ETSI TR 103 297 V1.1.1 (2017-07)

Satellite Earth Stations and Systems (SES); SC-FDMA based radio waveform technology for Ku/Ka band satellite service

DTR/SES-00366

General Information

• Status: Published
• Publication Date: 02-Jul-2017
• Technical Committee: SES SCN - Satellite Communications and Navigation
• Current Stage: 12 - Completion
• Due Date: 23-Jun-2017
• Completion Date: 03-Jul-2017

Standards Content (Sample)

TECHNICAL REPORT
Satellite Earth Stations and Systems (SES);
SC-FDMA based radio waveform technology
for Ku/Ka band satellite service

2 ETSI TR 103 297 V1.1.1 (2017-07)

Reference
DTR/SES-00366
Keywords
air interface, FDMA, satellite, wideband
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3 ETSI TR 103 297 V1.1.1 (2017-07)
Contents
Intellectual Property Rights . 5
Foreword . 5
Modal verbs terminology . 5
1 Scope . 6
2 References . 6
2.1 Normative references . 6
2.2 Informative references . 6
3 Symbols and abbreviations . 8
3.1 Symbols . 8
3.2 Abbreviations . 8
4 Introduction . 9
5 Return link . 10
5.1 Introduction . 10
5.2 DSNG use case . 11
5.2.1 Introduction. 11
5.2.2 Challenges. 12
5.2.3 Evaluation methodology . 13
5.2.3.1 Introduction . 13
5.2.3.2 System model description . 13
5.2.3.2.1 General system model . 13
5.2.3.2.2 Ground transmitter . 14
5.2.3.2.3 Satellite transponder . 14
5.2.3.2.4 Ground receiver . 14
5.2.3.3 DSNG simulation scenario . 16
5.2.3.4 Simulation methodology . 16
5.2.4 Performance analysis . 17
5.2.4.1 Spectral efficiency . 17
5.2.4.1.1 Introduction . 17
5.2.4.1.2 Single carrier usage . 17
5.2.4.1.3 Double carrier usage . 18
5.2.4.1.4 Four and more carrier usage . 19
5.2.4.2 Complexity . 20
5.2.5 Synthesis . 20
5.3 Broadband access use case . 21
5.3.1 Introduction. 21
5.3.2 Challenges. 21
5.3.2.1 Synchronization over the satellite channel . 21
5.3.2.2 Minimization of non-linear distortion in the satellite channel . 23
5.3.3 Evaluation methodology . 23
5.3.3.1 Synchronization acquisition . 23
5.3.3.2 Synchronization tracking . 25
5.3.3.3 Optimization of total degradation . 26
5.3.4 Performance analysis . 27
5.3.4.1 Synchronization accuracy . 27
5.3.4.2 Power efficiency . 28
5.3.4.3 Spectral efficiency . 30
5.3.4.4 Complexity . 31
5.3.5 Synthesis . 32
6 Forward Link . 32
7 Conclusions and Recommendations . 32
Annex A: Bibliography . 34
ETSI
4 ETSI TR 103 297 V1.1.1 (2017-07)
Annex B: Change History . 35
History . 36

