation performed with a real installation showedthat the model is accurate. The real usage of the systemduring training with first responder organizations showed thereal value of the system when there is the need for tacticaldecisions taking into account communication needs.

For the future it is planned to speed up the simulation byperforming multiple simulations in parallel and matching theresults together. Further the framework should be extendedsuch that it is configurable to allow using different frequenciesand different communication technologies.

ACKNOWLEDGMENT

The work described in this paper was partially funded bythe FP7 European Union FP7 research project ’Interoperabilityof data and procedures in large scale multinational disasterresponse actions’ IDIRA (project number 261726) [2].

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Fig. 5: IDIRA MICS coverage

Fig. 6: Incident Area A Coverage

Fig. 7: Communication Relay R1 coverage

Fig. 8: Incident Area C Coverage

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