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Fig. 1-1: Long distance communications
Satellite
Microwave
Ionosphere
Shortwave
Transatlantic cable ( fiber optics )
Fig. 1-2: VSAT in an interactive two-way network
VSAT TERMINALS
VSAT TERMINALS
VSAT TERMINALS
CentralHubStation
HOSTCOMPUTERS
VSAT TERMINALS
Fig.1-3: Main components of a SATCOM system
Space Segment
Ground Segment
Transmitters Receivers
Control
Station
( T T & C )
DownlinksUplinks
Fig1-4: Ground station architecture
Elevation angle E
Antenna axis
Local horizon
POWERSUPPLY
DIPLEXER TRACKING
IFDEMODULATOR
IFMODULATOR
MONITORING
CONTROL&
RFHIGH POWER
AMPLIFIER
RF-FRONT END
(low noise amp)
Baseband signals(from users)
Baseband signals(to users)
Fig. 1-5: Forces effecting a satellite
distance r
Centrifugal force =m v² /r
v
Gravitational force = GMm /r²
Satellite mass m
Earth
mass M
Fig. 1-6: Orbit of a MOLINYA satellite
Apogee
Perigee
Direction of the sun
Earth station
3995
7 km
548
km
Fig. 1-7: Trace of a MOLINYA satellite on the earth‘s surface
0 24
1
23 4
567
910
11 12
13
1415
16171819
2021
22
23
h
h h
h
h
hh
h
hh
hh
h h h
h
hh
hhh
hh
h
h8
Fig. 1-8: Development of SATCOM
TECHNIQUES
Frequencyreuse
Demandassigment
Onboardswitching
TECHNOLOGY
scanning beam30/20 GHzoptic ISL
switch matrix
14/12 GHz
beam forming
dualpolarization
6/4 GHz
monopolarization
1965 Past Present Future
Globalnetwork
Globalbeam
multispot beams
transponderhopping
SS-TDMA
SERVICES
Areonautical andland mobile
Private networks(VSAT)
Direct broadcasting
Domestic and regionaltelephony, TV, and data
Maritime mobile(L-band)
International trunkingtelephony and TV
increasingsatelite capacity
decreasingearth station size
FDMA/FMSCPC/FM
TDMA/PSKCDMA/PSK
Onboardprocessing
ISL
INTELSATI,II,III
IV
V
VI
INMARSAT
EUTELSAT 1TELECOM 1
SBS
TVSAT, TDFTELE-X, BSB
ACTS, ITALSATOLYMPUS
Fig 2-1: Antenna radiation pattern
α
θ
G
30 dBtyp
-3 dB
max,dB
3dB
θ1
3dBθ
α = θ /2 3dB
α = θ1
Gmax
3 dB down
D
side lobes
majorlobe
α(a) Polar representation
(b) Cartesian representation
Fig. 2-2: Antenna depointing errror
L
Txantenna
Rxantenna
PRPT
GT GR
αT αR
depointing
Fig. 2-3: Illumination level W
(a) Isotropic antenna
(b) Actual antenna
P
isotropic antenna
Power radiatedper unit solid angle
P / 4 π
G =1 t
G
P
x G
t
t
distance S
isotropic antenna
Power radiatedper unit solid angle
P / 4 π
Area A
Solid angle = A / S²
actual antenna
Power radiatedper unit solid angle(P /4 π) G
Power received on area A:=(P / 4 π) G (A / S²)=[(P G ) / 4 π S²] A
= W A
t
t
Fig. 2-4: Free space attenuation
1 5 10 50
210
200
190
180
170
LdB
FREQUENCY (GHz)
Fig. 2-5: Countour lines of G/Ts in dBi/K (uplink)
50
40
30
120 100 80
Latit
ude
(ºN
)
Longitude (ºW)
5
4
54
6
NY
MI
HO
DC
LA
SE
CHDE
PH
2
3
Fig. 2-6: Countour lines of EIRP in dBW (downlink)
50
40
30
120 100 80
Latit
ude
(ºN
)
Longitude (ºW)
37
36
35
363534
33
DE
SE
DCNY
MI
HO
LA
CH
PH
Fig. 2-7: Noise power passing through a receiver filter ( two-sided )
Power [W]