ETSI
5 ETSI TR 103 297 V1.1.1 (2017-07)
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 Technical Report (TR) has been produced by ETSI Technical Committee Satellite Earth Stations and Systems
(SES).
Modal verbs terminology
In the present document "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 TR 103 297 V1.1.1 (2017-07)
1 Scope
The present document aims at assessing the performance of a SC-FDMA-based radio waveform over geostationary
satellites in Ku/Ka band. Moreover, it aims at defining an evaluation framework for performance comparison with
existing waveform technologies (e.g. DVB-S2, DVB-S2X and DVB-RCS2), focusing on the radio and physical layers.
The present document deals with satellite return link only. The forward link is for further study. For the return link, two
use cases have been identified and treated so far, Satellite News Gathering (DSNG) and Broadband Access.
The present document provides a description of the waveforms to be compared; it identifies their key characteristics,
defines the system model used for comparison and presents comparative performance results in terms of spectral
efficiency. A complexity analysis is also performed.
2 References
2.1 Normative references
Normative references are not applicable in the present document.
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 EN 302 307: "Digital Video Broadcasting (DVB); Second generation framing structure,
channel coding and modulation systems for Broadcasting, Interactive Services, News Gathering
and other broadband satellite applications (DVB-S2)".
[i.2] DVB Document A83-2: "Digital video broadcasting (DVB); Second generation framing structure,
channel coding and modulation systems for broadcasting, interactive services, news gathering and
other broad-band satellite applications, Part II: S2-Extensions (DVB-S2X)-(Optional)", March
2014.
[i.3] ETSI TS 136 211 (V8.3.0): "LTE; Evolved Universal Terrestrial Radio Access (E-UTRA);
Physical channels and modulation (3GPP TS 36.211 version 8.3.0 Release 8)".
[i.4] DVB BlueBook A160: "Digital Video Broadcasting (DVB); Next Generation broadcasting system
to Handheld, physical layer specification (DVB-NGH)".
[i.5] Ciochina-Duchesne C., Castelain D., Bouttier A.: "Satellite profile in DVB-NGH," Advanced
Satellite Multimedia Systems Conference (ASMS) and 12th Signal Processing for Space
Communications Workshop (SPSC), Baiona, Spain, 5-7 September 2012.
[i.6] DVB Document A162: "Guidelines for Implementation and Use of LLS: ETSI EN 301 545-2",
February 2013.
[i.7] Recommendation ITU-R M.2047-0 (12-2013): "Detailed specifications of the satellite radio
interfaces of International Mobile Telecommunications-Advanced (IMT Advanced)".
[i.8] C. Ciochina: "Physical layer design for the uplink of mobile cellular radiocommunications
systems", PhD defence, July 2009.
ETSI
7 ETSI TR 103 297 V1.1.1 (2017-07)
[i.9] Okuyama S., Takeda K., Adachi F.: "MMSE Frequency-Domain Equalization Using Spectrum
Combining for Nyquist Filtered Broadband Single-Carrier Transmission," Vehicular Technology
Conference (VTC 2010-Spring), 16-19 May 2010.
[i.10] ETSI TR 102 376 (V1.1.1) (02-2005): "Digital Video Broadcasting (DVB); User guidelines for the
second generation system for Broadcasting, Interactive Services, News Gathering and other
broadband satellite applications (DVB-S2)".
[i.11] ETSI TR 102 376-2 (V1.1.1) (November 2015): "Digital Video Broadcasting (DVB);
Implementation guidelines for the second generation system for Broadcasting, Interactive
Services, News Gathering and other broadband satellite applications; Part 2: S2 Extensions
(DVB-S2X)".
[i.12] M. Morelli, C.-C. J. Kuo and M.-O. Pun: "Synchronization Techniques for Orthogonal Frequency
Division Multiple Access (OFDMA): A Tutorial Review", Proceedings of the IEEE, vol. 95, no. 7,
pp. 1394- 1427, July 2007.
[i.13] ETSI TS 136 213: "LTE; Evolved Universal Terrestrial Radio Access (E-UTRA); Physical layer
procedures (3GPP TS 36.213 Release 11)".
[i.14] D. Chu: "Polyphase Codes with Good Periodic Correlation Properties," IEEE Transactions on
Information Theory, vol. 18, no. 4, pp. 531-532, July 1972.
[i.15] Y. Wen, W. Huang and Z. Zhang: "CAZAC sequence and its Application in LTE Random
Access", In Proceedings of IEEE Information Theory Workshop, October 2006, pp. 544-547.
[i.16] F. Rossetto and M. Berioli: "On synchronisation for SC-FDMA waveform over geo satellite
networks" in Advanced Satellite Multimedia Systems Conference (ASMS) and 12th Signal
Processing for Space Communications Workshop (SPSC), 2012 6th, September 2012,
pp. 233-237.
[i.17] U. Mengali and M. Morelli: "Data-aided frequency estimation for burst digital transmission"
Communications, IEEE Transactions on, vol. 45, no. 1, pp. 23-25, January 1997.
[i.18] P. H. Moose: "A technique for orthogonal frequency division multiplex- ing frequency offset
correction," Communications, IEEE Transactions on, vol. 42, no. 10, pp. 2908-2914,
October 1994.
[i.19] Global Positioning System Standard Positioning Service Performance Standard, 4th edition,
September 2008.
[i.20] B. M. Popović: "Efficient Matched Filter for the Generalized Chirp-Like Polyphase Sequences"
IEEE Transactions on Aerospace and Electronic Systems, Vol. 30, No. 3, pp. 769-777, July 1994.
[i.21] Panasonic: "R1-071517: RACH Sequence Allocation for Efficient Matched Filter
Implementation", www.3gpp.org, 3GPP TSG RAN WG1, meeting 48bis, St Julians, Malta,
March 2007.
[i.22] D. Castelain, C. Ciochina-Duchesne, J. Guillet and F. Hasegawa: "SC-OFDM, a Low-Complexity
