SIST EN 301 926 V1.3.1:2017
(Main)Satellite Earth Stations and Systems (SES) - Radio Frequency and Modulation Standard for Telemetry, Command and Ranging (TCR) of Communications Satellites
Satellite Earth Stations and Systems (SES) - Radio Frequency and Modulation Standard for Telemetry, Command and Ranging (TCR) of Communications Satellites
The present document applies to the Telemetry, Command and Ranging (TCR) system of Communication Satellites
(geosynchronous or not), operating in the following frequency bands:
• 5 725 MHz to 7 025 MHz uplink, 3 400 MHz to 4 200 MHz and 4 500 MHz to 4 800 MHz downlink
("C-band");
• 12 750 MHz to 13 250 MHz, 13 750 MHz to 14 800 MHz and 17 300 MHz to 18 400 MHz uplink,
10 700 MHz to 12 750 MHz and 13 400 MHz to 13 650 MHz downlink ("Ku-band");
• 27 500 MHz to 30 000 MHz uplink, 17 700 MHz to 20 200 MHz downlink ("Commercial Ka-band").
Although not explicitly addressed in the present document, possible usage in other bands allocated to
FSS/MSS/BSS/SOS between 1 GHz to 51,4 GHz may be envisaged.
The TCR receiver and transmitter can have a frequency flexibility capability over a given RF band, Typical frequency
step is 100 kHz.
The present document sets out the minimum performance requirements and technical characteristics of the
ground/satellite Radio Frequency (RF) interface based on Frequency Modulation (FM), Phase Modulation (PM) and
Code Division Multiple Access (CDMA).
With the growing number of satellites, the co-location constraints and the maximization of bandwidth for
Communications Missions, real and potential interference cases have motivated the elaboration of the present document
for geostationary satellites based on CDMA techniques.
The present document addresses the following applications:
• Telemetry.
• Command (Telecommand).
• Ranging.
• Hosted Payload Management.
The aim of the present document is to replace and enhance the prior document ETSI EN 301 926 [i.2] (V1.2.1). The
present document's provisions also apply for use cases of autonomous control of hosted payloads. It is recognized that
hosted payloads may require only a subset of the functionality.
The present document applies to the typical TCR scenario shown on figure 1. The scenario includes multiple satellites,
which may be located in the same orbital location (GSO), or that can be in common view of a given TCR station during
NGSO phases (such as transfer phase to GEO, or during NGSO operations). These satellites may be controlled by m
different TCR ground stations. The TCR links defined in the present document have also to coexist with the
communication ground terminals also shown on figure 1. Some of the satellites to be controlled may use FM/PM
waveforms, and some may use a CDMA waveform, as defined later in the present document.
The scenario may also include, for some of the satellites, hosted payloads, which can be controlled independently of the
satellite platform and of the main payload.
The present document defines the modulation and coding on the TCR and HPM links. Modulation formats are specified
in clause 4 and coding in clause 7.
Satelitske zemeljske postaje in sistemi (SES) - Radiofrekvenčni in modulacijski standard za telemetrijo, vodenje in merjenje oddaljenosti (TCR) komunikacijskih satelitov
Ta dokument se uporablja za sistem za telemetrijo, vodenje in merjenje oddaljenosti (TCR) komunikacijskih satelitov (ki so ali niso geosinhroni), ki delujejo v naslednjih frekvenčnih pasovih:
• od 5725 MHz do 7025 MHz pri navzgornji povezavi, od 3400 MHz do 4200 MHz in od 4500 MHz do 4800 MHz pri navzdolnji povezavi (»pas C«);
• od 12.750 MHz do 13.250 MHz, od 13.750 MHz do 14.800 MHz in od 17.300 MHz do 18.400 MHz pri navzgornji povezavi, od 10.700 MHz do 12.750 MHz in od 13.400 MHz do 13.650 MHz pri navzdolnji povezavi (»pas Ku«);
• od 27.500 MHz do 30.000 MHz pri navzgornji povezavi, od 17.700 MHz do 20.200 MHz pri navzdolnji povezavi (»komercialni pas Ka«).
Čeprav ta dokument tega izrecno ne obravnava, je mogoče predvideti uporabo v drugih pasovih, dodeljenih za sistem FSS/MSS/BSS/SOS v območju od 1 GHz do 51,4 GHz.
Sprejemnik in oddajnik TCR lahko izkazujeta zmožnost prilagajanja frekvence v danem frekvenčnem pasu; običajni frekvenčni interval je 100 kHz.
Ta dokument določa minimalne zahteve glede zmogljivosti in tehnične lastnosti radiofrekvenčnega (RF) vmesnika zemeljske/satelitske opreme, ki temelji na frekvenčni modulaciji (FM), fazni modulaciji (PM) in neposrednem kodnem dostopu (CDMA).
Z vedno večjim številom satelitov so omejitve kolokacije in čim večje izkoriščenosti pasovne širine pri komunikacijskih misijah, resnični in potencialni primeri motenj botrovali izpopolnitvi tega dokumenta za geostacionarne satelite, ki temeljijo na tehnikah CDMA.
Ta dokument obravnava naslednje načine uporabe:
• telemetrija;
• vodenje (daljinsko vodenje);
• merjenje oddaljenosti;
• upravljanje gostujoče obremenitve.
Namen tega dokumenta je nadomestiti in izboljšati prejšnji dokument ETSI EN 301 926 [i.2] (V1.2.1). Določila tega dokumenta se uporabljajo tudi v primerih avtonomnega krmiljenja gostujočih obremenitev. Ugotovljeno je, da lahko gostujoče obremenitve zahtevajo samo podskupino funkcionalnosti.
Ta dokument se uporablja za običajni scenarij TCR, prikazan na sliki 1. Scenarij vključuje več satelitov, ki se lahko nahajajo na isti lokaciji v orbiti (GSO) ali so lahko v običajnem pogledu dane postaje TCR med fazami NGSO (kot je faza prenosa v GEO ali med operacijami NGSO). Te satelite je mogoče krmiliti z različnimi zemeljskimi postajami TCR: Povezave TCR, določene v tem dokumentu, morajo prav tako soobstajati v komunikacijskih zemeljskih terminalih, ki so ravno tako prikazani na sliki 1. Nekateri sateliti, ki jih je treba krmiliti, lahko uporabljajo valovne oblike FM/PM,
nekateri pa valovno obliko CDMA, kot je predeljeno v nadaljevanju tega dokumenta.
Scenarij lahko (za nekatere satelite) vključuje tudi gostujoče obremenitve, ki jih je mogoče krmiliti neodvisno od platforme satelita in glavne obremenitve.
Ta dokument opredeljuje modulacijo in kodiranje povezav TCR in HPM. Formati modulacije so podani v točki 4, kodiranje pa v točki 7.
General Information
Standards Content (Sample)
Draft ETSI EN 301 926 V1.3.0 (2017-06)
EUROPEAN STANDARD
Satellite Earth Stations and Systems (SES);
Radio Frequency and Modulation Standard
for Telemetry, Command and Ranging (TCR)
of Communications Satellites
2 Draft ETSI EN 301 926 V1.3.0 (2017-06)
Reference
REN/SES-00401
Keywords
coding, modulation, satellite, telemetry
ETSI
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3 Draft ETSI EN 301 926 V1.3.0 (2017-06)
Contents
Intellectual Property Rights . 5
Foreword . 5
Modal verbs terminology . 5
1 Scope . 6
2 References . 7
2.1 Normative references . 7
2.2 Informative references . 8
3 Definitions and abbreviations . 8
3.1 Definitions . 8
3.2 Abbreviations . 11
4 Modulation Requirements . 12
4.1 General . 12
4.2 Frequency and Phase Modulations . 13
4.2.1 Modulating waveforms . 13
4.2.2 PCM waveforms and data rates . 14
4.2.3 Use of subcarriers . 15
4.2.4 Choice of Subcarrier Frequencies . 15
4.2.5 Uplink Carrier Frequency Deviation (Frequency Modulation) . 16
4.2.6 Uplink PM Modulation Index . 16
4.2.7 Downlink PM Modulation Index . 16
4.2.8 Sense of Modulation . 16
4.2.9 Data Transition Density . 16
4.2.10 Modulation Linearity . 16
4.2.11 Residual Amplitude Modulation . 17
4.2.12 Residual Carrier, Out-of-band Emission and Discrete Spectral Lines . 17
4.3 Spread Spectrum Modulation . 18
4.3.1 General . 18
4.3.2 Chip Shaping . 20
4.3.3 Out-of-Band Emission and Discrete Spectral Lines . 20
4.4 Coherency Properties . 20
5 Requirements on Transmitted Signals . 21
5.1 Frequency Stability. 21
5.1.1 Uplink . 21
5.1.2 Downlink . 21
5.2 Turnaround Frequency Ratio . 21
5.3 Polarization. 21
5.4 Phase Noise . 21
5.4.1 Ground Transmitter. 21
5.4.2 On-board Transmitter . 22
6 Link Acquisition Requirements . 22
6.1 Link Acquisition Performance . 22
6.2 Phyical Layer Operations Procedures . 22
7 Coding and Interleaving . 23
7.1 Uplink . 23
7.2 Downlink . 23
Annex A (informative): Operational Configuration . 24
A.1 Introduction . 24
A.2 Configuration Baseline: on board spread spectrum transponder . 25
A.3 Configuration Alternative 1: on board dual mode receiver and on board dual mode transmitter . 26
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4 Draft ETSI EN 301 926 V1.3.0 (2017-06)
A.4 Configuration Alternative 2: on board dual mode receiver and phase modulation transmitter . 27
A.5 Configuration Alternative 3: on board dual mode receiver, phase modulation transmitter and
dedicated RG SS transmitter . 29
A.6 Configuration Alternative 4: on board dual mode multi-channel receiver and on board dual mode
transmitter (for hosted payload management) . 30
Annex B (informative): Hybrid Ranging process description . 32
B.1 Introduction . 32
B.2 Presentation . 32
B.3 Distance ambiguity resolution . 33
Annex C (informative): Modulator imperfections . 34
C.1 Phase imbalance . 34
C.2 BPSK phase imbalance . 34
C.3 QPSK phase imbalance . 34
C.4 Amplitude imbalance . 34
C.5 Data asymmetry . 35
C.6 Data bit jitter . 35
C.7 PN code asymmetry. 35
C.8 PN code chip jitter . 35
C.9 Chip transition time . 35
C.10 I/Q data bit skew . 36
C.11 I/Q PN code chip skew . 36
Annex D (informative): SRRC chip filtering . 37
Annex E (normative): PN code assignment, generation and set specification . 39
E.1 PN codes . 39
E.2 PN code assignment . 39
E.3 PN code generation . 39
E.3.1 PN code generator types . 39
E.3.1a Telecommand uplink or in-phase channel (Mode MTC2, MTC3 Acquisition) . 42
E.3.2 Ranging uplink or quadrature channel (Mode MTC2) . 42
E.3.3 Telecommand and ranging uplink (Mode MTC3 Tracking) . 43
E.4 Telemetry Downlink. 43
E.4.1 Coherent ranging mode (Mode MTM2) . 43
E.4.2 Non coherent mode (Mode MTM3) . 43
E.5 Baseline PN code set specification . 43
E.6 Extended PN code library. 45
E.7 Code Examples . 46
E.8 PN CODE REQUEST FORM . 49
E.8.1 Form . 49
E.8.2 Description and Instructions . 49
Annex F (informative): Performance computations . 51
Annex G (informative): Bandwidth considerations and assumptions . 52
History . 53
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5 Draft ETSI EN 301 926 V1.3.0 (2017-06)
Intellectual Property Rights
IPRs essential or potentially essential to the present document may have been declared to ETSI. The information
pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be found
in ETSI SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to ETSI in
respect of ETSI standards", which is available from the ETSI Secretariat. Latest updates are available on the ETSI Web
server (https://ipr.etsi.org/).
Pursuant to the ETSI IPR Policy, no investigation, including IPR searches, has been carried out by ETSI. No guarantee
can be given as to the existence of other IPRs not referenced in ETSI SR 000 314 (or the updates on the ETSI Web
server) which are, or may be, or may become, essential to the present document.
Foreword
This draft European Standard (EN) has been produced by ETSI Technical Committee Satellite Earth Stations and
Systems (SES), and is now submitted for the combined Public Enquiry and Vote phase of the ETSI standards EN
Approval Procedure.
Proposed national transposition dates
Date of latest announcement of this EN (doa): 3 months after ETSI publication
Date of latest publication of new National Standard
or endorsement of this EN (dop/e): 6 months after doa
Date of withdrawal of any conflicting National Standard (dow): 6 months after doa
Modal verbs terminology
In the present document "shall", "shall not", "should", "should not", "may", "need not", "will", "will not", "can" and
"cannot" are to be interpreted as described in clause 3.2 of the ETSI Drafting Rules (Verbal forms for the expression of
provisions).
"must" and "must not" are NOT allowed in ETSI deliverables except when used in direct citation.