N0
2
f[Hz]
Fig. 2-8: Earth-satellite-earth link
Total Link
Uplink Downlink
GG TR
P =P1
Rxi
1
L FRX L FTX
(C / N )0 U
PT
01
P =PTx
(C / N )0 T
T(C / N )0
Fig.2-9: Power transfer characteristic of a satellite transponder (single carrier operation)
LFRX
TRANSPONDER
UplinkDownlink
Φ P1i P1
o
LFTX
-20 -10 0
0
-10
OBOdB
INPUT POWER relative to saturation
OU
TP
UT
PO
WE
Rre
lativ
e to
sat
urat
ion
OB
O=
P /
(P )1 o
1 o
sat
IBO= P /(P ) =(Φ ) /(Φ )1i
1i sat SL sat SL
IBOdB
Fig. 3-1: Routing (a) One carrier per link (b) One carrier per station
A B C
A B C
satellite
t AB
tt t
tt
AC
BA BC
CA
CB
Tx
Rx
A B C
A B C
satellite
Tx
Rx
t + tBA t + tCAt + tAB AC BC CB
(a)
(b)
Fig. 3-2: Multiple Access (a) FDMA (b) TDMA (c) CDMA
(a)
TRANSPONDER
1
2
N
2
t
N
t
1
FDMA
time
frequency
N
21
FDMA
B
(b)
TRANSPONDER
1
2
N time
frequency
TDMA
TDMA
B
1
t
2
t N
t 1 2 N
(c)TRANSPONDER
1
2
N time
frequency
CDMA
Code
N
21
CDMAtime
Code
1
time
frequencyCode
N
Fig. 3-3: Types of multple access over the time-frequency plane
Frequency/Code Division(FD/CDMA)
Frequency/Time/Code Division(FD/TD/CDMA)
FrequencyDivision (FDMA)
Time Division(TDMA)
Code Division(CDMA)
Frequency/ TimeDivision (FD/TDMA)
Time/CodeDivision(TD/CDMA)
Basic Techniques
Showing signaloccupancy in Time Frequency Plane
Frame period
(System bandwidth)
Time
Fre
quen
cy
T
B
Fig.3-4: FDMA transmission schemes
(a) FDM/FM/FDMA
USER FDMMULTIPLEX
(SSB/SC)FM MODULATORUSER
USER
SL
from other stations
(c) SCPC/FDMA
USERUSERUSER
dataA/D
TDMMULTIPLEX
USER
USER
USER
FM MODULATOR
A/D
A/D
PSK MODULATOR
PSK MODULATOR
PSK MODULATOR
TX
TX
TX
TX
TX
(b) TDM/PSK/FDMA
SCPC/FM/FDMA
SCPC/PSK/FDMA
F1
F2
F3
Fig. 3-5: FDMA with „one carrier station“ for three stations
Multiplex
B
C
Demultiplexingand channelselection
to user
Voice- channels
Demodulators
Transmitter
Receiver
A
C
B
Modulator
(a) Transmitted carriers
(b) Baseband signal multiplex (FDM or TDM)
(c) Earth station A block diagramm
Transponder bandwidth
A
B
C
to B to C
to B
to Cto A
to A
Time if TDMFrequency if FDM
A B C
Fig. 3-6: Adjacent channel interfence
BI F
RECEIVERBANDWIDTH
GUARD BANDS
Adjacent channelinterference
TRANSPONDER BANDWIDTH
Fig. 3-7: Intermodulation (two sinusoidal signals) (a) equal amplitudes, (b), (c) unequal amplitudes
Frequency
Frequency
Frequency
Fifth-order Im products
Third-order Im products
Signals
3f -f1 2 2f -f1 2 f f1 2 2f -f12 3f -f12
3f -f1 2 2f -f1 2 f f1 2 2f -f12 3f -f12
3f -f1 2 2f -f1 2 f f1 2 2f -f12 3f -f12
Fig.3-8: Transfer characteristics of a non-linear amplifier in multicarrier operation
n>1intermodulation
products
-20 -10 0
0
-10
OBOdB
OBO= P /(P )no
1o sat
IBO= P /(P ) ni
1i sat
IBOdB
n=1
n>1
Fig. 3-9: Variation of (C/N0)T, (C/N0)D, (C/N0)U, (C/N0)IM
Saturation
Input back-off
Input power relative to saturation
(C/N ) (C/N )
(C/N )
(C/N )
0 0
0
0
IM U
D
T
(-3 to -16 dB) 0 dB
Car
rier
pow
er-t
o-no
ise
pow
er s
pect
ral d
ensi
ty, C
/N (
dBH
z)
0
Fig. 3-10: FDMA:Throughnput
100
50
1 5 10 15