Technique for High Performance Satellite Communications", ICSSC"2014, San Diego,
August 2014.
ETSI
8 ETSI TR 103 297 V1.1.1 (2017-07)
3 Symbols and abbreviations
3.1 Symbols
For the purposes of the present document, the following symbols apply:
α Roll-off factor
M DFT precoding size
N IDFT size
Ncar Number of carriers per transponder
CP length
NCP
N Number of guard subcarriers
guard
N Number of taps for the finite impulse response filter
taps
ovs Oversampling factor
ρ Code rate
Rs Symbol rate (baud)
3.2 Abbreviations
For the purposes of the present document, the following abbreviations apply:
3GPP Third Generation Partnership Project
AM/AM Amplitude Modulation/Amplitude Modulation
AM/PM Amplitude Modulation/Phase Modulation
APSK Amplitude Phase Shift Keying
AWGN Additive White Gaussian Noise
BER Bit-Error Ratio
BICM Bit Interleaved Coded Modulation symbols
CAZAC Constant Amplitude Zero AutoCorrelation
CCDF Complementary Cumulative Distribution Function
CFO Carrier Frequency Offset
CP Cyclic Prefix
DFT Discrete Fourier Transform
DL DownLink
DSNG Digital Satellite News Gathering
DVB Digital Video Broadcasting
DVB-NGH DVB New Generation Handheld
DVB-RCS DVB Return Channel via Satellite
DVB-S Digital Video Broadcasting via Satellite
FDE Frequency Domain Equalization
FDMA Frequency Division Multiple Access
FDT Frequency Domain Transmitter
FFT Fast Fourier Transform
FIR Finite Impulse Response
GEO Geostationary Orbit
GPS Global Positioning System
GT Guard Time
HPA High Power Amplifier
IBO Input Back-Off
ICI Inter-Carrier Interference
IDFT Inverse Discrete Fourier Transform
IMI Inter-Modulation Interference
IMT International Mobile Telecommunications
IMUX Input MUltipleXer filter
ISI Inter-Symbol Interference
INP Instantaneous Normalized Power
ITU-R International Telecommunication Union-Radiocommunications sector
LTE Long Term Evolution
MAI Multiple Access Interference
MLE Maximum Likelihood Estimator
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9 ETSI TR 103 297 V1.1.1 (2017-07)
MODCOD Modulation & Coding
MSE Mean-Squared Error
NC Not Compensated
NCC Network Control Centre
NR New Radio
OFDM Orthogonal Frequency Division Multiplex
PAPR Peak to Average Power Ratio
PER Packet Error Rate
PN Phase Noise
PRACH Physical Random Access CHannel
PSK Phase Shift Keying
OBO Output Back-Off
OFDMA Orthogonal Frequency Division Multiple Access
OMUX Output Multiplexer Filter
QAM Quadrature Amplitude Modulation
QPSK Quaternary Phase Shift Keying
RA Random Access
RACH Random Access Channel
RCST Return Channel Satellite Terminal
RF Radio Frequency
RTT Round Trip Time
SC Single Carrier
SC-FDMA Single Carrier-Frequency Division Multiple Access
SC-OFDM Single Carrier-Orthogonal Frequency Division Multiplexing
SC-TDM Single Carrier-Time Division Multiplexing
SE Spectral Efficiency
SIR Signal-to-Interference Ratio
SNG Satellite News Gathering
SNR Signal-to-Noise Ratio
SRRCF Square Root Raised Cosine Filter
SSPA Solid State Power Amplifier
TD Total Degradation
TDE Time Domain Equalization
TDM Time Division Multiplexing
TDMA Time Division Multiple Access
TDT Time Domain Transmitter
TE Timing Error
TWT Travelling Wave Tube
TWTA Travelling Wave Tube Amplifier
UE User Equipment
UL Uplink
ZC Zadoff-Chu
4 Introduction
The return link in satellite may correspond to different use cases.
The present document evaluates the performance of SC-FDMA radio interface for satellite broadband systems operating
in Ku or Ka band, focusing on the physical layer.
The presentdocument deals with satellite return link only. The forward link part is for further study. For the return link,
two use cases have been identified and treated so far, DSNG and Broadband access.
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10 ETSI TR 103 297 V1.1.1 (2017-07)
5 Return link
5.1 Introduction
The return link in satellite may correspond to different use cases.
The first use case that is described and simulated in the present document is a professional return link use case, in
practice a typical DSNG use case. Different relatively wide-band SC-OFDM signals (i.e. SC-FDMA with full subcarrier
allocation) are transmitted to the satellite by a few transmitters in the same band. The multiple access scheme is thus
FDMA and not SC-FDMA. These signals are not assumed synchronized neither in time nor in frequency, which implies
that a slight frequency guard band is sometimes needed, depending on the robustness of the modulation. This use case is
the same as the return link professional one considered in DVB-S2x [i.2]. This DSNG use case is illustrated in Figure 1.
Broadband access (DVB-RCS2) corresponds to another important return link use case. This use case is similar to LTE
uplink, where the different signals (not as wideband as in previous case), with SC-FDMA multiple access, are assumed
synchronized in time and frequency, which implies new constraints for insuring this synchronization. The number of
signals simultaneously transmitted in the same band is much higher than in the previous use case, which explains the
choice of the SC-FDMA multiple access scheme for obtaining a good efficiency. In this use case, the cyclic prefix [i.4],
[i.5] and [i.9] is used to relax the constraints on the synchronization, which means that its size are dimensioned for this
purpose. However and contrary to the DSNG use case, a frequency guard band is generally not necessary. This
broadband access use case is illustrated in Figure 1.

