SIST ETS 300 800 E1:2003

SLOVENSKI STANDARD
01-december-2003
Digitalna videoradiodifuzija (DVB) – Povratni kanal za kabelske TV (CaTV)
distribucijske sisteme
Digital Video Broadcasting (DVB); Interaction channel for Cable TV distribution systems
(CATV)
Ta slovenski standard je istoveten z: ETS 300 800 Edition 1
ICS:
33.170 Televizijska in radijska Television and radio
difuzija broadcasting
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN ETS 300 800
TELECOMMUNICATION July 1998
STANDARD
Source: EBU/CENELEC/ETSI-JTC Reference: DE/JTC-DVB-23
ICS: 33.020
Key words: DVB, broadcasting, digital, video, cable, TV, interaction
European Broadcasting Union Union Européenne de Radio-Télévision
EBU
UER
Digital Video Broadcasting (DVB);
Interaction channel for Cable TV distribution systems (CATV)
ETSI
European Telecommunications Standards Institute
ETSI Secretariat
Postal address: F-06921 Sophia Antipolis CEDEX - FRANCE
Office address: 650 Route des Lucioles - Sophia Antipolis - Valbonne - FRANCE
Internet: secretariat@etsi.fr - http://www.etsi.fr - http://www.etsi.org
Tel.: +33 4 92 94 42 00 - Fax: +33 4 93 65 47 16
Copyright Notification:
No part may be reproduced except as authorized by written permission. The copyright and the
foregoing restriction extend to reproduction in all media.
© European Telecommunications Standards Institute 1998.
© European Broadcasting Union 1998.
All rights reserved.
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ETS 300 800: July 1998
Whilst every care has been taken in the preparation and publication of this document, errors in content,
typographical or otherwise, may occur. If you have comments concerning its accuracy, please write to
"ETSI Standards Making Support Dept." at the address shown on the title page.

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ETS 300 800: July 1998
Contents
Foreword .5
1 Scope .7
2 Normative references.7
3 Abbreviations.7
4 Reference model.8
4.1 Protocol stack model .8
4.2 System model .9
5 DVB interaction channel specification for CATV networks.11
5.1 System concept .11
5.1.1 Out-Of-Band (OOB) / In-Band (IB) principle.11
5.1.2 Spectrum allocation.11
5.1.3 FDM/TDMA multiple access.12
5.1.4 Bit rates and framing .13
5.2 Lower physical layer specification.13
5.2.1 Forward Interaction path (Downstream OOB).15
5.2.1.1 Frequency range (Downstream OOB).15
5.2.1.2 Modulation and mapping (Downstream OOB).15
5.2.1.3 Shaping filter (Downstream OOB).16
5.2.1.4 Randomizer (Downstream OOB).18
5.2.1.5 Bit rate (Downstream OOB).18
5.2.1.6 Receiver power level (Downstream OOB).18
5.2.1.7 Summary (Downstream OOB).19
5.2.1.8 Bit error rate downstream OOB (informative).20
5.2.2 Forward Interaction Path (Downstream IB).20
5.2.3 Return Interaction Path (Upstream) .20
5.2.3.1 Frequency range (Upstream) .20
5.2.3.2 Modulation and mapping (Upstream) .20
5.2.3.3 Shaping filter (Upstream).21
5.2.3.4 Randomizer (Upstream) .22
5.2.3.5 Bit rate (Upstream) .22
5.2.3.6 Transmit power level (Upstream) .23
5.2.3.7 Carrier suppression when idle (Upstream).23
5.2.3.8 Summary (Upstream) .24
5.2.3.9 Packet loss upstream (informative).25
5.3 Framing.26
5.3.1 Forward Interaction path (Downstream OOB).26
5.3.1.1 Signalling Link Extended SuperFrame (SL-ESF) framing
format .26
5.3.1.2 Frame overhead .26
5.3.1.3 Payload structure.27
5.3.2 Forward Interaction path (Downstream IB) .34
5.3.3 Return Interaction Path (Upstream) .36
5.3.3.1 Slot Format .36
5.4 Slot timing assignment.38
5.4.1 Downstream slot position reference (Downstream OOB) .38
5.4.2 Downstream slot position reference (Downstream IB).39
5.4.3 Upstream slot positions.40
5.4.3.1 Rate 256 kbit/s.41
5.4.3.2 Rate 1,544 Mbit/s.41
5.4.3.3 Rate 3,088 Mbit/s.42
5.4.4 Slot position counter.43
5.5 MAC functionality .44

