Digital Switchover: An alternative solution towards
broadband access for all citizens
E. Pallis
1
, C. Mantakas
2
, G. Xilouris
3
, G. Gardikis
3
, A. Kourtis
3
1
Centre for Technological Research of Crete, Estavromenos, Heraklion , 71500 Greece
2
METIL Telecom consultant, Spetses, 18050, Greece,
3
National Centre for Scientific Research Demokritos, Institute of Informatics and
Telecommunications, Patriarxou Grigoriou, Agia Paraskevi, Athens, 15310, Greece
Keywords. Internet services, Dial-up networking
Abstract. The paper anticipates that the actions to be taken concerning the
Digital Switchover (transition form analogue to digital broadcasting – DSO) in
UHF are of strategic importance for the European Member Countries and most
candidate ones, as long as DSO arises as a possible and complementary solution
towards the deployment of Broadband Access Infrastructures, especially in less
favoured regions. Taking into account the networking potentialities of the new
digital TV in UHF (Terrestrial Digital Video Broadcasting – DVB-T) and the
broadband capabilities of the recent access technologies (i.e. WLAN, UMTS,
etc.), the paper proposes a networking infrastructure that utilises the DVB-T
stream in regenerative configurations for the realization of a common Ethernet
backbone capable to interconnect all citizens within the broadcasting area.
Citizens access this backbone via appropriate Distribution Nodes (DN), which
make use of broadband access technologies. Such an approach enables for a
multi-service capable environment (digital TV programmes, Interactive TV
programmes, Internet access, e-mail, video/audio on demand, etc.), which is
commonly shared among broadcasters, telecom operators and any active citizen
who creates, manipulates and distributes his own content to the entire
infrastructure (MPEG-21 approach).
1 Introduction
Despite the intrinsic technological differences between Telecommunications and
Digital Broadcasting sectors, a notion of convergence has been recently achieved not
only at technological level, but also at service level. This convergence was mainly
empowered in European level by the work carried out in the field of ‘Interactive
Broadcasting’, which was the subject of innovative work carried out by a number of
Pallis E., Mantakas C., Xilouris G., Gardikis G. and Kourtis K. (2004).
Internet services, Dial-up networking..
In Proceedings of the 1st International Workshop on Shaping the Broadband Society, pages 31-40
DOI: 10.5220/0001404200310040
Copyright
c
SciTePress
Research and Development projects in the 5th European Framework Programme. The
ultimate goal of these projects was to provide new affordable services to the users,
fulfilling two observed tendencies: i) the personalisation of services, that cannot be
offered by traditional one-to-many broadcasting networks, and ii) the consumption of
bandwidth hungry multimedia services that cannot be offered by existing
communication networks especially on the move. The objective of further
development of the subject of Interactive Broadcasting was confronted by the
European commission in a lately organised workshop that identified the technological
and service issues which require further R&D including: i) video and audio delivery
to mobile terminals, ii) traffic symmetry/asymmetry, iii) market prospects of the
introduction of new services and applications, vi) regulatory and spectrum issues, and
finally, and most predominant, the need of synergy (better than convergence) between
broadcasters and telecom operators towards the introduction of the next generation
networks (NGN).
In Sevilla European Council [1] Europe expressed its current interest for next
generation networks by defining the actions-to-be-taken and by identifying the issues
to be studied in depth (and in parallel) prior to the deployment of NGN. Two of these
issues are (as they appear in the Sevilla document) the “Digital Switchover” (i.e. the
transition from analogue to digital broadcasting), and the “Broadband access for all
citizens”.
Accomplishment of Europe’s vision for the next generation networks requires,
however, extensive study and in depth examination of the digital switchover and the
broadband access for all issues. Currently, there is no clear point that such action have
been taken, neither by the interesting sectors (broadcasting and telecommunication),
nor by the political and governmental authorities [2], [3], [4]. Major barriers are the
political authorities’ unawareness about the potentialities and advantages of the new
technologies, and the clashes between the broadcasting and telecommunication
sectors in the market field.
