LTE terminal for maritime applications

S.M. Anwar, E. Goron, Y. ToutainSatimo industries, Mirowavevision group

Shoaib.muhammad@satimo.fr

J.P. Péronne, S. HéthuinTHALES Communications & Security

Abstract— A complete communication terminal operating ina LTE frequency band is presented for operation in the maritimeenvironment. The objective is to propose an antenna system withelectronic or mechanical stabilization along with the LTE modemand control unit to provide at least a 10 nautical mile coveragearea along the coasts for low cost, high data rate (~10 Mbps)communications in the 800 MHz & 2600 MHz LTE frequencybands. The system for 2600 MHz communication usingelectronically selectable antennas has been developed andvalidated over a LTE test bench.

Index Terms—LTE; 4G; maritime; antenna; terminal; modem;communication system.

I. INTRODUCTION

The TMS (Terminal Marine Stabilisé) project is a Frenchconsortium composed of Thales Communications and Security,Satimo Microwavevision group, Alcatel Lucent, Deti, andInstitut Mine Télécom Bretagne. This project started inOctober 2012 for two years duration. The main objective ofthis project is to develop a complete communication system,suitable for the maritime environment. This system consists ofa LTE-based modem piloted by a CPU board, an intelligentantenna system adaptable to a harsh environment consideringthe roll and pitch of a ship and to avoid loss of communication.The antenna system should be intelligent in order to choose theoptimum beam direction for increased coverage distance.

This system should propose similar data rates and coverageas achieved by current LTE networks for groundcommunication and LOS (Line Of Sight) coverage.

There are various applications for such a system. All cargoships waiting at dock for loading / unloading can deploy thissystem to be connected. The fishing boats, weather boats, andother commercial ships can also use this system tocommunicate with land. In the marine research domain, thebuoys placed in sea can have this system to transferinformation useful for research. In addition, the touristsspending their holidays in coastal areas on boats can use thissystem to stay connected.

Actually, there are no such systems in the market providinghigh data rate internet coverage to coastal areas connectingthem to the terrestrial network. Satellite connection is the onlysolution used today to provide internet services to ships andoffshore platforms (Immarsat, Vsat, and Irridum). It has theadvantage of providing global coverage. However, the data ratedepends on the service chosen. The higher the data rate, the

larger, more bulky, and hence more costly is the antennasystem. For example, for a Ku band system, up to 1Mbpsservice can be achieved with an antenna diameter between1.2m and 2m, and for a C-band system, up to 10 Mbps datarates are achievable with an antenna diameter between 2m and2.4m. The cost of the whole satellite system (antenna,stabilization, and modem) varies between 5K€ to 50K€depending on the specifications. In addition, the monthlyservice cost is in the range of a few hundred €uros dependingon the chosen data rate.

Another alternative is to use the current 2G/3G services tocover the coastal areas. The system cost is quite lower than thesatellite solution because only a 3G dongle and a PC arerequired. A 1Mbps data rate was measured 3 nautical miles offfrom the coast in 3G, and a 100 Kbps measured at 5 nauticalmiles from the coast in 2G. The maximum coverage distance isabout 15 km from the base station, which are not always placedclose to the coast. The monthly cost of the services is less thana hundred euros.

The LTE terminal developed during this project shouldprovide at least a 10 nautical mile coverage area (ideallybetween 20 and 30 km) from the coast. Data rates between 2 to10 Mbps are envisaged to provide equivalent services as thesatellite solution. The total system cost goal is between 1K€and 2.5K€ depending on the system configuration. Themonthly service charges will be lower than a hundred euros.The initial objective is to cover the 2600 MHz LTE frequencyband (band 7) and eventually the 800 MHz LTE band (band20).

The paper is organized as follows. In section II, the LTEterminal system topology is presented with description of eachpart. Section III details some preliminary analysis about thecoverage distance using a simple propagation model. SectionIV includes prototype and the measurements with conclusionsand perspectives in the section V.

II. LTE TERMINAL SYSTEMThe proposed system block diagram is presented in Fig. 1.

It consists of a UE (User Equipment) module (Fig. 1b) whichincludes the LTE modem connected to the CPU (centralprocessing unit) through a USB connection (e.g. the HuaweiLTE modem [1]) or through a mini PCIe bus (e.g SIERRALTE module [2]). The CPU is powered by a power supplymodule converting the DC voltage, available aboard the ship,to 5V and 12V DC. There is an Ethernet output which can be

connected to a hub or a router to provide connection to a givennumber of users on board.

The antenna system module (Fig. 1a) has two antennas. Thereason for which is the spatial diversity essential to cancel themulti-path fading effects (explained in section III). Bothantennas can be stabilized electronically or mechanically. Inthe case of mechanical stabilization, we can useomnidirectional antennas with stabilizing device to account forthe roll and pitch of the ship and to keep the antenna in avertical position at all times.

In the case of electronically stabilized antenna system, wecan use a sectorial antenna. This antenna has to have anintelligent control system which decides which area toilluminate in order to connect to the eNodeB closest to theboat. In the first prototype, we use a GPS module along with agyroscope and accelerometer module. The idea is that using theGPS location of the boat and the information from thegyroscope and the accelerometer module, we can point to thedirection of the BTS whose position is already stored in theCPU memory. Eventually, this system will be replaced by amore intelligent signal processing called AFS (AutonomousFESA™ System) and based on algorithm designed by ThalesC&S to detect where the closest BTS is located.

(a)

(b)

Figure 1: Block diagram of the proposed system (a) the antenna system, with(b) the LTE terminal.

