ETSI ETS 300 800 ed.1 (1998-07)

SLOVENSKI STANDARD
SIST ETS 300 800 E1:2003
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

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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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

5.2.1.5 Bit rate (Downstream OOB).................................................18

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

5.2.3.3 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

5.2.3.8 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

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

5.5.1 MAC reference model................................................................................... 44

5.5.2 MAC concept ................................................................................................ 45

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

Downstream)....................................................................... 53

Downstream)....................................................................... 54

5.5.4 Sign-On and Calibration ............................................................................... 56

Downstream)....................................................................... 59

Downstream)....................................................................... 61

5.5.5 Default Connection Establishment................................................................ 61

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

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,

members in about 60 countries in the European broadcasting area; its headquarters is

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

This ETS is the baseline specification for the provision of interaction channel for Cable TV (CATV)

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

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

This clause presents the reference model for system architecture of narrowband interaction channels in a

For asymmetric interactive services supporting broadcast to the home with narrowband return channel, a

Physical layer: Where all the physical (electrical) transmission parameters are defined.

Transport layer: Defines all the relevant data structures and communication protocols like data

Application layer: Is the interactive application software and runtime environments (e.g. home shopping

This ETS addresses the lower two layers (the physical and transport) leaving the application layer open to

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

This ETS addresses the CATV network specific aspects only. The network independent protocols are

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 Channel (IC): A bi-directional IC is established between the service provider and

- 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.

- 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

broadcast channel. It is possible that this channel is not required in some simple

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

The CATV infrastructures can support the implementation of the return channel for interactive services

CATV can be used to implement interactive services in the DVB environment, providing a bi-directional

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

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

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

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

This interactive system is based either on OOB or IB downstream signalling. However, Set Top Boxes

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

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

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

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

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

MAC address: It is a 48-bit value representing the unique MAC address of the NIU. This MAC

NSAP address: It is a 160-bit value representing a network address. This address is provided

Upstream information may come from any user in the network and shall therefore also be differentiated at

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

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

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

aligned for all NIUs. However, since there is propagation delay in any transmission network, a time base

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

- reserved slots with fixed rate reservation (Fixed rate access: the user has a reservation of one or

- 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

- 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.

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

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