Wireless Pers Commun (2010) 52:637–649DOI 10.1007/s11277-008-9625-8

A DVB/IP QoS aware Backhaul Networking Environment

George Mastorakis · Evangelos Pallis ·George Kormentzas

Published online: 13 November 2008© Springer Science+Business Media, LLC. 2008

Abstract The paper discusses a DVB/IP backhaul networking environment that enablesusers to access triple-play IP services at a guaranteed end-to-end QoS level. Utilising theDVB-T stream in a regenerative configuration, it presents the formation of a QoS awarebackhaul that interconnects intermediate distribution nodes and service/content providers(e.g. ISPs, IPTV multicasters, etc.), for enabling always-on and triple-play services access,even from rural or dispersed areas. The capability of the proposed QoS aware DVB/IP back-haul networking environment is validated through experimental tests, that were conductedunder real transmission/reception conditions at a prototype infrastructure that conforms tothe discussed architectural design issues.

Keywords Backhaul · DVB/IP · DiffServ · End-to-end QoS · Experiments · SLAs

1 Introduction

The delivery of always-on and triple-play broadband IP services depends not only on theaccess network (considered as last mile network) but also on the connection from the local“point of presence” (typically a local exchange building) to the mainline or high-capacitybackbone network. This connection, which is known as “backhaul” and has been calledthe “middle mile”, constitutes a significant issue for accessing broadband services in small

G. Mastorakis · G. KormentzasDepartment of Information and Communication Systems Engineering, University of the Aegean,Samos, Greecee-mail: gmastor@aegean.gr

G. Kormentzase-mail: gkorm@aegean.gr

E. Pallis (B)Department of Applied Informatics and Multimedia, Technological Educational Institute of Crete,Heraklion, Greecee-mail: pallis@iit.demokritos.gr

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cities and/or in rural areas, i.e., in areas that are far away from the high-capacity backbone[1,2]. The backhaul connection to the nearest available main network node can be cur-rently addressed by a variety of technologies, including fibre optical, satellite and microwaveradio links [3]. The evolution of Digital Video Broadcasting (DVB) and its exploitation overterrestrial links through DVB-T for delivering not only digital TV bouquets but also IP multi-media services/content (Interactive Broadcasting) shapes a very promising and cost-effectivealternative backhaul solution, especially when combined with the appropriate reverse pathtechnologies.

DVB/IP backhaul and middle-mile solutions [4,5] comprise the DVB-T stream in a regen-erative configuration for interconnecting intermediate distribution nodes each one defininga user-access area (access network). It was experimentally verified [6] that the availablenetwork resources (i.e., the available bandwidth in the DVB-T stream), dedicated for IP ser-vices provision, were evenly shared among all distribution nodes and their users, given thatbest-effort scheme for services’ access has been utilised.

For optimum system’s efficiency and guaranteed Quality of Service (QoS), a dynamicmanagement system for traffic prioritization is required, allowing for optimised provision ofheterogeneous type traffics, in respect to the available spectrum and the services’/users’ QoSrequirements. In this context, the paper presents the design, integration and performanceevaluation of such a QoS aware mechanism that enhances the capability of DVB-T as anIP networking backhaul infrastructure, allowing the provision of services at a guaranteedquality.

Following this introductory section, the rest of the paper is structured as follows: Sect. 2gives an outline of previous authors’ works that this paper builds on. Section 3 presents theoverall architecture of a DVB/IP backhaul networking environment capable of enabling guar-anteed network QoS. Section 4 elaborates on the performance of such a QoS aware prototypeinfrastructure that conforms to the architectural design issues, and validates its capability,particularly for QoS sensitive content, such as multicast streams. Finally, Sect. 5 concludesthe paper.