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5.5.1 MAC reference model. 44
5.5.2 MAC concept . 45
5.5.2.1 Relationship between higher layers and MAC protocol . 45
5.5.2.2 Relationship between physical layer and MAC protocol . 45
5.5.2.3 Relationship between physical layer slot position counter
and MAC slot assignment . 46
5.5.2.4 Access modes (Contention / Ranging / Fixed rate /
Reservation). 46
5.5.2.5 MAC error handling procedures. 48
5.5.2.6 MAC messages. 48
5.5.3 MAC initialization and provisioning . 52
5.5.3.1 Provisioning Channel Message (Broadcast OOB
Downstream). 53
5.5.3.2 Default Configuration Message (Broadcast
Downstream). 54
5.5.4 Sign-On and Calibration . 56
5.5.4.1 Sign-On Request Message (Broadcast
Downstream). 59
5.5.4.2 Sign-On Response Message (Upstream
Contention or Ranging). 60
5.5.4.3 Ranging and Power Calibration Message
(Singlecast Downstream). 60
5.5.4.4 Ranging and Power Calibration Response
Message (Upstream reserved or contention Ranging) . 61
5.5.4.5 Initialization Complete Message (Singlecast
Downstream). 61
5.5.5 Default Connection Establishment. 61
5.5.5.1 Connect Message (Singlecast Downstream). 63
5.5.5.2 Connect Response (Upstream contention,
reserved or contention access). 66
5.5.5.3 Connect Confirm (Singlecast Downstream) . 67
5.5.6 Data connections. 67
5.5.6.1 Fixed rate access. 68
5.5.6.2 Contention based access. 68
5.5.6.3 Reservation access. 69
5.5.7 MAC link management . 72
5.5.7.1 Power and timing management . 73
5.5.7.2 TDMA allocation management. 73
5.5.7.3 Channel error management. 76
5.5.7.4 Link management messages. 76
Annex A (informative): Bibliography . 82
History. 83

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Foreword
This European Telecommunication Standard (ETS) has been produced by the Joint Technical Committee
(JTC) Broadcast of the European Broadcasting Union (EBU), Comité Européen de Normalisation
ELECtrotechnique (CENELEC) and the European Telecommunications Standards Institute (ETSI).
NOTE: The EBU/ETSI JTC Broadcast was established in 1990 to co-ordinate the drafting of
ETSs in the specific field of broadcasting and related fields. Since 1995 the JTC
Broadcast became a tripartite body by including in the Memorandum of Understanding
also CENELEC, which is responsible for the standardization of radio and television
receivers. The EBU is a professional association of broadcasting organizations whose
work includes the co-ordination of its members' activities in the technical, legal,
programme-making and programme-exchange domains. The EBU has active
members in about 60 countries in the European broadcasting area; its headquarters is
in Geneva.
European Broadcasting Union
CH-1218 GRAND SACONNEX (Geneva)
Switzerland
Tel: +41 22 717 21 11
Fax: +41 22 717 24 81
Digital Video Broadcasting (DVB) Project
Founded in September 1993, the DVB Project is a market-led consortium of public and private sector
organizations in the television industry. Its aim is to establish the framework for the introduction of
MPEG-2 based digital television services. Now comprising over 200 organizations from more than
25 countries around the world, DVB fosters market-led systems, which meet the real needs, and
economic circumstances, of the consumer electronics and the broadcast industry.
Transposition dates
Date of adoption of this ETS: 20 March 1998
Date of latest announcement of this ETS (doa): 31 October 1998
Date of latest publication of new National Standard
or endorsement of this ETS (dop/e): 30 April 1999
Date of withdrawal of any conflicting National Standard (dow): 30 April 1999

