SATELLITE COMMUNICATION SYSTEM based on WFMT Technology

09-Dec-11 VIO CONCEPT Ltd. 1

PROJECT OBJECTIVE The Project describes Satellite Communication System

( SCS) intended for connection of the mobile devices in Urban areas.

The developed SCS uses the Wavelet Filtered Multi-tone (WFMT) modulation proposed by author of this project.

WFMT modulation has several advantages before QPSK that common used in Satellite communications. • Low Peak-to-Average Ratio of WFMT signal (typical < 2 dB). • Programmable spectrum by changing form of the wavelets. • Compensation of phase and amplitude distortions inserted by

satellite transponder. • Compensation of distortions inserted by multipath propagation of

the electromagnetics waves in the urban area. WFMT modulation has the same energy efficiency as

single carrier QPSK modulation and the same immunity to multipath as multicarrier OFDM modulation.

Multipath propagation in Urban area

Common mode QPSK Satellite signal can not be received in the moving car in this area.

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 (old) QPSK 60 ns 30 ns

Satellite (WFMT) Wavelet QPSK 1 us 1.7 us

BACKGROUND The bandwidth efficient methods of modulation for

aircraft and space communication were developed and regulated by NASA.

Space Frequency Coordination Group (SFCG) approved an RF mask recommendation 17-2 in 1998, last revision

21-2 in 2002. SFCG rec. 17-2/21-2 becomes NASA policy for missions

to meet CCSDS Rec. 2.4.17A, 2.4.17B, and 2.4.18, approved 2001, contains specifications for Offset Quadrature Shift Keying (OQPSK)-type modulations: Gaussian Minimum Shift Keying (GMSK), Filtered-OQPSK, Shaped-OQPSK (S-OQPSK), Feher QPSK-Type B (FQPSK-B) and also higher-order coded modulations, i.e. 8-PSK TCM at 2.0, 2.25, 2.5, and 2.75 bits/symbol/Hz.

These modulations all conform to the SFCG mask.

SFCG MASK for Satellite channel

FILTERED OQPSK SPECTRUM (current Satellite communication system )

WFMT MULTI-QPSK SPECTRUM ( VDSL system)

WFMT based QPSK SPECTRUM (Satellite communication system)

WFMT

MATLAB SIMULATION OUTPUT SPECTRUM of Wavelet based QPSK Modulator

0.1 0.15 0.2 0.25-140

-120

-100

-80

-60

Frequency

Powe

r Spe

ctru

m M

agni

tude

(dB)

txSignal -60, rxSignal, Noise -140

WFMT based QPSK MODULATOR (Satellite communications system)

IFFT128 point P/S

0

0 127/ T

0 t0t1

t127t126

a0

a1

a2a3a4

a1

a4a3a2

W)t(

f

t

0

0

Sub-channelWavelet

T

Sub-channelWavelet

0 127/ T1/ T

Sub-channel wavelet spectrum

a0

fc

a1a2a3

a4

a1a2a3

a4

WFMT based QPSK DEMODULATOR (Satellite communications system)

W)t(DFFT

128 pointS/P

0

0127/ T

0t0t1

t127t126

0

0 a0a1a2a3a4

Information

+ + + +

demodulator

a0a1a2a3

Information

+ + + +

W)t(

FFT128 pointS/P

0

0127/ T

0t0t1

t127t126 0

0

a4

demodulator

eq1

eq2

eq3

eq4

eq5

eq6

eq7

eq8

eq9

Equalizer

^

Demodulation of Wavelets

Demodulation & Equalization of Wavelet

Sub-channelWavelet

T

Sub-channelmodulated Wavelet

D

Prototype wavelet spectrum

f0 127/ T1/ T

a0a1a2a3a4

a3

a4

a2a1

Parameters of Wavelet QPSK modulation versus standard QPSK and OFDM

Parameter Wavelet QPSK QPSK OFDM NOTES Channel Bandwidth 35 MHz 35 MHz 35 MHz

Data Rate ( max) 32 Mbps 32 Mbps 32 Mbps

Peak-to-Average Ratio 1~2 dB 1~2 dB 12 dB

FFT size 64 - 2048

Symbol duration 1 us 60 ns 70.6 us

Max. available multipath delay spread 1.7 us 30 ns 2.2 us

Cyclic prefix duration 3.5 us no 4.6 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 High Low

Immunity to narrowband interference High Low High

Immunity to Doppler effect High Medium Low

Rejection of adjacent channel High Medium Low