Figure 1: Return link use cases
Table 1: Return link use cases
DSNG use case Broadband access use case
Radio resource assigned per One or several full SC-FDMA Several sub-carriers of a
terminal carrier(s) SC-FDMA carrier
No need for synchronization Need for synchronization between
Operational constraints
between satellite terminals satellite terminals
FDMA type: Single terminal per SC-FDMA: Several terminals per
Multiple access scheme
SC-FDMA carrier SC-FDMA carrier
Comparison with existing
DVB-S2x DVB-RCS2
waveform technologies
In particular, the present document compares the performances for the return link of two types of radio interface:
• SC-TDM: this refers to current satellite communication standards such as DVB-S2 [i.1] and DVB-S2X [i.2]. It
corresponds to single carrier sequential transmission of modulation signals, with a spectrum shaped by a
root-raised cosine filter with different roll-off factors α. It was designed for satellite communications to
maximize the efficiency of HPA on-board satellite by minimizing the envelope variation of the signal and then
limiting the non-linear effects.
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11 ETSI TR 103 297 V1.1.1 (2017-07)
• SC-FDMA is a transmission technique derived from OFDMA via DFT precoding. SC-FDMA is exhibiting
low envelope variations and is having a natural compatibility with zero roll-off. As is the case for OFDMA
and all its precoded counterparts, SC-FDMA allows low complexity per-subcarrier equalization in the
frequency domain. In its full spectral allocation version, SC-FDMA is also coined SC-OFDM [i.22].
In the present document, the performance of the access scheme is not taken into account. Hence, the
performance of both SC-TDM and SC-FDMA waveform signals are compared by applying the same access
scheme to the spectrum.
The differences between the different signal types are illustrated in Table 2.
Table 2: The analysed signals
SC-FDMA SC-TDM = TDM SC-OFDM
Carrier multiplexing in a Single analogue carrier One or Multiple analogue One or Multiple analogue
channel bandwidth per Channel carriers per Channel carriers per Channel
Examples LTE uplink DVB-S2, DVB-S2X DVB-NGH