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1 Scope
This ETS is the baseline specification for the provision of interaction channel for Cable TV (CATV)
networks.
It is not intended to specify a return channel solution associated to each broadcast system because the
inter-operability of different delivery media to transport the return channel is desirable.
The solutions provided in this ETS for interaction channel for CATV networks are a part of a wider set of
alternatives to implement interactive services for DVB systems.
2 Normative references
This ETS incorporates by dated and undated reference, provisions from other publications. These
normative references are cited at the appropriate places in the text and the publications are listed
hereafter. For dated references, subsequent amendments to or revisions of any of these publications
apply to this ETS only when incorporated in it by amendment or revision. For undated references the latest
edition of the publication referred to applies.
[1] EN 50083-2: "Cabled Distribution Systems for television and sound signals".
[2] EN 300 429: "Digital Video Broadcasting (DVB); Framing structure, channel
coding and modulation for cable systems".
[3] EN 300 421: "Digital Video Broadcasting (DVB); Framing structure, channel
coding and modulation for 11/12 GHz satellite services".
[4] ITU Recommendation I.361 (11/95): "B-ISDN ATM layer specification".
[5] ITU-T Recommendation I.363: "B-ISDN ATM Adaptation Layer specification".
[6] EN 300 468: "Digital Video Broadcasting (DVB); Specification for Service
Information (SI) in DVB systems".
3 Abbreviations
For the purposes of this ETS, the following abbreviations apply:
ATM Asynchronous Transfer Mode
BC Broadcast Channel
BRA Basic Rate Access
CATV Community Antenna TeleVision / Cable TV
CRC Cyclic Redundancy Check
DAVIC Digital AudioVIsual Council
DVB Digital Video Broadcasting
EMC ElectroMagnetic Compatibility
ESF Extended SuperFrame
FAS Frame Alignment Signal
FDM Frequency Division Multiplex
FEC Forward Error Correction
IB In-Band
IC Interaction Channel
INA Interactive Network Adapter
IQ In-phase and Quadrature components
IRD Integrated Receiver Decoder
ISDN Integrated Services Digital Network
LFSR Linear Feedback Shift Register
LSB Least Significant Bit
MAC Media Access Control
MMDS Multi-channel Multi-point Distribution System
MPEG Motion Picture Expert Group
MSB Most Significant Bit
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NIU Network Interface Unit
NSAP Network Service Access Point
OOB Out Of Band
OSI Open Systems Interconnection
PM Pulse Modulation
PSK Phase Shift Keying
PSTN Public Switched Telephone Network
QAM Quadrature Amplitude Modulation
QoS Quality of Service
QPSK Quaternary PSK
RMS Root Mean Square
SL-ESF Signalling Link Extended Superframe
SMATV Satellite Master Antenna Tele-Vision
SNR Signal to Noise power Ratio
STB Set Top Box
STU Set Top Unit
TDMA Time Division Multiple Access
TS Transport Stream
VCI Virtual Channel Identifier
VPI Virtual Path Identifier
4 Reference model
This clause presents the reference model for system architecture of narrowband interaction channels in a
broadcasting scenario (asymmetric interactive services).
4.1 Protocol stack model
For asymmetric interactive services supporting broadcast to the home with narrowband return channel, a
simple communications model consists of the following layers:
Physical layer: Where all the physical (electrical) transmission parameters are defined.
Transport layer: Defines all the relevant data structures and communication protocols like data
containers, etc.
Application layer: Is the interactive application software and runtime environments (e.g. home shopping
application, script interpreter, etc.).
This ETS addresses the lower two layers (the physical and transport) leaving the application layer open to
competitive market forces.
A simplified model of the OSI layers was adopted to facilitate the production of specifications for these
nodes. Figure 1 points out the lower layers of the simplified model and identifies some of the key
parameters for the lower two layers. Following the user requirements for interactive services, no attempt
will be made to consider higher layers in this ETS.

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Layer Structure for Generic System Reference Model
Proprietary
layers
Higher medium
Network Independent
layers
Protocols
Access
mechanism
Packet structure
(Network Dependent
Modulation
Protocols)
Channel coding
Freq. range
Filtering
Equalisation
Power
Figure 1: Layer structure for generic system reference model
This ETS addresses the CATV network specific aspects only. The network independent protocols are
specified separately (ITU-T Recommendation I.361 [4]).
4.2 System model
Figure 2 shows the system model which is to be used within DVB for interactive services.
In the system model, two channels are established between the service provider and the user:
- Broadcast Channel (BC): A uni-directional broadband BC including video, audio and data.
The BC is established from the service provider to the users. It may include the Forward
Interaction path.
- Interaction Channel (IC): A bi-directional IC is established between the service provider and
the user for interaction purposes. It is formed by:
- Return Interaction path: From the user to the service provider. It is used to make
requests to the service provider or to answer questions. It is a narrowband channel.
Also commonly known as return channel.
- Forward Interaction path: From the service provider to the user. It is used to provide
some sort of information by the service provider to the user and any other required
communication for the interactive service provision. It may be embedded into the
broadcast channel. It is possible that this channel is not required in some simple
implementations which make use of the BC for the carriage of data to the user.
The user terminal is formed by the Network Interface Unit (NIU) and the Set Top Unit (STU). The NIU
consists of the Broadcast Interface Module (BIM) and the Interactive Interface Module (IIM). The user
terminal provides interface for both broadcast and interaction channels. The interface between the user
terminal and the interaction network is via the IIM.

