DVB - IHDN 012 rev.6
DVB - TM 2003 rev.1
In-Home Digital Network IHDN
The document summarises the common understanding for the work and the present status of
the AHG DVB-IHDN. For in-home digital networks, it presents the
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Scope
Applications
Architecture
Technical requirements
IHDN implementation examples
Basis for the work is the ISCM requirements document TM 1690 rev.1.
The document is the base of a new guidelines document describing the implementation and
use of In-Home Digital Networks.
1. Scope of the IHDN specifications
 Network lower layers and interfaces
The in-home network itself and its interfaces to the connected devices will be
specified. The specification is transparent to the higher layers. The presently installed
in-home networks like coaxial cables for RF distribution are part of the IHDN
architecture.
The IHDN provides interfaces to different broadband access networks, and broadcast
delivery and interaction media, for example the Telco network with xDSL, the
HFC/FTTx network, and all DVB scenarios with satellite, cable, terrestrial,
SMATV/MATV, MMDS/LMDS including the interaction channels.
 Network independent higher protocols
For example signalling and control between STB and storage device.
 Wireline in-home networks have first priority, wireless networks are future options
 IHDN implementation guidelines will be added
2. Applications of the IHDN
The IHDN supports all DVB based broadcast and interactive broadcast applications and DVB
relevant telecom based services:
 Use in private homes, for all types of terminals
Business applications are not specifically included.
 Broadcast and interactive multimedia services
Other (narrowband) applications like home control are not specifically
considered.
 Digital interconnection of devices like DVB-STBs, PCs, printers, storage devices
For example, a STB establishes logical links to a digital video recorder to store a TV
program, and to a PC to process data broadcast information.
 Connection of such devices to telecom networks
A STB or a PC can be connected to a telecom network via a network termination NT.
This enables many applications, e.g. a video-on-demand service via a NT to the STB
or a high speed Internet access via a cable modem to the PC.
3. Architecture
In-Home Digital Network IHDN, 06. 03. 1998
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The IHDN can be subdivided into a Home Access Network (HAN) for the connection to
external networks and a Home Local Network (HLN) for interconnections of user equipment to
clusters and between rooms.
In addition to the already specified access technologies DVB-S, -C, -T, -SMATV, -MMDS with
the interaction channels for interactive broadcast services, the IHDN-HAN specification will
focus on the definition of new interfaces and network terminations (NT), such as an xDSL
modem or an external cable modem. The existing DVB transmission systems form part of the
HAN architecture, but access the IRD without any influence from other sections of the HAN.
Different versions of HAN and HLN are possible. The prime candidate for the HAN with an
active Telco NT is an ATM interface with physical layer 25/51 Mbps. For all HLN networks the
IEEE 1394 interface with the long reach extension has been decided.
Figure 1 shows the extension of the DVB interactive systems reference model with the IHDN.
The network clouds on the left hand show logically the association to corresponding services
(broadcast, interactive broadcast, interactive multimedia services). Physically they may
overlap and not all of them may be used in parallel. New is the Telco broadband access
network, which enables broadband multimedia services, such as video on demand and
switched digital broadcast, over twisted pair lines with an xDSL modem. It may also be used
for interaction purposes in combination with any broadcast delivery network.
The HAN interconnects the various access networks and the network termination systems. NT
functionality may be integrated in the STB or PC as with the existing DVB systems, or in a
gateway device which feeds the access network directly to the HLN. IHDN specific is the
provision of new NT functionality for access networks.
Broadcasting
Delivery
Network
Broadcast
Channel
(e.g. Sat., CATV, terr., MMDS)
Set Top Box
existing
DVB
Return
Interaction Path
Camcorder
Network
Interface
Unit
Set Top
Unit
Interaction
Network
(e.g. PSTN/ISDN, CATV, Sat., MMDS)
Interaction
Channels
DVC
PC
Access Network
HAN-NT: HAN-Network Termination
HAN-NT
IHDN
specific
(e.g. xDSL, CATV/HFC)
Printer
IEEE
1394
HAN-NT
Forward
Interaction Path
HLN
Broadband
and Interaction
Channels
DVD
Gateway
HAN
IHDN interfaces
Fig.1: Reference model for interactive systems with extensions for IHDN
A high level IHDN architecture is shown in Fig. 2 with the attempt to demonstrate the various
possibilities to establish a HAN network and to interface the consumer devices STB/PC. In
contrast to Fig.1 the network clouds are now separated physically and also the in-home wiring
for the HAN is described physically (Coax, TP, UTP5). Not all broadcast and access networks
will be used in parallel but some of them. Chapter 5 discusses some implementation
examples.