This evaluation is performed in similar configurations as existing standards.
5.2 DSNG use case
5.2.1 Introduction
The most straightforward way of transmitting modulated information consists in using single carrier sequential
transmission of modulation signals as described in Figure 2. Bit interleaved coded modulation symbols (e.g. X-APSK
symbols) are mapped into physical layer frames of specified formats. Base-Band Filtering and quadrature modulation
shape the signal spectrum (for example squared-root raised cosine with different roll-off factors) before sending it in the
RF satellite channel. In the present document this waveform will be denoted as SC-TDM.

Figure 2: SC-TDM waveform generation
DVB-S2 [i.1] and DVB-S2X [i.2] use SC-TDM waveform. DVB-S2 employs QPSK, 8PSK, 16APSK and 32APSK
with α = 0,35 or 0,25 or 0,20. DVB-S2X reuses the DVB-S2 physical layer and employs in addition higher modulation
orders (64APSK, 128APSK and 256APSK) and sharper roll-off factors ( α = 0,15 or 0,10 or 0,05) to improve the
spectral efficiency.
SC-FDMA is a waveform that was introduced to improve the spectral efficiency in terrestrial networks. The goal of the
present document is to show that it is suitable for satellite communications too.
SC-FDMA waveform has been adopted for the uplink air interface of 3GPP LTE [i.3], in commercial use since 2009. In
a 3GPP LTE context, SC-FDMA represents not only the uplink waveform but also the multiple access scheme, the
users sharing the uplink channel in the frequency domain by being allocated different groups of adjacent subcarriers like
in a classic OFDMA system.
In the satellite world, SC-FDMA has been adopted as one of the waveforms for the satellite profile of DVB-NGH [i.4]
under its full spectral allocation form SC-OFDM [i.5]. SC-FDMA was also acknowledged as a promising technique for
future developments of DVB-RCS2 ([i.6], annex C). Moreover, the ITU-R recently issued its Recommendations [i.7]
for the satellite component of the IMT-Advanced radio interface(s) where both validated air interfaces rely on
SC-FDMA-based waveforms.
A SC-FDMA transmitter can be implemented in the frequency domain under the form of Discrete Fourier Transform
(DFT) - precoded OFDM waveform as described in Figure 3.
ETSI
12 ETSI TR 103 297 V1.1.1 (2017-07)

