Helicopter Satellite Communication System for Disaster Control - - PDF document

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Helicopter Satellite Communication System for Disaster Control Operations

Wataru Chujo Kashima Space Research Center National Institute of Information and Comm unications Technology 893-1, Hirai, Kashima, Ibaraki 314-8501 JAPAN E-mail ： chujo@nict.go.jp

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I. Role of satellite communication for disaster management II. Requirements for the helicopter satellite communication system (HSCS)

• III. Configuration of the HSCS considering the installation

issues

• IV. Experiment results – ground and flight tests –

V. Conclusion

Outline

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I . Role of satellite communication for disaster management

 Delay of the organization of the rescue attempt at the

first stage of the disaster due to the lack of information is pointed out.



A big earthquake, tsunami, a forest fire etc.

 Satellite communication is generally useful for information

gathering during the disaster.



A helicopter has high mobility and is effective as means

• f information gathering at the initial stage of the disaster.



However, the communication ability from a helicopter was poor.

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Conventional helicopter relay data transmission

Via relay station

Image acquisition Videoing the d isaster situation. The photograph y position is fixed simultaneously .

Disaster countermeasure headquarters Emergency medical hospital

Convent ional helicopt er communicat ion needs a ground relay st at ion wit hin range of t he helicopt er.

 Preparat ion of t he relay st at ion is difficult in t he

mount ainous area, sea et c.

 The ground relay st at ion prevent s the helicopt er

from high mobilit y.

 Service area is limit ed t o 20-30km.

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New Helicopter Satellite Communication System

14GHz band

Helicopt er Sat ellit e Communicat ion Syst em can t ransmit disast er scene direct ly via sat ellit e.

A ground relay st at ion is unnecessary. Prompt dispat ch to any place is possible.

Disaster countermeasu re headq uarters Emerge ncy medical hospital

Image acquisition

Dir ect Communication to Satellite

12GHz band 6

Project for technical standardization

 Frequency assignment to the aviation satellite

business in Ku band was recognized at the WRC- 2003.

The technical standard for helicopter satellite

communication is not enacted in Japan. A technical proposal of the helicopter satellite communication is needed.

A real experimental proof of a helicopter satellite

digital-communication system contributes to allow the efficient use of radio waves.

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I I . Requirements for the HSCS

(1) Small-size and light-weight (2) Continuous and effective communication link independent of the helicopter direction or position (3) Transmitting power not to endanger the crew members on board and not to interfere with other existing radio communication systems (5) Axial ratio and polarization characteristics to meet the regulated standards (6) Positioning of the photographing scene

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Main technical issues

Avoidance of the shadowing due to rotor blades Time diversity transmission for forward-link Blade-synchronized transmission for return-link Satellite tracking Combination of open- and closed-loop tracking Polarization tracking Automatic tracking based on calculated polarization

angle

Avoidance of the interference with other satellites Restriction of the off-axis power radiation Spread spectrum modulation

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Block diagram of the HSCS

K u

• b

a n d g e

• s

t a t i

• n

a r y s a t e l l i t e Base-station Helicopter

Encoder

384kbps

RF Equipme nts Up Converter Down Converter

audio signal data

Data and picture processing equipme nts

data data

Transmitting APAA Receiving APAA Ante nna Control Unit Up Converter Down Converter Modulator IMU Demodulator

audio signal

Vide

• signal

divider Vide

• camera a

nd gimbal equipments Position- estimating equipme nts GPS gyr

• data

video signal

ICS

audio signal

Demodulator Decoder Vide

• signal divider

Modulator

video signal data audio signal data

spea ker Microphone

64kbps 384kbps 64kbps 10

Helicopter rear （ Power supply） GPS Gyro Antenna Transmitting active phased array antenna Camera p

• d

Communication rack Position estimating and marking equipments

• III. Configuration of a helicopter satellite communication system

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Active phased array antenna

6 m m 200mm 500mm

An image picture of the APAA Block diagram of the APAA

MDL RX MDL RX MDL RX MDL RX MDL RX

ACU

Power radiation Feeder circuit Heat emitter Control signal RF signal MDL TX MDL TX MDL TX MDL TX MDL TX

ACU

Power radiation Feeder circuit Heat emitter Control signal RF signal 12

Specification of helicopter satellite Specification of helicopter satellite communication system (HSCS) communication system (HSCS)

1 Antenna type Act ive Phased Array An tenna 2 Frequency TX 14.0-14.5 GHz RX 12.25-12.75 GHz 3 Polariza tion Linear polarization 4 Azimuth scan angle 0-360 degree 5 Elevation scan angle 30-90 degree 6 EI RP more than 35 d BW （ designed value） 7 G/ T more than 0.5 dB/ K （ designed value） 8 Modulation ・ Return link; BPSK/ SS spread facto r 6 ・ Forward link; BPSK 9 FEC ½-convolut ion code + RS code（ 204,188） 10 Overall rate Tx 384 kbps Rx 64 kbps

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Specifications of a helicopter and payload Specifications of a helicopter and payload

N u m b e r

• f

p a s s e n g e r s4 e x c e p t f

• r

c r e w O p e r a t i n g h e i g h t O p e r a t i n g v e l

• c

i t y O p e r a t i n g b a n k a n g l e F l i g h t t i m e P

• w

e r c

• n

s u m p t i

• n

T

• t

a l w e i g h t O n b

• a

r d e q u i p m e n t s 5 F e e t 1 K n

• t

a b

• u

t 2 h

• u

r s a b

• u

t 2 . 5 k W a b

• u

t 4 5 ｋ ｇ H e l i c

• p

t e r （ A l l p a y l

• a

d m

• u

n t e d ） 1 5 °

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Time diversity transmission (TDT)

from base earth station to helicopter

 TDT is adopted to overcome the signal shadowing

caused by the rotating blades.