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Figure 2: A generic system reference model for interactive systems

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5 DVB interaction channel specification for CATV networks
The CATV infrastructures can support the implementation of the return channel for interactive services
suitable for DVB broadcasting systems.
CATV can be used to implement interactive services in the DVB environment, providing a bi-directional
communication path between the user terminal and the service provider.
5.1 System concept
The interactive system is composed of Forward Interaction path (downstream) and Return Interaction path
(upstream). The general concept is to use downstream transmission from the INA to the NIUs to provide
synchronization and information to all NIUs. This allows the NIUs to adapt to the network and send
synchronized information upstream.
Upstream transmission is divided into time slots which can be used by different users, using the technique
of Time Division Multiple Access (TDMA). One downstream channel is used to synchronize up to
8 upstream channels, which are all divided into time slots. A counter at the INA is sent periodically to the
NIUs, so that all NIUs work with the same clock. This gives the opportunity to the INA to assign time slots
to different users.
Three major access modes are provided with this system. The first one is based on contention access,
which lets users send information at any time with the risk to have a collision with other users'
transmissions. The second and third modes are contention-less based, where the INA either provides a
finite amount of slots to a specific NIU, or a given bit rate requested by a NIU until the INA stops the
connection on NIU's demand. These access modes are dynamically shared among time slots, which
allows NIUs to know when contention based transmission is or is not allowed. This is to avoid a collision
for the two contention-less based access modes.
Periodically, the INA will indicate to new users that they have the possibility to go through sign-on
procedure, in order to give them the opportunity to synchronize their clock to the network clock, without
risking collisions with already active users. This is done by leaving a larger time interval for new users to
send their information, taking into account the propagation time required from the INA to the NIUs and
back.
5.1.1 Out-Of-Band (OOB) / In-Band (IB) principle
This interactive system is based either on OOB or IB downstream signalling. However, Set Top Boxes
(STB) do not need to support both systems.
In the case of OOB signalling, a Forward Interaction path is added. This path is reserved for interactivity
data and control information only. The presence of this added Forward Information path is in that case
mandatory. However, it is also possible to send higher bit rate downstream information through a DVB
cable channel whose frequency is indicated in the forward information path.
In the case of IB signalling, the Forward Information path is embedded into the MPEG-2 TS of a DVB
cable channel. It is not mandatory to include the Forward Information path in all DVB cable channels.
Both systems can provide the same quality of service. However, the overall system architecture will differ
between networks using IB and OOB STBs. Both types of systems may exist on the same networks under
the condition that different frequencies are used for each system.
5.1.2 Spectrum allocation
Figure 3 indicates a possible spectrum allocation. Although not mandatory, a guideline is provided to use
the following preferred frequency ranges, 70 MHz to 130 MHz and/or 300 MHz to 862 MHz for the
Forward Interaction path (downstream OOB) and 5 MHz to 65 MHz for the Return Interaction path
(upstream), or parts thereof. To avoid filtering problems in the bi-directional RF amplifiers and in the
STBs, the upper limit 65 MHz for the upstream flow shall not be used together with the lower limit 70 MHz
for the downstream flow in the same system. For passive networks, the frequency range 5 MHz to 65 MHz
could be used bi-directionally. Furthermore, to avoid intermediate frequency impairments of STBs as well

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as analogue receivers in the same network, it could be necessary to leave out some parts of the range
5 MHz to 65 MHz which includes the intermediate frequency ranges of these appliances.
NOTE: To fix detailed limits for the usable frequency range(s), future investigations concerning
the intermediate frequency immunity of receivers shall be carried through.
DVB-C QAM 7/8 MHz channels
Downstream
70-130 MHz 300-862 MHz
....
Frequency (MHz)
....
QPSK interactive 1 or 2 MHz downstream OOB channel
5 - 65 MHz
QPSK interactive 1 or 2 MHz or 200 KHz upstream channels
Upstream
Figure 3: DVB preferred frequency ranges for CATV interactive systems
5.1.3 FDM/TDMA multiple access
A multiple access scheme is defined in order to have different users share the same transmission media.
Downstream information is sent broadcast to all users of the networks. Thus, an address assignment
exists for each user which allows the INA to send information singlecast to one particular user. Two
addresses are stored in STBs in order to identify users on the network:
MAC address: It is a 48-bit value representing the unique MAC address of the NIU. This MAC
address may be hard coded in the NIU or be provided by external source.
NSAP address: It is a 160-bit value representing a network address. This address is provided
by higher layers during communication.
Upstream information may come from any user in the network and shall therefore also be differentiated at
the INA using the set of addresses defined above.
Upstream and OOB downstream channels are divided into separate channels of 1 MHz or 2 MHz
bandwidth for downstream and 1 MHz or 2 MHz or 200 kHz for upstream. Each downstream channel
contains a synchronization frame used by up to 8 different upstream channels, whose frequencies are
indicated by the Media Access Control (MAC) protocol.
Within upstream channels, users send packets with TDMA type access. This means that each channel is
shared by many different users, who can either send packets with a possibility of collisions when this is
allowed by the INA, or request transmission and use the packets assigned by the INA to each user
specifically. Assuming each channel can therefore accommodate thousands of users at the same time,
the upstream bandwidth can easily be used by all users present on the network at the same time.
The TDMA technique utilizes a slotting methodology which allows the transmit start times to be
synchronized to a common clock source. Synchronizing the start times increases message throughput of
this signalling channel since the message packets do not overlap during transmission. The period
between sequential start times are identified as slots. Each slot is a point in time when a message packet
can be transmitted over the signalling link.
The time reference for slot location is received via the downstream channels generated at the delivery
system and received simultaneously by all set-top units. Note that this time reference is not sent in the
same way for OOB and IB signalling. Since all NIUs reference the same time base, the slot times are