THROUGHPUT(%)
Fig. 3-11: Network operating in TDMA
Frequency
FPowerspectraldensity
Repeater bandwidth
Stations A, B, C
Transmitting side Receiving side
same frequency F
TB
T F
Fig. 3-12: Burst generation
satellite
DMUX
(TDM)
users
R i
R =Σb Ri
A CB
TF
TB
TFR R
user bit streams to ABC
bit rate : R1
bit rate : R2
bit rate : R3
buffers PSKmodulator
TDMAtiming
preamblegenerator
+ toup-converter
preamble
BURST STRUCTURE(bit rate R)
time
Fig.3-13: Frame structure (INTELSAT/ EUTELSAT standard)
Reference burst
CDCVOW VOWSCTTYUniqueword
Carrier and bittiming recovery
VOW VOWSCTTYUniqueword
Carrier and bittiming recovery Traffic data
2 ms120 832 symbols
TDMA
RB TB RBTB
SymbolsGuard time64
176 24 8 8 32 32 8
RB1 a 2 b 1
176 24 8 8 32 32 n x 64
PreableSymbols
Symbols
x
Trafficburst
RB :TB :Unique word :
SC :
CDC :
TTY, VOW :
1 reference burst from reference station 1traffic burst from station xspecial bit pattern in the preamble which permits precise synchronisation (start of data) and phase ambiguity resolution (for non-differential decoding) at receiveservice channel (SC) contains alarms and various network management information
control and delay channel (CDC) contains the delay information (Dn) for synchronising the transmit burststelegraphy and telephony order wires for inter-station
communications
Fig. 3-14: Burst reception
B
satellite
burstfrom C
burstfrom B
burstfrom A
to usersDEMUX
to D
to D
to D
start offrame
reference burst
buffers
TDMAtiming
PSKdemodulator
bit streams to usersfromdown-converter bit rate R 1
bit rate R 2
bit rate R 3
= preamble
from ABC
Fig. 3-15: Evolution of the volume occupied by a geostationary satellite in the course of an orbital period (24h)
Nominal Geostationary satellite orbit
EARTH
Equator
Satellite drift NSEW 0.05°+-
Orbit eccentricity 0.001
75 km
85km75 km0.1°
Fig. 3-16: Burst assigment within the frame
TIME
DISTANCE
Station 1
ReferenceStation
Station n
Station N
SatelliteB0B0 BNBnB2B1
d2
dn
dN
Start of framek+1
Start of framek
B0
B1
Bn
BN
dN
dn
d1
SOTF1
n
d1
SOTFN
SOTF
Fig. 3-17: The relation between the start time on transmission SOTFn and the start time on reception SORFn for station n
Start of framek
Start of framek + m
Distance
Time
m T
Satellite
Station n
B0 B0
B0
F
Bn
Bn
R /cSORF SOTF
Dn n
n
dn
n
Fig. 3-18: Closed loop synchronisation
TIME
DISTANCE
Satellite B0 Bn B0
B0
SORFn SOTFn
D (j)n d n
Bn
Bn
d (j)0n
dn e (j)n
Reception
Station n
TransmissionBn
D (j+1)n d n
Bn
Target positionfor Bn
dn
B0
Fig. 3-19: Open loop synchronisation
Distribution of Timing and Values of D
satelliteposition
determination
Ran
ge m
easu
rem
ent D
ata
Ran
ge m
easu
rem
ent D
ata
satellite
• • • •1 2
Local TDMA Stations
A B C
Ranging stations
n
referencestation
Loop
bac
k ra
ngin
g
Loop
bac
k ra
ngin
g
Loop
bac
k ra
ngin
g
n
Fig. 3-20: The efficiency of the INTELSAT / EUTELSAT TDMA System
THROUGHPUT(%)
100
00 25 50
NUMBER OF ACCESSES
INTELSAT/EUTELSATTDMA SYSTEM
85.2%
Fig. 3-21: DS - CDMA