Realising the networking capabilities of the new digital television in UHF (DVB-T),
and the importance of broadband access technologies in the Information Society, this
paper presents and draws-up the routes towards a successful deployment of NGN, by
elaborating on the relation between “Digital Switchover” and the “Broadband Access
for all” issues. It proposes the use of the DVB-T stream in regenerative configurations
for the creation of a powerful backbone that interconnects distribution nodes within a
city. As these distribution nodes (local networks) make use of broadband access
technologies (i.e.WLAN, LMDS, MMDS, Optical) they enable all citizens to have
broadband access to the entire network and to be interconnected. Such a configuration
enables for multi-service capability, as the regenerative DVB-T creates a single
access network physical infrastructure, shared by multiple services (i.e. TV
programmes, interactive multimedia services, Internet applications, etc.).
Following this introductory section, the rest of this paper is structures as follows:
Section 2, presents the overall architecture of the proposed infrastructure, Sections 3
and 4 describe its functional components (regenerative DVB-T and Cell Main Nodes),
while Section 5 presents the principles of a real time dynamic bandwidth management
system (DBMS), required for optimised spectrum usage. Finally, Section 6 concludes
the paper.
30
2 Overall architecture
The overall architecture of such an infrastructure (see figure 1) comprises two core
subsystems: I) a number of Cell Main Nodes (CMN), and II) a central broadcasting
point (regenerative DVB-T). Each CMN enables a number of users/citizens
(geographically neighbouring the CMN) to access IP services hosted by the network.
The communication between the users and the corresponding CMN is achieved via
broadband point-to-multipoint links (i.e. WLAN). The CMN gathers all IP traffic
stemming from its users, and forwards it to the central broadcasting point (UHF
transmission point visible by all CMNs) via dedicated point-to-point links (uplinks).
IP traffic stemming from all CMNs is received by the broadcasting point, where a
process unit filters, regenerates and multiplexes them into a single transport stream
(IP-multiplex) along with digital TV programme(s), stemming from the TV
broadcaster(s), forming the final DVB-T "bouquet". The regenerated/combined traffic
is then broadcasted via the UHF channel at high data rates following the DVB-T
standard. Each user receives the appropriate IP reply signals indirectly via the
corresponding CMN, while receiving the digital TV programme directly via the UHF
channel. In such configuration both reverse and forward IP data traffic are
encapsulated into the common DVB-T stream, thus improving the flexibility and
performance of the Network.
The cellular conception that is adopted utilises DVB-T stream in a backbone topology
which interconnects all cells that are located within the broadcasting area. Thus, a
unique virtual common Ethernet backbone is created, which is present at every cell
(via its Cell Main Node). The IP traffic of this Ethernet is supplied by the DVB-T bit
stream. Users access the network via the appropriate Cell Main Node.
In such configuration, all kind of citizens/providers are co-equal users of the same
infrastructure via which they access (or provide) IP services. Such implementation
can be used and exploited as common infrastructure by 3G and B3G operators and
broadcasters having independent business plans and different users/clients.
Extension of this configuration will be achieved by using a regenerative satellite, in
order to interconnect nodes and users around Europe (see figure 2).
Citizens, who utilise common PSTN/ISDN/xDSL lines access the common Ethernet
backbone via an appropriate node (i.e. ISP node), who takes the responsibility to
redirect data traffic targeted to them (IP reply signals stemming from any other
user/citizen located within the same broadcasting area) to the UHF broadcasted
Ethernet backbone. These citizens are the usual passive consumers of predefined
content, accommodating best effort capabilities. This proposal is oriented to the active
users/citizens that can provide and manipulate their own services to the entire
Ethernet backbone (i.e. spin-off businessman, off line IP television multicasters, etc.).
The use of regenerative DVB-T configurations in conjunction with intermediate
distribution nodes (cell main nodes - CMNs) that utilize broadband uplinks,
constitutes a broadband access infrastructure capable to accommodate the active
users/citizens, i.e. those who create, manipulate and distribute their own content to the
entire network.
In this case, each CMN constitutes the ‘physical interface’ to the common Ethernet
backbone of:
A service/content provider.
31
The users/citizens of a local network (intranet) who access the entire network
indirectly via the appropriate CMN. This intranet may cover a part of the city (i.e.
neighbourhood, outskirts, industrial zone, etc.) or comprise the LAN of a business
centre that may be based on the IEEE 802.11x technology, for example.
The customers of a mobile network operator making use of 3G and B3G technology
(i.e. UMTS).