ETSI
6 Draft ETSI EN 301 926 V1.3.0 (2017-06)
1 Scope
The present document applies to the Telemetry, Command and Ranging (TCR) system of Communication Satellites
(geosynchronous or not), operating in the following frequency bands:
• 5 725 MHz to 7 025 MHz uplink, 3 400 MHz to 4 200 MHz and 4 500 MHz to 4 800 MHz downlink
("C-band");
• 12 750 MHz to 13 250 MHz, 13 750 MHz to 14 800 MHz and 17 300 MHz to 18 400 MHz uplink,
10 700 MHz to 12 750 MHz and 13 400 MHz to 13 650 MHz downlink ("Ku-band");
• 27 500 MHz to 30 000 MHz uplink, 17 700 MHz to 20 200 MHz downlink ("Commercial Ka-band").
Although not explicitly addressed in the present document, possible usage in other bands allocated to
FSS/MSS/BSS/SOS between 1 GHz to 51,4 GHz may be envisaged.
The TCR receiver and transmitter can have a frequency flexibility capability over a given RF band, Typical frequency
step is 100 kHz.
The present document sets out the minimum performance requirements and technical characteristics of the
ground/satellite Radio Frequency (RF) interface based on Frequency Modulation (FM), Phase Modulation (PM) and
Code Division Multiple Access (CDMA).
With the growing number of satellites, the co-location constraints and the maximization of bandwidth for
Communications Missions, real and potential interference cases have motivated the elaboration of the present document
for geostationary satellites based on CDMA techniques.
The present document addresses the following applications:
• Telemetry.
• Command (Telecommand).
• Ranging.
• Hosted Payload Management.
The aim of the present document is to replace and enhance the prior document ETSI EN 301 926 [i.2] (V1.2.1). The
present document's provisions also apply for use cases of autonomous control of hosted payloads. It is recognized that
hosted payloads may require only a subset of the functionality.
The present document applies to the typical TCR scenario shown on figure 1. The scenario includes multiple satellites,
which may be located in the same orbital location (GSO), or that can be in common view of a given TCR station during
NGSO phases (such as transfer phase to GEO, or during NGSO operations). These satellites may be controlled by m
different TCR ground stations. The TCR links defined in the present document have also to coexist with the
communication ground terminals also shown on figure 1. Some of the satellites to be controlled may use FM/PM
waveforms, and some may use a CDMA waveform, as defined later in the present document.
The scenario may also include, for some of the satellites, hosted payloads, which can be controlled independently of the
satellite platform and of the main payload.
The present document defines the modulation and coding on the TCR and HPM links. Modulation formats are specified
in clause 4 and coding in clause 7.
ETSI
7 Draft ETSI EN 301 926 V1.3.0 (2017-06)
COMMS SIGNAL COMMS SIGNAL
Satellite 1
COMMS STATIONS COMMS STATIO
Satellite 2
1 TC and RG
1 TM and RG
TCR STATIONS
TCR STATIONS
n TC and RG n TM and RG
1 HP TC 1 HP TM
HP STATIONS HP STATIONS
Satellite N
m HP TC m HP TM
INTERFERER/JAMMER
SPACE SEGMENT
LEOP/On Station/Emergency
GROUND SEGMENT GROUND SEGMENT
Collocation
Figure 1: Communications satellites scenario
2 References
2.1 Normative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
Referenced documents which are not found to be publicly available in the expected location might be found at
https://docbox.etsi.org/Reference/.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
The following referenced documents are necessary for the application of the present document.
[1] CCSDS 231.0-B-x: "TC Synchronization and Channel Coding".
[2] CCSDS 131.0-B-x: "TM Synchronization and Channel Coding".
NOTE: CCSDS standards always include the issue number on their numbering system; the parameter 'x' on
references [1] and [2] is understood as the highest published number and therefore latest issue of the
standard.
ETSI
8 Draft ETSI EN 301 926 V1.3.0 (2017-06)
2.2 Informative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
The following referenced documents are not necessary for the application of the present document but they assist the
user with regard to a particular subject area.
[i.1] ETSI TR 101 956: "Satellite Earth Stations and Systems (SES); Technical analysis of Spread
Spectrum Solutions for Telemetry Command and Ranging (TCR) of Geostationary
Communications Satellites".
[i.2] ETSI EN 301 926 (V1.2.1) (06-2002): "Satellite Earth Stations and Systems (SES); Radio
Frequency and Modulation Standard for Telemetry, Command and Ranging (TCR) of
Geostationary Communications Satellites".
3 Definitions and abbreviations
3.1 Definitions
For the purposes of the present document, the following terms and definitions apply:
binary channel: binary communications channel (BPSK has 1 channel, QPSK has 2 channels)
channel symbol rate: rate of binary elements, considered on a single wire, after FEC coding and channel allocation
NOTE: See figures 3, 4 and 5. This applies only to multi-channel modulations, thus to spread spectrum QPSK
modes and not to PM/FM modes.
Co-located Equivalent Capacity (CEC): number of collocated satellites that can be controlled with a perfect power
balanced link between the ground and the satellite
Code Division Multiple Access (CDMA): technique for spread-spectrum multiple-access digital communications that
creates channels through the use of unique code sequences
Command Link Transmission Unit (CLTU): telecommand protocol data structure providing synchronization for the
codeblock and delimiting the beginning of user data
NOTE: See [1], section 4 for further details.
data rate: total number of uncoded data bits per second after packet and frame encoding
NOTE: See figures 2, 3, 4 and 5. This is the Data Rate used in Link Budgets in ETSI TR 101 956 [i.1].
Direct Sequence Spread Spectrum (DSSS): form of modulation where a combination of data to be transmitted and a
known code sequence (chip sequence) is used to directly modulate a carrier, e.g. by phase shift keying
symbol rate: rate of binary elements, considered on a single wire, after FEC coding
NOTE: See figures 2 to 5.
ETSI
9 Draft ETSI EN 301 926 V1.3.0 (2017-06)
Figure 2: Functional stages of transmit chain for FM/PM modulation (MTC1/MTM1)
Figure 3: Functional stages of transmit chain for spread spectrum modulation MTC2
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10 Draft ETSI EN 301 926 V1.3.0 (2017-06)
Figure 4: Functional stages of transmission chain for spread spectrum modulation MTC3
Figure 5: Functional stages of transmission chain for spread spectrum modulation MTM2/MTM3
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11 Draft ETSI EN 301 926 V1.3.0 (2017-06)
3.2 Abbreviations
For the purposes of the present document, the following abbreviations apply:
ASN Abstract Syntax Notation
BCH Bose-Chaudhuri-Hocquenghem
BPSK Binary Phase Shift Keying
BSS Broadcast Satellite Service
CDMA Code Division Multiple Access
CEC Co-located Equivalent Capacity
CLTU Command Link Transmission Unit
CMM Carrier Modulation Modes
COM Communication channel
CW Continuous Wave
dBc decibels relative to the carrier
dBsd decibels relative to the maximum value of power spectral density
DSSS Direct Sequence Spread Spectrum
EOL End of Life
ESA European Space Agency
FEC Forward Error Correction
FM Frequency Modulation
FSS Fixed Satellite Service
GEO Geosynchronous Earth Orbit
GSO Geostationary Satellite Orbit
HP Hosted Payload
HPA High Power Amplifier
HPIU Hosted Payload Interface Unit
HPM Hosted Payload Management
ITU International Telecommunication Union
LDPC Low Density Parity Check
LEOP Launch and Early Orbit Phase
LSB Least Significant Bit
MAI Multiple Access Interference
MSB Most Significant Bit
MSS Mobile Satellite Service
MTC1 TeleCommand Mode 1
MTC2 TeleCommand Mode 2
MTC3 TeleCommand Mode 3
MTM1 TeleMetry Mode 1
MTM2 TeleMetry Mode 2
MTM3 TeleMetry Mode 3
NA Not Applicable
NGSO Non Geostationary Satellite Orbit
NRZ Non-Return to Zero
NRZ-L Non Return to Zero-Level
NRZ-M Non Return to Zero-Mark
OQPSK Offset Quaternary Phase Shift Keying
PCM Pulse Coded Modulation
PDF Probability Density Function
PLOP Physical Layer Operating Procedures
PM Phase Modulation
PN Pseudo Noise
PSD Power Spectral Density
QPSK Quaternary Phase Shift Keying
RF Radio Frequency
RG Ranging
SOS Space Operation Service
SP-L Split Phase-Level (alias Bi-Φ -Level or Manchester encoded)
sps symbol per second
SRRC Square Root Raised Cosine
SS Spread Spectrum
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12 Draft ETSI EN 301 926 V1.3.0 (2017-06)
TC TeleCommand
TCR Telemetry, Command and Ranging
TM TeleMetry
UQPSK Unbalanced Quaternary Phase Shift Keying
w.r.t with respect to
XML eXtensible Mark-up Language
4 Modulation Requirements
4.1 General
The generic system functional block diagram is shown in figure 6. Modulation modes and configurations are shown in
table 1.
Figure 6: Generic system functional block diagram
Table 1: Modulation modes and potential configurations
All FM/PM mode All spread mode Hybrid mode
Uplink MTC1: PCM/BPSK/FM or MTC2/MTC3: PCM/SRRC- MTC2/MTC3: PCM/SRRC-
PCM/BPSK/PM or UQPSK UQPSK
PCM(SP-L)/PM
Downlink (with ranging MTM1: PCM/BPSK/PM MTM2: PCM/SRRC-OQPSK MTM1: PCM/BPSK/PM
(see note): requires uplink (PN code clock/epoch sync to
present) uplink clock/epoch)
Downlink (without ranging: MTM1: PCM/BPSK/PM MTM3: PCM/SRRC-OQPSK MTM1: PCM/BPSK/PM
can operate without uplink (PN code clock/epoch
present) independent of uplink
clock/epoch)
NOTE: Further definition of ranging signals is given in following clauses.
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13 Draft ETSI EN 301 926 V1.3.0 (2017-06)
In order to retain backward compatibility with existing ground networks and to allow simple operation during LEOP, in
addition to the more recent Spread Spectrum modes, the existing FM/PM modulation modes are kept. It is envisaged
that telecommand and telemetry modulation formats shall be independently configurable, allowing for example the
following configuration possibilities (see also annex A for implementations and ETSI TR 101 956 [i.1]):
• all standard mode (as has existed in previous systems) using tone ranging on FM uplink (MTC1) and PM
(MTM1) downlink;
• all spread mode (Direct Sequence Spread Spectrum: DSSS) using PN spreading code regenerative ranging on
suppressed carrier up-and down-links (MTC2/MTC3 and MTM2);
• hybrid mode using PN spreading code ranging on suppressed carrier DSSS uplink (MTC2), and tone ranging
on PM downlink (MTM1).
On the spread spectrum (DSSS) mode downlink, there are 2 PN code sets defined, for coherent and non-coherent modes
(modes MTM2 and MTM3 respectively). The physical partitioning of the functions may not exactly follow that shown
in the system functional block diagram. The modulation configuration of the various modes is described in the rest of
clause 4. Possible allocation of modes to mission phases is defined in annex A.
On the spread spectrum (DSSS) mode uplink, there are two modes defined: MTC2 and MTC3. MTC2 is the uplink
mode from document ETSI EN 301 926 (V1.2.1) [i.2] in 2002. MTC3 is an add-on mode that could be used in case of
an aggravated multiple access interference (MAI) environment. MTC2 and MTC3 modulation characteristics along
with acquisition and tracking schemes are introduced in clause 4.3.1.
4.2 Frequency and Phase Modulations
4.2.1 Modulating waveforms
The following modulating waveforms are permitted:
• Telemetry (mode MTM1): a sine wave sub carrier, itself BPSK modulated by PCM data.
• Telecommand (mode MTC1): a sine wave subcarrier, itself BPSK modulated by PCM data.
NOTE: Except for SP-L between 8 ksps and 64 ksps (direct modulation).
• Ranging (mode MTC1 + MTM1): an unmodulated sinewave subcarrier or combination of a number of such
subcarriers.
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14 Draft ETSI EN 301 926 V1.3.0 (2017-06)
4.2.2 PCM waveforms and data rates
The PCM waveform formatting is defined in figure 7.
NRZ-L level A signifies symbol "1",
level B signifies symbol "0".
SP-L level A during the first half-symbol followed by level B during the second half-symbol signifies symbol "1",
level B during the first half-symbol followed by level A during the second half-symbol signifies symbol "0".
NOTE: SP‐L is also known in literature as bi ‐phase modulation or Manchester encoding.
NRZ-M level change from A to B or B to A signifies symbol "1",
no change in level signifies symbol "0".
Figure 7: PCM waveforms formatting
PCM data signals shall be limited to the waveforms and symbol rates given in table 2.
Table 2: PCM waveforms and rates
Function Symbol rate PCM waveform Special requirements
(symbols/s or sps)
Telecommand Between 250 sps up to NRZ-L Using subcarrier modulation
(Mode MTC1) 4 000 sps (see note) NRZ-M
Between 8 ksps up to SP-L Using PCM(SP-L)/PM modulation
64 ksps
Telemetry Between 1 ksps up to NRZ-L
(Mode MTM1) 64 ksps (see note) NRZ-M
SP-L
NOTE: Coherency between symbols and sub-carrier is required.