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ETS 300 800: July 1998
aligned for all NIUs. However, since there is propagation delay in any transmission network, a time base
ranging method accommodates deviation of transmission due to propagation delay.
Since the TDMA signalling link is used by NIUs that are engaged in interactive sessions, the number of
available message slots on this channel is dependent on the number of simultaneous users. When
messaging slots are not in use, an NIU may be assigned multiple message slots for increased messaging
throughput. Additional slot assignments are provided to the NIU from the downstream signalling
information flow.
There are different access modes for the upstream slots:
- reserved slots with fixed rate reservation (Fixed rate access: the user has a reservation of one or
several timeslots in each frame enabling, e.g. for voice, audio);
- reserved slots with dynamic reservation (Reservation access: the user sends control information
announcing his demand for transmission capacity. He gets grants for the use of slots);
- contention based slots (These slots are accessible for every user. Collision is possible and solved
by a contention resolution protocol);
- ranging slots (these slots are used upstream to measure and adjust the time delay and the power).
These slots may be mixed on a single carrier to enable different services on one carrier only. If one carrier
is assigned to one specific service, only those slot types will be used which are needed for this service.
Therefore a terminal can be simplified to respond to only those slot types assigned to the service.
5.1.4 Bit rates and framing
For the interactive downstream OOB channel, a rate of 1,544 Mbit/s or 3,088 Mbit/s may be used. For
downstream IB channels, no other constraints than those specified in the DVB cable specifications
(EN 300 429 [2]) exist, but a guideline would be to use rates multiples of 8 kbit/s.
Downstream OOB channels continuously transmit a frame based on T1 type framing, in which some
information is provided for synchronization of upstream slots. Downstream IB channels transmit some
MPEG-2 TS packets with a specific PID for synchronization of upstream slots (at least one packet
containing synchronization information shall be sent in every period of 3 ms).
For upstream transmission, the INA can indicate three types of transmission rates to users, specifically
3,088 Mbit/s, 1,544 Mbit/s or 256 kbit/s. The INA is responsible of indicating which rate may be used by
NIUs. It would imply all NIUs to be able to either transmit with 256 kbit/s, 1,544 Mbit/s or 3,088 Mbit/s.
Only the implementation of one of these bit rates would be mandatory.
Upstream framing consists of packets of 512 bits (256 symbols) which are sent in a bursty mode from the
different users present on the network. The upstream slot rates are 6 000 upstream slots/s when the
upstream data rate is 3,088 Mbit/s, 3 000 upstream slots/s when the upstream data rate is 1,544 Mbit/s
and 500 upstream slots/s when the upstream data rate is 256 kbit/s.
5.2 Lower physical layer specification
In this subclause, detailed information is given on the lower physical layer specification. Figures 4 and 5
show the conceptual block diagrams for implementation of this ETS.

