Satellite RF Fundamentals 1 Wireless Technologies Review: Satellite RF Fundamentals

Satellite RF Fundamentals 1

Wireless Technologies Review:Satellite RF Fundamentals

2Satellite RF Fundamentals

Announcements

Class web site http://teal.gmu.edu/coursepages.htm and click on TCOM 690 sect 3or go directly tohttp://teal.gmu.edu/ececourses/tcom690/fall2003/sect3/TCOM690-3-fall03.htm

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Objectives

Review fundamental concepts of wireless communications.

Provide basics of RF communications related to the operation of spacecraft.

Information provided will allow you to understand and perform an RF link calculation.

Enable you to do basic link calculations for the course project.


Satellite RF Communications Architecture

EARTH

Data to

Processor

ReceiverReceiver

Data to

Processor

Transmitter

Instrument

Data

Sensor

Spacecraft

GeostationaryRelay Satellite(s)

Space Link

OR

Space Link

Antenna


Modulator

Transmitter

Subsystems of Satellite RF Communications

Satellite transmitter-to-receiver link with typical loss and noise sources

PointingLoss

SpaceLoss

PolarizationLoss

AtmosphericLoss,

Rain Loss

PointingLoss

Galactic, Star,Terrestrial Noise

Demodulator

Receiver Noise

Antenna

Receiver

Power Amplifier

Antenna

InformationSource

Transmitter

InformationSink

ImplementationLoss

ReceiverSPACE

CHANNEL


Definitions & Some Basics

dB = 10 log10 (x); x is usually a power ratio dBW 10 log10 (watts)

For 100 watts; dBW = 10 log10 (100) = 20 dBW

dBm 10 log10 (milliwatts) For 100 watts; dBm = 10 log10 (100000) = 50 dBm

Carrier Frequency Units are Hz MHz = Hz x 106

GHz = Hz x 10 9

Frequency Bands (of interest) S-Band = 2-3 GHz X-Band = 7-8 GHz Ku-Band = 13-15 GHz Ka-Band = 23-28 GHz


Logarithmic Scale

dBW dBm

20 dBW 50 dBm100 Watts



0 dBW (Ref) 30 dBm1 Watts

-10 dBW 20 dBm0.1 Watts

-30 dBW 0 dBm (Ref)0.001 Watts(1 milliwatt)

-40 dBW -10 dBm0.0001 Watts

Always a 30 dB difference between dBm and dBW

A power below the reference level has negative value, for either dBm or dBW


+ f

- f

Doppler Shift

Doppler Rate

Nominal (at-rest) frequency

A

B

C

LOSAOS

EARTH

ORBIT

What is Doppler & Doppler Rate?

ss

s f VC

V ΔfShift Doppler

Vs = Radial velocity component between S/C and Site in the direction of the observer

C = Speed of Light = 2.997925 x 108 meters/sec.

Fs = Frequency of Transmission

s2s

s s f

VC

Va

Δt

Δfchange of rate Doppler

where as = rate of change of Vs = acceleration

Doppler shifts become greater as the frequencies become higher.

A B C


Phase lock loops

Enable receiving & tracking of Doppler shifted signals Used in virtually all spacecraft & ground station designs to

accommodate dynamic frequency changes

Doppler & Doppler Rate

Input Signal ±

Doppler

Phase & Frequency Comparer

Low PassFilter

Error Signal

VoltageControlledOscillator

FilteredError

Signal


Analog and Digital Data



Most instrument data starts out as analog data

Most analog data is converted to digital data (binary 2n)

3 bit system

Binary0 0 00 0 10 1 00 1 11 0 01 0 11 1 01 1 1

Analog01234567

1 0 1 1 1 1 1 1 0 1 0 0

5 7 6 4

Serial data stream transmitted

Volts

time

Volts

time

7

65

4



Why use digital data+ Better performance vs. noise+ Lends itself to computer processing & coding- Consumes more bandwidth

Sampling Rate Nyquist rate ( 2 fmax)

fmax – max frequency component of the original signal

Volts

t

Analog Signal

t

Digital Sampling

t

Digital Bit

Stream


Spectra Basics


Spectra (Baseband Signals)

t

V(t) = Asin2ft

Period = T

Time Domain

Fourier

Transform

Fourier

Transform

-dt

ftj2-e tvfv

Frequency Domain

-dt

ftj2-e tyfy

t

T

y(t)

Amplitude

Hz

T

1 f

A

x

xsin

Amplitude


½ M(0)

Spectra (Modulated Signal)

Given: an arbitrary modulating signal M(t)an arbitrary “carrier signal” cos 2fct

then the modulated signal V(t) M(t) cos 2fct

Find: The Fourier transform of V(t)

using the identity

Then:

Then: The Fourier transform of V(t) = V(f)A

M(t) of transform Fourier the is dt e tMfM-

tf j2- m

tf2jtfj2c

cc e)t(M2

1 M(t)e

2

1 t f2 cos tM

dte tM 2

1 dte tM

2

1 fV

-

)tf f(j2-

-

)tf f(j2- cmcm

M(0)

ffm-fm 0

-fc

f0

½ M(0)

fc

tfj2tfj2c

cc e2

1 e

2

1 t f2 cos


Coding/Spreading/Data Compression


The Effects of Channel Noise

In digital communications, raw data is put into the form of bits, 1’s and 0’s.

A carrier signal is modulated using this raw data for convenient transmission over the channel.

The carrier signal is subject to noise corruption in the channel, sometimes making it impossible to reconstruct the raw bits at the receiver. If a transmitted bit is received as its opposite (e.g., a 1 received

as a 0 or vice versa), then a “bit error” has occurred.

This results in a progressive loss of information at the receiver as the number of mistranslated bits grows.


BER and Eb/No

The rate at which bits are corrupted beyond the capacity to reconstruct them is called the BER (Bit Error Rate). A BER of less than 1 in 100,000 bits is generally desired for an

average satellite communications channel (also referred to as a BER of 10-5).

For some types of data, an even smaller BER is desired (10-7).

The BER is directly dependent on the Eb/No, which is the

Bit Energy-to-Noise Density ratio. Since the noise density present on the channel is difficult to

control, this basically means that BER can be reduced through using a higher powered signal, or by controlling other parameters to increase the energy transmitted per bit.

As the following chart shows, the BER will decrease (i.e., fewer errors) if the Eb/No increases.