2 Background Information—Work Motivation

The overall architecture of the backhaul networking infrastructure is depicted in Fig. 1. Itconsists of two core subsystems: (a) a central broadcasting point (regenerative DVB-T), and(b) a number of Cell Main Nodes (CMNs) distributed within the broadcasting area. EachCMN enables a number of users/citizens (geographically neighbouring the specific CMN)to access IP services that are hosted by the entire infrastructure (e.g. by the ISP, or by theIPTV multicaster as depicted in Fig. 1). The communication between the users and the cor-responding CMN (access network) is achieved via broadband point-to-multipoint links (i.e.WLAN, xDSL). The CMN gathers all IP traffic stemming from its own users and forwards itto the central broadcasting point (UHF transmission point visible by all CMNs) via dedicatedpoint-to-point uplinks. IP traffic stemming from all CMNs is received by the broadcastingpoint, where a process unit filters, regenerates and multiplexes it into a single transport stream(IP-multiplex) along with the digital TV programme(s) stemming from the TV broadcaster(s)(TV studio), towards forming the final DVB-T “bouquet”. Each user receives the appropriateIP reply signals indirectly via the corresponding CMN, while receiving custom digital TVprogrammes (e.g. MPEG-2) via the common DVB-T stream. In such configuration, bothreverse and forward IP data traffic is encapsulated into the common DVB-T stream, thusimproving the flexibility and performance of the networking infrastructure. Furthermore, the

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Broadcasting area (e.g. 100km radius)

CMN2 far away from the high-capacity

backbone

ISP at High capacity backbone

CMN1 WLAN Hot-Spot

in downtown F1

F2

Downlink DVB-T

Uplink from CMN

TV studio

TV Link

Regenerative DVB-T

Broadcasting area

UHF reception antenna

UHF transmission to broadcasting area

(TV programmes + IP traffic) F0

PSTN/ISDN

LEGEND

xDSL

xDSL

xDSL

IPTV Multicaster

Fig. 1 DVB/IP backhaul networking architecture

cellular conception that is adopted utilises the DVB-T stream in a backhaul topology, whichinterconnects all cells that are located within the broadcasting area with the high capacitycore, present and available at the ISP’s premises. Thus, triple play services available at theISP level (or in other provider located close to the high-capacity backbone), are “transferred”to every CMN via the DVB-T stream (the backhaul connection to the high-capacity network).

The configuration of the regenerative DVB-T (depicted in Fig. 2) in this backhaul net-working architecture is capable of:

• Receiving the users IP traffic over the uplinks (via the appropriate CMN—see PSTN/ISDNuplink and F1 in Fig. 1).

• Receiving any local digital TV programs and Internet services stemming from the TVstudio and the ISP respectively (see TV Link and F2 in Fig. 1).

• Creating and broadcasting a common UHF downlink that carries the digital TV programsand the IP data.

Following the configuration depicted in Fig. 2, the multiplexing device receives any type ofdata (IP and/or digital TV programs), adapts it into a final transport stream (IP to MPEG-2encapsulation) and finally broadcasts this stream to the entire broadcasting area following theDVB-T standard (COFDM scheme in the UHF band). In this respect, all users and providers

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IP/DVB MULTIPLEXER (TV+IP)

DVB-T Tx

Receiver 2

From CMN1

UHF broadcasting Local Ethernet

IP

Receiver Demodulator

From TV studio

TS

Receiver 1

Receiver 3 F 0

F 2

F 1

IP

IP

From ISP

From CMN2

Fig. 2 Regenerative DVB-T configuration

contribute to the creation of a backhaul (DVB-T stream) that is present and available withinthe entire broadcasting area.

In rural areas that are far away from a core backbone network and where only customPSTN/ISDN is currently available, access to triple-play services and always-on connectivitycannot be realized unless an extension of the core backbone to these regions is accom-plished. For these regions the exploitation of the proposed backhaul networking environmentis a very promising solution enabling not only the provision of triple-play services but alsoof always-on connectivity. The exploitation of the DVB-T stream in backhaul configurationsenables the fast interconnection between the core backbone and any CMN within the entirebroadcasting area.

The overall configuration of a rural based CMN is depicted in Fig. 3. It comprises DVB-Tcompliant equipment for receiving the common DVB-T stream (UHF channel), a reversepath channel (uplink communication from this CMN to the regenerative DVB-T), makinguse of the PSTN/ISDN technology (already available in this area) and an ADSL based accessnetwork. At this point it should be noted that the deployment of the ADSL technology inthe access network would not have been feasible due to high costs for the backhaul connec-tion (physical connection between this rural-based CMN and the nearest optical backbonenetwork). However, the proposed configuration enables the fast deployment of an ADSLnetwork, by exploiting the common DVB-T stream as a backhaul infrastructure, capable ofinterconnecting the core backbone (present in urban areas) with the rural based CMN. Suchan approach enables rural users to maintain always-on connectivity (over the ADSL network)and triple play services access over the common UHF beam.

