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Journées Micro-Drones 2004. Presentation High Data Rate Transmission System for Micro UAVs LEP> SCN Fabien MULOT: Internship ONERA-SUPAERO Vincent CALMETTES:

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Presentation on theme: "Journées Micro-Drones 2004. Presentation High Data Rate Transmission System for Micro UAVs LEP> SCN Fabien MULOT: Internship ONERA-SUPAERO Vincent CALMETTES:"— Presentation transcript:

1 Journées Micro-Drones Presentation High Data Rate Transmission System for Micro UAVs LEP> SCN Fabien MULOT: Internship ONERA-SUPAERO Vincent CALMETTES: Research SUPAERO

2 Journées Micro-Drones Presentation Plan of the presentation LEP> SCN Context of the study Video quality VS data rate trade-off Characterisation of the micro-UAV transmission channel Fade mitigation techniques Future studies and developments

3 Journées Micro-Drones Presentation Context of the study Study of a high data rate transmission from a video payload onboard a micro- UAV. LEP> SCN a. Reflection b. Shadowing c. Line of Sight b a c Monitoring Base station

4 Journées Micro-Drones Presentation Context of the study Transmission Band ISM band ,5 MHz Regulation LEP> SCN ("Tableau National de Répartition des Bandes de Fréquences“)

5 Journées Micro-Drones Presentation LEP> SCN Objectives of the study Objectives of the study High data rate source 640x480 pixels grey scale Camera, 8 bits JPEG coded Image 1Mbits/s target BER Semi urban environment, 1Km max from the emitter to the receiver Km/h speed QPSK modulation Shadowing and multipath resistant transmission Context of the study

6 Journées Micro-Drones Presentation Video quality VS data rate trade-off LEP> SCN Video Source Transmission Scheme Channel Reception Scheme Video monitoring

7 Journées Micro-Drones Presentation Video quality VS data rate trade-off LEP> SCN A D 2 modes of transmission 14 i/s low quality A 3.3 i/s high quality D Bit rate: 1.12 Mbits.s Ko 42 Ko 10 Ko

8 Journées Micro-Drones Presentation Characterisation of the micro-UAV transmission channel LEP> SCN JPEG Coding Transmission Scheme Channel ? Reception Scheme Video monitoring 1.12 Mbits.s -1

9 Journées Micro-Drones Presentation Micro-UAV transmission channel LEP> SCN Path loss A = (1/d) N N = [3 ….5] What is shadowing? Particular clutter (buildings dense woods) Scale of 100m 5 to 20dB What is multipath fading? Reflections, scattering on rough surfaces Constructive and destructive interference Scale of 6.25cm at 2.4Ghz 5 to 40 dB

10 Journées Micro-Drones Presentation LEP> SCN B) Tap Delay Line Model B) Tap Delay Line Model Y(t)  11 22 nn   1 (t)  2 (t)  n (t) X(t)  A) Statistic Power Delay Profiles A) Statistic Power Delay Profiles Statistic model Micro-UAV transmission channel C) channel Model C) channel Model

11 Journées Micro-Drones Presentation LEP> SCN Channel Characterisation Use of UMTS standard power delay profiles Coherence bandwidth Bc: 6KHz

12 Journées Micro-Drones Presentation LEP> SCN Issues: Frequency selective channel Inter Symbol Interferences Solutions: Channel coding Suited transmission techniques Micro-UAV transmission channel JPEG Coding Channel Coding Multipath Shadowing Frequency Selecticve Suited Reception Scheme JPEG Decoding 1.12 Mbits.s -1 Modulation Channel Decoding

13 Journées Micro-Drones Presentation Fade Mitigation Techniques Channel coding LEP> SCN JPEG Coding Channel Coding Multipath Shadowing Frequency Selctive Suited Reception Scheme JPEG Decoding 1.12 Mbits.s -1 Modulation Channel Decoding

14 Journées Micro-Drones Presentation Channel Coding LEP> SCN Objective: Spreading and correction of the bursts of errors Objective: Spreading and correction of the bursts of errors Architecture Architecture Reed Solomon (204/188) External Interleaver Convvolutional Code [177/188] Internal Interleaver Puncturing Target BER: => SNR=3.5 dB Target BER: => SNR=3.5 dB Pe=Pr.D 4 /(Ge.Gr) Pe=Pr.D 4 /(Ge.Gr) 100M500M1Km 0 dB of shadowing mw0.25mw4mW -20 dB of shadowing mw25mW0.4W

15 Journées Micro-Drones Presentation Fade Mitigation Techniques Transmission & Reception Techniques LEP> SCN JPEG Coding Channel Coding Multipath Shadowing Frequency Selective Suited Reception Scheme JPEG Decoding 1.12 Mbits.s -1 Modulation Channel Decoding 2. Mbits.s -1