Higher Eb/No Reduces the BER

10-3

10-4

10-5

10-6

BE

R

lower higherEb/No

Some ways of Increasing Eb/No

These methods can be expensive

• Increase signal power

• Use a bigger antenna

• Use a super cooled receiver

BER Versus Eb/No


Another Strategy to Reduce BER

10-3

10-4

10-5

10-6

BE

R

lower higherEb/No

BER Versus Eb/No

This change in performance can be achieved by using Error Correction Coding

Less expensive method of mitigating channel noise

Another strategy is to shift the whole curve over to the left

Now the same BER can be achieved using a lower Eb/No


Error Detecting versus Error Detecting/Correcting Codes

An error detecting code can only detect the presence of errors, not correct them. This implies error detection and a subsequent request for

retransmission.

There are times when retransmission of the message is not practical. If a spacecraft is transmitting a playback dump of a storage device while

making a short pass over a ground station, it may not have time to stop the transmission and retransmit in a short enough time.

An error detecting/correcting code, on the other hand, has the ability to detect a defined number of errors and correct them for a prescribed environment that caused the errors, which is commonly called Forward Error Correction (FEC). Usually, for a given code, more errors can be detected than can actually

be corrected.


Error Correction Codes

Error control coding aims to correct errors caused by noise and interference in a digital communications scheme.

In error control coding, the information bits are represented as another sequence of bits, also called coded symbols; this new sequence is sent over the channel.

This new sequence will use redundant information, often called parity bits, to provide error protection (e.g., send a 0 as 00000 and a 1 as 11111).

Now individual bit errors will not necessarily result in the incorrect decoding of the original information bits. For instance, if 1 or 2 of the five 0’s sent over the channel in the above

example are interpreted as 1’s at the receiver, the original 0 can still be decoded correctly if one makes a final decision based on the majority of the received coded symbols.


Types of Error Correction Codes

A rate 1/2 convolutional code, an example of one family of codes, is often used on NASA space communication links. 2 coded symbols for every 1 data symbol (i.e., 100% overhead) Provides improved performance in a Gaussian noise environment

The Reed-Solomon code, a special type of “block” code, also has the advantage of smaller bandwidth expansion and also has the capability to indicate the presence of uncorrectable errors. Provides improved performance in a bursty noise environment Overhead approximately 12%

Where a greater coding gain is needed than can be provided by the convolutional code or the Reed-Solomon code alone, the two codes are often concatenated to provide a higher error-correction performance. One code serves as the “outer” code, one as the “inner” code


Typical Encoded Link

Data Bits1 Mbps Rate ½

Convolutional Encoder

Modulator & Transmitter

Data symbols

2.24 Msps

LNA

Receiver

Convolutional Decoder

Data Bits1 Mbps

(with some errors)

Data symbols2.24 Msps

Antenna Antenna

R/SEncoder

R/SDecoder

fc

2.24 MHz

2.24 MHz

02.24 MHz

fc

02.24 MHz

1.12 MHz

Data symbols1.12 Msps

2 MHz

01 MHz

Data symbols

1.12 Msps

BasebandSignal

RFSignal

Note: Coding increases the bandwidth of the baseband RF signal


Example Error Correcting Performance

For a BER of 10-5, Theoretical Required Eb/N0 is as follows: Uncoded PSK: 9.6 dB Reed-Solomon (R-S) Coding: 6.0 dB Convolutional Coding (7,1/2)

PSK: 4.4 dB Convolutional + R-S

(no R-S interleave): ~3.0 dB Convolutional + R-S

(ideal R-S interleave): ~2.4 dB (7,1/2), where rate 1/2 indicates that

for every 1 bit into the encoder 2 symbols are output of the encoder and 7 is the number of shift registers used to generate the output symbol of the encoder.

Interleaving takes adjacent bits and separates them to help protect from interference.

Pe

(dB)Eb/No

10 -10

10 -9

10 -8

10 -7

10 -6

10 -5

10 -4

10 -3

10 -2

10 -1

1

1 2 3 4 5 6 8 9 10 11 120

THEORETICAL CURVES

IDEAL PSK, NO CODING

CONV. CODING (7, 1/2)

R-S CODING (255, 223)

CONV. + R-S (IDEAL INTERLEAVE)

CONV. + R-S (NO INTERLEAVE)


Data Compression

Data transmission and storage cost money. Despite this, digital data are generally stored in efficient ways such as

ASCII text or binary code. These encoding methods require data files about twice as large as

actually needed to represent the information.

Data compression is the general term for the various algorithms and programs developed to address this problem. A compression program converts data from an easy-to-use format for

one optimized for compactness. Basically it discards redundant data with a prescribed algorithm.

An uncompression program returns the information to its original form.

As an example of compression, a fax device compresses the data before it sends it to reduce the time needed to transmit the document. This can reduce the cost of transmission 10 or more times. Compression will be required for the Design Project Problem.


Spread Spectrum Definition

Spread Spectrum (SS) was developed originally as an anti-jamming technique. A jamming signal is a narrowband, high power signal which falls in the

bandwidth of the desired signal, thus disrupting communications Jamming can be intentional, or it can result from natural phenomena

such as multipath. SS works by spreading the desired signal over a much larger

bandwidth, Wss, much in excess of the minimum bandwidth W necessary to send the information. A spreading signal, or coding signal, which is independent of the data, is

used to accomplish spreading. At the receiver, the original data is recovered through a process called

despreading, in which a synchronized replica of the spreading signal is correlated with the received spread signal.

Spreading used in the NASA Tracking and Data Relay Satellite (TDRS) Reduce flux density of signals to meet Spectrum Management

requirements. Provide isolation for signals on same frequency.


Basic Spread Spectrum Technique: Direct Sequence

Multiplication by the spreading signal once spreads the signal bandwidth. Multiplication by the spreading signal twice recovers the original signal. The desired signal gets multiplied twice, but the jamming signal gets

multiplied only once. g(t) must be deterministic, since it must be generated at both the

transmitter and receiver, yet it must appear random to authorized listeners. Generally g(t) is generated as a pre-defined pseudo-random sequence of 1s and

–1s through the use of prescribed shift registers.

x x Filter Recovereddata

Signal x(t)Symbol (Data)

rate R

spreading codesignal g(t)

chip rate Rch

spreading codesignal g(t)

chip rate Rch

Rch 10 symbol (data) rate


Spreading: Effect of Spread Spectrum

Before Spreading

After Spreading

G(f)

w

Jammer with total power JJO = J/W

Gss(f)

wss

J'o = Jo (W/Wss)


Spreading: Overview of Various Spreading Techniques

Direct Sequencing (DS) is the SS technique described above. Allows separation between desired signals all at the same frequency &

polarization Aids in meeting required flux density regulations Enables range determination of spacecraft Rule of thumb – spreading chip rate x 10 of symbol (data) rate

In Frequency Hopping (FH), the frequency spectrum of the desired signal is shifted pseudorandomly over M different frequencies. Each hop lasts a very short time, making the presence of a jamming signal in any

one hopped frequency band much less effective. FS is still a form of SS, as it requires greatly expanded bandwidth to operate.