Upon a user’s request for IP services (e.g., Internet) that are hosted by the core high-capac-ity network, the corresponding IP data requests are forwarded by the ADSL modem to theIP-DSLAM module, which takes the responsibility of forwarding them to the local Ethernetof this CMN (rural based CMN). The local Ethernet, in turn, forwards them to the uplink inter-face module, which passes them to the central broadcasting point (regenerative DVB-T) viathe uplink chain (PSTN/ISDN network). For maintaining one-way communication betweenthe CMN and the regenerative DVB-T, the CMN comprises a routing mechanism that blocksdownlink data traffic from the regenerative DVB-T to the CMN via the PSTN/ISDN. Finally,the data requests reach the ISP via the common DVB-T UHF channel. The correspondingreply signals, are provided by the ISP to the regenerative DVB-T over the uplink (F2 in Fig. 1)and reach the Ethernet of the rural based CMN via the DVB-T UHF channel. Users receive

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UHF/OFDM Receiver and

Down Converter

DVB-T

MPEG-2 Demultiplexer

MPEG-2 Transport Stream

to IP adaptor

IP routing Uplink interface

ETHERNET

Uplink data traffic to regenerative

DVB-T

UHF Antenna

PC

DSL Modem

DSL Modem

PC

DSL Modem

8th IP Interactive user (Always ON)

PC

DVB-T stream(TV programmes + IP traffic)

Regenerative DVB-T

2nd IP Interactive user (Always ON)

IP-DSLAM

PSTN / ISDN

Telephone / Voice

Telephone device

Telephone device

Telephone device

1st IP Interactive user (Always ON)

TV

Simple tele-viewer

Set-Top-Box

Fig. 3 Overall configuration of a rural based CMN

the corresponding reply data via their CMN Ethernet over the IP-DSLAM module. It shouldbe noted that in such a configuration (regenerative), both the reverse and forward IP datatraffic is encapsulated into the common DVB-T stream (i.e., all IP data is in the same streamalong with the digital TV programs/bouquet).

The capability of the proposed DVB/IP backhaul networking environment for enabling tri-ple-play services access and always-on connectivity has been validated through tests that wereconducted under real transmission/reception conditions [6]. The tests proved that users/cit-izens of the proposed infrastructure could access triple-play IP services, such as Internet,VoIP, IPTV, etc., but in a best-effort scheme. In other words, end-to-end QoS provisioningat this infrastructure is a matter of (a) the bandwidth reserved for IP services in the DVB-Tstream, (b) the number of active CMNs—a CMN is considered as active even if a single useris accessing the common DVB-T stream via this CMN, (c) the number of simultaneous users(accessing unicast IP services) within the same CMN and (d) the uplink(s) attributes (e.g.bandwidth). As a result, QoS sensitive IP services, such as multicast streams (e.g. IPTV pro-grammes), could not be delivered at a specific quality level, unless QoS aware mechanismsare utilised, both in the core and the backhaul networks. At this point it should be noted thatguaranteed end-to-end QoS provisioning is also a matter of the access network attributes (e.g.WLAN/xDSL bandwidth allocation, etc.), however, beyond the scope of this paper. Buildingon the above context, the next section discusses the overall architecture of a DVB/IP backhaulnetworking environment capable of enabling guaranteed QoS provisioning.

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3 A DVB/IP QoS Aware Backhaul Infrastructure

In order to enable provision of IP services at a guaranteed quality, the previously presentedDVB/IP networking environment is enhanced with QoS aware modules, making use of trafficprioritisation techniques. More specifically, the described DVB/IP environment is enhancedwith DiffServ mechanisms [7,8], for the provision of IP traffic differentiation, both acrossthe backhaul and the backbone infrastructure. Figure 4 depicts the overall architecture of thedescribed DVB/IP infrastructure, featuring DiffServ-enabled modules.

In the below configuration, every CMN is considered as an entry-point to the DiffServdomain, classifying incoming IP traffic into a specific quality level, by marking accordinglythe Differentiated Service Field (DS Field) of every IP packet with a certain DifferentiatedService Code Point value (DSCP) [9], associating every data flow to a certain QoS class. Eachclass is created according to specific QoS requirements (bandwidth, one-way delay, packet-losses), following a certain Service Level Agreement (SLA), signed between the ServiceProvider (e.g. IPTV multicaster) and the users.

