SATELLITE COMMUNICATION SYSTEM

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Described satellite communication system for mobile users, which provide reliable high speed communication in multipath channel.

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SATELLITE COMMUNICATION SYSTEM

  1. 1. SATELLITE COMMUNICATION SYSTEM based on SC-WFMT Technology 12/2/2012 GUARNERI COMMUNICATION confidential 1
  2. 2. PROJECT OBJECTIVE • The Project describes a Satellite Communication System intended for connection of the mobile devices in Urban areas. • The proposed system uses a novel SC-WFMT modulation that was developed on basis of synthesis two technologies : well known SC-FDMA and WFMT technology that was proved during eight years research. • SC-WFMT modulation has several advantages before QPSK that commonly used in Satellite communications. – The programmable spectrum by changing form of the wavelets. – Compensation of phase and amplitude distortions inserted by the satellite transponder. – Compensation of distortions inserted by multipath propagation of the electromagnetic waves in the urban area. • SC-WFMT modulation has the same energy efficiency as a single carrier QPSK modulation and the same immunity to multipath as a multicarrier OFDM modulation. 12/2/2012 GUARNERI COMMUNICATION confidential 2
  3. 3. PROJECT OBJECTIVE ( continue) • Mobile satellite communication channel has been evaluated mainly with fading statistics of the signal. When the bandwidth of transmitting signal becomes wider, frequency selectivity of fading becomes a significant factor of the channel. Channel characteristics, not only signal variation but multipath delay spread were evaluated. A multipath measurement system was proposed and developed for mobile satellite applications. With this system and ETS-V satellite, multipath delay profiles are measured in various environments including Tokyo metropolis and Sapporo city at 1.5 GHz. Results show that the maximum excess delay is within 1 us and the maximum delay spread is 0.2 us at elevation angles of 40 to 47 degrees. In the wideband signal transmission of about 1MHz and more, designers should consider the effect of selective fading due to the multipath of land mobile satellite channel. For elevation angles of 5 to 20 degrees the maximum excess delay and delay spread are significantly increased. 12/2/2012 GUARNERI COMMUNICATION confidential 3
  4. 4. PROJECT OBJECTIVE ( continue) • Currently for satellite TV uses a QPSK modulation which is not able to provide reliable communication in multipath channel. • The bandwidth of Broadcast TV channel is 6~8 MHz, therefore direct receiving satellite TV on a mobile device is not possible in Urban areas. • SC-FDMA and SC-WFMT system are able to provide a communication in multipath channel with a maximum delay spread more than 10 us. Because of the possibility to change a spectrum form, • SC-WFMT has lower PAPR (5.3 dB) instead of SC-FDMA (7.5 dB). • Therefore the power of receiving signal will be at 1.8 times more than in case of SC-FDMA. 12/2/2012 GUARNERI COMMUNICATION confidential 4
  5. 5. Multipath propagation in Urban area 12/2/2012 GUARNERI COMMUNICATION confidential 5 Common mode QPSK Satellite signal can not be received in the moving car in this area. SC-WFMT based satellite signal can be received without errors.
  6. 6. Typical measured values of RMS delay spread ( Satellite – Ground channel) 12/2/2012 GUARNERI COMMUNICATION confidential 6 Environment Freq.(MHz) RMS Delay Spread Notes Urban 910 1300 ns avg., 3500 ns max New York Urban 892 10-25 us worst case San Franc. Suburban 910 200-310 ns typical case Average Suburban 910 1960-2110 ns extreme case Average Country 910 120 ns typical case Average Country 910 750 ns worst case Average Max. available RMS delay spread for different systems. SYSTEM MODULATION Symbol length Max . available RMS delay spread Wi-MAX OFDM 102.9 us 4.5 us Satellite QPSK 60 ns 30 ns Satellite SC-WFMT 144 us 11 us