Figure 3: SC-FDMA waveform generation
Bit interleaved coded modulation symbols (e.g. X-APSK symbols) are grouped in blocks of M symbols and are
precoded by an [MxM] DFT matrix. The M-sized output vector is then mapped onto M subcarriers represented by M out
of N inputs of the inverse DFT. N guard subcarriers are inserted at band edges on the remaining inputs. After an
guard
N-point Inverse Discrete Fourier Transform (IDFT), an N -length CP may be inserted. In systems where the
CP
transmitted signal experiences a multipath frequency selective channel, the role of the CP is to absorb the channel
delays and thus eliminate the interference between successive SC-FDMA symbols. In satellite scenarios, where the
channel is essentially line of sight with practically no frequency selectivity, the insertion of a CP is not necessarily
mandatory, depending on the FFT size, except when this CP is used to compensate time differences between the
transmitters as is the case in RCS2use case. Roll-off can optionally be implemented in the frequency domain, after DFT
precoding. SC-FDMA is compatible with zero roll-off implementations in a native manner.
In systems where there is no user specific multiple access (e.g. broadcasting on the forward link), or where multiple
access is achieved by other means, SC-FDMA with full spectral allocation is called SC-OFDM in order to clarify the
fact that SC-FDMA is only used as a waveform, and not as a multiple access scheme [i.22]. Since all data subcarriers
are active, there is no null subcarrier insertion in the subcarrier mapping process and thus N = N-M.
guard
Time-domain implementations of SC-OFDM are also possible both at the transmitter and receiver sides. Nevertheless,
less complex frequency domain implementations are usually preferred in practice.
5.2.2 Challenges
Thanks to a natural zero-roll off, SC-FDMA improves the spectral efficiency in linear communications channels.
However, what does happen in a satellite non-linear channel? The sensibility to non-linear effects depends on the PAPR
characteristics of the waveform.
During SC-FDMA waveform generation, DFT precoding restores the SC-like properties of the signal, alleviating the
high PAPR problem specific to OFDMA signals. Localized and distributed subcarrier allocations have the same
envelope variations as classical SC transmission [i.8]. Other types of allocation may degrade the PAPR. In the case of
SC-OFDM, since all subcarriers are allocated, the PAPR is thus identical to that of a SC signal.
For SC-FDMA, roll-off can optionally be implemented in the frequency domain, after DFT precoding, at subcarrier
level by the means of low complexity frequency domain processing. Nevertheless, SC-FDMA is by its nature
compatible with zero roll-off. When employed, the roll-off controls both the excess bandwidth and the envelope
variations of a signal. While high roll-off values reduce the signal's peak to average power ratio (PAPR), they also
increase the excess bandwidth, which penalizes the system's performance due to either frequency mask filtering issues,
or to increased inter-channel interference in multiple carriers per transponder scenarios.
SC-FDMA and SC transmission having the same roll-off factor display the same envelope variations, as further
described in relation to Figure 4.
The CCDF of PAPR, as defined in equation below as CCDF of instantaneous amplitudes (sample level), indicates that
at least one peak per block has an important amplitude and is susceptible to suffer clipping or severe distortion with a
certain probability, but gives no information on how many samples in that block are distorted. Yet, all of these samples
having important amplitudes cause degradation when passing through a nonlinear HPA. Severely clipping one single
peak in a large block has a negligible effect, while distortion (even mild) of a large number of samples might have
important consequences.
The distribution of the INP of a generic discrete signal v containing N symbols is defined as the probability that its
s
instantaneous normalized power is above a certain threshold γ :
INP(v)
⎧⎫
⎪⎪
⎪⎪vn[]
.
CCDF(INP)=>Pr γ
⎨⎬
N −1
s
⎪⎪1 2
vk[]
∑
⎪⎪
N
s
⎩⎭k =0
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13 ETSI TR 103 297 V1.1.1 (2017-07)
The CCDF of INP and the CCDF of PAPR tend asymptotically to the same value, but in the range of lower values of
γ
the CCDF of INP has a better resolution.
Figure 4 presents the CCDF of INP of SC-TDM and SC-FDMA waveforms with QPSK mapping and with different
roll-off factors. Signals are oversampled 4 times before CCDF computation. For SC-FDMA, N = 2 048, M = 1 728.
1,0E+00
SC-TDM 5%
SC-TDM 10%
SC-TDM 15%
1,0E-01
SC-TDM 25%
SC-TDM 35%
SC-OFDM 0%
SC-OFDM 5%
1,0E-02
SC-OFDM 10%
SC-OFDM 15%
SC-OFDM25%
1,0E-03
SC-OFDM 35%
1,0E-04
1,0E-05
0123456789 10
γ (dB)
Figure 4: CCDF of INP for SC-TDM and SC-FDMA/SC-OFDM with different roll-off factors
5.2.3 Evaluation methodology
5.2.3.1 Introduction
To compare the performance of the two waveforms described here above, an evaluation framework is defined for the
return link. This framework corresponds to the DSNG use case as defined in DVB-S2x [i.10]. Suitable channel models
for performance evaluation of DVB-S2/S2X in the various application areas are given in [i.10] and [i.11].
5.2.3.2 System model description
5.2.3.2.1 General system model
Transmission over a transparent satellite transponder is depicted in Figure 5.
Tra n smi tter HPA
UL interference
Ground
transmitter
IM UX OM UX
HPA
Satellite
fi l ter filter
transponder
Ground receiver
Ph a se
Recei ver
Noi se
DL interference AWGN
Figure 5: System model
ETSI
CCDF of INP
14 ETSI TR 103 297 V1.1.1 (2017-07)
5.2.3.2.2 Ground transmitter
A ground transmitter (terrestrial gateway, SNG van, etc.), generates signal representing the data to be transmitted,
physical layer headers and possible pilot symbols. This signal modulated and framed either as described in Figure 2 to
obtain a SC-TDM transmitted signal in conformity with the DVB-S2/S2X specifications [i.1] and [i.2], or as described
in Figure 3 to obtain a SC-OFDM signal. The signal is then transmitted onto the current carrier to the satellite
transponder. Uplink (UL) interference is modelled by adding in the adjacent channel a different signal carried by the
same type of waveform as the current transmission. Ground transmitter HPA is considered either ideal or satisfying the
characteristics in clause 4.4.1.1 of [i.11].
5.2.3.2.3 Satellite transponder
The transponder is composed of an input filter (IMUX) selecting the current carrier, a high power amplifier (HPA)
representing the non-linearity on board of the satellite and an output filter (OMUX) who reduces the out-of-band
emission due to the spectral regrowth after the HPA. IMUX and OMUX amplitude and group delay response models
are drawn from annex H.7 of the DVB-S2 specifications [i.1] and scaled for a reference transceiver bandwidth of
38 MHz. They are given in Figure 6. HPA is considered either ideal (linear channel) or non-linear TWTA. Two
non-linear TWTAs are considered, the conventional and the linearized TWT as drawn from [i.11] with AM/AM and
AM/PM characteristics given in Figure 7.