Time Hopping (TH) uses a coded sequence to turn the transmitter on and off in a pseudorandom fashion to counter a pulsed jamming signal. Requires, not more bandwidth, but a greater time duration for transmission. Not effective against continuous wave jammers, so it is usually combined with

other techniques. Hybrids of the three techniques above are often used.

DS/FH, FH/TH, or DS/FH/TH are examples.


Modulation Schemes


Definition of Modulation

Modulate means to change something In telecommunications, it means to change the amplitude,

frequency or phase of the carrier signal.

Digital symbols (usually bits) are transformed into waveforms by a process called digital modulation. These digital waveforms are then used to modulate the carrier.

The following slide shows some commonly used Pulse Code Modulation (PCM) waveforms.

Definition: Baseband signals are those signals that are used to modulate a high frequency carrier signal.


Pulse Code Modulation (PCM) Waveforms

1 1 1 1110 0 0 0 0

0

1

0

1

0

1

0

1

0

0

1

0

1

1

1 0 0 0 0 0 11111

NRZ-L

NRZ-M

NRZ-S

R-Z

Biø-L

Biø-S

Biø-M

NRZ-Level (or NRZ-Change)"One" is represented by one level"Zero" is represented by the other level

NRZ-Mark"One" is represented by a change in level"Zero" is represented by no change in level

NRZ-Space"One" is represented by no change in level"Zero" is represented by a change in level

RZ"One" is represented by a half-bit wide pulse"Zero" is represented by no pulse condition

Bi-Phase-Level (or SplitPhase, Manchester 11+ 180o )"One" is represented by a 10"Zero" is represented by a 01

Bi-Phase-SpaceA transition occurs at the beginning of every bit period"One" is represented by no second transition"Zero" is represented by a second transition one-half bit period later

Bi-Phase-MarkA transition occurs at the beginning of every bit period"One" is represented by a second transition one-half bit period later"Zero" is represented by no second transition

MIS-01 NG5061


Motivation for Modulation

It would be very difficult to send a baseband signal directly over a channel because antennas are used to transmit electromagnetic fields through space.

The size of an antenna depends on the wavelength of the signal to be transmitted. Often the antenna size is taken to be /4.

A baseband signal has a relatively low frequency and therefore a very large wavelength that is calculated as c/f, where c is the speed of light and f is the frequency. An antenna might need to be unacceptably long to directly transmit a baseband

signal. If the baseband information is first modulated on a high frequency carrier, then the

required antenna diameter will be much more reasonable.

In addition, by modulating carriers at different frequencies, more than one baseband signal may be sent over the same channel, thus increasing data throughput. This is call frequency multiplexing (similar to current radio and TV broadcasting).


The Carrier Wave/How to Modulate

The general form of a carrier wave is:

s(t) = A(t) cos [wct + ø(t)]

wc = carrier freqA(t) = amplitudeø(t) = phase

The carrier can be modulated by using the baseband signal to vary one or more of the above parameters over a duration of T, the symbol period.

Coherent modulation may be used when the receiver can exploit knowledge of the actual carrier phase.

Noncoherent modulation is used when knowledge of the absolute phase is unavailable. Less complicated, but comes with a performance degradation.

ModulatorS(t)

fc reference fc

x

xsin


QPSK versus BPSK

BPSK modulation results in 1 symbol/Hz, where QPSK modulation results in 2 symbols/Hz). As a result, the spectrum of QPSK is narrower than that of BPSK. The mainlobe of QPSK is half the width of the BPSK spectrum

mainlobe.

The probabilities of bit error for BPSK and QPSK are equal, but QPSK can support twice the data rate that BPSK can.

Higher orders of PSK can be designed (8-PSK, 16-PSK, etc.), but there is a tradeoff (higher required power or higher BER).


0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

0 2 4 6 8 10 12Theoretical Required Eb/N0 for BER of 10 , dB

Re

qu

ire

d R

F B

an

dw

idth

/ D

ata

Ra

te

BPSK, Uncoded

QPSK, Uncoded

QPSK, Rate 1/2 Coded

BPSK, Rate 1/2 Coded

-5

Comparison of Spectra for BPSK and QPSK for a Given Data Rate

BPSK

QPSK

Two states

for BPSK

1 0

BPSK 1 = 180 DEGREES 0 = 0 DEGREES Inphase and

Quadrature biphase signals

QPSK: Delay Data by 90 degrees on 1 channel

IQ

1a

0b

0a1b

Four states for QPSK

Coding Gain

Bandwidth Difference

Coding Gain

Bandwidth Difference


Noise Basics


Sources of System Noise

The presence of noise degrades the performance of a satellite link The noise present in a satellite communications system (often called the

“system noise”) comes from many different sources Some of it is injected via the antenna from external sources Some of the noise is generated internally by various receiver

components The noise which comes in through the antenna can be seen as random

noise emissions from different sources, and it is also called the sky noise Terrestrial sources such as lightning, radio emissions, and the

atmosphere Solar radiation Galactic background (moon, stars, etc.)

The receiver-generated noise can be caused by various receiver components Results from thermal noise caused by the motion of electrons in all

conductors The principal components that generate noise are the active devices

such as LNA and random noise stemming from passive elements, such as the line from the antenna to the receiver


Noise Temperature of a Device

Noise temperature is a useful concept in communications receivers, since it provides a way of determining how much thermal noise is generated by active and passive devices in the receiving system The physical noise temperature of a device, Tn, results in a noise

power of Pn = KTnBK = Boltzmann’s constant = 1.38 x 10-23 J/K; K in dBW = -228.6 dBW/KTn = Noise temperature of source in KelvinsB = Bandwidth of power measurement device in hertz

Because satellite communications systems work with weak signals, it is mandatory to reduce the noise in the receiver as far as possible Generally the receiver bandwidth is made just large enough to

pass the signal, in order to minimize noise power


The System Noise Temperature

To determine the performance of a receiving system, we must find the total thermal noise against which the signal must be demodulated. The combination of all the noisy devices plus the antenna noise.

This can be done by representing the receiver components as noiseless devices with their individual gains and, at their inputs, noise sources with the same noise power as the original noisy components. The next slide shows how this is done for an earth station receiver.

It is then easy mathematically to combine all of the noise sources into one noise source, located at the input of a noiseless receiver. The noise temperature of this source, Ts, is called the system noise

temperature. The total noise power can then be calculated easily, for link

budget purposes, as Pn = KTsBG. G is the total gain of the receiver. B is the bandwidth of interest.