  7. 7. NOVEL MODULATIONS • SC-FDMA modulation was developed for uplink of cellular LTE system. This modulation has a low peak-to-average power ratio (PAR) ~6.5 dB and uses multicarrier transmission and cyclic prefix for decreasing of multipath distortions. • SC-WFMT modulation has the same immunity to multipath distortion like SC-FDMA but not use cyclic prefix. The Spectrum of SC-WFMT signal has not out-of-band side lobes. SC-WFMT transmitter may be realized without the complex DFT and IDFT cores. 12/2/2012 GUARNERI COMMUNICATION confidential 7
  8. 8. Introduction to SC-FDMA • SC-FDMA can be regarded as the discrete Fourier transform (DFT)-spread OFDMA, where time domain data symbols are transformed into the frequency domain by DFT before going through OFDMA modulation. The orthogonality of the users steams from the fact that each user occupies different subcarriers in the frequency domain, similar to the case of OFDMA. Because the overall transmit signal is a single carrier signal, PAPR is inherently low compared to the case of OFDMA which produces a multicarrier signal. SC-FDMA uses the cyclic prefix like OFDM. • SC-FDMA has the same immunity to multipath distortion as OFDM and the same spectrum of the transmitted signal. Because PAR of SC-FDMA is only ~7.5 dB and PAR of OFDM is about 10~12.5 dB, the SC-FDMA system needs in significant lower power of the RF transmitter. • Unfortunately, SC-FDMA comprises DFT and IDFT cores these are high complexity devices. For processing of N-point DFT N^2 operations are required. For N-point FFT, only N*log2(N) operations are required. This is the reason why SC-FDMA is used only in narrowband LTE uplink. • 12/2/2012 GUARNERI COMMUNICATION confidential 8
  9. 9. SC-FDMA SYSTEM 12/2/2012 GUARNERI COMMUNICATION confidential 9
  10. 10. Introduction to SC- WFMT • In SC-WFMT system information symbols come to WFMT Transmitter, which generates a single carrier signal with the spectrum and peak-to- average ratio which depend of the defined wavelet form. This signal comes to M-point FFT core. After a fft transform and subcarrier mapping the signal arises to the digital filter. The filtered signal is added to a number of pilot signals. After M-point IFFT transform in the SC-WFMT signal inserts a cyclic prefix. Because of this cyclic prefix the SC-WFMT signal has the same an immunity to multipath distortion as OFDM or SC- FDMA signal . • The PAR of SC-WFMT signal is about 5~7.5 dB, that's significantly less than PAR of OFDM (10~12 dB) and SC-FDMA (7~8.5dB). • Because of absence of DFT the SC-WFMT system can be used for transmission of broadband signals like TV or broadcast satellite. Note that, in SC-WFMT system, both FFT and IFFT transforms have the same order(M) and may use the same physical core. 12/2/2012 GUARNERI COMMUNICATION confidential 10
  11. 11. SC-WFMT System 12/2/2012 GUARNERI COMMUNICATION confidential 11
  12. 12. 0 5 10 15 -6 -5 -4 -3 -2 -1 0 PAPR in dB CCDF CCDF of TX signal CCDF in baseband CCDF in passband Spectrum and CCDF of PARP for SC-WFMT signal (Wavelet filter 1) 12/2/2012 GUARNERI COMMUNICATION confidential 12 PAPR= 7.5 dB PAPR=5.5 dB 0.5 0.52 0.54 0.56 0.58 0.6 0.62 0.64 0.66 0.68 -100 -90 -80 -70 -60 -50 -40 -30 Normalized Frequency (rad/sample) Power/frequency(dB/rad/sample) Spectrum of TXIF signal after IF filter 65 dB
  13. 13. Spectrum and CCDF of PARP for SC-WFMT signal (Wavelet filter 2) 12/2/2012 GUARNERI COMMUNICATION confidential 13 0 5 10 15 -6 -5 -4 -3 -2 -1 0 PAPR in dB CCDF CCDF of TX signal CCDF in baseband CCDF in passband PAPR=6 dB PAPR=3.5 dB 0.54 0.56 0.58 0.6 0.62 0.64 0.66 0.68 -100 -90 -80 -70 -60 -50 -40 -30 Normalized Frequency (rad/sample) Power/frequency(dB/rad/sample) Spectrum of TX IF signal after IF filter
  14. 14. Spectrum and CCDF of PARP for SC-WFMT signal (Wavelet filter 3) 12/2/2012 GUARNERI COMMUNICATION confidential 14 0 5 10 15 -6 -5 -4 -3 -2 -1 0 PAPR in dB CCDF CCDF of TX signal CCDF in baseband CCDF in passband PAPR=5.3 dB PAPR=2.5 dB 0.55 0.6 0.65 0.7 0.75 -90 -80 -70 -60 -50 -40 -30 Normalized Frequency (rad/sample) Power/frequency(dB/rad/sample) Spectrum of TXIF signal after IF filter