Figure 6: IMUX and OMUX filter characteristics

Figure 7: Conventional and Linearized TWTA characteristics
5.2.3.2.4 Ground receiver
At the ground receiver, the useful signal is corrupted by adjacent downlink (DL) interferers, AWGN and optional phase
noise. When the presence of phase noise (PN) is simulated, the critical mask drawn in Figure 8 and described in
annex H.8, table H.4 of the DVB-S2X [i.2] is used.
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Figure 8: Phase noise characteristics
The receiver is either a classical time-domain SC-TDM receiver with fractional equalization or a SC-OFDM receiver
with frequency domain per subcarrier equalization. Equalization is followed by a time-domain linear phase noise
correction.
Ideal frequency synchronization is considered. Time synchronization is genie-aided (based on correlation with the
transmitted signal, ideally supposed as known). Linear minimum mean square error (MMSE) equalization is employed
using long-term auto-correlation and cross-correlation coefficients computed through a genie-aided approach. Phase
noise estimation and correction is realistic, based only on Start of Frame sequence and pilot resources of S2 frame. A
simple method reduced to a piecewise linear interpolation between reference resources is used [i.11]. For both
waveforms, phase noise compensation is performed after equalization, at symbol rate.
The SC-TDM receiver, depicted in Figure 9, employs a fractional time domain equalization implemented in the time
domain with a N = 41 taps finite impulse response filter with an oversampling rate ovs = 2.
taps
Figure 9: SC-TDM receiver
SC-FDMA receiver, depicted in Figure 10, performs low-complexity equalization in the frequency-domain, allowing an
important reduction of the number of required operations with respect to time-domain equalization. Frequency domain
equalization is performed at subcarrier level (one coefficient per subcarrier), after DFT.

Figure 10: SC-FDMA/SC-OFDM receiver
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5.2.3.3 DSNG simulation scenario
A professional use case scenario of video contribution and distribution is considered. One or several video contributors
share the same transponder, making either simple or multiple carrier usage. The cases of one, two and four contributors
are represented in Figure 11 a), b) and c) respectively. In case of several-carrier usage, each carrier is used by a different
operator, which optimizes his scheme independently and uses its own IMUX/OMUX pair.
Carrier spacing is denoted ∆f as in Figure 11 d).

