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Concept Design of Satellite Communications System

for Next Generation Marine Observation

- Broadband IP network down to Underwater -

Naoto KADOWAKI, Ryutaro SUZUKI

, Hiromitsu WAKANA

, Takashi TAKAHASHI

,

Hiroshi YOSHIDA, Takafumi KASAYA

Kenichi ASAKAWA

and Yasuhisa ISHIHARA

National Institute of Information and Communications Technology

4-2-1 Nukui-Kitamachi, Koganei, Tokyo, 184-8795 Japan

Japan Agency for Marine-Earthe Science and Technology

2-15 Natsushima-cho, Yokosuka, Kanagawa, 237-0061 Japan

Abstract- Importance of marine observations and devel-

opments has been increasingly recognized as a key to many

grand challenges of human beings such as development of

The amount of data obtained by marine devices is increasing

because many kinds of data from simple ones like tempera-

ture to video image and scanned image of seabed are needed

required for secure operation of underwater facilities such

-

works for marine observations to carry huge data in real-

-

I. INTRODUCTION

Marine and underwater mineral resources are important to

keep lasting economic growth because the most part of Japanese

economic zone is occupied with the oceans. Explorations of

natural resources in the region of seabeds in exclusive economic

zone (EEZ) have done using ships and underwater vehicles. It

is well known that there are huge amount of methane hydrate

comparative with that of natural gas consumed in 96 years in

Japan. Natural gas is also expected to exist in East China Sea.

Survey of hydrothermal deposits has also been conducted as a

lot of rare metals contained there.

It is also important to assess environmental problems includ-

ing global warming so that oceans cover 70 % of the Earths

surface. Ocean has been playing an important role to keep

stable climate. Its heat capacity is about 1,000 times larger than

-

ly exhausted carbon dioxide . However explicit temperature-rise has been observed even in deeper waters. Continuous

seabed monitoring and sea bottom survey are also needed to

catch the omens of catastrophic earthquakes which periodically

happen at underwater plate boundaries. Until now, we have,

however, held survey of a tiny percent of entire oceans because

of deep-sea-bound.

Marine and underwater researches and developers use lots of

sensors for surveys, explorations and operations. These sensors

are installed on/in research vessels, buoys, and underwater plat-

form. There are lots of movable underwater platforms: human

occupied vehicles (HOVs), remotely operated vehicles (ROVs),

autonomous underwater vehicles (AUVs), and gliders. The ad-

vantages of AUVs utilization is reducing operation cost because

of support ship less, and enabling them to go where HOVs or

ROVs have trouble reaching.

The amount of data obtained by marine observation is

thought to be increasing rapidly because of increase of number

of observation and adopting new type of sensors such as high

definition cameras, side scan sonars, and multi-narrow echo

beam sounder. Real time monitoring must be needed for secure

operation of underwater facilities such as oil rigs. It is fresh

in our memories that the accident at the underwater oil well in

Gulf of Mexico brought huge damage to the area. Real time or

rapid analysis of these data is also the key to solve other social

or scientific issues, but current communication systems con-

necting vessels, buoys or underwater platforms are not able to

carry huge amount of data. In order to provide solutions for this

issue, the authors propose to utilize satellite communications

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system as the marine observation information network.

II. CURRENT INFORMATION NETWORKIN VESSEL, VEHICLEANDMARINE OBSERVATION SYSTEM

Most research vessels in Japan are currently using INMAR-

SAT. Its maximum communication rate is about a few hundreds

kbit/s. The vessels in JAMSTEC do not use a satellite or direct

communications to transfer huge amount of data which are ob-

tained through surveys. Mooring and drifting buoys have small

and low power satellite communication system such as AR-

GOS[1] and ORBCOMM[2] because buoys are not able to have

of the small amount of data and accessibility of Iridium. These

communications are mostly peer to peer. On the other hand, un-

derwater communication is limited to use acoustical communi-

cation. The HOV, Shinkai 6500 and the AUV, Urashima [3] in

JAMSTEC use acoustic transceiver systems for communication

between the vehicle and the support vessel only. These com-

munications are completely peer to peer. There is no practical

multi-node communication protocol for underwater system.