Individual active users and implicit service providers, who access the common
Ethernet backbone via the corresponding CMN in order to create, manipulate and
provide their own content to the entire network (i.e. e-businessmen). (Also individual
passive users, who request predefined content/services via common
PSTN/ISDN/xDSL links and receive them via the UHF beam).
Br oadcastingarea
(i .e .50k mradius)
CM N atoutskir ts
(i.e.40 k mfrom
regenerative
DVB
T)
CM Nat
In du s trial zone
CM N at
metr opolis
dow ntow nwit h
WLAN
F
1
F2
F3
Downl i n
k
DVB T
Uplink
formCM N
TV studio
TV Link
Regenerative
DVB T
Br oadcasting
area
UHF
reception
an tenn a
UHFtr ansmissionto
broadcastingare a
(TVpr ogr a mmes+IP tr affic)
F
0
PS TN/ISDN
MHP
LEGEND
MMDS/
LMDS
Wir eless
Opt ic al
IS DN
PSTN
xDSL
Fig. 1. Overview of the network configuration, where the common Ethernet backbone, access
by both active and passive users/citizens, is present in the entire broadcasting area
32
F
0
City1,Node1
City2,Node2
City3,Node3
F2
Fa
F1
D ownlink
DV
B
S
U plink
DV
B
S
CM N
u
p
link
DV
B
T
downlink
WLA
N
Reg en erative
satellite
TV studio
UMTS
CM
N
/BS
Fb
F
c
F
F
F
UMTS
DVB S&DV
B
T
televiewer
s
DV
B
T
broadcastin
g
area
DV
B
T&UMTS
device
F3
CM N
CM N
DV
B
S&UMTS
devic
e
Fig. 2. Interconnecting nodes and citizens across Europe via the television stream
3 Configuration of the regenerative DVB-T
The proposed architecture of the regenerative DVB-T, which is depicted in figure 3, is
capable to:
Receive the users/citizens IP traffic over terrestrial uplinks (via the appropriate CMN
in the case of intra-metropolitan communication – see F1, F2, and F3 at figure 3).
Receive any local digital TV programme (stemming from the TV studio
broadcasters).
Broadcast a common UHF downlink that carries the IP data targeting to all CMNs
(located within the broadcasting area) and the digital TV programmes. Following the
configuration depicted in figure 3, the multiplexing device must be able to receive any
type of data (IP and/or digital TV programmes), to adapt any IP and MPEG-2 traffic
into a common DVB-T transport stream (IP to MPEG-2 encapsulation), and finally to
broadcast the common DVB-T stream following the DVB-T standard (COFDM
scheme in the UHF band).
In the case that inter-metropolitan communication is required (communication and
data exchange between users/citizens of different cities within Europe), the
regenerative DVB-T must be able to i) receive the requests for IP services via the
satellite downlink stemming from users/citizens located in another region, and any
digital TV programme (stemming from the TV studio broadcasters either form the
same country or from a distant one – via the DVB-S stream), and ii) transmit any IP
33
and/or digital TV programmes, destined to other metropolitan area(s), to the satellite
for cities interconnection (see figure 3).
4 Cell main nodes configuration (wlan case)
The overall configuration of the CMN that utilises WLAN technology is depicted in
figure 4. This part of the infrastructure is compliant with the IEEE 802.11xx standard.
Its physical layer is based on Spread Spectrum techniques, using either Direct
Sequence or Frequency Hopping. Such a network will allow for the realisation of
point-to-multipoint communication between the CMN and the citizens/users.
The WLAN network configuration follows a cellular architecture, as outlined in
figure 4 (for a single cell). Such a configuration comprises an Access Point (AP) at
the cell main node site, which maintains a full duplex communication with the Station
Adapters (SA) at the citizen’s/users’ site. The output from each SA is in IP form,
which can be transparently processed by the upper layers of the software of the end-
user’s terminal.
Each CMN enables a number of users (geographically neighbouring the CMN) to
access IP services hosted by the network. The communication between users and the
corresponding CMN is via broadband point-to-multipoint links. The CMN gathers all
IP traffic stemming from its users, and forwards it to the central broadcasting point
(UHF transmission point visible by all CMNs) via dedicated point-to-point links
(uplinks). IP traffic stemming from all CMNs is received by the broadcasting point,
where a process unit filters, regenerates and multiplexes them into a single transport
stream (IP-plex) along with a digital TV programme (stemming from the TV
broadcaster) forming the final DVB-T "bouquet". The regenerated/combined data
traffic is then broadcasted to all CMNs via the UHF channel at high data rates
following the DVB-T standard. Each user receives the appropriate IP reply signals
indirectly via the corresponding CMN, while receiving the digital TV programme
directly via the UHF channel.