ETSI
15 Draft ETSI EN 301 926 V1.3.0 (2017-06)
4.2.3 Use of subcarriers
The subcarriers and modulating waveforms that shall be used are listed in table 3.
Table 3: Subcarriers used with FM or PM RF carriers
Function Subcarrier (kHz) Modulation waveform Subcarrier waveform
Telecommand 8 or 16 (up to 4 ksps) NRZ-L, NRZ-M Sine (up to 4 ksps)
(Mode MTC1)
Telemetry 2 to 300 (up to 64 ksps) NRZ-L Sine (up to 64 ksps)
(Mode MTM1) NRZ-M
SP-L
Ranging 2 to 500 None (CW Tone) Sine
(Mode MTM1 + MTC1)
4.2.4 Choice of Subcarrier Frequencies
For telecommand transmission using a subcarrier, only two subcarrier frequencies are permitted.
The subcarrier frequency shall be 8 kHz for all telecommand rates up to 2 000 sps. A 16 kHz subcarrier shall be used
only in cases where the 4 000 sps symbol rate is needed or when required by the operator. No subcarrier shall be used
for symbol rates above 4 000 sps.
The choice of the ranging and telemetry subcarrier frequencies shall take into account the requirements of:
• carrier acquisition by the ground receivers;
• compatibility between ranging and telemetry;
• occupied bandwidth.
Modulation of subcarriers used for telemetry and telecommand shall be BPSK (for ranging the subcarriers are
unmodulated tones).
The following requirements shall be met for TC and TM subcarriers:
• for NRZ-L and NRZ-M signal waveforms, the subcarrier frequency shall be a multiple (integer) of the symbol
rate from 4 to 1 024;
• for SP-L signal waveforms, the subcarrier frequency shall be an even integer multiple of the symbol rate from
4 to 1 024;
• at each transition in the PCM formatted waveform, the subcarrier shall be reversed in phase;
• the transitions in the PCM formatted waveform shall coincide with a subcarrier zero crossing to within ±2,5 %
of a subcarrier period;
• at all times, for more than 25 % of a subcarrier period after a phase reversal, the phase of the modulated
subcarrier shall be within ±5° of that of a perfect BPSK signal;
• for NRZ-L and SP-L waveforms, the beginning of the symbol intervals shall coincide with a positive-going
subcarrier zero crossing for symbols "1" and with a negative-going zero crossing for symbols "0";
• for NRZ-M waveforms, the beginning of the symbol intervals shall coincide with a subcarrier zero crossing.
ETSI
16 Draft ETSI EN 301 926 V1.3.0 (2017-06)
4.2.5 Uplink Carrier Frequency Deviation (Frequency Modulation)
The FM deviation (modulation depth) is stated in table 4.
Table 4: FM uplink frequency deviation
Function Deviation
(kHz)
Telecommand (PCM/BPSK/FM) (Mode MTC1) Up to ±400 kHz
Ranging Earth-to-space (FM) (Mode MTC1) Up to ±400 kHz
(total deviation of all simultaneous major and minor tones)
4.2.6 Uplink PM Modulation Index
Minima and maxima of the modulation index are stated in table 5.
Table 5: PM modulation index
Function Minimum Maximum
(radians peak) (radians peak)
Telecommand (PCM/BPSK/PM) (Mode MTC1) 0,2 1,4
Telecommand (SP-L) (Mode MTC1) 0,2 1,0
Ranging Earth-to-Space (PM) (mode MTC1) 0,2 1,4
4.2.7 Downlink PM Modulation Index
Minima and maxima of the modulation index are stated in table 6.
Table 6: PM modulation index
Function Minimum Maximum
(radians peak) (radians peak)
Telemetry (PCM/BPSK/PM) (Mode MTM1) 0,1 1,5
Ranging Space-to-Earth (PM) (Mode MTM1) 0,01 1,5
NOTE: Effective ranging modulation index considering the power sharing due to re-modulated
uplink noise.
4.2.8 Sense of Modulation
A positive going video signal (modulated TM subcarrier and/or ranging) shall result in an advance of the phase of the
downlink Radio Frequency carrier.
4.2.9 Data Transition Density
a) To ensure recovery of the symbol clock by the ground demodulators, the transition density in the transmitted
PCM waveform shall not be less than 125 in any sequence of 1 000 consecutive symbols.
b) To ensure recovery of the symbol clock by the ground demodulators, the maximum string of either ones or
zeros shall be limited to 64 symbols.
c) When the specifications in a) and b) are not ensured for the channel by other methods, a pseudo ‐randomizer in
conformance with [2], section 9 shall be used.
4.2.10 Modulation Linearity
The phase deviation, as a function of the video voltage applied to the modulator, shall not deviate from the ideal linear
response by more than ±3 % of the instantaneous value for deviations up to 1,5 rad peak.
ETSI
17 Draft ETSI EN 301 926 V1.3.0 (2017-06)
4.2.11 Residual Amplitude Modulation
Residual amplitude modulation of the phase modulated RF signal shall be less than 2 %.
4.2.12 Residual Carrier, Out-of-band Emission and Discrete Spectral Lines
a) The residual power in the modulated carrier shall be greater than ‐15 dBc for space ‐Earth and ‐10 dBc for
Earth‐space links.
b) Discrete lines in the unmodulated transmitted RF signal spectrum, caused by baseband or RF bandwidth
limitations, non‐linearity of the channel, digital implementation of the frequency synthesis, or any other effects
shall be less than ‐45 dBc inside the occupied bandwidth.
c) Modulation shall not result in the introduction of lines with power greater than ‐30 dBc in the occupied
bandwidth.
d) Modulation shall not result in the introduction of discrete spectral lines greater than ‐30 dBc in the frequency
-5
range of ±2,67 × 10 × f around the carrier at frequency f .
c c
e) For the case of filtered SP ‐L modulation, the spectral lines at the even multiples of the symbol rate shall not be
higher than ‐20 dBc.
f) The out ‐of‐band emission due to the modulation shall comply with the following emission mask.
Figure 8: Out-of-Band Emission Mask
The mask is interpreted as follows:
• dBsd is dB attenuation in a 4 kHz bandwidth, relative to the maximum power in any 4 kHz band within the
necessary bandwidth.
• For frequencies offset from the assigned frequency less than the 50 % of the necessary bandwidth (B ), no
n
attenuation is required.
ETSI
18 Draft ETSI EN 301 926 V1.3.0 (2017-06)
• At a frequency offset equal to 50 % of the necessary bandwidth, an attenuation of at least 8 dB is required.
• Frequencies offset more than 50 % of the necessary bandwidth should be attenuated by the following mask:
∙ ||
40 ∙ log +8 ( )
where is the frequency displaced from the center of the emission bandwidth.
4.3 Spread Spectrum Modulation
4.3.1 General
The spread modulation formats shall be:
• Telecommand Uplink: Square Root Raised Cosine filtered Unbalanced QPSK (SRRC-UQPSK).
• Telemetry Downlink: SRRC filtered Offset QPSK (SRRC-OQPSK).
The spread modulation modes shall be as follows:
• Mode MTC2: spread spectrum telecommand uplink.
• Mode MTC3: spread spectrum telecommand uplink (alternative PN code structure).
• Mode MTM2: spread spectrum telemetry downlink, coherent mode (long PN code).
• Mode MTM3: spread spectrum telemetry downlink, non-coherent mode (short PN code).
The Spread Spectrum modulation characteristics shall be as defined in table 7. The modulation modes listed shall be
available for communications between the Spacecraft and the Earth Terminal for a range of data rates. Symbol rates
referred to in the present document include the channel coding overhead whenever channel coding is applied. The
Symbol rate shall be selected depending on requirements, link budget and multiple access capabilities. Modulator
imperfections are defined in annex C.
Table 7: Spread spectrum link modulation modes
Telecommand link, Telecommand link, Coherent telemetry Non-coherent
Mode MTC2 Mode MTC3 link, Mode MTM2 telemetry link,
Mode MTM3
Symbol Rate In the range 0,1 ksps - In the range 0,1 ksps - In the range 0,1 ksps - In the range 0,1 ksps -
300 ksps and < 10 % of 300 ksps and < 10 % of 300 ksps and < 10 % of 300 ksps and < 10 % of
spreading code rate spreading code rate spreading code rate spreading code rate
Baseline values:
n
500 × 2 sps
n= 0 to 9
Channel Symbol rate =Symbol Rate =Symbol Rate =Symbol Rate (Same =Symbol Rate
on I channel (sps) symbols on both (Same symbols on both
channels) channels)
Channel Symbol rate PN code only = I channel symbol rate =I channel symbol rate =I channel symbol rate
on Q channel (sps) (same symbols on both (Same symbols on both (Same symbols on both
channels) channels) channels)
Data format NRZ-L NRZ-L, NRZ-M NRZ-L NRZ-L
NRZ-M NRZ-M NRZ-M
PN code family I Gold code Acquisition: Gold code, Truncated Gold code
channel Tracking: truncated m-sequence
m-sequence or
truncated Gold
sequence
n n n m n
PN Code length I
2 -1 Acquisition 2 -1, (2 -1) × 2 2 -1
channel
n = 9 to 12 n = 9 to 12 n = 9 to 12 n = 9 to 12
Tracking m = 6 to 12
n m
(2 -1) × 2 , n = 9 to 12,
m = 6 to 12
ETSI
19 Draft ETSI EN 301 926 V1.3.0 (2017-06)
Telecommand link, Telecommand link, Coherent telemetry Non-coherent
Mode MTC2 Mode MTC3 link, Mode MTM2 telemetry link,
Mode MTM3
Code I epoch None None Received Q code of None
reference MTC2
PN code family Q Truncated Truncated m-sequence Truncated Gold code
channel m-sequence or truncated Gold m-sequence
or truncated Gold sequence or truncated Gold
sequence sequence
n m n m n m n
PN Code length Q
(2 -1) × 2 (2 -1) × 2 (2 -1) × 2 2 -1
channel
n = 9 to 12 n = 9 to 12 n = 9 to 12 n = 9 to 12
m = 6 to 12 m = 6 to 12 m = 6 to 12
Code Q epoch I code I code x + 1/2 chips 1/2 chip delay w.r.t I of
reference (x > 20 000) Delay w.r.t non-coherent mode
I ch of MTM2 return link
Spreading code rate In the range In the range Identical to In the range
(Mc/s) 0,5 to 10 Mcps 0,5 to 10 Mcps Received code 0,5 to 10 Mcps
Baseline values:
1,023 Mcps and
3,069 Mcps
Modulation SRRC-UQPSK Acquisition: SRRC- SRRC-OQPSK SRRC-OQPSK
UQPSK
Tracking: SRRC-QPSK
I/Q power ratio Between 10:1 and 1:1 Acquisition: between 1:1 1:1
10:1 and 1:1
Tracking: 1:1
Ranging service Yes Yes Yes No
possible
NOTE 1: Data formats NRZ-L and NRZ-M are defined in clause 4.2.2, figure 7.
NOTE 2: The term 'Gold code' is used to indicate codes with controlled and limited cross-correlation. Strictly speaking for
'n' or 'm' being a multiple of 4 one cannot define Gold codes (3-value cross-correlation). However, one can
identify and define 'good' codes (5-value cross-correlation codes).
The Telecommand uplink signal in mode MTC2 shall be a spread spectrum SRRC-UQPSK modulated signal with:
• during acquisition, a short PN code on the I Channel and a long PN code on the Q channel, no data are
transmited during this phase;
• once locked, during tracking phase the data are added and carried by I Channel.
The Telecommand uplink signal in mode MTC3 shall be a spread spectrum SRRC-QPSK modulated signal with:
• during acquisition, a short PN code on the I Channel and a long PN code on the Q channel without data and
with I/Q power ratio up to 10 (UQPSK);
• during tracking phase, a long PN code is applied on I channel, synchonized with Q channel one and with I/Q
power ratio equal to 1 (QPSK). No change on Q channel.
Tracking phase begins with a two-section acquisition sequence. The first is a constant data (unmodulated) section which
provides for detection of the I code change. The second section is modulated with alternating data which provides for
symbol clock acquisition.
See detailed schematic on figure 9.
ETSI
20 Draft ETSI EN 301 926 V1.3.0 (2017-06)
Figure 9: MTC3 mode scheme
The coherent mode telemetry downlink signal in mode MTM2 shall be a spread spectrum SRRC-OQPSK modulated
signal with data on the Q channel and on the I channel. MTM2 supports ranging by transmission of a long PN code on
the downlink I channel synchronized to the code received on the mode MTC2/MTC3 uplink Q channel. A delayed
version of this code is transmitted on the downlink Q channel.
Mode MTM3 s
...