The obtained data is recorded into digital recording media, be-

ing analyzed after their dives. Recently, researches of wireless

underwater communication networks [4][5] are focused but

those do not include the communication with the satellites. Un-

derwater cable network systems, in contrast, have been used for

multi disciplinary observations with high-capacity data trans-

mission. [6]-[8]

A seamless wireless communication between marine plat-

forms and land stations achieves all seasons, wide area observa-

tions. This technique also enables quick responses to various

scenarios for example remarkable data acquisition or instrument

trouble. Therefore, a wide-band interactive communication will

bring us a new stage of ocean researches and explorations.

III. CONCEPT DESIGN OF INFORMATION NETWORK

FORMARINE OBSERVATION

3.1 Underwater multi-node communication system

We propose the seamless communication system between

marine platforms and land stations. The marine platforms

should be mutually connected because the platforms will be

and so on. Fig. 1 shows an image of marine communication in

the near future. Higher data transmission rate is also needed for

underwater explorations so that sea-bottom and sub-sea bottom

images obtained have higher resolution. High frequency acous-

tic waves are drastically attenuated in sea water thus a high-

speed transmission is limited to short range communications.

Ochi and his team [9] achieved 100 kbit/s acoustical communi-

cation in range of 500 m. This acoustical communication rate

exceeds of other previous researches, but still less than that

of radio wave. It is reported [10] that a short wave laser beam

ranges about 100 m in deep sea and laser beam can be modulat-

ed up to 20 MHz. If communication like laser will be improved,

the underwater communication rate will be comparable within

air in short range. Ad-hoc communication may solve these cur-

rent underwater communication divide.

Fig. 2 shows the conceptual image of the multidisciplinary

Figure 1 An image of the seamless communication network

Figure 2 Conceptual image of underwater multidisciplinary observation

system using satellite communication

Seismometer

Electromagnetometer

HD cameraChemical sensors

Satellite

To landstation

Underwaterobservatory

Mooringcommunication buoy

Hydrothermal deposit or other natural resources

Cable or acoustic communication

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observation system for the various scientific purposes using

satellite communication. Until now, we have not used the real-

time data acquisition from underwater instruments. We will beable to get high-capacity underwater data and to operate the un-

derwater instruments on demand using the satellite communica-

tions. However, data transmission in the sea is serious problem

for actual operation of this system. If we will adapt such system

for the mining of natural resources, there is a possibility to be

able to use the wire communication for data transmit from the

sea-bottom instrument, because it is easier to carry out the min-

ing in the shallower depth.

3.2 Satellite Communications Links

Satellite access link should be bidirectional, but the capac-

ity of forward link from land base station to vessels, buoys and

AUVs for command and control is thought to be smaller than

return link to transmit data obtained.

Transmitting data from buoys to land base station, amount

of data is still not so large because the kinds of data are air/

water temperature, and so on. Then ordinary mobile satellite

communications system in L/S band can be used. On the other

hand, transmitting data from AUVs and ocean facilities such as

oil rigs requires higher capacity because they obtain high capac-

-

nal is required if direct satellite access link is needed. In case

that AUVs can establish high capacity link to a support vessel,

high e.i.r.p. earth terminal is required on the support vessel with

shaking cancellation function.

3.3 Wireless Ad-Hoc Networks on The Ocean

In case that sensing probes are delivered relatively close area

around support vessels or buoys, there is a possibility to utilize

wireless ad-hoc network. When autonomous floating devices

such as wave gliders[11] or Mobile Offshore Structures[12]

are in practical use, they also can be used as platforms. Fig. 3

shows the concept of marine observation network which wave

glider is used as the communications platform. If we implement

a base station based on IEEE802.11a/b/g/n on a support vessel

or buoy, circular area with diameter from 1 to 2 km will be able

to be covered. In order to extend the distance, antenna gain of

base station should be raised, but MAC protocol with direc-

tional antenna should be employed. If we can use WiMAX base

station, the communication distance is expected to be expanded

to several kilo-meters, but propagation phenomenon between

probes on sea surface and the base station on vessel should be

studied.

3.4 Issues of R&D

(1) Real-Time Data Gathering

Current data gathering from buoys is achieved by ARGOS

and ORBCOMM satellite systems. Both satellite systems are

with transmission rate up to 4,800 bit/s. Because of LEO con-

stellation and very low data rate, it is impossible to gather glob-

al data in real time. Real time data gathering is a very important

factor in case, for example, for operation of marine facilities

and monitoring propagation of tsunami after a big earthquakeoccurs. In order to make sure unbroken link connectivity and

launched in LEO, or several number of GEO satellite should be

used, and high capacity data link in L- or S-band should be ad-

opted.