Noise figure can also be used to specify the noise generated within a deviceNF = (S/N)in/(S/N)out

The noise figure of a device is related to its noise temperature by:Td = T0(NF - 1), where T0, the reference temperature, is usually 290° K (room

temperature)

NFdB = 3 dB; NF= 103/10= 2

Td = 290 (2-1) = 290° K The receiver gain and the system noise temperature can be

combined as a ratio, Gr/Ts, often just written as G/T For example, if the receive antenna is 50 dBi and the system noise

temperature is 500° K , then Gr/Ts = 50-10log (500) 23.0 dB/° K The G/T is often used as a figure of merit for an earth station

As G/T goes up, so does the quality of the earth station

Noise Figure and the G/T Figure of Merit

RF AMP


The Calculation of System Noise Temperature (Cont’d)

Example:

LNA DEMODULATOR IF AMP RECEIVERTsky = 50°

3 dB

Loss = L

L

1

NFLNA = 3 dB = 2GLNA = 30 dB

Ts @ Reference Point

NFDC = 10 dB = 10GDC = 30 dB

NFIF = 10 dB = 10GIF = 30 dB

NFR = 10 dB = 10GR = 30 dB

System Noise Temperature Ts °K

...

GG

T1NF

G

T1NFT1NFT1TT

DCLNA

oIF

LNA

oPCoLNAoskys

...

1000x1000

2901 10

1000

2901 10290)1 2(290)5.0 1()50(5.0

...0026.6.229014525

462 °K

5.01

10/ 310 dB

To is reference temperature of each device = 290°K (assumed)


Components


Components of Interest

Antennas Receive & transmit RF (radio frequency) energy Size/type selected directly related to frequency/required gain

360°0 dBi

Omni Antenna (idealized) Directional (Hi-Gain) Antenna

Gain Pattern

Side Lobes

Boresight

Peak Gain = X dBi

-3 dB Beamwidth

Gain is relative to isotropic with units of dBi

Isotropic antenna

serial "Dryden AK490 Final"

test_range "Anechoic Chamber"dB maxPlot_max 10efficiency 95.113

dBicRHCP_max 5.716MHzf 2209 OAgainmax 5.642

On-axis gain max dBdB_per_div 2Test_date "May 22, 2002"

0

10

20

30

40

50

6070

8090100110

120

130

140

150

160

170

180

190

200

210

220

230

240250

260 270 280290

300

310

320

330

340

350

Theta Cut

plot1mtheta

plot2mtheta

Three_dB

mthetastep

180

360 mtheta step

180

i_3dB

10002

degreesphi 0

serial "Dryden AK490 Final"

test_range "Anechoic Chamber"dB maxPlot_max 10efficiency 95.113

dBicRHCP_max 5.716MHzf 2209 OAgainmax 5.642

On-axis gain max dBdB_per_div 2Test_date "May 22, 2002"

0

10

20

30

40

50

6070

8090100110

120

130

140

150

160

170

180

190

200

210

220

230

240250

260 270 280290

300

310

320

330

340

350

Theta Cut

plot1mtheta

plot2mtheta

Three_dB

mthetastep

180

360 mtheta step

180

i_3dB

10002

degreesphi 0

Omni Antenna (typical)


Components of Interest (Cont’d)

Antennas (cont’d) Polarization: the orientation of the electrical field vector;

specifically, the figure traced as a function of time by the extremity of the vector at a fixed location in space, as observed along the direction of propagation

To minimize polarization loss, the transmit and receive antennas should have the same polarization.

Linear Polarization Vertical

Linear PolarizationHorizontal

Circular Polarization Left hand

Circular PolarizationRight hand



Filters & Diplexers

Diplexer

Receive fr

Transmit ft

fr (2106.4 MHz)

ft (2287.5 MHz)

A

f

Band Pass Filter

A

ff1 f2

f1 – f2

Diplexer provides isolation between transmit & receive signals



Transmitters (modulators) & Receivers (demodulators)

Transponders & Transceivers

TransmitterOriginal Signal

f

ReceiverOriginal Signal

Diplexer

Transmitter

ReceiverTransponderMode

TransceiverMode

Power Amplifier

TransmitterPower

AmplifierG = 13 dB

1 watt (0 dBW) 20 watt (13 dBW)

Switch

A

fc

x

xsin

A

fc

x

xsin


Link Equation and Examples(Stop Here)


Link Equation

For an isotropic antenna in free space conditions, the power supplied to

the antenna, PT, is uniformly distributed on the surface of a sphere of

which the antenna is the center The power flux-density is the power radiated by the antenna in a given

direction at a sufficiently large distance, d, per unit of surface area is:

The power flux-density radiated in a given direction by antenna having

a gain, GT, in that direction is:

The equivalent isotropically radiated power (EIRP) = PT GT

The power received by an antenna with area AR is:

The gain of any antenna, for example GR, is:

distance d ;d 4

P density flux Power

2

T

i

d 4AGP

Apfd P2

R T T

R R

fc

λ;λ A 4

G2

r

R

2

TT

d 4G P

(pfd) density flux Power


Link Equation (Cont’d)

In general, dBdBRdBdBR (L))(G(EIRP))(P

dBdBRdBdBR losses) all (Σ)(G(EIRP))(P

GT

PTd

HypotheticalSphere

Receiving Antenna Area = AR

)derivation for backup (seeMHzf log 20 kmd log 20 32.44dB(L) Loss Path Space Free

λ

d 4 2 L where

L

GEIRP

λd 4

G EIRP

λd 4

GGP

d 4

AGP P R

2R

2R T T

2R T T

R


The power received to noise density is related to the data rate by the energy per bit as follows:

The actual Eb/N0 can be compared to the required Eb/N0 to see how much “margin” the system contains.

If the margin is not high enough, or is less than 0 dB, then, using the link budget, a system engineer can easily determine how the communication system needs to be improved to achieve the desired performance.

Link Equation

KT N density, spectral noise theLet o

LossesKTG

EIRP N

P Hz 1 in

noise

power the Then

r

o

r dBdBdB

rdB

dBo

r Losses - K - T

G EIRP

N

P

R N

E

N

P

ro

b

ro

r

dB

dBo

r

ro

b R - N

P

N

E

dB

RateBit R received Energy/bit N

E

ro

b

dB dReq'o

b

ro

b

N

E

N

E Margin

dB

dB dReq'o

b

N

E

where:

is related to BER (see theoretical curves for given modulation and coding scheme)

where K = Boltzmann’s constant = 1.38 x 10-23 J/K; K in dBW = -228.6 dBW/K

T = system noise temperature in Kelvins


Link Budget Analysis

A link budget is an engineering tool for satellite communication systems, used to demonstrate and analyze link performance Generally the desired end result is Bit Error Rate (BER), or the Eb/N0

required to achieve a desired BER

Link performance is analyzed in terms of: Transmit power Antenna parameters (e.g. gain) Received system noise levels (usually specified as noise temperature) Other factors (e.g. propagation losses, interference, intermodulation)

As for any budget, numbers are added and subtracted together in a table format, with the “bottom line” at the bottom Factors that contribute to a higher Eb/N0 are added as positive numbers,

like “credits” Factors that contribute to a lower Eb/N0 are added as negative numbers,

like “debits”


Additional Losses on a Real Satellite Link

On an ideal link, the only power loss term would be the path loss caused by the dispersion of the transmit power over the transmitter-to-receiver range.