EUROPEAN STANDARD
Satellite Earth Stations and Systems (SES);
Radio Frequency and Modulation Standard
for Telemetry, Command and Ranging (TCR)
of Communications Satellites
2 ETSI EN 301 926 V1.3.1 (2017-10)
Reference
REN/SES-00401
Keywords
coding, modulation, satellite, telemetry
ETSI
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ETSI
3 ETSI EN 301 926 V1.3.1 (2017-10)
Contents
Intellectual Property Rights . 5
Foreword . 5
Modal verbs terminology . 5
1 Scope . 6
2 References . 7
2.1 Normative references . 7
2.2 Informative references . 8
3 Definitions and abbreviations . 8
3.1 Definitions . 8
3.2 Abbreviations . 11
4 Modulation Requirements . 12
4.1 General . 12
4.2 Frequency and Phase Modulations . 13
4.2.1 Modulating waveforms . 13
4.2.2 PCM waveforms and data rates . 14
4.2.3 Use of subcarriers . 15
4.2.4 Choice of Subcarrier Frequencies . 15
4.2.5 Uplink Carrier Frequency Deviation (Frequency Modulation) . 16
4.2.6 Uplink PM Modulation Index . 16
4.2.7 Downlink PM Modulation Index . 16
4.2.8 Sense of Modulation . 16
4.2.9 Data Transition Density . 16
4.2.10 Modulation Linearity . 16
4.2.11 Residual Amplitude Modulation . 17
4.2.12 Residual Carrier, Out-of-band Emission and Discrete Spectral Lines . 17
4.3 Spread Spectrum Modulation . 18
4.3.1 General . 18
4.3.2 Chip Shaping . 20
4.3.3 Out-of-Band Emission and Discrete Spectral Lines . 20
4.4 Coherency Properties . 20
5 Requirements on Transmitted Signals . 21
5.1 Frequency Stability. 21
5.1.1 Uplink . 21
5.1.2 Downlink . 21
5.2 Turnaround Frequency Ratio . 21
5.3 Polarization. 21
5.4 Phase Noise . 21
5.4.1 Ground Transmitter. 21
5.4.2 On-board Transmitter . 22
6 Link Acquisition Requirements . 22
6.1 Link Acquisition Performance . 22
6.2 Phyical Layer Operations Procedures . 22
7 Coding and Interleaving . 23
7.1 Uplink . 23
7.2 Downlink . 23
Annex A (informative): Operational Configuration . 24
A.1 Introduction . 24
A.2 Configuration Baseline: on board spread spectrum transponder . 25
A.3 Configuration Alternative 1: on board dual mode receiver and on board dual mode transmitter . 26
A.4 Configuration Alternative 2: on board dual mode receiver and phase modulation transmitter . 27
ETSI
4 ETSI EN 301 926 V1.3.1 (2017-10)
A.5 Configuration Alternative 3: on board dual mode receiver, phase modulation transmitter and
dedicated RG SS transmitter . 29
A.6 Configuration Alternative 4: on board dual mode multi-channel receiver and on board dual mode
transmitter (for hosted payload management) . 30
Annex B (informative): Hybrid Ranging process description . 32
B.1 Introduction . 32
B.2 Presentation . 32
B.3 Distance ambiguity resolution . 33
Annex C (informative): Modulator imperfections . 34
C.1 Phase imbalance . 34
C.2 BPSK phase imbalance . 34
C.3 QPSK phase imbalance . 34
C.4 Amplitude imbalance . 34
C.5 Data asymmetry . 35
C.6 Data bit jitter . 35
C.7 PN code asymmetry. 35
C.8 PN code chip jitter . 35
C.9 Chip transition time . 35
C.10 I/Q data bit skew . 36
C.11 I/Q PN code chip skew . 36
Annex D (informative): SRRC chip filtering . 37
Annex E (normative): PN code assignment, generation and set specification . 39
E.1 PN codes . 39
E.2 PN code assignment . 39
E.3 PN code generation . 39
E.3.1 PN code generator types . 39
E.3.1a Telecommand uplink or in-phase channel (Mode MTC2, MTC3 Acquisition) . 42
E.3.2 Ranging uplink or quadrature channel (Mode MTC2) . 42
E.3.3 Telecommand and ranging uplink (Mode MTC3 Tracking) . 43
E.4 Telemetry Downlink. 43
E.4.1 Coherent ranging mode (Mode MTM2) . 43
E.4.2 Non coherent mode (Mode MTM3) . 43
E.5 Baseline PN code set specification . 43
E.6 Extended PN code library. 45
E.7 Code Examples . 46
E.8 PN CODE REQUEST FORM . 49
E.8.1 Form . 49
E.8.2 Description and Instructions . 49
Annex F (informative): Performance computations . 51
Annex G (informative): Bandwidth considerations and assumptions . 52
History . 53
ETSI
5 ETSI EN 301 926 V1.3.1 (2017-10)
Intellectual Property Rights
Essential patents
IPRs essential or potentially essential to the present document may have been declared to ETSI. The information
pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be found
in ETSI SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to ETSI in
respect of ETSI standards", which is available from the ETSI Secretariat. Latest updates are available on the ETSI Web
server (https://ipr.etsi.org/).
Pursuant to the ETSI IPR Policy, no investigation, including IPR searches, has been carried out by ETSI. No guarantee
can be given as to the existence of other IPRs not referenced in ETSI SR 000 314 (or the updates on the ETSI Web
server) which are, or may be, or may become, essential to the present document.
Trademarks
The present document may include trademarks and/or tradenames which are asserted and/or registered by their owners.
ETSI claims no ownership of these except for any which are indicated as being the property of ETSI, and conveys no
right to use or reproduce any trademark and/or tradename. Mention of those trademarks in the present document does
not constitute an endorsement by ETSI of products, services or organizations associated with those trademarks.
Foreword
This European Standard (EN) has been produced by ETSI Technical Committee Satellite Earth Stations and Systems
(SES).
National transposition dates
Date of adoption of this EN: 20 September 2017
Date of latest announcement of this EN (doa): 31 December 2017
Date of latest publication of new National Standard
or endorsement of this EN (dop/e): 30 June 2018
Date of withdrawal of any conflicting National Standard (dow): 30 June 2018
Modal verbs terminology
In the present document "shall", "shall not", "should", "should not", "may", "need not", "will", "will not", "can" and
"cannot" are to be interpreted as described in clause 3.2 of the ETSI Drafting Rules (Verbal forms for the expression of
provisions).
"must" and "must not" are NOT allowed in ETSI deliverables except when used in direct citation.
ETSI
6 ETSI EN 301 926 V1.3.1 (2017-10)
1 Scope
The present document applies to the Telemetry, Command and Ranging (TCR) system of Communication Satellites
(geosynchronous or not), operating in the following frequency bands:
• 5 725 MHz to 7 025 MHz uplink, 3 400 MHz to 4 200 MHz and 4 500 MHz to 4 800 MHz downlink
("C-band");
• 12 750 MHz to 13 250 MHz, 13 750 MHz to 14 800 MHz and 17 300 MHz to 18 400 MHz uplink,
10 700 MHz to 12 750 MHz and 13 400 MHz to 13 650 MHz downlink ("Ku-band");
• 27 500 MHz to 30 000 MHz uplink, 17 700 MHz to 20 200 MHz downlink ("Commercial Ka-band").
Although not explicitly addressed in the present document, possible usage in other bands allocated to
FSS/MSS/BSS/SOS between 1 GHz to 51,4 GHz may be envisaged.
The TCR receiver and transmitter can have a frequency flexibility capability over a given RF band, Typical frequency
step is 100 kHz.
The present document sets out the minimum performance requirements and technical characteristics of the
ground/satellite Radio Frequency (RF) interface based on Frequency Modulation (FM), Phase Modulation (PM) and
Code Division Multiple Access (CDMA).
With the growing number of satellites, the co-location constraints and the maximization of bandwidth for
Communications Missions, real and potential interference cases have motivated the elaboration of the present document
for geostationary satellites based on CDMA techniques.
The present document addresses the following applications:
• Telemetry.
• Command (Telecommand).
• Ranging.
• Hosted Payload Management.
The aim of the present document is to replace and enhance the prior document ETSI EN 301 926 [i.2] (V1.2.1). The
present document's provisions also apply for use cases of autonomous control of hosted payloads. It is recognized that
hosted payloads may require only a subset of the functionality.
The present document applies to the typical TCR scenario shown on figure 1. The scenario includes multiple satellites,
which may be located in the same orbital location (GSO), or that can be in common view of a given TCR station during
NGSO phases (such as transfer phase to GEO, or during NGSO operations). These satellites may be controlled by m
different TCR ground stations. The TCR links defined in the present document have also to coexist with the
communication ground terminals also shown on figure 1. Some of the satellites to be controlled may use FM/PM
waveforms, and some may use a CDMA waveform, as defined later in the present document.
The scenario may also include, for some of the satellites, hosted payloads, which can be controlled independently of the
satellite platform and of the main payload.
The present document defines the modulation and coding on the TCR and HPM links. Modulation formats are specified
in clause 4 and coding in clause 7.
ETSI
7 ETSI EN 301 926 V1.3.1 (2017-10)
Figure 1: Communications satellites scenario
2 References
2.1 Normative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
Referenced documents which are not found to be publicly available in the expected location might be found at
https://docbox.etsi.org/Reference/.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
The following referenced documents are necessary for the application of the present document.
[1] CCSDS 231.0-B-x: "TC Synchronization and Channel Coding".
[2] CCSDS 131.0-B-x: "TM Synchronization and Channel Coding".
NOTE: CCSDS standards always include the issue number on their numbering system; the parameter 'x' on
references [1] and [2] is understood as the highest published number and therefore latest issue of the
standard.
ETSI
8 ETSI EN 301 926 V1.3.1 (2017-10)
2.2 Informative references
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee
their long term validity.
The following referenced documents are not necessary for the application of the present document but they assist the
user with regard to a particular subject area.
[i.1] ETSI TR 101 956: "Satellite Earth Stations and Systems (SES); Technical analysis of Spread
Spectrum Solutions for Telemetry Command and Ranging (TCR) of Geostationary
Communications Satellites".
[i.2] ETSI EN 301 926 (V1.2.1) (06-2002): "Satellite Earth Stations and Systems (SES); Radio
Frequency and Modulation Standard for Telemetry, Command and Ranging (TCR) of
Geostationary Communications Satellites".
3 Definitions and abbreviations
3.1 Definitions
For the purposes of the present document, the following terms and definitions apply:
binary channel: binary communications channel (BPSK has 1 channel, QPSK has 2 channels)
channel symbol rate: rate of binary elements, considered on a single wire, after FEC coding and channel allocation
NOTE: See figures 3, 4 and 5. This applies only to multi-channel modulations, thus to spread spectrum QPSK
modes and not to PM/FM modes.
Co-located Equivalent Capacity (CEC): number of collocated satellites that can be controlled with a perfect power
balanced link between the ground and the satellite
Code Division Multiple Access (CDMA): technique for spread-spectrum multiple-access digital communications that
creates channels through the use of unique code sequences
Command Link Transmission Unit (CLTU): telecommand protocol data structure providing synchronization for the
codeblock and delimiting the beginning of user data
NOTE: See [1], section 4 for further details.
data rate: total number of uncoded data bits per second after packet and frame encoding
NOTE: See figures 2, 3, 4 and 5. This is the Data Rate used in Link Budgets in ETSI TR 101 956 [i.1].
Direct Sequence Spread Spectrum (DSSS): form of modulation where a combination of data to be transmitted and a
known code sequence (chip sequence) is used to directly modulate a carrier, e.g. by phase shift keying
symbol rate: rate of binary elements, considered on a single wire, after FEC coding
NOTE: See figures 2 to 5.