  15. 15. SC-WFMT performance in AWGN (uncoded QPSK) 12/2/2012 GUARNERI COMMUNICATION confidential 15 -2 0 2 4 6 8 10 12 -4.5 -4 -3.5 -3 -2.5 -2 -1.5 -1 -0.5 0 EbNo dB probabilityoferror SCWFMT BER performance noncoded RS code 10 Wavelet 2 Wavelet 3 Wavelet 1
  16. 16. Output signal of SC-WFMT transmitter 12/2/2012 GUARNERI COMMUNICATION confidential 16 0 2 4 6 8 10 12 14 x 10 5 -0.1 -0.08 -0.06 -0.04 -0.02 0 0.02 0.04 0.06 0.08 0.1 Tx IF signal
  17. 17. 256QAM constellation diagram -0.6 -0.4 -0.2 0 0.2 0.4 0.6 -0.6 -0.4 -0.2 0 0.2 0.4 0.6Quadrature In-Phase Scatter plot 12/2/2012 GUARNERI COMMUNICATION confidential 17
  18. 18. 4096QAM constellation diagram -60 -40 -20 0 20 40 60 -60 -40 -20 0 20 40 60 Quadrature In-Phase Scatter plot 12/2/2012 GUARNERI COMMUNICATION confidential 18
  19. 19. SC-WFMT (mod QAM256) signal spectrum after multipath channel 12/2/2012 GUARNERI COMMUNICATION confidential 19
  20. 20. Constellation diagram of received SC-WFMT signal after equalizer. 12/2/2012 GUARNERI COMMUNICATION confidential 20
  21. 21. Equalizer coefficients 12/2/2012 GUARNERI COMMUNICATION confidential 21 0 20 40 60 80 100 120 140 -0.2 -0.1 0 0.1 0.2 0.3 0.4 0.5 0.6 real and image components of corrector(equalizer) real after filter real + noise imag+noise imag after filter
  22. 22. Frame correlator output 12/2/2012 GUARNERI COMMUNICATION confidential 22 0 0.5 1 1.5 2 2.5 3 3.5 4 x 10 4 -15 -10 -5 0 5 10 15 20 frame correlator output TRAINING SYMBOL DATA SYMBOL DATA SYMBOL DATA SYMBOL
  23. 23. Frame correlator output (details) 12/2/2012 GUARNERI COMMUNICATION confidential 23 2000 4000 6000 8000 10000 12000 -10 -5 0 5 10 15 frame correlator output DATA SYMBOL Cyclic Prefix
  24. 24. Constellation diagram on output of non-linear RF AMPLIFIER 12/2/2012 GUARNERI COMMUNICATION confidential 24 -1 -0.5 0 0.5 1 -1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 Quadrature In-Phase RX constellation diagram Real and Image components of SC-WFMT Signal on the output of non-linear RF POWER AMPLIFIER : MODEL: Hyperbolic tangent , Gain = 20 dB, IIP3 = 40 dB, AM/PM distortion = 2◦ / dB. Peak power of signal = 1 dB point.
  25. 25. Correction of distortion of RF amplifier (peak of signal = +1dB-point + 2 dB) 12/2/2012 GUARNERI COMMUNICATION confidential 25 Before correction After correction -1 -0.5 0 0.5 1 -1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 Quadrature In-Phase RX constellation diagram before NPA corrector -1 -0.5 0 0.5 1 -1 -0.5 0 0.5 1 Quadrature In-Phase RX constellation diagram Rapp Model , sat. point 31 dB
  26. 26. Parameters of SC-WFMT modulation versus QPSK and OFDM for satellite appl. 12/2/2012 GUARNERI COMMUNICATION confidential 26 Parameter SC-WFMT QPSK OFDM NOTES Channel Bandwidth 8 MHz 8 MHz 8 MHz Data Rate (QPSK mode) 16 Mbps 16 Mbps 16 Mbps Peak-to-Average Ratio 5~6 dB 5~6 dB 12 dB Number of subcarriers 1025 1 2048 Symbol duration 144 us 125 ns 300 us Max. available multipath delay spread 11 us 30 ns 20 us Cyclic prefix duration 16 us no 50 us Satellite transponder RF power (peak) ~ 10 W ~ 10 W ~ 160 W Complexly of Transmitter Medium Low Medium Complexity of Receiver High Low Medium Immunity to phase noise and carrier frequency offset High Medium Low Immunity to narrowband interference High Low High Immunity to Doppler effect High High Low Rejection of adjacent channel High Low Medium
  27. 27. SC-WFMT in return satellite channel 12/2/2012 GUARNERI COMMUNICATION confidential 27 SC-WFMT system with Wavelet form 1 can be successfully used in return satellite channel because of high sensitivity of the ground receiver.
  28. 28. MULTI USER SATELLITE SYSTEM 12/2/2012 GUARNERI COMMUNICATION confidential 28
  29. 29. THANK YOU 12/2/2012 GUARNERI COMMUNICATION confidential 29 Contact : Roman Vitenberg Email: r.m.vitenberg@gmail.com Tel:+972547800501

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