All IP traffic stemming from these QoS aware CMNs, passes through a DiffServ corerouter located in regenerative DVB-T (see Fig. 5). This DiffServ core router analyzes the DSfield of all IP packets and forwards them according to a specific Per-Hop-Behavior (PHB)[10] to all CMNs, i.e. to the entire broadcasting area.

Figure 5 depicts the configuration of the regenerative DVB-T utilizing a DiffServ corerouter for IP traffic prioritization, ensuring that services will be delivered according to spe-cific QoS requirements. Figure 6, on the other hand, presents the overall configuration of aDSL-based CMN (i.e. CMN with DSL technology in the access network—namely CMN2in Fig. 1), utilizing a DiffServ edge router for classifying the IP traffic according to specificservices and users’ priorities.

Following this network configuration, traffic originated from a user located within a cer-tain CMN (i.e. service provider such as the IPTV Multicaster in CMN1) and destined toanother user placed in a different CMN (e.g. end-user in CMN2), is classified and forwardedaccording to specific QoS requirements.

Fig. 4 Overall architecture of the QoS aware DVB/IP infrastructure

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IP/DVB MULTIPLEXER (TV+IP)

DVB-T Tx

Receiver 2

From CMN1

UHF broadcasting Local Ethernet

IP

Receiver Demodulator

From TV studio

TS

Receiver 1

Receiver 3 F 0

F 2

F 1

IP

IP

From ISP

From CMN2 DiffServ Core Router

Fig. 5 DiffServ aware regenerative DVB-T configuration

UHF/OFDM Receiver and

Down Converter

DVB-T

MPEG-2 Demultiplexer

MPEG-2 Transport Stream

To IP adaptor

DiffServ Edge Router

Uplink interface

ETHERNET

Uplink data traffic to regenerative

DVB-T

UHF Antenna

PC

DSL Modem

DSL Modem

PC

DSL Modem

8th IP Interactive QoS aware user

(Always ON)

PC

DVB-T stream(TV programmes + IP traffic)

Regenerative DVB-T

2nd IP Interactive QoS aware user

(Always ON)

IP-DSLAM

PSTN / ISDN

Telephone / Voice

Telephone device

Telephone device

Telephone device

1st IP Interactive QoS aware user

(Always ON)

TV

Simple tele-viewer

Set-Top-Box

Fig. 6 Overall configuration of a DiffServ aware rural based CMN

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4 Experimental Validation of the Proposed DVB/IP QoS Aware Backhaul Solution

4.1 Setup of the Testbed

Towards validating the overall system’s performance and evaluating its capability for end-to-end QoS provisioning, several experiments were conducted under real transmission/receptionconditions environment, including:

• The regenerative DVB-T platform, where the common DVB-T stream is created in chan-nel 40 of the UHF band (i.e. 622–630 MHz), utilizing 8 K operation mode with 16QAMmodulation scheme, 7/8 code rate, 1/32 guard interval and the multi-protocol encapsula-tion mechanism (MPE) for the distribution of IP datagrams.

• A DiffServ core router located in the regenerative DVB-T, able to analyse and forward(according to the implemented PHBs) the incoming networking traffic stemming fromDiffServ edge routers.

• A QoS aware CMN (namely CMN1 in Fig. 1), located in an urban area, hosting theIPTV multicaster. The communication between this CMN and the regenerative DVB-Tplatform was based on a one-way point-to-point link of IEEE 802.11 g technology. Inorder to emulate, however, a real service-scenario, where multiple IPTV services arestemming from multiple different IPTV multicasters, that located in the same CMN, theMGEN [11] traffic generator was used, configured so that multiple UDP streams over IPto be delivered simultaneously from the same PC (i.e. via the same network interface),but over different communication/protocol ports. The CMN was configured in order tomanage the multicast traffic by utilizing the SMCRoute application [12]. Each one ofthe multicast UDP streams was utilizing a bandwidth of 1 Mbps and was transmitted inConstant Bit Rate (CBR), with packet size of 1,024 bytes for a period of 180 s.