transponder
RecoveredData signal
v(t)LPF
CODEsync
Data signalbit rateR =1/T
⊗ ⊗⊗ ⊗2cosω t
r(t) u(t)
s(t)
p(t)m(t)
b b
cp(t) cosω tc
1T ⌠⌡ (.)dt
T
0b
b
CODEgenerator
CODEgenerator
recovereddata signal
m(t)
p(t)
m(t) p(t)
p(t)
Tb
Tc
(chip)
Chip rate R = 1/Tc c
Fig. 3-22: The effect of spreading in te frequency
-R f R c bb
power fluxdensity(W/Hz)
modulation bym(t)
modulation bym(t)p(t)
Rc-Rcfrequency
Fig. 3-23: Jammer reducing effect of DSSS
information
after spreading
jammer
after despreading
after bandpass filtering
B
Bc
B
ω
ω
ω
ω
ω
Fig. 3-24: Frequency Hopping: FH-CDMA
Modulator Demodulator
transponder
Frequencysynthesizer
CODEgenerator
CODESync
Data signalbit rateR =1/Tb b
m(t)
cosω (t)tc
f = f , f ,..., fc 1 2 n
p(t)
Chip rate R = 1/Tc c
Frequencysynthesizer
CODEgenerator
m(t)
Chip rate R = 1/Tc c
LPFr(t)
p(t)
cosω (t)tc
f = f , f ,..., fc 1 2 n
Fig. 3-25: FH: Frequency domain
Frequency
B
Time
TFrequency
Frequency
psd
psdspectrum ofcarriermodulated by m(t)
b
Long term RF spectrum
B
b
H
Fig. 3-26: Pseudo random sequences: (a) Generation (b) AFK (c) Power spectral density
0
δ
R (δ)p
r2 -1-1
r2 -1 chips
Tc frequency
∆ f =R /(2 -1)r
c
(c) CODE POWER SPECTRAL DENSITY(b) CODE CORRELATION FUNCTION :
(a) CLOCKOSCILLATOR
f=1/Tc
a2a1
shift register(r stages)
ar-1
a =0 or 11
Example (r=3)
a =11 a =02
1 2 3Output
Shift register status
0111010
0011101
1001110
Repeat
Output codesequence(1 period)
Code chips
Rate R =1/Tc c
Period 2 -1 chips 2 ´ones´ 2 -1 ´zeros´
r-1
r-1
r
. . .
Fig. 3-27: Code acquisition in a DS-CDMA system
EnableTracking
(peak absolutevalue)
s (t)
s (t)m(t) p(t) to
detector
NoEnvelopedetector
Codegenerator
CodeshiftBPF Threshold
⊗⊗
2
4
1
3
1
2
3 4
Yes
s (t) s (t)
Fig. 3-28: Code tracking in a DS-CDMA system
Envelopedetector
CODEgenerator
Loopfilter
BPF
EnvelopedetectorBPF
Advance
Delay
+
-3
R (δ+T /2)p c
δ
δ
δ
1
2
e(δ)=3 1 2-
e(δ)
R (δ-T /2)p c
Fig. 3-29: Spread spectrum transmission in a DS-CDMA system
A B C D
psd = Power spectral densityf = Frequency
psd = Power spectral densityf = Frequency
Transponder
Datasignal
Recovereddata signal
undesiredsignals
Spreading DespreadingA D
CB
ff0 W
psdpsd
RF bandwidthB
fc ff
psd psd
fc W0
noise + other users+ jammer
Fig. 4-1: ALOAH-Protocoll: (a) without collision, (b) with collision
(a)
(b)
SpaceSatellite
Station X
Station Y
Station Z
Time
X Y
ACK X ACK Y
ACK X
ACK Y
ACK YACK X
X
X
Y
Y
Space
Satellite
Station X
Station Y
Station Z
Time
Possible detectionof collision
Retransmissionafter randomdelay
(NO ACK)
Fig:4-2: Pure ALOHA, Slotted ALOHA: Efficiency
0.01 0,05 0.1 0.5 1 5 10
0.5
0.4
0.3
0.2
0.1
0
1/e
1/2e18%
36%
NORMALIZED OFFERED CHANNEL TRAFFIC, G (PACKETS/SLOT)
CH
AN
NE
L T
HR
OU
GH
PU
T, S
(P
AC
KE
TS
/SLO
T)
SlottedALOHAS=Ge-G
PureALOHAS=Ge -2G
Fig. 4-3: Averrage transmission delays
a = fraction of bandwith not used for reservation
(typ. 0.7 to 0.9)
Channel throughput
ALOHASlotted-ALOHA
2 Round trips
1 Round trip
Ave
rage
tran