For a real satellite communications link, many other losses need to be considered as well. Polarization loss, caused by the a mismatch between the

transmitting and receiving antennas. Rain attenuation and atmospheric loss. The receiver implementation loss. Pointing loss, caused by imperfect pointing of the antennas Miscellaneous other losses.

In the link budget, these losses are sometimes listed as line items subtracted from the received power, but some of them may be combined in different ways.


Sample Link Budget (direct to ground)

Encoder& Transmitter

I = 75 MBPS

Q = 75 MBPS

LNA Receiver

Decoder

Loss = 1.13 dB

Gain = 4.84 dBi

SPACE

G/T = 33.3 dB/K

11m Ground Antenna

11.6 dBW 10.49 dBW EIRP = 15.31 dBW Hz dB 95.95oN

C

data

I Q

dB 19.12roN

bE

dB 25.4D'REQoN

bE

Implementation Loss = 2.0 dB

MARGIN = 5.94 dB

Decoded Data

Σ Losses = 0.67 dB Polarization loss178.95 dB space loss @ 2575 KM and 5 elevation0.45 dB atmospheric loss1.2 dB rain loss

8212.5 MHz

QPSK

Alaska SAR Facility 11 meter antenna


Example Link Budget (direct to ground)*** DOWNLINK MARGIN CALCULATION*** GSFC C.L.A.S.S. ANALYSIS #1 DATE & TIME: 4/ 1/99 10:13:39 PERFORMED BY: Y.WONG LINKID: EOS-AM/SGS FREQUENCY: 8212.5 MHz RANGE: 2575.0 km MODULATION: QPSK I CHANNEL Q CHANNEL --------- --------- DATA RATE: 75000.000 kbps DATA RATE: 75000.000 kbps CODING: RATE 1/2 CODED CODING: RATE 1/2 CODED BER: 1.00E-05 BER: 1.00E-05 99.95 AVAILABILITY GR EL=5 DEGREES PARAMETER VALUE REMARKS --------------------------------------------------------------------------------------------------------------------- 01. USER SPACECRAFT TRANSMITTER POWER - dBW 11.60 NOTE A; EOL 02. USER SPACECRAFT PASSIVE LOSS - dB 1.13 NOTE A 03. USER SPACECRAFT ANTENNA GAIN - dBi 4.84 NOTE A include multipath loss 04. USER SPACECRAFT POINTING LOSS - dB .00 NOTE A 05. USER SPACECRAFT EIRP - dBWi 15.31 1 - 2 + 3 - 4 06. POLARIZATION LOSS - dB .67 NOTE A 07. FREE SPACE LOSS - dB 178.95 NOTE B 08. ATMOSPHERIC LOSS - dB .45 NOTE B; EL: 5.0 DEG 09. RAIN ATTENUATION - dB 1.20 Include Scintillation loss 1.1 dB 10. MULTIPATH LOSS - dB .00 NOTE A 11. GROUND STATION G/T - dB/DEGREES-K 33.30 G/T with rain at 5 degrees 12. BOLTZMANN'S CONSTANT - dBW/(Hz*K) -228.60 CONSTANT 13. RECEIVED CARRIER TO NOISE DENSITY - dB/Hz 95.95 5 - 6 - 7 - 8 - 9 - 10 + 11 - 12 I CHANNEL Q CHANNEL --------- --------- 14. I-Q CHANNEL POWER SPLIT LOSS - dB 3.01 3.01 NOTE B; 1.00 TO 1.00 15. MODULATION LOSS - dB .20 .20 NOTE A 16. DATA RATE - dB-bps 78.75 78.75 NOTE A 17. DIFFERENTIAL ENCODING/DECODING LOSS - dB .20 .20 NOTE A 18. USER CONSTRAINT LOSS - dB 1.60 1.60 2 dB Includes diff encoding and modulation losses 19. RECEIVED Eb/No - dB 12.19 12.19 13 - 14 - 15 - 16 - 17 - 18 20. IMPLEMENTATION LOSS - dB 2.00 2.00 21. REQUIRED Eb/No - dB 4.25 4.25 I: NOTE B; Q: NOTE B 22. REQUIRED PERFORMANCE MARGIN - dB 3.00 3.00 NOTE A 23. MARGIN - dB 2.94 2.94 19 - 20 - 21 - 22 NOTE A: PARAMETER VALUE FROM USER PROJECT - SUBJECT TO CHANGE NOTE B: FROM CLASS ANALYSIS IF COMPUTED


TDRSS Return Link Power Received

For ease of calculation, TDRSS defines the relationship between data rate and the signal power level received isotropically at TDRS (Prec) for a Bit Error Rate of 10-5

Ideal required Prec = RbdB + K For rate 1/2 coded signals, assume: K = -221.8 (MA); -231.6 (SSA); -245.2

(KuSA); -247.6 (KaSA) Due to defining the Prec isotropically at TDRS, the predicted received

power is calculated the same as identified earlier (see Link Equation slide); however, GR is set to 1 (= 0 dB) for the isotropic antenna. (i.e.,

Prec = Pr = GRGTPT(/4R)2 Watts) In dB, this can be expressed as PR = GR + GT + PT + 20Log(/4R) dBW

Margin = Predicted Prec – Ideal Prec – Other Losses Other Losses are treated as debits and encompass items such as

polarization loss (mismatch of the transmit polarization with receiving polarization), pointing loss (inability of transmit antenna to point to receiving antenna), incompatibility loss, and interference degradation.