• A QoS aware CMN (namely CMN2 in Fig. 1), located in a rural area 10 km away from theregenerative DVB-T platform, where only PSTN/ISDN is currently available, which can-not (primarily and in principle) enable for always-on connectivity. However, by exploitingthe common DVB-T stream in backhaul configuration, this CMN (placed within the samebuilding as the local PSTN exchanger) enables for always-on connectivity and access totriple-play services.

The total available bandwidth of the DVB-T stream (20.5 Mbps) was statically allocatedbetween the MPEG-2 and IP services as follows: 16.5 Mbps were dedicated to a bouquetof five digital TV programmes (MPEG-2 live and non-live broadcasts), while the remaining4 Mbps were dedicated to IP services, i.e. one IP channel for both multicast and unicast ser-vices. In this context, the overall network performance of the described DVB/IP infrastructurewas initially evaluated, providing one UDP multicast stream (1 Mbps CBR with packet sizeof 1,024 bytes long) over the IP channel of the DVB-T “bouquet”. The experimental resultsindicated an average one way delay [13] of 30 ms and no packet-losses [14] during the 180 sevaluation period.

The next set of experiments was designed in order to evaluate the network performancewhen the IP channel is congested by multiple multicast streams under the Best Effort scheme,i.e. when the available bandwidth of 4 Mbps in the DVB-T stream is evenly shared amongmultiple UDP streams requiring more than 4 Mbps (in total) for efficient provision. Towardsthese, the MGEN tool was configured so that five UDP flows to be competing for the 4 MbpsIP channel, each one at 1 Mbps (CBR) with packet size of 1,024 bytes long, as previouslydescribed. It was experimentally measured that in such scenario the average one-way delayand the packet-loss ratio were about 200 ms and 23% respectively (per UDP stream). These

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results indicated that the network performance was degraded compared to the initial exper-iment, due to the process, the buffering and the encapsulation attributes of the IP/DVBmultiplexer (a matter however of the input-to-output traffic ratio).

4.2 DVB/IP with Guaranteed End-to-end QoS Provisioning

Towards enabling end-to-end QoS provisioning for the multicast traffic of the experimentdescribed above, the QoS aware modules were activated and configured for supporting thepre-mentioned five UDP streams at three possible quality classes: a Premium service class(Expedited Forwarding Per Hop Behaviour—EF PHB) [15], an Olympic Model service class(Gold, Silver, and Bronze services, Assured Forwarding Per Hop Behaviour—AF PHB) [16],and a Best Effort service class. More specifically, the first multicast stream (STREAM1) wasassociated with EF PHB for been guaranteed, according to a pre-defined SLA, a one-waydelay below a maximum threshold of 50 ms, no packet-losses and assured bandwidth. Threemulticast streams (STREAM2, STREAM3, STREAM4), each one been associated with oneof the three levels of AF PHB (Gold, Silver and Bronze classes); i.e. services classified as“Gold class AF PHB” were of higher priority than services classified as “Silver and BronzeAF PHB”, and therefore receive more beneficial treatment from DiffServ aware modules.The SLAs for these streams were defined as follows; one-way delay and packet-losses tobe below the maximum thresholds of 50 ms and 0.5% for STREAM2, 100 ms and 1.5%for STREAM3, 150 ms and 1.5% for STREAM4. Finally, the last UDP multicast stream(STREAM5) was associated with a Best Effort service class utilizing the remaining networkresources.

In this context, IP traffic stemming from the IPTV multicaster passes through the accessnetwork to the DiffServ edge router in CMN1, where it is classified into one of the describedQoS classes, before entering the DiffServ domain (see Fig. 7). More specifically, a filteringmechanism segregates the incoming UDP streams by analysing their UDP segment headerfield (i.e. port number), and forwards each one to the respective marker. This marker, in turn,assigns a specific DSCP value, into the DS field of each IP packet (i.e. 101110 for EF PHB).This is a standardised value for specific QoS classes, as indicated in [9,10]. As a result, theoutput of the DiffServ router at CMN1 are the UDP multicast streams, each one associatedwith a certain PHB before received by the DiffServ core router located in the regenerativeDVB-T (see Fig. 5).