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Figure 4: Conceptual block diagram for the NIU OOB transceiver
Figure 5: Conceptual block diagram for the OOB Head-end transceiver

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ETS 300 800: July 1998
Figure 6: Conceptual block diagram for the IB NIU transceiver
Figure 7: Conceptual block diagram for the IB head-end transceiver
5.2.1 Forward Interaction path (Downstream OOB)
5.2.1.1 Frequency range (Downstream OOB)
The frequency range is not specified as mandatory although a guideline is provided to use the following
preferred frequency ranges, 70 MHz to 130 MHz and/or 300 MHz to 862 MHz or parts thereof, in order to
simplify the tuner of the NIU. Frequency stability shall be in the range – 50 ppm measured at the upper
limit of the frequency range.
5.2.1.2 Modulation and mapping (Downstream OOB)
QPSK modulation is used as a means of encoding digital information over wireline or fibre transmission
links. The method is a subset of Phase Shift Keying (PSK) which is a subset of Phase Modulation (PM).
Specifically QPSK is a four level use of digital PM. Quadrature signal representations involve expressing
an arbitrary phase sinusoidal waveform as a linear combination of a cosine wave and a sine wave with
zero starting phases.
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QPSK systems require the use of differential encoding and corresponding differential detection. This is a
result of the receivers having no method of determining if a recovered reference is a sine reference or a
cosine reference. In addition, the polarity of the recovered reference is uncertain.
Differential encoding transmits the information in encoded phase differences between the two successive
signals. The modulator processes the digital binary symbols to achieve differential encoding and then
transmits the absolute phases. The differential encoding is implemented at the digital level.
The differential encoder shall accept bits A, B in sequence, and generate phase changes as follows:
Table 1: Phase changes associated with bit A, B
A B Phase Change
0 0 none
0 1 +90°
1 1 180°
1 0 -90°
In serial mode, A arrives first. The outputs I, Q from the differential encoder map to the phase states as in
figure 8.
Q
01 11
I
00 10
Figure 8: Mapping for the QPSK constellation (downstream OOB)
The phase changes can also be expressed by the following formulas (assuming the constellation is
mapped from I and Q as shown in subclause 5.2.2.2):
·()( )( )( )
AI=¯Q Q¯+Q¯I·Q¯I I
kk--11k-k1 k k-k1 k-k1

BI=¯·()Q(I¯+I)¯(I·Q¯)(Q Q)
kk--11k-k1 k-k1 k k-k1
where k is the time index.
I/Q amplitude imbalance shall be less than 1,0 dB, and phase imbalance less than 2,0°.
5.2.1.3 Shaping filter (Downstream OOB)
The time-domain response of a square-root raised-cosine pulse with excess bandwidth parameter a is
given by:
pt 4apt t
sin[(1-+a)] cos[(1+a)]
T T T
() =
gt
pat 4 t
[(-1 )]
T T
where T is the symbol period.
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The output signal shall be defined as:
St( )=·[I g(-t nT·) cos(-22ppf t) Q·-g(t nT·) sin( f t)]
∑
ncn c
n
with I and Q equal to ±1, independently from each other, and f the QPSK modulator's carrier frequency.
n n c
The QPSK modulator divides the incoming bit stream so that bits are sent alternately to the in-phase
modulator I and the out-of-phase modulator Q. These same bit streams appear at the output of the
respective phase detectors in the demodulator where they are interleaved back into a serial bit stream.
The occupied bandwidth of a QPSK signal is given by the equation:
f
b
Bandwidth = (1 + a);
f = bit rate;
b
excess bandwidth = 0,30.
a =
For both bit rates, 1,544 Mbit/s (Grade A) and 3,088 Mbit/s (Grade B), the power spectrum at the QPSK
transmitter shall comply to the power spectrum mask given in table 2 and figure 9. The power spectrum
Mask shall be applied symmetrically around the carrier frequency.
Table 2: QPSK downstream transmitter power spectrum
| (f - f ) / f | Power spectrum
c N
£ 1-a0 – 0,25 dB
at 1
-3 – 0,25 dB
at 1+a£ -21 dB
‡ 2£ -40 dB
H(f)
in-band ripple r < 0.5 dB
m
| (f - f ) / f |
c N
r Nyquist ripple r .< 0.5 dB
m N
0 dB
-3dB r out-of-band
N
rejection
-21 dB > 40dB
-40 dB
1 2
1-a1+a
Figure 9: QPSK downstream transmitter power spectrum
QPSK systems require the use of differential encoding and corresponding differential detection. This is a
result of the receivers having no method of determining if a recovered reference is a sine reference or a
cosine reference. In addition, the polarity of the recovered reference is uncertain.
Differential encoding transmits the information in encoded phase differences between the two successive
signals. The modulator processes the digital binary symbols to achieve differential encoding and then
transmits the absolute phases. The differential encoding is implemented at the digital level.