The LTE UE module is separated from the antenna systemmodule in the first prototype. Eventually, this module will beintegrated inside the antenna module. For the current

configuration, we have a multi-point connector carrying power,control lines, and location information from the UE module tothe antenna module. The RF connections between the modemand the antennas are carried through separate low loss RFcables.

In order to survive the harsh maritime conditions (e.g highlevels of humidity), the whole system should be compatiblewith the IP67 industrial standard.

III. PROPAGATION MODEL

In order to validate the need for a spatial diversity betweenthe antennas for the proposed system, a simple propagationmodel was used and is presented in Fig. 2. This model is basedon the work presented in [3], where it was concluded thatvertical polarization is more suitable for maritime propagationthan the horizontal one.

There are two possible propagation paths between the BTSand the ship as shown in Fig. 2. One is the direct LOS pathand the other is the longer path where the energy transmittedby the eNodeB antenna is reflected by the ocean surface andarrives at the antenna on boat. To consider the worst casescenario, a reflection coefficient value (ρ) of -1 is used, whichmeans that all energy is reflected from the ocean surface.

Figure 2: Propagation model

Using this simple propagation model, one can easily findthe propagation loss from the eNodeB antenna to the twoantennas on boat following the two propagation pathsmentioned above. Using the information from [3], path fadingcurves were calculated for both antennas. The results areshown in Fig.3.

Figure 3: Path fading curves for transmission between two antennas on shipand the eNodeB on land (for h1 = 50 m, h2 = 5 m, and Δ = 0.4 m)

The above results show us that using a single antenna thecombination of the energy from the two propagation paths issuch that we have sharp dips in E-field at certain distancesfrom the BTS. These dips correspond to complete loss ofcommunication between the ship and the BTS because thesignal energy coming directly and indirectly is completely outof phase.

(a)

(b)

(c)

Figure 4: Demonstrator for LTE based terminal system (a) complete systemon a tripod, (b) antennas, (c) UE module

To avoid this loss of communication, we need to use twoantennas, instead of one, separated by a distance Δ. Theoptimum value of Δ depends on the compromise between thetotal mast length we can tolerate on a given ship, the minimum

signal detection level, and the coverage distance we want toachieve. To find the optimum value, path fading curves forboth antennas are calculated and their sum is plotted in Fig. 3(green curve). We can see that loss of communications can beavoided using this spatial diversity by intelligently choosingthe value of Δ.

IV. DEMONSTRATOR AND MEASUREMENTS

A first demonstrator has been fabricated and tested atSatimo industries, Brest, France (Fig. 4).

The antennas used here each have 8 sectors so that theycan illuminate a given area. There is no need for mechanicalstabilization for such an antenna because their beamwidth issignificantly larger in the elevation plane to take into accountthe roll and pitch of the ship. The diameter of the antenna is 53cm, with a height of 23 cm, and a weight less than 5Kilograms.

(a)

(b)

(c)

Figure 5: Measured results for the 8 sector antenna system, (a) Azimuth plane,(b) Elevation plane, (c) VSWR

The radiation patterns of the antenna have been measuredseparately inside an anechoic chamber at Satimo Industries,Brest, France. The results are shown in Fig. 5. From the

azimuth patterns we can see that a minimum cross-over gaingain of 8.1 dBi is maintained with a maximum gain of about10 dBi (Fig. 5a). The elevation patterns (Fig. 5b) show us amaximum gain of 10 dBi with a 3 dB beamwidth of 40°. TheVSWR is lower than 2 over the 2.5 GHz to 2.7 GHz LTEfrequency band (Fig. 5c).

The LTE UE module is attached to the mast and connectedto the antennas using a multi-point connector and two low lossRF cables (Fig. 4). An Ethernet cable is connected from theUE module to the user PC to have the internet connection. Thesize of this module is 16.9 x 22.3 x 8.5 cm with a weight of2.1 Kilograms.

All the system (antennas, cables, and UE module) complywith the IP67 industrial standard to survive the harsh maritimeenvironment.

To validate the demonstrator, an LTE test bench setup wasused at Imagine lab, Brest, France [4]. The modem wasconnected to the LTE BTS at Imagine lab using their LTE Simcards. Initial results showed that the connection was possibleand we could control the antenna sector switching through theUE module and surf on the internet. Further tests on board aship are planned later this year and the results will bepresented during the conference.

V. CONCLUSIONS

A first of its kind complete LTE based communicationsystem is presented. It is composed of:

- A rugged terminal (UE) based on LTE modem and aCPU unit.

- Two multi-sector antennas for spatial diversity,controlled by the UE using the GPS positioning,gyroscope and accelerometer module information.

Initial tests have validated the system performance andconnectivity to the LTE test network.

Further tests are planned in near future. This systemprovides an attractive alternative to highly costly and bulkysatellite communications systems, proposing high data ratecommunications covering the coastal regions up to at least 10nautical miles.

ACKNOWLEDGEMENT

This work is funded by OSEO, Region Bretagne, and localauthorities under the grants FUI N° F1204014E (SATIMO)and N°F1204015E + F1011013E1 (THALES C&S).

REFERENCES

[1] http://www.modem3g.eu/huawei-e398-lte-usb-modem.html.[2] http://www.sierrawireless.com/en/productsandservices/AirPrime/Wirele

ss_Modules/High-speed/EM7700.aspx.[3] Y.M. Le Roux, J. Menard, C. Toquin, J.P. Jolivet, and F. Nicolas,

“Experimental measurements of propagation characteristics for maritimeradio links,” 9th Int. Conf. on Intelligent transport systemstelecommunications (ITST), pp. 364–369, Lille, France, Oct. 2009.

[4] http://imaginlab.fr/blog-en/?page_id=70