ETSI
9 ETSI EN 301 926 V1.3.1 (2017-10)
MTC1 / MTM1
Ranging
Tones
RF
Carrier
PM or FM
Modulation
Symbol Rate
Subcarrier
Data Waveform BPSK
Channel Coding
Source Formating Modulation
Scope of this Document
Channel Coding
Bit Rate
Pseudo- Differential Convolutional
Block Code
Start Sequence
(optional) Randomizer Coder Coder
ASM
BCH, R-S, LDPC
(optional) (optional) (optional)
Figure 2: Functional stages of transmit chain for FM/PM modulation (MTC1/MTM1)
Figure 3: Functional stages of transmit chain for spread spectrum modulation MTC2
ETSI
10 ETSI EN 301 926 V1.3.1 (2017-10)
Figure 4: Functional stages of transmission chain for spread spectrum modulation MTC3
MTM2 / MTM3
Chip Rate
I Ch. PN Code
I Channel
Waveform
BPSK
Formating
Modulation
Symbol Rate
RF
Carrier
Data Channel Coding
Channel Symbol Rate
Source (*)
(*) Refer to
MTC1 / MTM1
Q Channel
Waveform
BPSK
Formating
Modulation
Chip Rate Q Ch. PN Code
Scope of this Document
Figure 5: Functional stages of transmission chain for spread spectrum modulation MTM2/MTM3
ETSI
11 ETSI EN 301 926 V1.3.1 (2017-10)
3.2 Abbreviations
For the purposes of the present document, the following abbreviations apply:
BCH Bose-Chaudhuri-Hocquenghem
BPSK Binary Phase Shift Keying
BSS Broadcast Satellite Service
CDMA Code Division Multiple Access
CEC Co-located Equivalent Capacity
CLTU Command Link Transmission Unit
CMM Carrier Modulation Modes
COM Communication channel
CW Continuous Wave
dBc decibels relative to the carrier
dBsd decibels relative to the maximum value of power spectral density
DSSS Direct Sequence Spread Spectrum
EOL End of Life
ESA European Space Agency
FEC Forward Error Correction
FM Frequency Modulation
FSS Fixed Satellite Service
GEO Geosynchronous Earth Orbit
GSO Geostationary Satellite Orbit
HP Hosted Payload
HPA High Power Amplifier
HPIU Hosted Payload Interface Unit
HPM Hosted Payload Management
ITU International Telecommunication Union
LDPC Low Density Parity Check
LEOP Launch and Early Orbit Phase
LSB Least Significant Bit
MAI Multiple Access Interference
MSB Most Significant Bit
MSS Mobile Satellite Service
MTC1 TeleCommand Mode 1
MTC2 TeleCommand Mode 2
MTC3 TeleCommand Mode 3
MTM1 TeleMetry Mode 1
MTM2 TeleMetry Mode 2
MTM3 TeleMetry Mode 3
NA Not Applicable
NGSO Non Geostationary Satellite Orbit
NRZ Non-Return to Zero
NRZ-L Non Return to Zero-Level
NRZ-M Non Return to Zero-Mark
OQPSK Offset Quaternary Phase Shift Keying
PCM Pulse Coded Modulation
PDF Probability Density Function
PLOP Physical Layer Operating Procedures
PM Phase Modulation
PN Pseudo Noise
PSD Power Spectral Density
QPSK Quaternary Phase Shift Keying
RF Radio Frequency
RG Ranging
SOS Space Operation Service
SP-L Split Phase-Level (alias Bi-Φ -Level or Manchester encoded)
sps symbol per second
SRRC Square Root Raised Cosine
SS Spread Spectrum
TC TeleCommand
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12 ETSI EN 301 926 V1.3.1 (2017-10)
TCR Telemetry, Command and Ranging
TM TeleMetry
UQPSK Unbalanced Quaternary Phase Shift Keying
w.r.t with respect to
4 Modulation Requirements
4.1 General
The generic system functional block diagram is shown in figure 6. Modulation modes and configurations are shown in
table 1.
Figure 6: Generic system functional block diagram
Table 1: Modulation modes and potential configurations
All FM/PM mode All spread mode Hybrid mode
Uplink MTC1: PCM/BPSK/FM or MTC2/MTC3: PCM/SRRC- MTC2/MTC3: PCM/SRRC-
PCM/BPSK/PM or UQPSK UQPSK
PCM(SP-L)/PM
Downlink (with ranging MTM1: PCM/BPSK/PM MTM2: PCM/SRRC-OQPSK MTM1: PCM/BPSK/PM
(see note): requires uplink (PN code clock/epoch sync to
present) uplink clock/epoch)
Downlink (without ranging: MTM1: PCM/BPSK/PM MTM3: PCM/SRRC-OQPSK MTM1: PCM/BPSK/PM
can operate without uplink (PN code clock/epoch
present) independent of uplink
clock/epoch)
NOTE: Further definition of ranging signals is given in following clauses.
In order to retain backward compatibility with existing ground networks and to allow simple operation during LEOP, in
addition to the more recent Spread Spectrum modes, the existing FM/PM modulation modes are kept. It is envisaged
that telecommand and telemetry modulation formats shall be independently configurable, allowing for example the
following configuration possibilities (see also annex A for implementations and ETSI TR 101 956 [i.1]):
• all standard mode (as has existed in previous systems) using tone ranging on FM uplink (MTC1) and PM
(MTM1) downlink;
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13 ETSI EN 301 926 V1.3.1 (2017-10)
• all spread mode (Direct Sequence Spread Spectrum: DSSS) using PN spreading code regenerative ranging on
suppressed carrier up-and down-links (MTC2/MTC3 and MTM2);
• hybrid mode using PN spreading code ranging on suppressed carrier DSSS uplink (MTC2), and tone ranging
on PM downlink (MTM1).
On the spread spectrum (DSSS) mode downlink, there are 2 PN code sets defined, for coherent and non-coherent modes
(modes MTM2 and MTM3 respectively). The physical partitioning of the functions may not exactly follow that shown
in the system functional block diagram. The modulation configuration of the various modes is described in the rest of
clause 4. Possible allocation of modes to mission phases is defined in annex A.
On the spread spectrum (DSSS) mode uplink, there are two modes defined: MTC2 and MTC3. MTC2 is the uplink
mode from document ETSI EN 301 926 (V1.2.1) [i.2] in 2002. MTC3 is an add-on mode that could be used in case of
an aggravated multiple access interference (MAI) environment. MTC2 and MTC3 modulation characteristics along
with acquisition and tracking schemes are introduced in clause 4.3.1.
4.2 Frequency and Phase Modulations
4.2.1 Modulating waveforms
The following modulating waveforms are permitted:
• Telemetry (mode MTM1): a sine wave sub carrier, itself BPSK modulated by PCM data.
• Telecommand (mode MTC1): a sine wave subcarrier, itself BPSK modulated by PCM data.
NOTE: Except for SP-L between 8 ksps and 64 ksps (direct modulation).
• Ranging (mode MTC1 + MTM1): an unmodulated sinewave subcarrier or combination of a number of such
subcarriers.
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14 ETSI EN 301 926 V1.3.1 (2017-10)
4.2.2 PCM waveforms and data rates
The PCM waveform formatting is defined in figure 7.
NRZ-L level A signifies symbol "1",
level B signifies symbol "0".
SP-L level A during the first half-symbol followed by level B during the second half-symbol signifies symbol "1",
level B during the first half-symbol followed by level A during the second half-symbol signifies symbol "0".
NOTE: SP‐L is also known in literature as bi ‐phase modulation or Manchester encoding.
NRZ-M level change from A to B or B to A signifies symbol "1",
no change in level signifies symbol "0".
Figure 7: PCM waveforms formatting
PCM data signals shall be limited to the waveforms and symbol rates given in table 2.
Table 2: PCM waveforms and rates
Function Symbol rate PCM waveform Special requirements
(symbols/s or sps)
Telecommand Between 250 sps up to NRZ-L Using subcarrier modulation
(Mode MTC1) 4 000 sps (see note) NRZ-M
Between 8 ksps up to SP-L Using PCM(SP-L)/PM modulation
64 ksps
Telemetry Between 1 ksps up to NRZ-L
(Mode MTM1) 64 ksps (see note) NRZ-M
SP-L
NOTE: Coherency between symbols and sub-carrier is required.
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15 ETSI EN 301 926 V1.3.1 (2017-10)
4.2.3 Use of subcarriers
The subcarriers and modulating waveforms that shall be used are listed in table 3.
Table 3: Subcarriers used with FM or PM RF carriers
Function Subcarrier (kHz) Modulation waveform Subcarrier waveform
Telecommand 8 or 16 (up to 4 ksps) NRZ-L, NRZ-M Sine (up to 4 ksps)
(Mode MTC1)
Telemetry 2 to 300 (up to 64 ksps) NRZ-L Sine (up to 64 ksps)
(Mode MTM1) NRZ-M
SP-L
Ranging 2 to 500 None (CW Tone) Sine
(Mode MTM1 + MTC1)
4.2.4 Choice of Subcarrier Frequencies
For telecommand transmission using a subcarrier, only two subcarrier frequencies are permitted.
The subcarrier frequency shall be 8 kHz for all telecommand rates up to 2 000 sps. A 16 kHz subcarrier shall be used
only in cases where the 4 000 sps symbol rate is needed or when required by the operator. No subcarrier shall be used
for symbol rates above 4 000 sps.
The choice of the ranging and telemetry subcarrier frequencies shall take into account the requirements of:
• carrier acquisition by the ground receivers;
• compatibility between ranging and telemetry;
• occupied bandwidth.
Modulation of subcarriers used for telemetry and telecommand shall be BPSK (for ranging the subcarriers are
unmodulated tones).
The following requirements shall be met for TC and TM subcarriers:
• for NRZ-L and NRZ-M signal waveforms, the subcarrier frequency shall be a multiple (integer) of the symbol
rate from 4 to 1 024;
• for SP-L signal waveforms, the subcarrier frequency shall be an even integer multiple of the symbol rate from
4 to 1 024;
• at each transition in the PCM formatted waveform, the subcarrier shall be reversed in phase;
• the transitions in the PCM formatted waveform shall coincide with a subcarrier zero crossing to within ±2,5 %
of a subcarrier period;
• at all times, for more than 25 % of a subcarrier period after a phase reversal, the phase of the modulated
subcarrier shall be within ±5° of that of a perfect BPSK signal;
• for NRZ-L and SP-L waveforms, the beginning of the symbol intervals shall coincide with a positive-going
subcarrier zero crossing for symbols "1" and with a negative-going zero crossing for symbols "0";
• for NRZ-M waveforms, the beginning of the symbol intervals shall coincide with a subcarrier zero crossing.
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16 ETSI EN 301 926 V1.3.1 (2017-10)
4.2.5 Uplink Carrier Frequency Deviation (Frequency Modulation)
The FM deviation (modulation depth) is stated in table 4.
Table 4: FM uplink frequency deviation
Function Deviation
(kHz)
Telecommand (PCM/BPSK/FM) (Mode MTC1) Up to ±400 kHz
Ranging Earth-to-space (FM) (Mode MTC1) Up to ±400 kHz
(total deviation of all simultaneous major and minor tones)
4.2.6 Uplink PM Modulation Index
Minima and maxima of the modulation index are stated in table 5.
Table 5: PM modulation index
Function Minimum Maximum
(radians peak) (radians peak)
Telecommand (PCM/BPSK/PM) (Mode MTC1) 0,2 1,4
Telecommand (SP-L) (Mode MTC1) 0,2 1,0
Ranging Earth-to-Space (PM) (mode MTC1) 0,2 1,4
4.2.7 Downlink PM Modulation Index
Minima and maxima of the modulation index are stated in table 6.
Table 6: PM modulation index
Function Minimum Maximum
(radians peak) (radians peak)
Telemetry (PCM/BPSK/PM) (Mode MTM1) 0,1 1,5
Ranging Space-to-Earth (PM) (Mode MTM1) 0,01 1,5
NOTE: Effective ranging modulation index considering the power sharing due to re-modulated
uplink noise.
4.2.8 Sense of Modulation
A positive going video signal (modulated TM subcarrier and/or ranging) shall result in an advance of the phase of the
downlink Radio Frequency carrier.
4.2.9 Data Transition Density
a) To ensure recovery of the symbol clock by the ground demodulators, the transition density in the transmitted
PCM waveform shall not be less than 125 in any sequence of 1 000 consecutive symbols.
b) To ensure recovery of the symbol clock by the ground demodulators, the maximum string of either ones or
zeros shall be limited to 64 symbols.
c) When the specifications in a) and b) are not ensured for the channel by other methods, a pseudo ‐randomizer in
conformance with [2], section 9 shall be used.
4.2.10 Modulation Linearity
The phase deviation, as a function of the video voltage applied to the modulator, shall not deviate from the ideal linear
response by more than ±3 % of the instantaneous value for deviations up to 1,5 rad peak.
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17 ETSI EN 301 926 V1.3.1 (2017-10)
4.2.11 Residual Amplitude Modulation
Residual amplitude modulation of the phase modulated RF signal shall be less than 2 %.
4.2.12 Residual Carrier, Out-of-band Emission and Discrete Spectral Lines
a) The residual power in the modulated carrier shall be greater than ‐15 dBc for space ‐Earth and ‐10 dBc for
Earth‐space links.
b) Discrete lines in the unmodulated transmitted RF signal spectrum, caused by baseband or RF bandwidth
limitations, non‐linearity of the channel, digital implementation of the frequency synthesis, or any other effects
shall be less than ‐45 dBc inside the occupied bandwidth.
c) Modulation shall not result in the introduction of lines with power greater than ‐30 dBc in the occupied
bandwidth.
d) Modulation shall not result in the introduction of discrete spectral lines greater than ‐30 dBc in the frequency
-5
range of ±2,67 × 10 × f around the carrier at frequency f .
c c
e) For the case of filtered SP ‐L modulation, the spectral lines at the even multiples of the symbol rate shall not be
higher than ‐20 dBc.
f) The out ‐of‐band emission due to the modulation shall comply with the following emission mask.
Figure 8: Out-of-Band Emission Mask
The mask is interpreted as follows:
• dBsd is dB attenuation in a 4 kHz bandwidth, relative to the maximum power in any 4 kHz band within the
necessary bandwidth.
• For frequencies offset from the assigned frequency less than the 50 % of the necessary bandwidth (B ), no
n
attenuation is required.
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18 ETSI EN 301 926 V1.3.1 (2017-10)
• At a frequency offset equal to 50 % of the necessary bandwidth, an attenuation of at least 8 dB is required.