As a trial of usage of a GEO satellite in S-band, JAMTEC

and NICT conducted a demonstration of communication sys-

tems between support vessel Natsushima and land base station

in Yokosuka by ETS-VIII in 2007 [13].

(2) Implementation of Earth Stations

Implementing earth stations on vessels (ESV) has been done

for Inmarsat application, ETS-VIII experiments by JAMSTEC

and NICT mentioned above, and Ka-band ESV has been dem-

onstrated as one of WINDS experiments done by JAMTEC and

JAXA. The biggest issue is implementing compact earth termi-

nal on sensing probes such as buoys or AUVs. The earth termi-

nal should be as small as possible not to occupy much space in

the probes. Especially, there are several severe constraints exist

Figure 3 Marine Observation Network with Wace Glider

WINDS

WiMax or Wireless LAN

Wave Glider

Wave GliderAUV

AUV

Sensors

Acoustic Transducer

Acoustic Data

Transmission

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in case of earth terminal on AUVs. Antenna on-board should be

-

ellite pointing function even in severely bad weather condition

that shaking 45 degrees. In addition, all equipment should not

be corrupted by water pressure when AUV is operated in deep

sea.

(3) Radio Wave Propagation on Sea Surface

In order to implement wireless ad-hoc network between sens-

ing probes and support vessel, propagation phenomenon should

be studied, and MAC protocol for directional antenna utilization

should be adopted in order to extend communication coverage

and ensure the data transmission.

(4) Antenna for Ad-Hoc Networks

Antennas on sensing probes must stand high water pressure

and should be small so that the antenna can be mounted on

small probes. Fortunately, small-sized modems for wireless

LAN and WiMAX are commercially available. It should beeasy to put them in non-conductive pressure housing made of

synthetic resin or ceramics[14]. These modems can be connect-

ed to CPUs by USB. As their transmission rate is 480 Mbit/s

(high speed), 12 Mbit/s (full speed) and 1.5M/bit/s (low speed)

in case of USB2.0, their electrical connection through underwa-

ter connectors or feed-throughs should be easy.

(5) Underwater Broadband Communication Technology

The only underwater communication system is acoustic wave

communication system. Therefore, communication capacity is

limited up to 100 kbit/s as mentioned above. There is a strongrequirement to develop much higher capacity communication

technology for underwater data transmission. Deep sea laser

communication technology is a good candidate to such appli-

cations. Multi-node communication protocol is also required

technology for multidisciplinary observation.

IV. EXPERIMENTAL SYSTEM DEVELOPMENT PLAN

4.1 Proposal of Experimental System using WINDS

Low rate data gathering from buoys is already done by AR-

GOS or ORBCOMM satellite communications system though

real time data gathering is not achieved. The biggest issue is to

realize broadband connectivity from ocean. Though gathering

data from all types of marine devices via satellite directly is ide-

al, it is not feasible because required conditions to install earth

station on marine devices have wide variety due to those size,

shape and many other circumstances. Therefore, we propose

a simple system configuration as the first step of demonstra-

tion. In this proposal, we propose to use Japanese experimental

satellite WINDS to connect between a support vessel and a

land base station and utilize wireless LAN (WLAN) to connect

probes like AUVs and a support vessel. WINDS features ac-

tive phased array antenna (APAA) to provide global coverage

and high data rate capability from 1.5 Mbit/s to 1.2 Gbit/s with

stage demonstration is shown by Fig. 4. We assume that AUV

and stores it in high capacity storage during diving, and after

surfacing, the data is sent to the vessel by WLAN and transmit-

ted to WINDS from the vessel.

The earth station on vessel (ESV) is based on compact VSAT(C-VSAT) developed for usage in APAA coverage area. C-

VSAT can provide the transmission rate of 1.6, 6.5, 25, 52, and

104 Mbit/s. Antenna of C-VSAT must be modified to cancel

shaking of vessel and equipped within radome to protect from

seawater. WLAN equipment on AUV should be protected from

water pressure during diving. WLAN antenna on AUV should

be as small as possible not to disturb navigating, then it is dif-

on vessel had better to have higher gain to carry high capacity

data from AUV and to extend communication distance between

AUV and vessel. Yagi antenna can provide high gain capabil-

ity from 12 to 19 dBi, and planner antenna can provide up to 13

dBi in 2.4 ~ 2.5 GHz band, but direction control mechanism is

needed to point AUV on sea surface.