Fig. 7 DiffServ edge router QoS mechanisms

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Fig. 8 DiffServ core router mechanisms

The marked UDP streams are received by the regenerative DVB-T interface (i.e. Receiver1 in Fig. 5) and forwarded to the DiffServ core router. This router utilizes a filtering mecha-nism, which segregates the incoming marked multicast streams by analysing the DS field ofthe IP packet headers and forwards them accordingly to a specific shaper (see Fig. 8). Eachshaper reserves a portion of the available network resources (i.e. from the 4 Mbps IP channelin the DVB-T “bouquet”) according to the priority level of every IP multicast service asdefined in their associated SLAs. The outgoing differentiated traffic is then forwarded to theIP/DVB multiplexer and broadcasted using a DVB-T transmitter (see Fig. 5).

The experimental results, regarding the one-way delay and the packet loss ratio of eachUDP stream, are depicted in Figs. 9 and 10 respectively, for the total 180 s performanceevaluation period. From Fig. 9, it can be observed that the average one-way delay, whenthe DiffServ mechanisms are disabled, is about 200 ms for each UDP stream. On the otherhand, when the DiffServ mechanisms are enabled, the one UDP stream classified as EF

Fig. 9 Average one-way delay for UDP multicast streams

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Fig. 10 Packet Loss ratio for UDP multicast streams

(STREAM1) experiences an average one-way delay of less than 50 ms, while the three UDPstreams classified as AF (STREAM2, STREAM3, STREAM4) experience average one-waydelays of less than 50, 100 and 150 ms respectively. In both cases, the BE multicast streamexperiences similar one-way delays.

Similarly, from Fig. 10 it can be deduced that when the DiffServ mechanisms are dis-abled, each UDP stream experiences an average packet-loss of about 23%. On the otherhand, when the DiffServ mechanisms are activated, UDP streams associated with Premium(EF PHB) and Gold (AF1 PHB) service classes, experienced no packet-losses. The UDPmulticast streams associated with Silver (AF2 PHB) and Bronze (AF3 PHB) service clas-ses experienced packet-losses (the values observed are below the threshold defined in theSLAs), however under the upper threshold (a threshold of about 2–3% defined in [17])for a good network performance and network QoS provisioning of multicast services. Theexperimental results also indicate, that the best effort UDP stream (STREAM5) experienced95% packet losses when QoS aware mechanisms were enabled, conforming to the respec-tive SLA. The utilization of the QoS aware mechanisms by configuring the DiffServ edgeand core routers according to the QoS requirements for each UDP stream, results in an opti-mized performance of the network for the provision of multicast streams through the DVB/IPinfrastructure.

Effectively, it can be deduced that the pre-defined SLAs were respected by the entiresystem, both at the core and backhaul network, and the introduced QoS aware mechanismsimproved the overall network performance, setting the basis for end-to-end QoS provisioning.

5 Conclusions

The paper presented a DVB/IP backhaul networking environment that can efficiently distrib-ute IP services at a guaranteed end-to-end QoS. Utilising the DVB-T stream in a regenerativeconfiguration, it described the creation of a backhaul among intermediate communicationnodes and service/content providers (e.g. ISPs, IPTV multicasters, etc.), for enabling users

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to access IP triple-play services, even from rural or dispersed areas. For optimum system’sefficiency and guaranteed network QoS provisioning, DiffServ aware modules were utilisedboth at the backhaul (DiffServ core router) and at the CMN level (DiffServ edge router),capable to adapt incoming IP traffic according to specific QoS requirements. The perfor-mance of such a Backhaul DVB/IP infrastructure was evaluated by conducting a numberof tests under real transmission/reception conditions, concerning the QoS of UDP multi-cast streams. It was experimentally verified that the exploitation of DiffServ traffic policyand prioritisation mechanisms enhance the utilisation of DVB-T technology as a networkingbackhaul infrastructure, capable to offer optimized spectrum utilisation according to servicesQoS requirements.

References

1. Philpott, M. (2003). Broadband technologies and rural areas. The Journal of The CommunicationsNetwork, 2(1), 9–16.

2. Boscher, C., Hill, N., Lainé, P., & Candido, A. (2004). Providing always-on broadband access to under-served areas. Alcatel Telecommunications Review, Part 4/1, 127–132.

3. EC Buckley study. (2004). Alternatives for extending broadband coverage to underserved EU regions, inthe context of the Digital Divide Forum.

4. Mastorakis, G., Pallis, E., Mantakas, C., Kormentzas, G., & Skianis, C. (2006). Exploiting digital switc-hover for broadband services access in rural areas. Journal of Communications, 1(6), 45–50.