• Frequencies offset more than 50 % of the necessary bandwidth should be attenuated by the following mask:
| |∙
40 ∙ log +8 ( )
where is the frequency displaced from the center of the emission bandwidth.
4.3 Spread Spectrum Modulation
4.3.1 General
The spread modulation formats shall be:
• Telecommand Uplink: Square Root Raised Cosine filtered Unbalanced QPSK (SRRC-UQPSK).
• Telemetry Downlink: SRRC filtered Offset QPSK (SRRC-OQPSK).
The spread modulation modes shall be as follows:
• Mode MTC2: spread spectrum telecommand uplink.
• Mode MTC3: spread spectrum telecommand uplink (alternative PN code structure).
• Mode MTM2: spread spectrum telemetry downlink, coherent mode (long PN code).
• Mode MTM3: spread spectrum telemetry downlink, non-coherent mode (short PN code).
The Spread Spectrum modulation characteristics shall be as defined in table 7. The modulation modes listed shall be
available for communications between the Spacecraft and the Earth Terminal for a range of data rates. Symbol rates
referred to in the present document include the channel coding overhead whenever channel coding is applied. The
Symbol rate shall be selected depending on requirements, link budget and multiple access capabilities. Modulator
imperfections are defined in annex C.
Table 7: Spread spectrum link modulation modes
Telecommand link, Telecommand link, Coherent telemetry Non-coherent
Mode MTC2 Mode MTC3 link, Mode MTM2 telemetry link,
Mode MTM3
Symbol Rate In the range 0,1 ksps - In the range 0,1 ksps - In the range 0,1 ksps - In the range 0,1 ksps -
300 ksps and < 10 % of 300 ksps and < 10 % of 300 ksps and < 10 % of 300 ksps and < 10 % of
spreading code rate spreading code rate spreading code rate spreading code rate
Baseline values:
n
500 × 2 sps
n= 0 to 9
Channel Symbol rate =Symbol Rate =Symbol Rate =Symbol Rate (Same =Symbol Rate
on I channel (sps) symbols on both (Same symbols on both
channels) channels)
Channel Symbol rate PN code only = I channel symbol rate =I channel symbol rate =I channel symbol rate
on Q channel (sps) (same symbols on both (Same symbols on both (Same symbols on both
channels) channels) channels)
Data format NRZ-L NRZ-L, NRZ-M NRZ-L NRZ-L
NRZ-M NRZ-M NRZ-M
PN code family I Gold code Acquisition: Gold code, Truncated Gold code
channel Tracking: truncated m-sequence
m-sequence or
truncated Gold
sequence
n n n m n
PN Code length I
2 -1 Acquisition 2 -1, (2 -1) × 2 2 -1
channel
n = 9 to 12 n = 9 to 12 n = 9 to 12 n = 9 to 12
Tracking m = 6 to 12
n m
(2 -1) × 2 , n = 9 to 12,
m = 6 to 12
ETSI
19 ETSI EN 301 926 V1.3.1 (2017-10)
Telecommand link, Telecommand link, Coherent telemetry Non-coherent
Mode MTC2 Mode MTC3 link, Mode MTM2 telemetry link,
Mode MTM3
Code I epoch None None Received Q code of None
reference MTC2
PN code family Q Truncated Truncated m-sequence Truncated Gold code
channel m-sequence or truncated Gold m-sequence
or truncated Gold sequence or truncated Gold
sequence sequence
n m n m n m n
PN Code length Q
(2 -1) × 2 (2 -1) × 2 (2 -1) × 2 2 -1
channel
n = 9 to 12 n = 9 to 12 n = 9 to 12 n = 9 to 12
m = 6 to 12 m = 6 to 12 m = 6 to 12
Code Q epoch I code I code x + 1/2 chips 1/2 chip delay w.r.t I of
reference (x > 20 000) Delay w.r.t non-coherent mode
I ch of MTM2 return link
Spreading code rate In the range In the range Identical to In the range
(Mc/s) 0,5 to 10 Mcps 0,5 to 10 Mcps Received code 0,5 to 10 Mcps
Baseline values:
1,023 Mcps and
3,069 Mcps
Modulation SRRC-UQPSK Acquisition: SRRC- SRRC-OQPSK SRRC-OQPSK
UQPSK
Tracking: SRRC-QPSK
I/Q power ratio Between 10:1 and 1:1 Acquisition: between 1:1 1:1
10:1 and 1:1
Tracking: 1:1
Ranging service Yes Yes Yes No
possible
NOTE 1: Data formats NRZ-L and NRZ-M are defined in clause 4.2.2, figure 7.
NOTE 2: The term 'Gold code' is used to indicate codes with controlled and limited cross-correlation. Strictly speaking for
'n' or 'm' being a multiple of 4 one cannot define Gold codes (3-value cross-correlation). However, one can
identify and define 'good' codes (5-value cross-correlation codes).
The Telecommand uplink signal in mode MTC2 shall be a spread spectrum SRRC-UQPSK modulated signal with:
• during acquisition, a short PN code on the I Channel and a long PN code on the Q channel, no data are
transmited during this phase;
• once locked, during tracking phase the data are added and carried by I Channel.
The Telecommand uplink signal in mode MTC3 shall be a spread spectrum SRRC-QPSK modulated signal with:
• during acquisition, a short PN code on the I Channel and a long PN code on the Q channel without data and
with I/Q power ratio up to 10 (UQPSK);
• during tracking phase, a long PN code is applied on I channel, synchonized with Q channel one and with I/Q
power ratio equal to 1 (QPSK). No change on Q channel.
Tracking phase begins with a two-section acquisition sequence. The first is a constant data (unmodulated) section which
provides for detection of the I code change. The second section is modulated with alternating data which provides for
symbol clock acquisition.
See detailed schematic on figure 9.
ETSI
...
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.RPXQLNDFLMVNLKVDWHOLWRYSatellite Earth Stations and Systems (SES) - Radio Frequency and Modulation Standard for Telemetry, Command and Ranging (TCR) of Communications Satellites33.070.40SatelitSatelliteICS:Ta slovenski standard je istoveten z:ETSI EN 301 926 V1.3.1 (2017-10)SIST EN 301 926 V1.3.1:2017en01-december-2017SIST EN 301 926 V1.3.1:2017SLOVENSKI
STANDARD
EUROPEAN STANDARD SIST EN 301 926 V1.3.1:2017
ETSI ETSI EN 301 926 V1.3.1 (2017-10) 2
Reference REN/SES-00401 Keywords coding, modulation, satellite, telemetry ETSI 650 Route des Lucioles F-06921 Sophia Antipolis Cedex - FRANCE
Tel.: +33 4 92 94 42 00
Fax: +33 4 93 65 47 16
Siret N° 348 623 562 00017 - NAF 742 C Association à but non lucratif enregistrée à la Sous-Préfecture de Grasse (06) N° 7803/88
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ETSI ETSI EN 301 926 V1.3.1 (2017-10) 3 Contents Intellectual Property Rights . 5 Foreword . 5 Modal verbs terminology . 5 1 Scope . 6 2 References . 7 2.1 Normative references . 7 2.2 Informative references . 8 3 Definitions and abbreviations . 8 3.1 Definitions . 8 3.2 Abbreviations . 11 4 Modulation Requirements . 12 4.1 General . 12 4.2 Frequency and Phase Modulations . 13 4.2.1 Modulating waveforms . 13 4.2.2 PCM waveforms and data rates . 14 4.2.3 Use of subcarriers . 15 4.2.4 Choice of Subcarrier Frequencies . 15 4.2.5 Uplink Carrier Frequency Deviation (Frequency Modulation) . 16 4.2.6 Uplink PM Modulation Index . 16 4.2.7 Downlink PM Modulation Index . 16 4.2.8 Sense of Modulation . 16 4.2.9 Data Transition Density . 16 4.2.10 Modulation Linearity . 16 4.2.11 Residual Amplitude Modulation . 17 4.2.12 Residual Carrier, Out-of-band Emission and Discrete Spectral Lines . 17 4.3 Spread Spectrum Modulation . 18 4.3.1 General . 18 4.3.2 Chip Shaping . 20 4.3.3 Out-of-Band Emission and Discrete Spectral Lines . 20 4.4 Coherency Properties . 20 5 Requirements on Transmitted Signals . 21 5.1 Frequency Stability. 21 5.1.1 Uplink . 21 5.1.2 Downlink . 21 5.2 Turnaround Frequency Ratio . 21 5.3 Polarization. 21 5.4 Phase Noise . 21 5.4.1 Ground Transmitter. 21 5.4.2 On-board Transmitter . 22 6 Link Acquisition Requirements . 22 6.1 Link Acquisition Performance . 22 6.2 Phyical Layer Operations Procedures . 22 7 Coding and Interleaving . 23 7.1 Uplink . 23 7.2 Downlink . 23 Annex A (informative): Operational Configuration . 24 A.1 Introduction . 24 A.2 Configuration Baseline: on board spread spectrum transponder . 25 A.3 Configuration Alternative 1: on board dual mode receiver and on board dual mode transmitter . 26 A.4 Configuration Alternative 2: on board dual mode receiver and phase modulation transmitter . 27 SIST EN 301 926 V1.3.1:2017
ETSI ETSI EN 301 926 V1.3.1 (2017-10) 4 A.5 Configuration Alternative 3: on board dual mode receiver, phase modulation transmitter and dedicated RG SS transmitter . 29 A.6 Configuration Alternative 4: on board dual mode multi-channel receiver and on board dual mode transmitter (for hosted payload management) . 30 Annex B (informative): Hybrid Ranging process description . 32 B.1 Introduction . 32 B.2 Presentation . 32 B.3 Distance ambiguity resolution . 33 Annex C (informative): Modulator imperfections . 34 C.1 Phase imbalance . 34 C.2 BPSK phase imbalance . 34 C.3 QPSK phase imbalance . 34 C.4 Amplitude imbalance . 34 C.5 Data asymmetry . 35 C.6 Data bit jitter . 35 C.7 PN code asymmetry. 35 C.8 PN code chip jitter . 35 C.9 Chip transition time . 35 C.10 I/Q data bit skew . 36 C.11 I/Q PN code chip skew . 36 Annex D (informative): SRRC chip filtering . 37 Annex E (normative): PN code assignment, generation and set specification . 39 E.1 PN codes . 39 E.2 PN code assignment . 39 E.3 PN code generation . 39 E.3.1 PN code generator types . 39 E.3.1a Telecommand uplink or in-phase channel (Mode MTC2, MTC3 Acquisition) . 42 E.3.2 Ranging uplink or quadrature channel (Mode MTC2) . 42 E.3.3 Telecommand and ranging uplink (Mode MTC3 Tracking) . 43 E.4 Telemetry Downlink. 43 E.4.1 Coherent ranging mode (Mode MTM2) . 43 E.4.2 Non coherent mode (Mode MTM3) . 43 E.5 Baseline PN code set specification . 43 E.6 Extended PN code library. 45 E.7 Code Examples . 46 E.8 PN CODE REQUEST FORM . 49 E.8.1 Form . 49 E.8.2 Description and Instructions . 49 Annex F (informative): Performance computations . 51 Annex G (informative): Bandwidth considerations and assumptions . 52 History . 53
ETSI ETSI EN 301 926 V1.3.1 (2017-10) 5 Intellectual Property Rights Essential patents
IPRs essential or potentially essential to the present document may have been declared to ETSI. The information pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be found in ETSI SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to ETSI in respect of ETSI standards", which is available from the ETSI Secretariat. Latest updates are available on the ETSI Web server (https://ipr.etsi.org/). Pursuant to the ETSI IPR Policy, no investigation, including IPR searches, has been carried out by ETSI. No guarantee can be given as to the existence of other IPRs not referenced in ETSI SR 000 314 (or the updates on the ETSI Web server) which are, or may be, or may become, essential to the present document. Trademarks The present document may include trademarks and/or tradenames which are asserted and/or registered by their owners. ETSI claims no ownership of these except for any which are indicated as being the property of ETSI, and conveys no right to use or reproduce any trademark and/or tradename. Mention of those trademarks in the present document does not constitute an endorsement by ETSI of products, services or organizations associated with those trademarks. Foreword This European Standard (EN) has been produced by ETSI Technical Committee Satellite Earth Stations and Systems (SES).
National transposition dates Date of adoption of this EN: 20 September 2017 Date of latest announcement of this EN (doa): 31 December 2017 Date of latest publication of new National Standard or endorsement of this EN (dop/e):
30 June 2018 Date of withdrawal of any conflicting National Standard (dow): 30 June 2018
Modal verbs terminology In the present document "shall", "shall not", "should", "should not", "may", "need not", "will", "will not", "can" and "cannot" are to be interpreted as described in clause 3.2 of the ETSI Drafting Rules (Verbal forms for the expression of provisions). "must" and "must not" are NOT allowed in ETSI deliverables except when used in direct citation.