4.2 Antenna

4.2.1 Requirements

Though ESV will be installed on a support vessel, it should

Figure 4 Conceptual image of demonstration System using WINDS

Rising up after survey

Data transferby WLAN

Data transmissionto land base station

Support vessel

WINDS

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better to be as small as possible considering applicability to oth-

er small platforms such as buoys. On the other hand, high data

rate transmission requires larger aperture of antenna. In order to

develop antenna for ESV, requirements are listed as followings:

- Frequency bands are 28GHz band for transmit and 18GHz

band for receive.

- Antenna polarization must be vertical for transmitting andreceiving.

- The transmitting data rate should be more than 1.6 Mbit/s

which is the lowest rate of C-VSAT.

- Beam control range of Azimuth: 0~360 and Elevation:

45TBD to point satellite in any attitude of vessel.

- Beam control function to cancel shaking of vessel must be

realized.

- ITU-R recommendations S.524-9 of the off-axis e.i.r.p den-

As the AUV antenna is required as possible as small, the

minimum antenna aperture diameter will be 45cm due to the

ITU-R recommendations, and besides, the azimuth and eleva-

tion angles of the beam must be controlled to point the satellite

and to compensate the ship rolling and pitching. For the consid-

erations of those conditions, it is suitable to control the azimuth

direction by mechanical revolution mechanism and elevation di-

rection by mechanical or electrical mechanism. Fig. 5 and Fig.

The Fig. 5 is a planer active array antenna of 45cm aperture

diameter that is applied the mechanical beam pointing mecha-

nism for both azimuth and elevation directions. Fig. 6 is a

planer active phased array antenna that is installed to direct thezenith direction and its aperture diameter of 55cm. This antenna

is applied the mechanical control mechanism for the azimuth

direction and electrically controlled mechanism for the eleva-

tion direction. Both antennas consist of active array antenna

installed transmitting and receiving modules behind the array

-

rotary joints.

The antenna needs a radome to protect from sea water. The

balljar type radome and the disk type radome will be used for

Fig. 5 and Fig. 6 respectively. The balljar radome become large

amount of water drag. On the other side, the disk radome has an

As the disk type of radome is more critical for vertical pressure,

Fig. 7 and Fig. 8 show the block diagrams of the transmitting

antenna and the receiving antenna, respectively. Each antenna

Figure 6 Planer active phased array antenna with mechanical

beam pointing (azimuth) and electrical beam pointing (elevation)

Figure 5 Planer active phased array antenna with mechanical

beam pointing mechanism for azimuth and elevation

(600mm)

(500mm)

Planer Antenna

(450mm)

(450mm)

Radome

Rotation AxisRadome

(650mm )

(200mm)

Antenna DriveMechanism

Planer Antenna

(550mm)

(550mm)

#1

#2

#3

#4

#49

#50

13-Elements Waveguide

Slot Subarray

Solid State Power

Amplifier

Phase

Shifter

Pre-Amplifier

Figure 7 Phased array design of transmiting antenna

#1

#2

#3

#4

#48

#49

Low NoiseAmplifier

PhaseShifter

Low NoiseAmplifier

18-Elements WaveguideSlot Subarray

Figure 8 Phased array design of receiving antenna

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is used to the waveguide slot array antenna for the reduction

of antenna feed loss, and the sub-array feed method is used to

used only for active phased array antenna in Fig. 6.

Fig. 9 shows the calculated e.i.r.p. of the transmit antenna

of Fig. 5 with allowable maximum limit of ITU-R S.524-9 for

both vertical and horizontal planes. To satisfy the ITU-R limit,

spread spectrum techniques will be applied.

4.2.3 Development Plan

For the development of those antennas, following subjects

must be considered.

- Possibility of common antenna for both transmitting and

receiving,

- To make sure to provide required data rate based on charac-

teristics of antenna, and

- Development of the water-resistant and the pressure-resis-

tant radome to protect the antenna.

V. CONCLUSIONS

Marine observation becomes more important than ever for

keep lasting economic growth or keeping environment. On theother hand, communication networks for marine observation is

still narrowband and high capacity data cannot be transmitted.

The authors have started conceptual study for developing com-

munications network for next generation marine observation

utilizing satellite communication systems in order to provide

solutions for real time high capacity data gathering from ocean.

under discussion is described in this paper. We plan to proceed

this study and develop demonstration system as early as pos-

sible.

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