a) Single carrier usage b) 2-carrier usage

c) 4-carrier usage d) Carrier spacing for multiple carrier usage
Figure 11: Video contribution and distribution use case
In a single carrier scenario, the multiple access is performed in TDMA or by using different transponders. Note that this
can be performed also in the multiple-carrier scenario.
5.2.3.4 Simulation methodology
Performance is evaluated as following, in compliance with [i.10] and [i.11].
In a first step, in non-linear channels, for each MODCOD the optimum functioning point of the HPA is determined. The
input/output back-off (IBO/OBO) is defined as the measured power ratio (in dB) between the input/output signal power
and the HPA's saturation level. A large range of IBO values was tested and for each such value the MODCOD's
performance is represented under the form of Packer Error Rate (PER) versus CSat/N, where CSat is the signal power at
the output of the IMUX and N is the AWGN level at the input of the receiver measured in the reference bandwidth of
38 MHz divided by the number of carriers N per transponder. CSat/N is thus representative of the signal-to-noise ratio
car
(SNR) at the input of the receiver, plus a penalty caused by OBO and OMUX filtering. The HPA optimum functioning
point (corresponding to a couple (IBO , OBO )) was selected as the one maximizing the performance for a target
opt opt
-3
PER = 10 . Here, maximizing the performance means minimizing CSat/N. All following simulations for each
MODCOD are considered as being performed at its optimal IBO . In addition to the required CSat/N, the
opt
corresponding spectral efficiency (SE) was considered, for the reference bandwidth of 38 MHz/(as bandwidth reference
is constant, this metrics is proportional to the total data rate per transponder). Strictly speaking, this spectral efficiency
is calculated as (b/s/Hz), where ρ is the code rate.
SE=×ρ N × R /(38.10 / N )
bits s car
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In a second step, modulation rate (R ) (for all use cases) and carrier spacing ∆f (for multiple carrier usage use cases) are
s
optimized. This optimization is conducted separately for SC-TDM and SC-FDMA/SC-OFDM. For all MODCODs (at
their respective IBO ) a range of different (Rs, ∆f) values was tested and PER versus CSat/N performance was plotted.
opt
-3
The CSat/N values were identified for a target PER=10 and the associated spectral efficiency and for each tested (Rs,
∆f) couple, the variation of spectral efficiency (given by the different MODCODS) was plotted versus CSat/N. The
optimum (Rs, ∆f) couple was selected as the one overall maximizing the performance (i.e. minimizing CSat/N and
opt
maximizing the spectral efficiency). For multiple carrier usage, simulation results show that, for all scenarios, the
optimum carrier spacing ∆f equals the reference transponder spacing divided the number of used carriers, i.e.
opt
∆f = 20 MHz for 2-carrier usage and ∆f = 10 MHz for 4-carrier usage.
opt opt
5.2.4 Performance analysis
5.2.4.1 Spectral efficiency
5.2.4.1.1 Introduction
In the performance figures, the spectral efficiency SE is drawn versus CSat/N. The gain (or no gain) depends on
CSat/N. In order to synthesize the results, three SE range values were considered:
• Small data-rate: 1,6 - 2 b/s/Hz
• Medium data-rate: 2 - 3,5 b/s/Hz
• High data-rate: 3,5 - 6 b/s/Hz
For each SE range, the average SE was calculated for each transmission mode, which allows to simply compare the
waveforms in Table 3, Table 4 and Table 5.
5.2.4.1.2 Single carrier usage
The results for the single carrier usage are depicted below. The results are provided without any HPA ("No HPA"), or
with the linearized HPA ("Lin. HPA") or with the Conventional HPA ("Conv. HPA"). They are also provided with
phase noise ("PN") or without phase noise (no "PN" mention).

Figure 12: Single carrier usage performance
α = roll-off.
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Table 3 compares performances of SC-FDMA/SC-OFDM with zero roll-off to SC-TDM with 5 % roll-off. This
comparison is performed for each SE range and for each amplifier, with and without PN.
Table 3: SE gains of no roll-off over 5 % roll-off, single carrier usage
Low SE Medium SE High SE
(0,45 - 2 b/s/Hz) (2 - 3,5 b/s/Hz) (3,5 - 6 b/s/Hz)
No PN PN No PN PN No PN PN
[%] [%] [%] [%] [%] [%]
No HPA 0,5 0,7 0,1 0,4 1,2 1,1
Linearized HPA -0,9 -0,8 -0,9 -0,8 0,2 0,3
Conventional HPA -0,9 -1 -1 -0,9 -0,4 -0,5

In this scenario, with an HPA, the zero roll-off system (SC-FDMA) only brings a small advantage for large spectral
efficiencies, above 3,5 b/s/Hz. Taking into account the phase or not does not change the conclusions. As expected, with
no HPA, the zero roll-off system always improves performances.
5.2.4.1.3 Double carrier usage
The following figures provide the same results in the two-carrier use case. The different parameters, e.g. Rs or Δf, were
optimized for each specific scenario.

Figure 13: Double carrier usage performance
Table 4: SE gains of no roll-offs over 5 % roll-off, double carrier usage
Small SE Medium SE High SE
(0,45 - 2 b/s/Hz) (2 - 3,5 b/s/Hz) (3,5 - 6 b/s/Hz)
No PN PN No PN PN No PN PN
[%] [%] [%] [%] [%] [%]
No HPA 1,1 1,3 0,9 1,2 1,5 1,8
Linearized HPA 0,6 0,9 0,6 0,8 1,1 1,3
Conventional HPA
0,4 0,6 0,
...