ETSI ETSI EN 301 926 V1.3.1 (2017-10) 6 1 Scope The present document applies to the Telemetry, Command and Ranging (TCR) system of Communication Satellites (geosynchronous or not), operating in the following frequency bands: • 5 725 MHz to 7 025 MHz uplink, 3 400 MHz to 4 200 MHz and 4 500 MHz to 4 800 MHz downlink ("C-band"); • 12 750 MHz to 13 250 MHz, 13 750 MHz to 14 800 MHz and 17 300 MHz to 18 400 MHz uplink, 10 700 MHz to 12 750 MHz and 13 400 MHz to 13 650 MHz downlink ("Ku-band"); • 27 500 MHz to 30 000 MHz uplink, 17 700 MHz to 20 200 MHz downlink ("Commercial Ka-band"). Although not explicitly addressed in the present document, possible usage in other bands allocated to FSS/MSS/BSS/SOS between 1 GHz to 51,4 GHz may be envisaged. The TCR receiver and transmitter can have a frequency flexibility capability over a given RF band, Typical frequency step is 100 kHz. The present document sets out the minimum performance requirements and technical characteristics of the ground/satellite Radio Frequency (RF) interface based on Frequency Modulation (FM), Phase Modulation (PM) and Code Division Multiple Access (CDMA). With the growing number of satellites, the co-location constraints and the maximization of bandwidth for Communications Missions, real and potential interference cases have motivated the elaboration of the present document for geostationary satellites based on CDMA techniques. The present document addresses the following applications: • Telemetry. • Command (Telecommand). • Ranging. • Hosted Payload Management. The aim of the present document is to replace and enhance the prior document ETSI EN 301 926 [i.2] (V1.2.1). The present document's provisions also apply for use cases of autonomous control of hosted payloads. It is recognized that hosted payloads may require only a subset of the functionality. The present document applies to the typical TCR scenario shown on figure 1. The scenario includes multiple satellites, which may be located in the same orbital location (GSO), or that can be in common view of a given TCR station during NGSO phases (such as transfer phase to GEO, or during NGSO operations). These satellites may be controlled by m different TCR ground stations. The TCR links defined in the present document have also to coexist with the communication ground terminals also shown on figure 1. Some of the satellites to be controlled may use FM/PM waveforms, and some may use a CDMA waveform, as defined later in the present document. The scenario may also include, for some of the satellites, hosted payloads, which can be controlled independently of the satellite platform and of the main payload. The present document defines the modulation and coding on the TCR and HPM links. Modulation formats are specified in clause 4 and coding in clause 7. SIST EN 301 926 V1.3.1:2017
ETSI ETSI EN 301 926 V1.3.1 (2017-10) 7
Figure 1: Communications satellites scenario 2 References 2.1 Normative references References are either specific (identified by date of publication and/or edition number or version number) or non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the referenced document (including any amendments) applies. Referenced documents which are not found to be publicly available in the expected location might be found at https://docbox.etsi.org/Reference/. NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee their long term validity. The following referenced documents are necessary for the application of the present document. [1] CCSDS 231.0-B-x: "TC Synchronization and Channel Coding". [2] CCSDS 131.0-B-x: "TM Synchronization and Channel Coding". NOTE: CCSDS standards always include the issue number on their numbering system; the parameter 'x' on references [1] and [2] is
understood as the highest published number and therefore latest issue of the standard. SIST EN 301 926 V1.3.1:2017
ETSI ETSI EN 301 926 V1.3.1 (2017-10) 8 2.2 Informative references References are either specific (identified by date of publication and/or edition number or version number) or non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the referenced document (including any amendments) applies. NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee their long term validity. The following referenced documents are not necessary for the application of the present document but they assist the user with regard to a particular subject area. [i.1] ETSI TR 101 956: "Satellite Earth Stations and Systems (SES); Technical analysis of Spread Spectrum Solutions for Telemetry Command and Ranging (TCR) of Geostationary Communications Satellites". [i.2] ETSI EN 301 926 (V1.2.1) (06-2002): "Satellite Earth Stations and Systems (SES); Radio Frequency and Modulation Standard for Telemetry, Command and Ranging (TCR) of Geostationary Communications Satellites". 3 Definitions and abbreviations 3.1 Definitions For the purposes of the present document, the following terms and definitions apply: binary channel: binary communications channel (BPSK has 1 channel, QPSK has 2 channels) channel symbol rate: rate of binary elements, considered on a single wire, after FEC coding and channel allocation NOTE: See figures 3, 4 and 5. This applies only to multi-channel modulations, thus to spread spectrum QPSK modes and not to PM/FM modes. Co-located Equivalent Capacity (CEC): number of collocated satellites that can be controlled with a perfect power balanced link between the ground and the satellite Code Division Multiple Access (CDMA): technique for spread-spectrum multiple-access digital communications that creates channels through the use of unique code sequences Command Link Transmission Unit (CLTU): telecommand protocol data structure providing synchronization for the codeblock and delimiting the beginning of user data NOTE: See [1], section 4 for further details. data rate: total number of uncoded data bits per second after packet and frame encoding NOTE: See figures 2, 3, 4 and 5. This is the Data Rate used in Link Budgets in ETSI TR 101 956 [i.1]. Direct Sequence Spread Spectrum (DSSS): form of modulation where a combination of data to be transmitted and a known code sequence (chip sequence) is used to directly modulate a carrier, e.g. by phase shift keying symbol rate: rate of binary elements, considered on a single wire, after FEC coding NOTE: See figures 2 to 5. SIST EN 301 926 V1.3.1:2017
ETSI ETSI EN 301 926 V1.3.1 (2017-10) 9 Data SourceChannel CodingWaveformFormatingBPSK ModulationRangingTonesPM or FM ModulationRFCarrierSymbol RateScope of thisDocumentSubcarrierMTC1 / MTM1Block Code (optional)BCH, R-S, LDPCPseudo-Randomizer(optional)Start SequenceASMDifferentialCoder(optional)ConvolutionalCoder(optional)Bit RateChannel Coding Figure 2: Functional stages of transmit chain for FM/PM modulation (MTC1/MTM1)
Figure 3: Functional stages of transmit chain for spread spectrum modulation MTC2 SIST EN 301 926 V1.3.1:2017
ETSI ETSI EN 301 926 V1.3.1 (2017-10) 10
Figure 4: Functional stages of transmission chain for spread spectrum modulation MTC3 Data SourceI Channel BPSK ModulationRFCarrierScope of thisDocumentQ Channel BPSK ModulationI Ch. PN CodeQ Ch. PN CodeChannel Symbol RateChip RateChip RateChannel Coding(*)WaveformFormatingWaveformFormatingSymbol RateMTM2 / MTM3(*) RefertoMTC1 / MTM1 Figure 5: Functional stages of transmission chain for spread spectrum modulation MTM2/MTM3 SIST EN 301 926 V1.3.1:2017
ETSI ETSI EN 301 926 V1.3.1 (2017-10) 11 3.2 Abbreviations For the purposes of the present document, the following abbreviations apply: BCH Bose-Chaudhuri-Hocquenghem BPSK Binary Phase Shift Keying BSS Broadcast Satellite Service CDMA Code Division Multiple Access CEC Co-located Equivalent Capacity CLTU Command Link Transmission Unit CMM Carrier Modulation Modes COM Communication channel CW Continuous Wave dBc decibels relative to the carrier dBsd decibels relative to the maximum value of power spectral density DSSS Direct Sequence Spread Spectrum EOL End of Life ESA European Space Agency FEC Forward Error Correction FM Frequency Modulation FSS Fixed Satellite Service GEO Geosynchronous Earth Orbit GSO Geostationary Satellite Orbit HP Hosted Payload HPA High Power Amplifier HPIU Hosted Payload Interface Unit HPM Hosted Payload Management ITU International Telecommunication Union LDPC Low Density Parity Check LEOP Launch and Early Orbit Phase LSB Least Significant Bit MAI Multiple Access Interference MSB Most Significant Bit MSS Mobile Satellite Service MTC1 TeleCommand Mode 1 MTC2 TeleCommand Mode 2 MTC3 TeleCommand Mode 3 MTM1 TeleMetry Mode 1 MTM2 TeleMetry Mode 2 MTM3 TeleMetry Mode 3 NA Not Applicable NGSO Non Geostationary Satellite Orbit NRZ Non-Return to Zero NRZ-L Non Return to Zero-Level NRZ-M Non Return to Zero-Mark OQPSK Offset Quaternary Phase Shift Keying PCM Pulse Coded Modulation PDF Probability Density Function PLOP Physical Layer Operating Procedures PM Phase Modulation PN Pseudo Noise PSD Power Spectral Density QPSK Quaternary Phase Shift Keying RF Radio Frequency RG Ranging SOS Space Operation Service SP-L Split Phase-Level (alias Bi-Φ -Level or Manchester encoded) sps symbol per second SRRC Square Root Raised Cosine SS Spread Spectrum TC TeleCommand SIST EN 301 926 V1.3.1:2017
ETSI ETSI EN 301 926 V1.3.1 (2017-10) 12 TCR Telemetry, Command and Ranging TM TeleMetry UQPSK Unbalanced Quaternary Phase Shift Keying w.r.t with respect to 4 Modulation Requirements 4.1 General The generic system functional block diagram is shown in figure 6. Modulation modes and configurations are shown in table 1.
Figure 6: Generic system functional block diagram Table 1: Modulation modes and potential configurations
All FM/PM mode All spread mode Hybrid mode Uplink MTC1: PCM/BPSK/FM or PCM/BPSK/PM or PCM(SP-L)/PM MTC2/MTC3: PCM/SRRC-UQPSK MTC2/MTC3: PCM/SRRC-UQPSK Downlink (with ranging (see note): requires uplink present) MTM1: PCM/BPSK/PM MTM2: PCM/SRRC-OQPSK (PN code clock/epoch sync to uplink clock/epoch) MTM1: PCM/BPSK/PM Downlink (without ranging: can operate without uplink present) MTM1: PCM/BPSK/PM MTM3: PCM/SRRC-OQPSK (PN code clock/epoch independent of uplink clock/epoch) MTM1: PCM/BPSK/PM NOTE: Further definition of ranging signals is given in following clauses.
In order to retain backward compatibility with existing ground networks and to allow simple operation during LEOP, in addition to the more recent Spread Spectrum modes, the existing
FM/PM modulation modes are kept. It is envisaged that telecommand and telemetry modulation formats shall be independently configurable, allowing for example the following configuration possibilities (see also annex A for implementations and ETSI TR 101 956 [i.1]): • all standard mode (as has existed in previous systems) using tone ranging on FM uplink (MTC1) and PM (MTM1) downlink; SIST EN 301 926 V1.3.1:2017
ETSI ETSI EN 301 926 V1.3.1 (2017-10) 13 • all spread mode (Direct Sequence Spread Spectrum: DSSS) using PN spreading code regenerative ranging on suppressed carrier up-and down-links (MTC2/MTC3 and MTM2); • hybrid mode using PN spreading code ranging on suppressed carrier DSSS uplink (MTC2), and tone ranging on PM downlink (MTM1). On the spread spectrum (DSSS) mode downlink, there are 2 PN code sets defined, for coherent and non-coherent modes (modes MTM2 and MTM3 respectively). The physical partitioning of the functions may not exactly follow that shown in the system functional block diagram. The modulation configuration of the various modes is described in the rest of clause 4. Possible allocation of modes to mission phases is defined in annex A. On the spread spectrum (DSSS) mode uplink, there are two modes defined: MTC2 and MTC3. MTC2 is the uplink mode from document ETSI EN 301 926 (V1.2.1) [i.2] in 2002. MTC3 is an add-on mode that could be used in case of an aggravated multiple access interference (MAI) environment. MTC2 and MTC3 modulation characteristics along with acquisition and tracking schemes are introduced in clause 4.3.1. 4.2 Frequency and Phase Modulations 4.2.1 Modulating waveforms The following modulating waveforms are permitted: • Telemetry (mode MTM1): a sine wave sub carrier, itself BPSK modulated by PCM data. • Telecommand (mode MTC1): a sine wave subcarrier, itself BPSK modulated by PCM data. NOTE: Except for SP-L between 8 ksps and 64 ksps (direct modulation). • Ranging (mode MTC1 + MTM1): an unmodulated sinewave subcarrier or combination of a number of such subcarriers. SIST EN 301 926 V1.3.1:2017
ETSI ETSI EN 301 926 V1.3.1 (2017-10) 14 4.2.2 PCM waveforms and data rates The PCM waveform formatting is defined in figure 7.
NRZ-L level A signifies symbol "1",
level B signifies symbol "0". SP-L level A during the first half-symbol followed by level B during the second half-symbol signifies symbol "1",
level B during the first half-symbol followed by level A during the second half-symbol signifies symbol "0". NOTE: SP‐L is also known in literature as bi‐phase modulation or Manchester encoding. NRZ-M level change from A to B or B to A signifies symbol "1",
no change in level signifies symbol "0".