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Coax
TP
IEEE 1394
UTP5
Terrestrial
MMDS/LMDS
DCB-C, S, T,...
PSTN/ISDN, RCC,
ATM
MMDS
transceiver
Camcorder
DECT
DECT
Wireless Local Loop
Printer
Set Top Box
DECT
transceiver
long reach
IEEE 1394
PSTN/ISDN
Satellite
CATV/HFC
Sat-NT
DVC
Cable-NT
DVD
cable modem
Multimedia PC
Broadband
Access Network
Broadcast/ Access
Network
Telco-NT
xDSL modem
Home
Access Network
Home
Local Network
Fig. 2: High level physical architecture of an In-home Network
The HAN for a Telco broadband access is based on an active NT with ADSL/VDSL. An active
NT separates the access network and home environment, and permits the use of
transmission systems and functionality. The passive NT case, where the in-home distribution
is simply an extension of the access network, is both complex from the transmission point of
view and functionally limited, and so is not covered by this specification.
For a CATV/HFC network, several solutions for the HAN are possible: That is a cable modem
without any network termination functionality which serves as physical extension of the
CATV/HFC network. Other solutions are cable-NTs with active or passive termination
functionalities. A passive cable NT will be mounted on the home entry point. The in-home
coax can now feed to the termination points for interactive services which are STB, PC or an
external cable modem. The cable modem with active NT case could be based on ATM as for
the Telco broadband NT but other options such as IEEE 1393 long reach, USB or Ethernet
may also be considered. It terminates the interactive services while all DVB broadcast
services are directly passed to STB or PC.
The Home Local Network for internal terminal-to-terminal communication is IEEE 1394 based.
The standard IEEE 1394-1995 physical layer is restricted to a cable length of 4.5 m. The cable
length can be extended using long reach 1394 with POF (50 m) or UTP (100 m) cable and
100 Mbps bitrate. The 1394 repeater converts POF/UTP 1394 signals to standard 1394
signals and vice versa and links the clusters.
The long reach specification of IEEE 1394 is not yet finalised.
4. Technical Requirements for IHDN
Edt. comment: A split of the technical requirements for HAN and HLN could structure the list.
 Broadband digital bi-directional interconnection of devices
 Multiple internal and external logical connections simultaneously
 Scaleable bitrate for each logical connection
 Channel capacity at least 50 Mbps, and up to 200 Mbps (half duplex)
Transport of decoded video streams (ITU-R rec. 601) is not required.
 Capable of real-time services
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Video and audio real-time transport are guaranteed without disturbance, even when
parallel applications are using the same network within the bandwidth limitations .
The network is transparent and supports protocols like MPEG-TS, ATM, and IP. It may
support protocols like MPEG-PS and DVC-SD.
Self organising network
Devices may be added to or removed from the network without interruption or
manual reconfiguration of the IHDN.
Fair multiple access to the IHDN for several devices
Number of devices connected to the IHDN: min. 2, max. 16
Max. distance of the network: 50 m without repeater, > 50 m with repeater
Compliance with interference limits (especially for wireless solutions)
Simple wiring with few wires in a thin cable, simple connectors
Network management tbd.
Security tbd.
5. IHDN implementation examples
Different versions for HAN and HLN are possible. Chapter 5.1 discusses two implementation
examples with an active Telco-NT based on ADSL. The in-home coax will be used to provide
all types of DVB broadcast and interactive services and the ADSL modem will be used to
provide additional multimedia services but also as a means for DVB interaction channel.
Chapters 5.2 and 5.3 show implementation examples where DVB-broadcast services and
interactive services are provided via CATV/HFC network to the STB and PC. In 5.2 the cable
modem will be used to terminate actively the cable network at the home entry point. Both user
terminals STB and PC will use the cable modem for DVB interaction channel purposes and
therefore it has to be DVB compliant. In 5.3 the cable modem will be used in parallel to DVB
broadcast and interactive services. It might be proprietary and will provide additional
multimedia services to STB and PC.
Each of the implementation examples shows a consistent solution for broadcast and
interactive services. Additional solutions and combinations are possible.