Example Simple TDRS Link Budget using Prec Equation

*** RETURN LINK CALCULATION -- NETWORK SYSTEMS ENGINEER ANALYSIS ***GSFC C.L.A.S.S. ANALYSIS #0 DATE & TIME: 03/03/03 10: 1:31 PERFORMED BY: R. BROCKDORFF USERID: EOS-AM LINKID: KSA8L RELAY SYS.: TDRS-East TO STGT SERVICE: FREQUENCY: DATA GROUP/MODE: POLAR: RANGE CASE: ALTITUDE: ELEVATION: RANGE: KuSA 15003.4 MHz DG-2 MODE-2A LCP MAXIMUM 710.6 Km 1.5 Deg 44592.7 Km---------------------------------------------------------------------------------------------------- I CHANNEL Q CHANNEL DATA RATE = 75000.00 KBPS DATA RATE = 75000.00 KBPS MOD TYPE = QPSK MOD TYPE = QPSK SYMBL FMT = NRZ-M SYMBL FMT = NRZ-M RATE 1/2 CODED RATE 1/2 CODED ---------------------------------------------------------------------------------------------------- SPACE-SPACE LINK NOTES------------------------------------------------------ -------------------------------- 1 USER TRANSMIT POWER, dBW 12.00 User Provided Data 2 PASSIVE LOSS, dB 1.80 User Provided Data 3 USER ANTENNA GAIN, dBi 44.30 User Provided Data 4 POINTING LOSS, dB 2.20 User Provided Data 5 USER EIRP, dBW 52.30 (1)-(2)+(3)-(4) 6 SPACE LOSS, dB 208.95 CLASS Analysis 7 ATMOSPHERIC LOSS, dB 0.00 Not Considered 8 MULTIPATH LOSS, dB 0.00 Not Considered 9 POLARIZATION LOSS, dB 0.10 User Provided Data 10 SSL RAIN ATTENUATION, dB 0.00 User Provided Data 11 Prec AT INPUT TO TDRS, dBW -156.75 (5)-(6)-(7)-(8)-(9)-(10) 12 Required Prec AT INPUT TO TDRS, dBW -163.44 -245.2 + 10*log (Data Rate) 13 DYNAMICS LOSS, dB 0.00 Not Considered 14 USER CONSTRAINT LOSS, dB 0.00 CLASS Analysis 15 RFI LOSS, dB 0.00 CLASS Analysis 16 MARGIN, dB 6.69 (11)-(12)-(13)-(14)-(15)

• Slight difference in simplified link budget vs detailed link budget due to exact customer configuration and space-to-ground link effects


Sample Link budget (thru TDRS)

Encoder& Transmitter

I = 75 MBPS

Q = 75 MBPS Gain = 44.30 dBi

Space

12 dBW 10.2 dBW EIRP = 52.30 dBW

15003.4 MHz

QPSK

Receiver

Decoder

data

Decoded Data

LNA

Space Ground Link

QPSK

I = 150 Msps Q = 150 Msps

Prec is defined here for a unity gain antenna and BER = 10-5

Predicted Prec = -156.75 dBWIdeal Required Prec = -163.44 dBWMargin = 6.69 dB

Loss = 1.8 dBLoss = 2.2 dB

Σ Losses = 0.10 dB Polarization loss208.95 dB space loss @ 44592.7 KM and 1.5 elevation

Transparent to the link budget when using the ideal Prec equation

Note: Significantly more EIRP needed as compared to a direct downlink (52.3 vs. 15.31 dBW)


Geometric Coverage (Ground)

Florida ground station with spacecraft altitudes 400, 800, and 1200 km

400 km

800 km

1200 km

Merritt Island

Elevation angle is the angle between local horizontal at ground station and spacecraft



Merritt Island

Ground station elevation angles of 0, 10, and 20 degrees

El = 0O

El = 10O

El = 20O



Building

Antenna limits

Another antenna

Effects of terrain and antenna limitationsElevation angel = 0°

Merritt Island

Spacecraft altitude = 1200 km



Svalbard Location

Coverage circle for Svalbard at a spacecraft altitude of 400 km

0° elevation angel



Spacecraft Orbit of 400 KM, 65 deg inc circularHawaii (HAW3), Alaska (AGIS), Wallops Island (WPSA), Svalbard (SGIS), McMurdo (MCMS)

Svalbard

AGIS

WPSA

MCMS

HAW3



Spacecraft Orbit of 400 KM, 98 deg inc circularHawaii (HAW3), Alaska (AGIS), Wallops Island (WPSA), Svalbard (SGIS), McMurdo (MCMS)

AGIS

WPSA

HAW3


Geometric Coverage (TDRS)

Spacecraft height = 500 km

Synsat location

Coverage

No coverage

Synchronous Satellite Coverage at 319 deg long


TDRS Basics


NASA’s Tracking and Data Relay Satellite (TDRS)

The TDRSs are in geosynchronous orbit at allocated longitudes A geostationary satellite is in a circular orbit parallel to and 35786.43 km above the

equator with an angular velocity that matches that of the earth. It hovers above a fixed point on the equator and therefore appears to be motionless.

A geosynchronous satellite has the same orbit period as a geostationary satellite, but its orbit may be elliptical and inclined. A geosynchronous satellite in an inclined circular orbit moves in a figure-8 pattern as viewed from

earth. To maintain a geosynchronous orbit, a satellite must periodically make east-west corrections or it

will drift in longitude.

The TDRSs, along with supporting ground systems, make up NASA’s Space Network.

The Space Network was established to act as a bent-pipe relay (i.e., repeater) and dramatically increase coverage to low earth orbiting satellites as compared to a worldwide network of ground stations. The SN dramatically increased tracking and data acquisition (T&DA) coverage from

15% to 85% per orbit of low earth orbiting spacecraft as well as decreased operational costs (see coverage slides for depiction). Requires ~ 30 dB additional EIRP vs direct to ground

Today, 100% line-of-sight coverage can be provided to LEO customers. Use of 2 TDRS constellation has a Zone of Exclusion (ZOE) Use of 3 TDRS constellation does not have ZOE


TDRSS Constellation

F-5174°WTDW

F-7171°W

(in storage)

F-1049°W

F-6047°WTDS

F-4041°WTDE

F-3275°WTDZ

WHITE SANDS COMPLEX

GUAM REMOTE GROUND TERMINAL

TDRS-8170.7°W

TDRS-I149.5°W

McMurdo Ground StationMcMurdo TDRS Relay System

(McMurdo, Antarctica)

TDRS-J150°W


TDRSS FIELDS OF VIEW

WHITESANDSCOMPLEX

0/360180W

GUAM

-180W

174° TDW 94°

121°321°

41° TDE

127° 47° TDS 327°

254°TDW

275° TDZ

355° 195°

TDRS VIEWS BASED ON 600KM USER ALTITUDE AT THE EQUATOR

91°171° F-7

251° F-7


TDRSS Ground Segment

TWO FUNCTIONALLY IDENTICAL, GEOGRAPHICALLY SEPARATED GROUND TERMINALS AT THE WHITE SANDS TEST FACILITY

THE WHITE SANDS COMPLEX (WSC) HAS FIVE SPACE TO GROUND LINK TERMINALS (SGLTs)

A SIXTH SGLT HAS BEEN INSTALLED AT THE REMOTE GROUND TERMINAL ON GUAM AS AN EXTENDED WSC SGLT

DATA SERVICES MANAGEMENT CENTER

OPERATIONAL HUB LOCATED AT WSC

FOR COORDINATING ALL SPACE

NETWORK ACTIVITIES BETWEEN

CUSTOMERS AND SN


Space Segment: Tracking and Data Relay Satellite (F1 - F7)