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5.2.1.4 Randomizer (Downstream OOB)
After addition of the Forward Error Correction (FEC) bytes (see subclause 5.3), all of the 1,544 Mbit/s (or
3,088 Mbit/s) data is passed through a six register Linear Feedback Shift Register (LFSR) randomizer to
xx++ 1
ensure a random distribution of ones and zeroes. The generating polynomial is: . Byte/serial
conversion shall be MSB first. A complementary self-synchronizing de-randomizer is used in the receiver
to recover the data.
Figure 10: Randomizer
Figure 11: De-randomizer
5.2.1.5 Bit rate (Downstream OOB)
The bit rate shall be 1,544 Mbit/s or 3,088 Mbit/s. Only one of the bit rates is mandatory in the NIU.
Symbol rate accuracy should be within ± 50 ppm.
5.2.1.6 Receiver power level (Downstream OOB)
The receiver power level shall be in the range 42 to 75 dBmV rms (75 W) at its input.

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5.2.1.7 Summary (Downstream OOB)
Table 3: Summary (Downstream OOB)
Transmission rate 1,544 Mbit/s for Grade A
3,088 Mbit/s for Grade B
Modulation Differentially encoded QPSK
Transmit filtering Filtering is alpha = 0,30 square root raised cosine
Channel spacing 1 MHz for Grade A
2 MHz for Grade B
Frequency step size 250 kHz (centre frequency granularity)
Randomization After addition of the FEC bytes, all of the 1,544 Mbit/s (or 3,088 Mbit/s)
data is passed through a six register Linear Feedback Shift Register
(LFSR) randomizer to ensure a random distribution of ones and
zeroes. The generating polynomial is: xx++ 1.
Byte/serial conversion shall be MSB first.
A complementary self-synchronizing de-randomizer is used in the
receiver to recover the data.
Differential encoding The differential encoder shall accept bits A, B in sequence, and
generate phase changes as follows:
A B Phase change
0 0 none
0 1 +90°
1 1 180°
1 0 -90°
In serial mode, A arrives first.
Signal constellation The outputs I, Q from the differential encoder map to the phase states
as in figure 12.
Frequency range recommended but not mandatory 70 MHz to 130 MHz and/or
300 MHz to 862 MHz
Frequency stability ± 50 ppm measured at the upper limit of the frequency range
Symbol rate accuracy ± 50 ppm
Carrier suppression > 30 dB
I/Q amplitude < 1,0 dB
imbalance
I/Q phase imbalance < 2,0°
Receive power level at 42 - 75 dBmV rms (75 W)
input
Transmission rate 1,544 Mbit/s for Grade A
3,088 Mbit/s for Grade B
Transmit spectral mask A common mask for both bit rates: 1,544 Mbit/s (Grade A) and
3,088 Mbit/s (Grade B) is given in table 2 and figure 9.
Q
01 11
I
00 10
Figure 12
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ETS 300 800: July 1998
5.2.1.8 Bit error rate downstream OOB (informative)
-10
Bit error rate at the NIU should be less than 10 (after error correction, i.e. 1 error in 2 hours at
1,5 Mbit/s) at C/N > 20 dB for downstream transmission. C/N is the Carrier-to-Noise ratio relevant for the
demodulation process (Nyquist bandwidth for white noise).
5.2.2 Forward Interaction Path (Downstream IB)
The IB Forward Interaction Path shall use a MPEG-2 TS stream with a modulated QAM channel as
defined by EN 300 429 [2]. Frequency range, channel spacing, and other lower physical layer parameters
should follow that specification.
5.2.3 Return Interaction Path (Upstream)
5.2.3.1 Frequency range (Upstream)
The frequency range is not specified as mandatory although a guideline is provided to use the 5 MHz to
65 MHz. Frequency stability shall be in the range ± 50 ppm measured at the upper limit of the frequency
range.
5.2.3.2 Modulation and mapping (Upstream)
The unique word (CC CC CC 0D, see subclause 5.3 for upstream framing) is not differentially encoded,
the outputs I, Q map to the phase states as in figure 13.
Q
01 11
I
00 10
Figure 13: Mapping for the QPSK constellation (upstream)
For the remainder of the packet, the differential encoder shall accept bits A, B in sequence, and generate
phase changes as follows. It starts with the first information di-bit and is initialized with the last di-bit of the
unique word, i.e. (A,B = 0,1) since conversion is made MSB first.
Table 4: Phase changes corresponding to bits A, B
A B Phase change
0 0 none
0 1 +90°
1 1 180°
1 0 -90°
Phase changes correspond to the following formulas (assuming I and Q are mapped to the constellation
as for the unique word):
AI=¯·()Q(Q¯+Q)¯(I·Q¯)(I I)
kk--11k-k1 k k-k1 k-k1

