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 1 Outline 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 2 1
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 of information gathering at the initial stage of the disaster. However, the communication ability from a helicopter was poor. 3 Conventional helicopter relay data transmission Videoing the d isaster situation. The photograph y position is fixed simultaneously . Image acquisition Via relay station Disaster Emergency countermeasure medical headquarters 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. 4 2
New Helicopter Satellite Communication System Dir ect Communication to Satellite 12GHz band 14GHz band Image acquisition Disaster Emerge ncy countermeasu re medical headq uarters hospital 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. 5 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. 6 3
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 7 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 8 4
Block diagram of the HSCS 64kbps 64kbps 384kbps 384kbps K u - b a n d g e o s t a t i o n a r y s a t e l l i t e Helicopter Base-station Receiving Transmitting RF APAA APAA Equipme nts Ante nna Control Up Converter Down Converter Unit Up Converter Down Converter Modulator Demodulator IMU Modulator Demodulator data data Decoder Encoder data audio signal video signal data audio signal audio signal audio signal ICS Microphone Vide o signal divider spea ker Position- video signal estimating Vide o signal equipme nts data divider Data and picture data processing equipme nts Vide o camera a nd GPS gyr o gimbal equipments 9 III. Configuration of a helicopter satellite communication system GPS Gyro Antenna Helicopter rear （ Power supply ） Position Camera p o d estimating and Transmitting active marking phased array antenna equipments Communication rack 10 5
Active phased array antenna m MDL RX MDL TX m 0 0 6 MDL TX MDL RX MDL RX MDL TX RF signal RF signal MDL TX MDL RX 200mm 500mm Control signal Control signal MDL RX MDL TX ACU ACU Heat emitter Heat emitter Power radiation Power radiation An image picture of the APAA Feeder circuit Feeder circuit Block diagram of the APAA 11 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 more than 35 d BW （ designed value ） 6 EI RP more than 0.5 dB/ K （ designed value ） 7 G/ T ・ Return link; 8 Modulation BPSK/ SS spread facto r 6 ・ Forward link; BPSK ½ -convolut ion code + RS code （ 204,188 ） 9 FEC 10 Overall rate Tx 384 kbps Rx 64 kbps 12 6
Specifications of a helicopter and payload Specifications of a helicopter and payload N u m b e r o f p a s s e n g e r s4 e x c e p t f o r c r e w 5 0 0 0 F e e t O p e r a t i n g h e i g h t H e l i c o p t e r O p e r a t i n g v e l o c i t y 1 0 0 K n o t （ A l l p a y l o a d m o u n t e d ） 1 5 ° O p e r a t i n g b a n k a n g e l F l i g h t t i m e a b o u t 2 h o u r s P o w e r c o n s u m p t i o n a b o u t 2 . 5 k W O n b o a r d e q u i p m e n t s a b o u t 4 5 0 ｋ ｇ T o t a l w e i g h t 13 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 14 7
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 15 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. Blade-shadowing period Shadowing interval Burst length Transmitter data Transmitter data time 16 8
Position estimation and marking 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 . 17 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 18 9
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 19 I V. Experiment results -Preliminary experiment- Ground test for forward- and return-link Flight test for forward-link forward-link return-link 20 10
Experiment results for forward-link TDTs Received signal level ( 2dB/div) 9ms 30ms 13dB Time ( 10ms/div) 21 Experimental results for forward-link TDTs 1.E-01 Fixed blade Four TDTs 1.E-02 Bit Error Rate 1.E-03 Two TDTs 1.E-04 1.E-05 theory 1.E-06 1.E-07 1.E-08 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Eb/No [dB] 22 11
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