Upon a user’s request for inter-cell communication (i.e. between the specific user and
any other content provider/user/server of the entire infrastructure), the AP and the IP
backbone, as well as the router and the dynamic bandwidth management system
(DBMS – see section 5) at the CMN, provides the necessary information (i.e. data
requests, data acknowledgements) to the entire metropolitan network via the common
downlink backbone (created at the regenerative DVB-T, see figure 3). The
corresponding reply signals are received by a DVB-T compliant downlink adapter (in
the CMN) via the common DVB-T stream (in the UHF band), and are forwarded to
the appropriate user via the user’s SA (see figure 4).
In this respect, the uplink of figure 4 may be named (according to the ordinary
terminology) as the reverse path channel for the active user (carrying the data
requests/acknowledgements), who requires access to services/content hosted by any
provider within the entire network. The same physical link may be also named as the
forward channel for an interactive user who accesses the services hosted by the active
user.
34
IP
IP/ DVBMUL TI PL E XE R(TV+IP)
DV
B
T
Tx
Receiv er2
Fro mCe ll
MainNodes
UHF br oadcasting
Loca lEtherne
t
IP
Rece iv er
Demodul a t or
FromTV
studio
TS
Receiv er1
Receiv er3
Receiv er
demodulator
de mu ltiplexer
TV
progr amm e(s)
F0
F3
F2
F1
Fro mregenerative
satellite
(DV B Sdow nlink)
F
Re
m ultiplexer
DV
B
S
Tx
Toregenerative
satellite
(DV B Suplink)
Fa
IP
IP
IP
Fig. 3. Overall configuration of the regenerative DVB-T

UHF/OFD
M
Receiv er and
DownCon verter
DVB
TTran sp ortStrea m
MPEG
2Demultiplexe
r
MPEG
2
Tran spo rtStream
ToIP ad aptor
IP rou ting
QPS
K
Modulator
Mic rowave
Tra n smitter
ETHERN ET
1
st
Wi r e l e ssLA
N
Access Point
Nth(=10)Wi rel es
s
LA NA cce ssPoint
To
regenerative
DVB T
UHFAnt enna
P
C
Station
Adapter
WLAN
EuropeanETSI
Standard
Station
Adapter
P
C
Station
Ada
p
te
r
IPInteractive
user
Acti veUser
P
C
T
V
SettopBox
Simple user
Tele view er
UHF
antenn a
M ultimedia
Serv e r
ContentProvider
IP TVmultica s t e r
UHFchannel
(TV prog ra mmes+IPtrafficfr omallCMNs)
F0
Regen era tive
DVB T
IPInteractiv e
user
CellMainNode
Act iveuser
P a rticipa t ing in
strea mcr e a t io n
In te r a ctiv e TV
Program m e(off
line )
Push/Carousel
Dynamic
Bandwidth
Management
Sy s t e m
(DBMS)
Fig. 4. Overall configuration of the CMN with WLAN
35
Both reverse and forward IP data traffic are encapsulated into the common DVB-T
stream:
The ‘Active user’ and the ‘IP interactive users’ generate the IP traffic that is carried
via the DVB-T stream to all broadcasting area.
Data IP traffic targeted to these users (and stemming from any other CMN within the
broadcasting area) is supplied by the DVB-T stream to the local Ethernet, via the
UHF channel.
5 Dynamic Bandwidth Management System
The proposed configuration enables for a multi-service capable platform, as long as
the regenerative DVB-T creates a single access network physical infrastructure,
shared by multiple services (i.e. TV programmes, interactive IP multimedia services,
Internet applications, etc.). In such a configuration, a real time and dynamic
management of the bandwidth is mandatory, in order to enhance the capability of
DVB-T platform as a networking infrastructure and allow the provision of multiple
kinds of services everywhere, anytime and over any type of network. The consequent
adoption of this bandwidth-on-demand proposed capability, allows an optimised
provision of heterogeneous types of traffic in respect to the available spectrum.