smis
sion
del
ay
12e
1e
1a
Reservation
SREJ-ALOHA
Fig. 4-4: Selective Rejection ALOAH
CHANNELmessage 1
message 2 Retransmission of message 1
Retransmission of message 2
Retransmission interval formessage 1
collision
TIME1 2 3 4 51 2 3 4
3 4 5 1 2 3
Fig. 4-5: Pure ALOAH, Slotted ALOAH: Collision Diagrams
PureALOHA
Time
Collision windowis two messageintervals
Colliding packets
S-ALOHA
Collision windowis one messageinterval
Time
Colliding packets
Fig. 4-6: TDMA, FDMA CDMA: Comparison of throughput
100
50
0
THROUGHPUT(%)
CDMA
1 20 40 60NUMBER OF ACCESSES
TDMA
FDMAFDMA
Fig. 5-1: Use of an ISL to increase the systems capacity
SATELLITE
1 2 3
SATELLITE 1 SATELLITE 2ISL
1 2 3
(a) (c)
(b) (d)
SATELLITE 1 SATELLITE 2
1 2 3
SATELLITE 1 SATELLITE 2ISL
1 2 3
Fig. 5-2: Extension of system coverage (a) by using an ISL (b) by using a station comon to both networks (c) by using a terrestrial network
SATELLITE 1 SATELLITE 2
1 2+
ISL(a) (b)
(c) SATELLITE 1 SATELLITE 2
12
SATELLITE 1 SATELLITE 2
1 2
Fig. 5-3: Increase of the minimum elevation angle of earth station
E = 5° E = 20°
30°
ISL
(a) (b)
E = 5° E = 20°
Fig. 5-4: Complete coverage of the United States in spite of saturation of the orbital arc
Intersatellite link
Limit of coverage
Fig. 5-5: Example of global network
North and Central American Star
North American Star
Pacific Islands StarAustralian Indonesien Star
Eastern Asia Star
Western Asia Star
African Star
95 ° W
135 ° W
175 ° W145 ° E
105 ° E
65 ° E
25 ° E
0°E W European Star
15 ° W
South American Star60 ° W
'Local' Satellites
276 mS
242 mS
180 mS
96 mS
120 mS
Fig. 6-1: Regenerative versus transparent transponder
Regenerative Transponder
LNA Demodulator Remodulator
Conventional Transponder
Uplink Downlink
Local Oscillator
TWT
LNA TWT
Local Oscillator
⊗
Fig. 6-2: Bit error rates
Bit
erro
r ra
te
10-2
-3
-4
-5
-6
-7
-8
-9
10
10
10
10
10
10
10
BPSK, QPSK,OK-QPSK and MSK
(Gray-coded)
DE-BSK and DE-QPSKB-BPSKD-QPSK
E/N (dB)0
E = energy per bit E = E if no codingE = E if coding
N = one-sided noise spectral density (W/Hz)
0
b
c
Fig. 6-3: SATCOM-link with a transparent transponder
Bit ErrorProbability
(BEP)
downlinkuplink
conventional transponder
( C / N )0 T
Fig. 6-4: SATCOM-link with a regenerative transponder
downlink
DEMOD REMOD
uplink
BEPD
BEPU
(C/N )0 U
(C/N )0 D
Fig. 6-5: Comparison of station – to - station
BER = 10
A = Conventional Transponder(QPSK)
B= Regenerative Transponder (QPSK up, QPSK down)
C = Regenerative Transponder (D. QPSK up, QPSK down)
(E/N ) (E/N )
α =0
U
D
0-4
(E/N ) (dB)10 15 20
(E/N )
(dB)
20
15
10
14
12
10
8
6
4
2
0 dB
α
AB
C
0
U
D
0
Fig. 6-6: Bit error rates
10-2-3-4-5-6-7
-8
10101010
1010 8 10 12 1 4 15 1 6 17 18 9 11 13 ENb0(dB)
QP SKTW TA IBO 2.0 dBReg en.HPA IBO 3.0 d B 7.0 d B 1 2.0 d BC ONVE NTION ALReg.
10-2
-3
-4
-5
-6
-7
-8
10
10
10
10
10
108 10 12 14 15 16 17 18 9 11 13
EN
b
0(dB)
BIT ERROR RATE
QPSKTWTA IBO 2.0 dB
Regen.HPA IBO 3.0 dB
7.0 dB 12.0 dB
CONVENTIONAL
Reg.