BI=¯·()Q(I¯+I)¯(I·Q¯)(Q Q)
kk--11k-k1 k-k1 k k-k1
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ETS 300 800: July 1998
where k is the time index.
I/Q amplitude imbalance shall be less than 1,0 dB, and phase imbalance less than 2,0°.
5.2.3.3 Shaping filter (Upstream)
The time-domain response of a square-root raised-cosine pulse with excess bandwidth parameter a is
given by:
pt 4apt t
sin[(1-+a)] cos[(1+a)]
T T T
gt() =
pa
t 4 t
[(-1 )]
T T
where T is the symbol period.
The output signal shall be defined as:
St( )=·∑ [I g(t-nT·) cos(-22ppf t) Q·-g(t nT·) sin( f t)]
ncn c
n
with I and Q equal to ±1, independently from each other, and f the QPSK modulator's carrier frequency.
n n c
The QPSK modulator divides the incoming bit stream so that bits are sent alternately to the in-phase
modulator I and the out-of-phase modulator Q. These same bit streams appear at the output of the
respective phase detectors in the demodulator where they are interleaved back into a serial bit stream.
The QPSK signal parameters are:
RF bandwidth BW = (f / 2) · (1 + a)
b
Occupied RF spectrum [f - BW/2 , f + BW/2]
c c
Symbol rate f = f / 2
s b
Nyquist frequency f = f / 2
N s
with f = bit rate, f = carrier frequency and a = excess bandwidth.
b c
For all three bit rates: 256 kbit/s (Grade A), 1,544 Mbit/s (Grade B) and 3,088 Mbit/s (Grade C), the power
spectrum at the QPSK transmitter shall comply to the power spectrum mask given in table 5 and
figure 14. The power spectrum mask shall be applied symmetrically around the carrier frequency.
Table 5: QPSK upstream transmitter power spectrum
| (f - f ) / f | Power Spectrum
c N
£ 1-a0 – 0,25 dB
at 1
-3 – 0,25 dB
at 1+a£ -21 dB
‡ 2£ -40 dB
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ETS 300 800: July 1998
H(f)
in-band ripple r < 0.5 dB
m
| (f - f ) / f |
c N
r Nyquist ripple r .< 0.5 dB
m N
0 dB
-3dB r out-of-band
N
rejection
-21 dB > 40dB
-40 dB
1a2
1-a1+
Figure 14: QPSK upstream transmitter power spectrum
The specifications which shall apply to QPSK modulation for the upstream channel are given in table 4.
5.2.3.4 Randomizer (Upstream)
The unique word shall be sent in clear (see subclause 5.3). After addition of the FEC bytes, randomization
shall apply only to the payload area and FEC bytes, with the randomizer performing modulo-2 addition of
the data with a pseudo-random sequence. The generating polynomial is xx++ 1 with seed all ones.
We assume the first value coming out of the pseudo-random generator taken into account is 0. Byte/serial
conversion shall be MSB first. The binary sequence generated by the shift register starts with 00000100…
The first "0" is to be added in the first bit after the unique word.
A complementary non self-synchronizing de-randomizer is used in the receiver to recover the data.
The de-randomizer shall be enabled after detection of the unique word.
Figure 15: Randomizer
5.2.3.5 Bit rate (Upstream)
Three grades of modulation transmission rate are specified. Upstream bit-rates for modulation grades A,
B and C are as follows:
Grade Rate
A 256 kbit/s
B 1,544 Mbit/s
C 3,088 Mbit/s
A QPSK modulator (NIU transmitter) may support A, B and C grades of transmission rate. Only the
implementation of one of these grades should be mandatory. A QPSK demodulator (INA receiver) shall
support at least one grade A, B or C, but may support all grades.

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ETS 300 800: July 1998
Symbol rate accuracy should be within ± 50 ppm.
For grade A, the rate is 500 slots/s. For grade B, the rate is 3 000 slots/s. For grade C, the rate is
6 000 slots/s.
5.2.3.6 Transmit power level (Upstream)
At the output, the transmit power level shall be in the range 85 to 113 dBmV rms (75 W). In some
geographic areas, it may be necessary to cover the range 85 to 122 dBmV rms (75 W). However, high
power may lead to ElectroMagnetic Compatibility (EMC) problems. This power shall be adjusted by steps
of 0,5 dB by MAC messages coming from the INA.
5.2.3.7 Carrier suppression when idle (Upstream)
The carrier suppression shall be more than 60 dB below nominal power output level, over the entire power
output range. A terminal is considered to be idle if it is 3 slots before an imminent transmission or 3 slots
after its most recent transmission.

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ETS 300 800: July 1998
5.2.3.8 Summary (Upstream)
Table
...