• Forward (FWD): link from TDRSS Ground Station through TDRS to Customer Spacecraft• Return (RTN): link from Customer Spacecraft through TDRS to TDRSS Ground Station

Single Access AntennaDual frequency communications

and tracking functions: S-band TDRSS (SSA) K-band TDRSS (KSA) K-band auto-tracking

4.9 meter shaped reflector assembly

SA equipment compartment mounted behind reflector

Two axis gimballing

Space-to-Ground-Link AntennaTDRS downlink2.0 meter parabolic reflectorDual orthogonal linear polarization TDRS:

single horn feedorthomode transducer

Two axis gimballed

Omni Antenna (S-band) and Solar Sail

Multiple Access Antenna30 helices:

12 diplexers for transmit30 receive body mounted

Single commanded beam, transmit20 adapted beams for receiveGround implemented receive function

Solar arrayPower output is approximately 1800 watts


Multiple Access (MA) vs Single Access (SA)

Multiple Access (MA): Fixed S-band frequency (2106.4 MHz fwd and 2287.5 MHz rtn) Fixed polarization (left hand circular) Low data rate (<= 300 kbps) Forward service operations are time-shared amongst customers Return service supports multiple customers simultaneously

(lower service cost to customer vs SA) Phased array antenna and beamforming equipment allow for spatial discrimination between

customers; PN spreading provides additional discrimination Return Demand Access Service allows customers to have a dedicated return link

continuously (lower service cost to customer) Single Access (SA):

Multiple frequency bands (S-band, Ku-band, Ka-band) S-band: selectable frequency (2025.8 – 2117.9 MHz fwd; 2200-2300 MHz rtn) Ku-band: fixed frequency (13775 MHz fwd; 15003.4 MHz rtn) Ka-band: selectable frequency (22550-23550 MHz fwd; 25250-27500 MHz rtn) S-band and K-band simultaneously

Selectable polarization (left or right hand circular) High data rate (up to 300 Mbps) Forward service operations are time-shared amongst customers Return service operations are time-shared amongst customers (higher service cost

to customer vs MA)


Data Rates Associated with Space Network Services

3. For customer data configurations, see 450-SNUG, Space Network Users’ Guide 4. Current WSC configuration supports 7 Mbps5. Guam Remote Ground Terminal (GRGT) is not currently configured to support TDRS F8-F106. F8 may experience lower G/T performance less than 12 hrs per day

Service WSC & TDRS F1-F7 Capabilities(3) WSC & TDRS F8-F10 Capabilities

Forward Up to 7MBps; EIRP = 43.6 dBW (normal); 48.5 dBW (high)

Up to 7 MBps; EIRP = 43.6 dBW (normal); 48.5 dBW (high)

Return Up to 6 Mbps; G/T (min) = 9.0 dB/K Up to 6 Mbps; G/T (min) = 9.0 dB/K

Forward Up to 25 Mbps(4); Autotrack EIRP = 46.5 dBW (normal); 48.5 dBW (high)

Up to 25 Mbps(4); Autotrack EIRP = 46.5 dBW (normal); 48.5 dBW (high)

Return Up to 300 Mbps; Autotrack G/T = 24.4 dB/K Up to 300 Mbps; Autotrack G/T = 24.4 dB/K

Forward N/A Up to 25 Mbps(5); Autotrack EIRP = 63 dBW

Return N/A Up to 300 Mbps/800 Mbps(1); Autotrack G/T = 26.5 dB/K

Number of Single Access LinksSSA: 2/TDRS; 10/WSC; 2/GRGTKuSA: 2/TDRS; 10 KuSA/WSC; 2/GRGT

SSA: 2/TDRS; 10/WSC; 2/GRGT(5)

KuSA: 2/TDRS (2); 10/WSC; 2/GRGT(5)

KaSA: 2/TDRS (2); 8/WSC(5)

Multiple Access

Forward 1/TDRS @ up to 300 kbps; 4/WSC; 1/GRGTEIRP = 34 dBW

1/TDRS @ up to 300 kbps; 4/WSC(5)

EIRP = 42 dBW (LEOFOV)

Return 5/TDRS @ up to 300 kbps; 20/WSC; 2/GRGT;Formed Beam G/T= 3.1 dB/K (Does not include DAS)

5/TDRS @ up to 3 Mbps; 20/WSC(5)

G/T = 4.5 dB/K (LEOFOV) (6)

User Tracking Range, 1&2 way Doppler Range, 1&2 way Doppler(No Ka-band Tracking)

1. Spacecraft only2. The SN can simultaneously support S-band or Ku/Ka-band (F8-

F10 only) forward and/or return services through 1 SA antenna to the same ephemeris. F8-F10 cannot simultaneously support Ku/Ka-band services through 1 SA antenna.

S-Band

Single

Access

Ku-Band

Ka-Band

Notes:


Spectrum Management


Purpose of Spectrum Management

Ensure that the system in which time and money has been invested to develop provides the required quality of service (i.e., Bit Error Rate) when it is deployed or installed.

Apply order to the use of the orbit/spectrum resource.

Provide technical bases for coordination.

Ensure that systems operate as intended.

Promote the efficient use of the radio frequency spectrum.

Accommodate new services, applications and technology.


Frequency Allocations

The radio frequency spectrum is a national and international resource whose use is governed by Federal statutes and international treaty. Internationally: The International Telecommunication Union

(ITU), which is a specialized agency of the United Nations, acts as the global spectrum coordinator and develops binding international treaty governing the use of the radio spectrum by some 40 different services around the world. The Radio Regulations contain a number of provisions governing the way

the radio frequency spectrum is to be used. Nationally (within the US): responsibility is broken into 2 areas:

National Telecommunications and Information Agency (NTIA) manages the Government spectrum

Federal Communications Commission (FCC) manages the non-government spectrum

The international and national Table of Allocations shows what segments of the radio frequency spectrum are to be used by which services.


Spectrum Allocations Available to NASA LEO Missions for Telecommunications


Background Material


References

“Digital Communications,” Bernard Sklar “Antennas,” J.D. Ravs “Space Network Users’ Guide,” Rev. 8, June 2002,

http://gdms.gsfc.nasa.gov/ Sign on as Guest Select CCMS Select Document Library Select Code 450

“Error Bounds for Convolutional Codes and Asymmetrically Optimum Decoding Algorithum,” A.J. Viterbi, IEEE Trans information Theory, Vol. IT13, April 1967, pp 260-169

“Principles of Digital Communications and Coding,” A.J. Viterbi and J.K. Omura

“Ground Network Users’ Guide,” February 2001, http://www.wff.nasa.gov/~code452/

“Digital Communications,” Kamilo Feher Consultative Committee for Space Data Systems (CCSDS)

http://www.CCSDS.ORG


Compression: Lossy versus Lossless Compression

A lossless compression technique means that the restored data file is identical to the original. This is necessary for many types of data, like executable code,

word processing files, etc. GIF images are examples of lossless compressed files.

