SATELLITE COMMUNICATION SYSTEM

SATELLITE COMMUNICATION SYSTEM

based on SC-WFMT Technology

12/2/2012 GUARNERI COMMUNICATION confidential 1

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.


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.

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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.

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Multipath propagation in Urban area


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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.

Typical measured values of RMS delay spread ( Satellite – Ground channel)


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

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.


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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.

•


SC-FDMA SYSTEM


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.

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SC-WFMT System


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0 5 10 15-6

-5

-4

-3

-2

-1

0

PAPR in dB

CC

DF

CCDF of TX signal

CCDF in baseband

CCDF in passband

Spectrum and CCDF of PARP for SC-WFMT signal (Wavelet filter 1)


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)

Pow

er/frequency (dB

/rad/sam

ple

)

Spectrum of TX IF signal after IF filter

65 dB



0 5 10 15-6

-5

-4

-3

-2

-1

0

PAPR in dB

CC

DF

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


Pow

er/

frequency (

dB

/rad/s

am

ple

)




0 5 10 15-6

-5

-4

-3

-2

-1

0

PAPR in dB

CC

DF

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


Pow

er/

frequency (

dB

/rad/s

am

ple

)


SC-WFMT performance in AWGN (uncoded QPSK)


-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

pro

babili

ty o

f err

or

SCWFMT BER performance

noncoded

RS code

10

Wavelet 2

Wavelet 3

Wavelet 1

Output signal of SC-WFMT transmitter


0 2 4 6 8 10 12 14

x 105

-0.1

-0.08

-0.06

-0.04

-0.02

0

0.02

0.04

0.06

0.08

0.1 Tx IF signal

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

0.6Q

uadra

ture

In-Phase

Scatter plot


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4096QAM constellation diagram

-60 -40 -20 0 20 40 60

-60

-40

-20

0

20

40

60

Quadra

ture

In-Phase

Scatter plot


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SC-WFMT (mod QAM256) signal spectrum after multipath channel


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Constellation diagram of received SC-WFMT signal after equalizer.


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Equalizer coefficients

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0 20 40 60 80 100 120 140-0.2

-0.1

0

0.1

0.2

0.3

0.4

0.5

0.6real and image components of corrector(equalizer)

real after filter

real + noise

imag+noise

imag after filter

Frame correlator output


22

0 0.5 1 1.5 2 2.5 3 3.5 4

x 104

-15

-10

-5

0

5

10

15

20frame correlator output

TRAINING

SYMBOL

DATA

SYMBOL

DATA

SYMBOL

DATA

SYMBOL

Frame correlator output (details)


23

2000 4000 6000 8000 10000 12000

-10

-5

0

5

10

15

frame correlator output

DATA SYMBOL

Cyclic Prefix

Constellation diagram on output of non-linear RF AMPLIFIER


-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

Quadra

ture

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.

Correction of distortion of RF amplifier (peak of signal = +1dB-point + 2 dB)


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

Quadra

ture

In-Phase

RX constellation diagram before NPA corrector

-1 -0.5 0 0.5 1

-1

-0.5

0

0.5

1

Quadra

ture

In-Phase

RX constellation diagram

Rapp Model , sat. point 31 dB

Parameters of SC-WFMT modulation versus QPSK and OFDM for satellite appl.


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

SC-WFMT in return satellite channel


SC-WFMT system with

Wavelet form 1 can be

successfully used in

return satellite channel

because of high sensitivity

of the ground receiver.

MULTI USER SATELLITE SYSTEM


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THANK YOU


Contact : Roman Vitenberg

Email: [email protected] Tel:+972547800501

mailto:[email protected]