16 Journées Micro-Drones Presentation QPSK + Equalization LEP> SCN Architecture Architecture Channel coding Channel coding SSRC Roll Off = 0.4 SSRC Roll Off = 0.4 Equalizer Equalizer Bandwidth : 1.5 Mhz Bandwidth : 1.5 Mhz JPEG source coding Coding +Puncturing SRRC Filtering QPSK Mapping SRRC Filtering Adaptive filtering Demapping Decoding + deinterleaving JPEG decoding Training sequence generator Channel

17 Journées Micro-Drones Presentation QPSK + Equalization LEP> SCN Equalization Equalization LMS algorithm LMS algorithm  Channel impulse response <= 1symbol MLSE using a Viterbi algorithm MLSE using a Viterbi algorithm  Several Symbols  M k Complexity  1024 state trellis JPEG Coding Channel Coding Multipath Shadowing MLSE 1024 states JPEG Decoding 1.12 Mbits.s -1 QPSK Channel Decoding 2. Mbits.s Msymb.s -1 QPSK 1.5 Mhz

18 Journées Micro-Drones Presentation OFDM LEP> SCN Advantage: Advantage: Transmission of high data rate while keeping a non frequency selective channel. Transmission of high data rate while keeping a non frequency selective channel. Bandwidth efficient Bandwidth efficient Architecture Architecture Channel coding mandatory Channel coding mandatory OFDM Symbol duration =50 µs OFDM Symbol duration =50 µs 10 times the channel impulse response 10 times the channel impulse response S 1 (k)..S n (k) S/P 0 0 IFFTIFFT CP Symbol mapping P/S 2 N points padding Channel Guard Interval Insertion Coding OFDM emitter Frequency

19 Journées Micro-Drones Presentation OFDM LEP> SCN Taking into account Taking into account The symbol duration 50µs The symbol duration 50µs the length of the cyclic prefix the length of the cyclic prefix The data rate after coding The data rate after coding The insertion of training symbols for equalization The insertion of training symbols for equalization 64 points FFT 64 points FFT Bandwidth: 1.3Mhz Bandwidth: 1.3Mhz JPEG Coding Channel Coding Multipath Shadowing JPEG Decoding 1.12 Mbits.s -1 QPSK Channel Decoding 2. Mbits.s Msymb.s -1 QPSK 1.3 Mhz OFDM 64pts IFFT 20 Ksymb OFDM 64 pts FFT

20 Journées Micro-Drones Presentation DSSS + Rake LEP> SCN Advantages of Direct Sequence Spread Spectrum: Advantages of Direct Sequence Spread Spectrum: Rake uses time diversity Resistant to noise and interference Architecture Architecture OVSF spreading codes OVSF spreading codes PN scrambling sequence PN scrambling sequence Rake receiver Rake receiver Power Frequency Noise Spread signal Power Frequency Narrow Band Information signal After Despreading Spread Noise IQ Scrambling code Up sampling SRRC Filtering QPSK Mapping IQ Spreading code Coding

21 Journées Micro-Drones Presentation ∫dt 2 2 1 1  IQ demapper 3 3 4 4 Path Search Descramble Despread Integrate and Dump Channel estimation y(t-  1 ) y(t-  2 ) y(t-  3 ) y(t-  4 ) y(t) g*(t-  1 ) g*(t-  2 ) g*(t-  3 ) g*(t-  4 ) MRC DSSS + Rake LEP> SCN Rake Receiver Architecture Rake Receiver Architecture

22 Journées Micro-Drones Presentation DSSS + Rake LEP> SCN JPEG Coding Channel Coding Multipath Shadowing JPEG Decoding 1.12 Mbits.s -1 QPSK Channel Decoding 2. Mbits.s Msymb.s -1 QPSK 72.6 Mhz DSSS 51.2 Msymb.s -1 Rake

23 Journées Micro-Drones Presentation Future studies and developments LEP> SCN

24 Journées Micro-Drones Presentation Future studies and developments LEP> SCN Evaluation of a system based on existing commercial technologies: Evaluation of a system based on existing commercial technologies: WI-FI [802.11b] WI-FI [802.11b] DSSS DSSS 1 to 11 Mbps 1 to 11 Mbps WI-FI [802.11g] WI-FI [802.11g] OFDM OFDM 1 to 54 Mbps 1 to 54 Mbps Baseband Processor Transceiver External PA ATHEROS 5523 ATHEROS 5112 FPGA Baseband Processor Transceiver ATHEROS 5523 ATHEROS 5112 USB 2.0 Interface ATHEROS AR5005uX ? FEC ?

25 Journées Micro-Drones Presentation LEP> SCN Thank you Questions ?

26 Journées Micro-Drones Presentation Analog VS Digital Digital Camera Digital Camera JPEG processing to deduce the bandwidth JPEG processing to deduce the bandwidth Onboard storage of the data is possible Onboard storage of the data is possible Digital signals are more resistant against multipath distortions Digital signals are more resistant against multipath distortions I.e Use of COFDM I.e Use of COFDM Already existing technologies working in the ISM band Already existing technologies working in the ISM band Dynamically reconfigurable system parameters Dynamically reconfigurable system parameters No need to adjust to tune the transmitter board No need to adjust to tune the transmitter board Analog transmission requires more power Analog transmission requires more power


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