On the other hand, data files that represent images, among others, do not have to be kept in perfect condition. A lossy compression technique allows a small level of noisy

degradation to the original data. Lossy techniques are much more effective at compression than

lossless methods: for a digital image, JPEG can achieve a 12-to-1 compression ratio, as opposed to a 2-to-1 ratio for GIF.


Link Equation: Pr/N0 for Cascaded Links

Often a satellite communications link will consist of more than one point-to-point path. For example, a satellite at low earth orbit often will send its data up to a

satellite at high earth orbit, which will then relay the data down to a ground station.

For a two-path system, the total Pr/N0 can be found as:

As an example, if a link has uplink Pr/N0 of 60 dB-Hz and a

downlink Pr/N0 of 60 dB-Hz, then the overall Pr/N0 is 57 dB-Hz. Sometimes either the uplink or the downlink will be much more

high powered than the other. In this case, the total Pr/N0 will be almost identical to that of the weaker

link, and the link budget for the stronger link need not even be done at all.

Down0rUp0r

Total0r

)/N(P1

)/N(P1

1)/N(P


Link Equation: Geometric Coverage (TDRS)

TDRSS Satellite System: Areas of non coverage


Space Segment: Tracking and Data Relay Satellites

TDRSSGroundStation

TDRSSGroundStation

NASA andCustomerGround

Operations

NASA andCustomerGround

Operations

Space-Space Link

Fwd: 2.025-2.120 GHz (S-band)

2.1064 GHz (MA)13.775 GHz (Ku-band)22.55-23.55 GHz (Ka-band)

Fwd: 2.025-2.120 GHz (S-band)


Space-Space Link

Fwd: 2.025-2.120 GHz (S-band)


Fwd: 2.025-2.120 GHz (S-band)


Space-Ground Link

Fwd: 14.6-15.225 GHz

Rtn: 13.4-14.05 GHz

Space-Ground Link

Fwd: 14.6-15.225 GHz

Rtn: 13.4-14.05 GHz

1 of 2 Single Access (SA) Antennas S & Ku-Band for F1-F7 S, Ku, & Ka-Band for F8-F10Field of View (Primary): ±22° E-W, ±28.0° N-S Extended FOV (HIJ only): ±76.8° E-W*, ±30.5° N-S**

S-Band Phased – Array forMultiple-Access (MA) Service

1 Fwd, 5 Rtn Links for F1-F7***

1 Fwd, 5 Rtn Links for F8-F10Field of View (Primary): ±13° conical

RTNLink

FWDLink

CustomerSpacecraft

* - 76.8° outboard** - 24°E-W (inboard)*** - Demand Access Service allows large expansion on the number of non-coherent return link services available through F1 – F7

Primary site atWhite Sands, NM- STGT- WSGTU

Additional site atGuam to supportTDRS at 85E- GRGT

Primary site atWhite Sands, NM- STGT- WSGTU

Additional site atGuam to supportTDRS at 85E- GRGT

Satellite RF Fundamentals

Spectrum: Available Allocations for the Ground Network and/or the Space Network

Only bands that support both the Ground Network (GN) and the Space Network (SN) on a primary basis.

Basic capabilities of the Ground Network at S-band are: Command rates to 32 kbps (note) Telemetry and mission data rates

to 10 Mbps (note) Support available from selected

sites worldwide Basic capabilities of the Space

Network at S-band are: Command rates to 300 kbps PN

spread Telemetry and mission data rates

to 6 Mbps Virtually global support.

Efforts to control the inter-service interference are under-way within the ITU-R.

S-bandS-band

Note: Maximum support data rate is dependent on the particular ground station capabilities


Bands only support Ground Network operations on a primary basis

The 7190-7235 MHz band may be used to command subject to the earth station being coordinated with terrestrial systems operating in the bands that might experience interference.

The 8025-8400 MHz and 8450-8500 MHz bands may be used for transmissions in the space-Earth direction.

Basic capabilities of the Ground Network at X-band are: Telemetry and mission data rates

to 150 Mbps (note)

X-bandX-bandS5.460 Additional allocation: the band 7 145 - 7 235 MHz is also allocated to the space research (Earth-to-space) service on a primary basis, subject to agreement obtained under No. S9.21. The use of the band 7 145 -7 190 MHz is restricted to deep space; no emissions to deep space shall be effected in the band 7 190 - 7 235 MHz.

Note: Maximum support data rate is dependent on the particular ground station capabilities



Bands only support Space Network Operations (13.775 GHz forward/15.0034 GHz return) on a secondary basis

For TDRSS advanced publications received prior to January 31 1992, the 13.775 GHz forward link operates on a primary basis with respect to the Fixed-Satellite Service (E-S).

Basic capabilities of the Space Network at Ku-band are: Forward link will support up to

25 Mbps. Return link will support up to

300 Mbps. Virtually global support.

Ku-bandKu-band



The pair of Ka-band allocations (22.55-23.55 GHz and 25.25-27.5 GHz) support only the Space Network on a primary basis.

The 25.5-27 GHz band is available globally on a primary basis for S-E transmissions from Earth-exploration satellites.

Basic capabilities of the Space Network at Ka-band are: Forward links in the 22.55-23.55

GHz band will support data rates up to 25 Mbps.

Return links in the 25.25-27.5 GHz band will support data rates up to 300/800 Mbps (note)

Ka-bandKa-band

Note: Capable of supporting 800 Mbps with upgrades to the TDRSS ground stations



Spectrum: Definition of Spectrum Allocations

Space Research Service: A radiocommunication service in which spacecraft or other objects in space are used for scientific or technological research purposes.

Space Operation Service: A radiocommunication service concerned exclusively with the operation of spacecraft, in particular space tracking, space telemetry and space telecommand.

Earth Exploration-Satellite Service: A radiocommunication service between earth stations and one or more space stations, which may include links between space stations, in which: information relating to the characteristics of the Earth and its natural phenomena, including data relating

to the state of the environment, is obtained from active sensors or passive sensors on Earth satellites; similar information is collected from airborne or Earth-based platforms; such information may be distributed to earth stations within the system concerned; platform interrogation may be included. This service may also include feeder links necessary for its operation.

Meteorological-Satellite Service: An earth exploration-satellite service for meteorological purposes.

Inter-Satellite Service: A radiocommunication service providing links between artificial satellites.

Documents

Satellite RF Fundamentals 1 Wireless Technologies Review: Satellite RF Fundamentals