Figure 7: PCM waveforms formatting PCM data signals shall be limited to the waveforms and symbol rates given in table 2. Table 2: PCM waveforms and rates Function Symbol rate (symbols/s or sps) PCM waveform Special requirements Telecommand (Mode MTC1) Between 250 sps up to 4 000 sps (see note)
Between 8 ksps up to 64 ksps NRZ-L NRZ-M
SP-L Using subcarrier modulation
Using PCM(SP-L)/PM modulation Telemetry (Mode MTM1) Between 1 ksps up to 64 ksps (see note) NRZ-L NRZ-M SP-L
NOTE: Coherency between symbols and sub-carrier is required.
ETSI ETSI EN 301 926 V1.3.1 (2017-10) 15 4.2.3 Use of subcarriers The subcarriers and modulating waveforms that shall be used are listed in table 3. Table 3: Subcarriers used with FM or PM RF carriers Function Subcarrier (kHz) Modulation waveform Subcarrier waveform Telecommand (Mode MTC1)
8 or 16 (up to 4 ksps) NRZ-L, NRZ-M Sine (up to 4 ksps) Telemetry (Mode MTM1) 2 to 300 (up to 64 ksps) NRZ-L NRZ-M SP-L Sine (up to 64 ksps) Ranging (Mode MTM1 + MTC1) 2 to 500 None (CW Tone) Sine
4.2.4 Choice of Subcarrier Frequencies For telecommand transmission using a subcarrier, only two subcarrier frequencies are permitted. The subcarrier frequency shall be 8 kHz for all telecommand rates up to 2 000 sps. A 16 kHz subcarrier shall be used only in cases where the 4 000 sps symbol rate is needed or when required by the operator. No subcarrier shall be used for symbol rates above 4 000 sps. The choice of the ranging and telemetry subcarrier frequencies shall take into account the requirements of: • carrier acquisition by the ground receivers; • compatibility between ranging and telemetry; • occupied bandwidth. Modulation of subcarriers used for telemetry and telecommand shall be BPSK (for ranging the subcarriers are unmodulated tones). The following requirements shall be met for TC and TM subcarriers: • for NRZ-L and NRZ-M signal waveforms, the subcarrier frequency shall be a multiple (integer) of the symbol rate from 4 to 1 024; • for SP-L signal waveforms, the subcarrier frequency shall be an even integer multiple of the symbol rate from 4 to 1 024; • at each transition in the PCM formatted waveform, the subcarrier shall be reversed in phase; • the transitions in the PCM formatted waveform shall coincide with a subcarrier zero crossing to within ±2,5 % of a subcarrier period; • at all times, for more than 25 % of a subcarrier period after a phase reversal, the phase of the modulated subcarrier shall be within ±5° of that of a perfect BPSK signal; • for NRZ-L and SP-L waveforms, the beginning of the symbol intervals shall coincide with a positive-going subcarrier zero crossing for symbols "1" and with a negative-going zero crossing for symbols "0"; • for NRZ-M waveforms, the beginning of the symbol intervals shall coincide with a subcarrier zero crossing. SIST EN 301 926 V1.3.1:2017
ETSI ETSI EN 301 926 V1.3.1 (2017-10) 16 4.2.5 Uplink Carrier Frequency Deviation (Frequency Modulation) The FM deviation (modulation depth) is stated in table 4. Table 4: FM uplink frequency deviation Function Deviation (kHz) Telecommand (PCM/BPSK/FM) (Mode MTC1) Up to ±400 kHz Ranging Earth-to-space (FM) (Mode MTC1) (total deviation of all simultaneous major and minor tones) Up to ±400 kHz
4.2.6 Uplink PM Modulation Index Minima and maxima of the modulation index are stated in table 5. Table 5: PM modulation index Function Minimum (radians peak) Maximum (radians peak) Telecommand (PCM/BPSK/PM) (Mode MTC1) 0,2 1,4 Telecommand (SP-L) (Mode MTC1) 0,2 1,0 Ranging Earth-to-Space (PM) (mode MTC1) 0,2 1,4
4.2.7 Downlink PM Modulation Index Minima and maxima of the modulation index are stated in table 6. Table 6: PM modulation index Function Minimum (radians peak) Maximum (radians peak) Telemetry (PCM/BPSK/PM) (Mode MTM1) 0,1 1,5 Ranging Space-to-Earth (PM) (Mode MTM1) 0,01 1,5 NOTE: Effective ranging modulation index considering the power sharing due to re-modulated uplink noise.
4.2.8 Sense of Modulation A positive going video signal (modulated TM subcarrier and/or ranging) shall result in an advance of the phase of the downlink Radio Frequency carrier. 4.2.9 Data Transition Density a) To ensure recovery of the symbol clock by the ground demodulators, the transition density in the transmitted PCM waveform shall not be less than 125 in any sequence of 1 000 consecutive symbols. b) To ensure recovery of the symbol clock by the ground demodulators, the maximum string of either ones or zeros shall be limited to 64 symbols. c) When the specifications in a) and b) are not ensured for the channel by other methods, a pseudo‐randomizer in conformance with [2], section 9 shall be used. 4.2.10 Modulation Linearity The phase deviation, as a function of the video voltage applied to the modulator, shall not deviate from the ideal linear response by more than ±3 % of the instantaneous value for deviations up to 1,5 rad peak. SIST EN 301 926 V1.3.1:2017
ETSI ETSI EN 301 926 V1.3.1 (2017-10) 17 4.2.11 Residual Amplitude Modulation Residual amplitude modulation of the phase modulated RF signal shall be less than 2 %. 4.2.12 Residual Carrier, Out-of-band Emission and Discrete Spectral Lines a) The residual power in the modulated carrier shall be greater than ‐15 dBc for space‐Earth and ‐10 dBc for Earth‐space links. b) Discrete lines in the unmodulated transmitted RF signal spectrum, caused by baseband or RF bandwidth limitations, non‐linearity of the channel, digital implementation of the frequency synthesis, or any other effects shall be less than ‐45 dBc inside the occupied bandwidth. c) Modulation shall not result in the introduction of lines with power greater than ‐30 dBc in the occupied bandwidth. d) Modulation shall not result in the introduction of discrete spectral lines greater than ‐30 dBc in the frequency range of ±2,67 × 10-5 × fc around the carrier at frequency fc. e) For the case of filtered SP‐L modulation, the spectral lines at the even multiples of the symbol rate shall not be higher than ‐20 dBc. f) The out‐of‐band emission due to the modulation shall comply with the following emission mask.
Figure 8: Out-of-Band Emission Mask The mask is interpreted as follows: • dBsd is dB attenuation in a 4 kHz bandwidth, relative to the maximum power in any 4 kHz band within the necessary bandwidth. • For frequencies offset from the assigned frequency less than the 50 % of the necessary bandwidth (Bn), no attenuation is required. SIST EN 301 926 V1.3.1:2017
ETSI ETSI EN 301 926 V1.3.1 (2017-10) 18 • At a frequency offset equal to 50 % of the necessary bandwidth, an attenuation of at least 8 dB is required. • Frequencies offset more than 50 % of the necessary bandwidth should be attenuated by the following mask:
40∙log∙||+8()
where is the frequency displaced from the center of the emission bandwidth. 4.3 Spread Spectrum Modulation 4.3.1 General The spread modulation formats shall be: • Telecommand Uplink: Square Root Raised Cosine filtered Unbalanced QPSK (SRRC-UQPSK). • Telemetry Downlink: SRRC filtered Offset QPSK (SRRC-OQPSK). The spread modulation modes shall be as follows: • Mode MTC2: spread spectrum telecommand uplink. • Mode MTC3: spread spectrum telecommand uplink (alternative PN code structure). • Mode MTM2: spread spectrum telemetry downlink, coherent mode (long PN code). • Mode MTM3: spread spectrum telemetry downlink, non-coherent mode (short PN code). The Spread Spectrum modulation characteristics shall be as defined in table 7. The modulation modes listed shall be available for communications between the Spacecraft and the Earth Terminal for a range of data rates. Symbol rates referred to in the present document include the channel coding overhead whenever channel coding is applied. The Symbol rate shall be selected depending on requirements, link budget and multiple access capabilities. Modulator imperfections are defined in annex C. Table 7: Spread spectrum link modulation modes
Telecommand link, Mode MTC2 Telecommand link, Mode MTC3 Coherent telemetry link, Mode MTM2 Non-coherent telemetry link, Mode MTM3 Symbol Rate In the range 0,1 ksps - 300 ksps and < 10 % of spreading code rate Baseline values: 500 × 2n sps n= 0 to 9 In the range 0,1 ksps - 300 ksps and < 10 % of spreading code rate In the range 0,1 ksps - 300 ksps and < 10 % of spreading code rate In the range 0,1 ksps - 300 ksps and < 10 % of spreading code rate Channel Symbol rate on I channel (sps) =Symbol Rate =Symbol Rate =Symbol Rate (Same symbols on both channels) =Symbol Rate (Same symbols on both channels) Channel Symbol rate on Q channel (sps) PN code only = I channel symbol rate (same symbols on both channels) =I channel symbol rate (Same symbols on both channels) =I channel symbol rate (Same symbols on both channels) Data format NRZ-L
NRZ-M NRZ-L, NRZ-M NRZ-L
NRZ-M NRZ-L NRZ-M PN code family I channel Gold code Acquisition: Gold code, Tracking: truncated
m-sequence or truncated Gold sequence Truncated m-sequence Gold code PN Code length I channel 2n-1 n = 9 to 12 Acquisition 2n-1, n = 9 to 12 Tracking
(2n-1) × 2m, n = 9 to 12, m = 6 to 12 (2n-1) × 2m n = 9 to 12 m = 6 to 12 2n-1 n = 9 to 12 SIST EN 301 926 V1.3.1:2017
ETSI ETSI EN 301 926 V1.3.1 (2017-10) 19
Telecommand link, Mode MTC2 Telecommand link, Mode MTC3 Coherent telemetry link, Mode MTM2 Non-coherent telemetry link, Mode MTM3 Code I epoch reference None None Received Q code of MTC2 None PN code family Q channel Truncated m-sequence
or truncated Gold sequence Truncated m-sequence or truncated Gold sequence Truncated m-sequence or truncated Gold sequence Gold code PN Code length Q channel (2n-1) × 2m n = 9 to 12 m = 6 to 12 (2n-1) × 2m n = 9 to 12 m = 6 to 12 (2n-1) × 2m n = 9 to 12 m = 6 to 12 2n-1 n = 9 to 12 Code Q epoch reference I code I code x + 1/2 chips (x > 20 000) Delay w.r.t I ch of MTM2 1/2 chip delay w.r.t I of non-coherent mode return link Spreading code rate (Mc/s) In the range
0,5 to 10 Mcps Baseline values: 1,023 Mcps and 3,069 Mcps In the range
0,5 to 10 Mcps Identical to Received code In the range
0,5 to 10 Mcps Modulation SRRC-UQPSK Acquisition: SRRC-UQPSK Tracking: SRRC-QPSK SRRC-OQPSK SRRC-OQPSK I/Q power ratio Between 10:1 and 1:1 Acquisition: between 10:1 and 1:1 Tracking: 1:1 1:1 1:1 Ranging service possible Yes Yes Yes No NOTE 1: Data formats NRZ-L and NRZ-M are defined in clause 4.2.2, figure 7. NOTE 2: The term 'Gold code' is used to indicate codes with controlled and limited cross-correlation. Strictly speaking for 'n' or 'm' being a multiple of 4 one cannot define Gold codes (3-value cross-correlation). However, one can identify and define 'good' codes (5-value cross-correlation codes).
The Telecommand uplink signal in mode MTC2 shall be a spread spectrum SRRC-UQPSK modulated signal with: • during acquisition, a short PN code on the I Channel and a long PN code on the Q channel, no data are transmited during this phase; • once locked, during
tracking phase the data are added and carried by I Channel. The Telecommand uplink signal in mode MTC3 shall be a spread spectrum SRRC-QPSK modulated signal with: • during acquisition, a short PN code on the I Channel and a long PN code on the Q channel without data and with I/Q power ratio up to 10 (UQPSK); • during
tracking phase, a long PN code is applied on I channel, synchonized with Q channel one and with I/Q power ratio equal to 1 (QPSK). No change on Q channel. Tracking phase begins with a two-section acquisition sequence. The first is a constant data (unmodulated) section which provides for detection of the I code change. The second section is modulated with alternating data which provides for symbol clock acquisition. See detailed schematic on figure 9. SIST EN 301 926 V1.3.1:2017
ETSI ETSI EN 301 926 V1.3.1 (2017-10) 20
Figure 9: MTC3 mode scheme The coherent mode telemetry downlink signal in mode MTM2 shall be a spread spectrum SRRC-OQPSK modulated signal with data on the Q channel and on the I channel. MTM2 supports ranging by transmission of a long PN code on the downlink I channel synchronized to the code received on the mode MTC2/MTC3 uplink Q channel. A delayed version of this code is transmitted on the downlink Q channel. Mode MTM3 shall be a spread spectrum SRRC-OQPSK modulated signal with the data on the Q channel and on the I channel. MTM3 does not support ranging. A short (Gold) PN code is transmitted on the I channel and a half chip delayed Gold code is transmitted on the Q channel. For all spread PN coded transmissions, the data shall be modulo-2 added
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