5.1 IHDN with active Telco-NT for Telco broadband access
Figures 3a and 3b show implementation examples where DVB-broadcast services will be
provided via in-home coax to the STB and PC. DVB interactive services via any kind of DVB
interaction channel may be supported in parallel. Additional interactive broadband services will
be delivered via Telco-NT to STB and PC.
Figure 3a shows a HAN based on a Telco-NT with ATM interfaces on STB and PC. The inhome coax provides all DVB broadcast and interactive services, whereas the Telco
broadband access provides additional interactive services to the STB and PC.
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TV
Camera
all DVB broadcast and
interactive systems
DVB
In-home Coax
IEEE 1394
ATM
xDSL
modem
Splitter
Telco-NT
TP
DVC/
DVHS
STB
UTP5
1394
Repeater
ATM
long reach
1394
ATM
DVB
UTP5
1394
Repeater
PC
IEEE 1394
ATM
POTS
Printer
HAN
Fig. 3a:
HLN
IHDN implementation with Telco broadband access.
HAN with ATM interfaces at the STB and PC, HLN with IEEE 1394.
Figure 3b shows a similar version for Telco broadband access where the STB does not have
an ATM interface. An NIU is used to interconnect the Telco-NT and STB. The NIU terminates
ATM and outputs data to the IEEE 1394 HLN. In this way data provisioning for the PC is also
possible and it may replace the direct Telco-NT to PC connection.
TV
Camera
all DVB broadcast and
interactive systems
DVB
DVC/
DVHS
STB
In-home Coax
TP
xDSL
modem
Splitter
Telco-NT
IEEE1394
1394
Repeater
UTP5
ATM
NIU
long reach
1394
ATM
1394
Repeater
DVB
PC
UTP5
ATM
IEEE1394
POTS
HAN
Fig. 3b:
HLN
Printer
IHDN implementation with Telco broadband access. The STB
does not have an ATM interface. NIU interconnects ATM-based
HAN and IEEE 1394-based HLN.
5.2 IHDN with active Cable-NT for CATV/HFC broadband access
Figure 4a shows a version with CATV/HFC broadband access. The cable modem is now the
active NT for all interactive services, while the STB or PC terminates the DVB broadcast
service DVB-C. The Cable-NT is directly connected to the HLN via IEEE 1394. Both STB and
PC communicate via IEEE 1394 with the cable modem for interactive services. The interaction
channel is provided via IEEE 1394 to the Cable-NT and the HFC network. Therefore the cable
modem has to be DVB compliant.
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This solution enables a defined termination of the HFC network at the entry point of the home
and avoids ingress via the in-home coax. The Cable-NT is the single DVB-RC termination
point for all terminals.
TV
Camera
DVB-C
DVB
STB
In-home Coax
DVC/
DVHS
IEEE1394
Cable-NT
other
CATV
Cable
Modem
1394
Repeater
IEEE 1394
long reach
1394
IEEE 1394
DVB
ATM
PC
ATM
IEEE1394
Printer
Access Home
Fig. 4a:
1394
Repeater
HLN
HAN
IHDN implementation with CATV/HFC broadband access.
The cable modem is a real NT for interactive services with
IEEE 1394 interface directly connected to the HLN.
5.3 IHDN with Cable modem for CATV/HFC broadband access
Figure 4b shows a solution which uses the in-home coax network as a physical extension of
the HFC network for broadcast and interactive services. The access network is terminated in
the STB, or in the DVB interface card of a PC, or in an external cable modem. If there is an
ATM interface to the STB, a cable modem can provide ATM based multimedia services as
well to the STB. The HAN is not mandatory for all alternatives. Besides ATM interface,
Ethernet or IEEE 1394 are possible interfaces between cable modem and PC.
TV
Camera
DVB-C and
interaction channel
In-home Coax
DVB
STB
STB
ATM
DVC/
DVHS
IEEE1394
CATV
1394
Repeater
long reach
1394
ATM
In-home
Coax
Cable
Modem
DVB
other
ATM
1394
Repeater
PC
IEEE1394
ATM
Printer
Access Home
Fig. 4b:
Editors:
HAN
HLN
IHDN implementation with CATV/HFC broadband access.
The cable modem provides additional multimedia services via
ATM interface.
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Walter Tengler, Rainer Lüder
Siemens AG
Tel.: +49 89 722 47374
E-mail: walter.tengler@oen.siemens.de