 Two- and four-times TDTs have been investigated.  Time interval of TDTs was properly selected by taking

the rotating speed and size of the blades in consideration.

TDTs

Forward link

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Remote control from the base station

 Control of helicopter transmitting power  Instruction of photographing place  Voice instruction to crew

Helicopter onboard communication equipments

Satellite auto-tracking Transmitting signal cut when receiving signal is lost. Switch on/off and control of the onboard transmitter Reduction of the off-axis radiation power using spread

spectrum modulation

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Blade synchronized transmission

 Signal is sent during the interval of the rotating

blades.

 Blade intervals are detected by a magnetic detector

fitted to the blade rotor.

 Signal transmission interval is controlled at the

modulator.

Burst length Blade-shadowing period Shadowing interval Transmitter data Transmitter data

time

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Position estimation and marking

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Onboard video camera can capture disaster scenes under the instruction from the base station.



Position data of the helicopter using GPS is combined with the direction data of the video camera to calculate the accurate position of the captured object onboard.



Captured video pictures are sent to the base station with the position data of the helicopter and video- captured object.

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Satellite tracking for helicopter

• 1. Open loop tracking

Theoretical calculation using the data obtained from the position and attitude sensors onboard

• 2. Closed loop tracking

Antenna beam control based on the received signal level

• 3. Combined open and closed loop tracking

Pinpointing based on the received signal level after coarse direction using the calculation

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Polarization tracking

 Polarization tracking for a liner polarization  Calculation of satellite polarization angle based on

coordinate of the helicopter body

 Coordinate transformation between the satellite and

helicopter using data of the satellite (longitude and polarization angle) and helicopter (roll , pitch and yaw angle).

 Automatic polarization tracking by setting the

calculated polarization angle to the antenna control unit

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I V. Experiment results

• Preliminary experiment-

 Ground test for forward- and return-link  Flight test for forward-link

forward-link return-link

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13dB 9ms 30ms

Received signal level ( 2dB/div)

Experiment results for forward-link

TDTs Time ( 10ms/div)

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1.E-08 1.E-07 1.E-06 1.E-05 1.E-04 1.E-03 1.E-02 1.E-01 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Eb/No [dB]

Bit Error Rate

Experimental results for forward-link

Fixed blade Four TDTs Two TDTs theory TDTs

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Experimental results for return-link

1E-07 1E-06 1E-05 1E-04 1E-03 1E-02 1E-01

2 4 6 8

Eb/No [dB]

RS-off FEC-on theory

BER

Blade synchronized

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右旋回飛行1 °A Z 誤差 4 8 1 2 1 6 2 2 4 2 8 3 2 3 6 2 4 6 8 1 1 2 時間[ s e c ] 角度 [ d e g ] . 5 1 1 . 5 2 2 . 5 3 3 . 5 4 4 . 5 誤差角度[ d e g ] A Z A Z 誤差

Satellite tracking performance Satellite tracking performance during a helicopter flight during a helicopter flight （

Body inclination angle, 10 degrees Body inclination angle, 10 degrees）

time [sec]

A zimuth angle [deg] Error angle [deg ]

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Verification of transmission protection Verification of transmission protection （

Interference measurements to neighboring satellites Interference measurements to neighboring satellites）

 Transmission from helicopter can automatically stop  when a tracking error angle becomes large.  when a receiving level becomes below a limited

value.

 when the posture of a helicopter inclines beyond

anticipation.

 when onboard equipments fail.

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Verification of a satellite tracking performance Measurement of communication quality Operation check of transmission protection Picture transmission and position fixing

• Final flight test -

14GHz

Kashima Space Research Cent er

Image acquisition 12GHz 14GHz 12GHz

Gifu area in cent ral Japan

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Picture sent from helicopter in Gifu area and received at Kashima station via satellite

640x480 pixel

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position data of the helicopter and video- captured object on the map

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Conclusion

(1) A helicopter satellite communication system (HSCS) was successfully developed and demonstrated for the first time. (2) Key technologies of the HSCS for disaster control

• perations were experimentally demonstrated.

(3) The developed HSCS system provides a real time information collection and transmission directly via a satellite. (4) R&D aiming at small-size, light-weight and wide-band HSCS is proceeding. (5) Continuous R&D collaborated with disaster management bodies will be carried out.

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Acknowledgements

I would like to thank Masaki Satoh, Yoshiyuki Fujino, and their colleague in Kashima Space Research Center, NICT. The helicopter satellite communication system were developed by their group as a technical examination service regarding satellite digital communication technology for the transmission of disaster and emergency information that was funded by Ministry of Internal Affairs and Communications, Japan.

References

[1] Masaki Satoh, et al., "Helicopter-Satellite Communication System Developed for Transmission of Disaster and Emergency Information, " AIAA-2003-2319.