5. Pallis, E., et al. (2006). Digital switchover in UHF: The ATHENA concept for broadband access. EuropeanTransactions on Telecommunications, 17(2), 175–182.

6. Mastorakis, G., Pallis, E., & Kormentzas, G. (2007). A fusion DVB/IP networking environment for pro-viding always-on connectivity and triple-play services to urban and rural areas. IEEE Network Magazine,21(2), 21–27.

7. Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z., & Weiss, W. (1998). An architecture for differ-entiated services. RFC 2475, IETF.

8. Babiarz, J., Chan, K., & Baker, F. (2006). Configuration guidelines for DiffServ service classes. RFC4594, IETF.

9. Nichols, K., Blake, S., Baker, F., & Black, D. (1998). Definition of the differentiated services field (DSField) in the IPv4 and IPv6 Headers. RFC 2474, IETF.

10. Brim, S., Carpenter, B., & Le Faucheur, F. (2002). Per hop behaviour identification codes. RFC 2836,IETF.

11. The Multi-Generator (MGEN) Version 4.2 (Online). Available from http://pf.itd.nrl.navy.mil/mgen/.12. SMCRoute command line tool to manipulate the multicast routes. Version 0.92 (Online). Available from

http://www.cschill.de/smcroute/.13. Almes, G., Kalidindi, S., & Zekauskas, M. (1999). A one-way delay metric for IPPM. RFC 2679, IETF.14. Almes, G., Kalidindi, S., & Zekauskas, M. (1999). A one-way packet loss metric for IPPM. RFC 2680,

IETF.15. Jacobson, V., Nichols, K., & Poduri, K. (1999). An expedited forwarding PHB. RFC 2598, IETF.16. Heinanen, J., Baker, F., Weiss, W., & Wroclawski, J. (1999). Assured forwarding PHB group. RFC 2597,

IETF.17. Miras, D., Sadagic, A., Teitelbaum, B., Leigh, J., El Zarki, M., & Liu, H. (2002). A survey of network

QoS needs of advanced internet applications. Internet2 QoS Working Group.

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Author Biographies

George Mastorakis received his B.Eng. (Hons) in Electronic Engineer-ing from University of Manchester Institute of Science and Technology(UMIST) in 2000 and his M.Sc. in Telecommunications from UniversityCollege London (UCL), in 2001. He is a Ph.D. candidate in Informationand Communication Systems Engineering Department of the Univer-sity of the Aegean in Greece. His current research activities are in digitalinteractive television, networking traffic analysis, resource management,quality of service and broadband networks.

Evangelos Pallis received his Ph.D. in Telecommunications in 2002from the University of East London. His is currently working as anassistant professor in ATEI of Crete, as a researcher in the Centre forTechnological Research of Crete and as a research associate in the NCSRDemokritos. His research interests are in the fields of digital interactivetelevision, broadband wireless networks and distribution systems, net-work and services convergence and multimedia interactive applications.He has more than 70 publications in international referred journals andconference in the above areas.

George Kormentzas is currently Assistant Professor in the Universityof the Aegean, Department of Information and Communication Sys-tems Engineering. He is also Associate Researcher with the Instituteof Informatics and Telecommunications at the National Centre forScientific Research ‘Demokritos’. George Kormentzas was born inAthens, Greece on 1973. He received the Diploma in Electrical and Com-puter Engineering and the Ph.D. in Computer Engineering both from theNational Technical University of Athens (NTUA), Greece, in 1995 and2000, respectively. He has been actively working for many years on thearea of network management and quality of service of computer andcommunication systems where he has introduced the concept of abstractinformation model, an ancestor of next generation networking middle-ware, which constitutes his main current research interest along withevent-based distributed systems. Other current research activities takeupon issues concerning end-to-end multimedia QoS provision, optimi-

zation and coexistence of broadband heterogeneous wired/wireless networks. He has published extensively inthe fields above, in international scientific journals, edited books and conference proceedings. After invitation,George Kormentzas is member of the IFIP WG6.6 (Management of Networks and Distributed Systems) ofthe TC6-Communication Systems. He also acts as a Chancellor of the IEEE Student Branch of the Universityof Aegean and he is member of CNOM and TCII IEEE technical committees.

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