Towards this, a real time Dynamic Bandwidth Management System is utilised,
operating within the distribution node and managing the distribution of bit rate of IP
traffic, in order to provide optimal allocation of the bandwidth available for the
uplink. Referring to figure 5, the total bandwidth of the uplink (from the CMN to the
regenerative DVB-T) of e.g. 7 Mbps is sliced into Virtual IP Channels and each
channel into a number of services, whose bit rate can be variable and dynamically
changed. Each service can be allocated one or more PIDs within the transport stream.
Uplinkfr om aCM Ntoth eregenerativeDVBT
Virt ualIP
Chann el3
0,5Mbps
Virt ualIP
Chan nel2
1Mbps
Virt ualIP
Chan nel1
1,5Mbps
Virt ualIP 
Channel 0
04Mbps
Service
1
Servi ce
3
Servi ce
2
PID
1
PI
D
2
Modifiedby th eCMN
DBMS
Fig. 5. Bandwidth slicing in a DVB-T transport stream
6 Conclusions
This paper presented an approach towards the realization of broadband access next
generation networks (NGN), by taking into account the networking potentialities of
36
the new digital TV in UHF (Terrestrial Digital Video Broadcasting – DVB) and the
broadband capabilities of the recent access technologies. It described the overall
architecture of a networking platform that makes use of regenerative DVB-T
configurations for the realization of a common Ethernet backbone capable to
interconnect all citizens within the broadcasting area, who access it via the
appropriate distribution node over broadband links. Such an approach enables for a
multi-service capable platform (digital TV programmes, Interactive TV programmes,
Internet access, e-mail, video/audio on demand, etc.), which is commonly shared
among broadcasters, telecom operators and any active citizen who creates,
manipulates and distributes his own content to the entire infrastructure.
Acknowledgements
The proposed approach has been adopted by ATHENA (Digital Switchover:
Developing infrastructures for broadband access, FP6-507312) project in the Sixth
Framework of IST, (thematic priority IST-2002-2.3.1.3 ‘Broadband for all’), and will
be implemented in a medium sized city (Heraklion, Crete, Greece). ATHENA would
delve into the Digital Switchover to address the Broadband access for all, alleviating
the digital divide. It would pave the way for key European researchers to propose cost
effective broadband infrastructure in cities and in rural areas based on DVB-T
technology and take advantage of the eminent transition towards digital broadcasting
in UHF. The consortium partners of ATHENA (distributed across industry, research
institutes and universities in Europe) are: NCSR Demokritos Project Co-ordinator
(Greece), Space Engineering (Italy), Thales Broadcast and Multimedia (France),
Rhode & Schwarz (Germany), Centre for Technological Research of Crete (Greece),
Telscom (Switzerland), Rundfunk Berlin-Brandenburg (Germany), T-Systems Nova
(Germany), University Politchnica Bucharest (Romania), PRISM-CNRS (France),
Temagon (Greece), and University of Bournemouth (U.K).
References
1. “eEurope 2005: An information society for all. An action plan to be presented in view of the
Sevilla European Council, 21/22 June 2002”, Communication from the Commission to the
Council, the European Parliament, the Economic and Social Committee and the Committee
of the regions.
http://europa.eu.int/information_society/eeurope/news_library/documents/eeurope2005/eeur
ope2005_en.pdf
2. “Barriers to widespread access to new services and applications of the information society
through open platforms in digital television and third generation mobile communications”,
February 2003, organised by DG Information Society A1.
http://europa.eu.int/information_society/topics/telecoms/regulatory/publiconsult/documents/
211_29_en.pdf
3. “Digital switchover in broadcasting” a document created by BIPE consulting on behalf of
the European Commission (Directorate General Information Society) and which was the
subject for a public hearing organised by DG A1 (June 2002) provided by BIPE consulting.
37
http://europa.eu.int/information_society/topics/telecoms/regulatory/studies/documents/final
_report_120402.pdf
4. “Public consultation on the study on Digital Switchover in Broadcasting”, 1st July 2002,
organised by DG Information Society A1.
http://europa.eu.int/information_society/topics/telecoms/regulatory/publiconsult/comments/
digital_switchover/list_of_comments_on_digital_switchover.htm
38