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)