Fig. 6-7: Permissible interfence level
18
17
16
15
14
13
12
11
10
12 13 14 15 16 17 18
(E/N )
(dB)
non regenerative repeater(E/N ) = 11 dB
regenerative repeater(E/N ) = 9 dB
BER = 10QPSK
(E/N ) (dB)
-4
0 T0 I
0 T
0 T without I
Fig. 6-8: Interconnection of two networks with carriers of different capacity
a)
low ratestation
high ratestation
b)
conventional satellitelow rate
transponderhigh rate
transponder
regenerativesatellite
high ratestationlow rate
stationlow ratestation
high ratestation
MICROWAVE SWITCH MATRIX
from high ratestation
tohigh ratestation
high rate streamhigh rate stream
low rate streams
distribution
DEMOD
combiner
REMOD
DEMOD
DEMOD
REMOD
REMOD
BASEBANDSWITCHMATRIX
low rate streams
fromlow ratestations
tolow ratestations
Fig. 6-9: Single beam regenerative scanning satellite network
DEMOD REMODMEMORY(RAM)
CONTROL
BFN
scan beam
beam dwell area
Fig. 6-10: Regenerative transponder using FDMA on the uplink and TDM on the downlink
1
f
1
f2
f
M
2
M
DEM
DEM
DEM
DEM
DEMDE
MU
LTIP
LEX
ER
TD
MM
ULT
IPLE
XE
R
LO
f
M
f
1
f
2
FDMA
LNA
f1
f2
fM
TWT
fTDM
MOD
FDMA uplinktime
frequency continuous mode
TDM downlinktime
frequency
M
21
continuous mode
1 2 M
BA
SE
BA
ND
SW
ITC
HIN
G
MA
TR
IX
⊗
Fig.7-1: ITU regions
Region1
Region3
Region2
3
2
Fig. 7-2: ITU allocations by priority classification
Style of Typeused to designate
allocation:
Permitted Allocations
Secondary Allocation
Equal rights with PRIMARY but PRIMARY has prior choice of frequencies
These services shall not cause harmful interference to or claim protection from stations of a PRIMARY or permitted service
RESOURCE
PRIMARY ALLOCATIONS
Fig. 7-3: ITU allocations by geographical region
Worldwide allocations
ITU Region I ITU Region II ITU Region III
Individual Nationalfootnotes
Fig. 7-4: Western hemisphere frequency assignments
6/ 4 GHzC band
8/ 7 GHzX band
14/ 11 GHzK band
30/ 20 GHzK band
100010002500 3000
Down links Up links7.0754.2 4.53.7 6.4255.9253.4 4.8
300 500 75 650300 500
7.25 7.75 7.9 8.4
500 500
10.7 10.95 11.2 11.45 11.7 12.2 12.7 13.2 14.0 14.5 14.8 17.3 17.8 18.1
250 250 250 250 500 500 500 500 300 500 300
17.7 20.2 21.2 27.0 30.0 31.0
a
a
AssignmentGHz
BandwidthMHz
Government FSS Government FSS
Government FSS Government FSS
International FSS
FSS FSS
FSS BSS FSSFSS
BSS
FSS FSS
FSS: Fixed Satellite ServiceBSS: Broadcasting Satellite Service
Fig. 7-5: GPS Genauigkeitsstufen
Trägerphasen -Messung
Code - Messung
ABSOLUT
DIFFERENTIAL
1 2 5 1 2 5 10 20 50 1 2 5 10 20 50 100mm cm m
Positionsfehler
Statische
Vermessung
Dynamische
Vermessung
DGPSRohdaten
DGPS
Pos.-Daten
P-Code(Militär)
(Zivil)C-Code
C-Codemit S/A(Zivil)
Fig. 7-6: ELLIPSO: Three inclined elliptical and circular equitorial orbit
Fig. 7-7: Teledisc‘s Standard Terminal Multi Access Method
1 3
4
567
8 9
2
1 3
4
567
8 9
2
1 3
4
567
8 9
2
1 3
4
567
8 9
2
Supercell
CELL SCAN PATTERN
Cell 9 illuminated in all supercells
11 3
3
4
4
64
5 6 7 8 92
2
CELL SCAN CYCLE
Sup
erce
ll (S
DM
)
Cell (TDM)
Scan Cycle = 23.11 msec per Supercell
Transmit/Receive Time = 2.276 msec/CellGuard Intervall = 0.292 msec
. . .
. . .
1
1
3
3
4
4
5
5
512 Bit Packet
512
Bit
Pac
ket
7
7
1440
1440
6
6
2
2
CHANNEL MULTIPLEXING IN A CELL
2.276 msec/Cell 2.276 msec/Cell
400 MHz . . .
. . .
Cha
nnel
Channel
UP LINK (FDM) DOWN LINK (ATM)
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