DIPLOMA WORK

EDUCATIONAL-QUALIFICATION LEVEL“MASTER”

INVESTIGATION OF MODULATION SCHEME AND

TRANSMITTER NONLINEARITY IMPACT ON ADS-B MESSAGES

TRANSMISSION VIA SATELLITE LINKPerformed by Bezsmertna D.V.Supervisor prof. Grekhov A.M

Theses:1. Grekhov A.M. Investigation of modulation scheme impact on ADS-B messages transmission via satellite link/ A.M.Grekhov, D.V. Bezsmertna // XIII International scientific and practical conference of young researchers and students “Polit. Contemporary problems of science”. – National Aviation University, Kyiv. – 2013.2. Kharchenko V.P. Investigation of modulation scheme and amplifiers nonlinearity on ADS-B messages transmission via satellite link / V.P. Kharchenko, A.M. Grekhov, D.V. Bezsmertna // International scientific and technical conference “AVIA-2013”. – National Aviation University, Kyiv (Ukraine).:NAU 2013. – Vol.2. – P.7.50-7.53Articles:Kharchenko V.P. Investigation of modulation scheme and transmitter nonlinearity impact on ADS-B messages transmission via OFDM satellite link/ V.P. Kharchenko, A.M.Grekhov, D.V.Bezsmertna // Bulletin of the National Aviation University. – 2014, in press.

Approbation of work results

Topic actuality • Air traffic increases steadily over the years that lead to

the increase of flights through the Poles, oceans and regions with reduced radar coverage and current ATM network can’t handle with it. Thus, there is a need that standards of safety and efficiency should be maintained or even enhanced.

• Therefore, there arises a necessity of conversion from the expensive ground-based systems to the cheap satellite-based systems that provide global coverage.

• As a solution, there are used the latest Iridium satellite constellation and developed program of Automatic Dependent Surveillance Broadcast (ADS-B).

Goal and task of diploma work•to construct the original models of satellite communication channel "Equipped ADS-B aircraft-to-Iridium satellite-to-Ground Station“

•to investigate the dependencies of model parameters for ensuring efficient, accurate and high rate data transmission.

The developed communication subsystemNext generation CNS / ATM system

Iridium Satellite System is LEO satellite communications services that provide voice and data communication anytime and everywhere on the Earth surface.Benefits:• Large satellite constellation

that ensures global coverage;• Low propagation delays, low

power requirements that provide direct interface with the system;• Provide service in the wake of a

natural disasters;• Provide voice and data services.

The development of surveillance subsystemAutomatic Dependent Surveillance Broadcast (ADS-B) is kind of surveillance that provide communication between aircrafts and between aircraft and the ground through data transmission link of broadcast type.

Benefits:• Safer flight• Accurate Weather

reports (FIS-B)• Terrain overlay• TIS –B information• Surrounding traffic

information• Accurate Management

ADS-B technologies with Iridium LEO constellation provide global, real-time aircraft position information, weather information, full coverage over oceanic airspace, polar routes, remote and mountainous regions, where ground station network is impossible and impractical to employ.

ADS-B and Iridium NEXT

Satellite communication link modeling

“Aircraft-to-Satellite-to-Ground Earth Station” link modeling

Ground Station Downlink Receiver

FEC, Demodulator, OFDM receiver

Aircraft Uplink TransmitterFEC, BPSK,QPSK,16QAM, 64QAM, OFDM transmitter

Error Rate Calculation, SNR estimation

Bernoulli Binary

Generator

Uplink Path

Satellite Transponder

Downlink Path

The transmitter generates random data which is sent over the channel.

Model construction and function description

Before sending, signal has to be adapted to the channel conditions by using a specific adaptive modulation (BPSK, QPSK, 16QAM, 64QAM) and coding schemes. Transmitted data also use OFDM transmission technique: signal need to be conformed into an OFDM symbol by performing frequency-time transformation and addition of a guard period.

Aircraft transmitter construction

From aircraft transmitter signal is sent over the transmission channel in free space, during which losses and interferences arise. Then, data is received by transponder and retransmitted back to the ground station.

Satellite transponder, uplink and downlink path construction

Ground station performs reverse operation of transmitter.

Ground station construction

Dependencies of a SNR on free path losses for different modulation modes, transponder noise temperatures and channel bandwidths

Aeronautical satellite channel simulation

NOFDM=1; amplifier nonlinearity - disabled; transponder linear gain -1 dB

Dependencies of a SNR on free path losses for different modulation modes, transponder noise temperatures, number of OFDM symbols

Amplifier nonlinearity - disabled; amplifier linear gain - 1 dB

Dependencies of a SNR on free path losses for different modulation modes and types of amplifier nonlinearity

Tnoise= 20 K, NOFDM=1; B = 3.5 MHz

Dependencies of a SNR on free path losses for different modulation modes and cyclic prefix values

Tnoise= 290 K, NOFDM=1; B = 3.5 MHz

ConclusionThe most efficient, accurate high data transmission can be provided by an optimal combination of model parameters: modulation schemes, coding, noise temperature, channel bandwidth, number of OFDM and cyclic prefix.Obtained results: 1.The 64QAM provides highest data transfer rate but sensitive to noises. BPSK and QPSK are more robust to the interferences;2.The reduction of transponder noise temperature, channel bandwidth and cyclic prefix leads to more efficient data transfer;3.The greater the number of OFDM the higher the value of SNR;4.The higher the average input power, more accurate signal is received.

Developed model of satellite communication channel allows to investigate and analyze the effectiveness of error detection and correction.It can be used for finding an optimal methods for ensuring efficient, accurate and high rate data transmission.It can be used as basic model for real satellite communication link investigation, development and construction in order to provide communication and surveillance between two airplanes and ground stations by using several satellites.

Conclusion

Thanks for your attention!