The 5th PSU-UNS International Conference on Engineering and

Technology (ICET-2011), Phuket, May 2-3, 2011 Prince of Songkla University, Faculty of Engineering

Hat Yai, Songkhla, Thailand 90112

Li Xuan¹, Liu Jing¹, Sungchol Cho¹, Jin Xianshu¹,

S. Kamolphiwong², T.Ang-Chuan²,T. Sribuddee³, Ta Bahung⁴, Quincy Wu⁵, Basuki Suhardiman

6, Sunyoung Han*

¹Department of Computer Science and Engineering Konkuk University, 1 Hwayang, Gwangjin, Seoul 143-701, Korea

²Department of Computer Engineering, Faculty of Engineering, Prince of Songkla University, Thailand

³UniNet-ThaiREN, Thailand

⁴National Agency for Science and Technology Information, Vietnam

⁵National Chi Nan University, Taiwan 6Bandung Institute of Technology, Indonesia

{lxahtena, jing8100, cschol, hyunsook}@cclab.konkuk.ac.kr

Abstract: IPTV becomes one of the most popular

multimedia applications in recent years. It supports not

only the traditional voice and data services but also the

new service types such as VoD, broadcast TV, live TV

and so on. However, because of limited network resource

and users’ increasing requirement about QoS, it is

difficult to guarantee QoS of multimedia IPTV. So in this

paper, we study on the overlay multicast-based IPTV and

design a scheme and test bed based on multi-channel and

overlay network for improving QoS of IPTV.

Key Words: Multi-channel / Overlay / QoS of IPTV /

Multicast

1. INTRODUCTION

With the rapid development of Internet, the general

Internet services (such as Web service, FTP service,

video and audio download, etc.) cannot satisfy people's

demand any more. The multimedia service with higher

quality is required more and more. The Internet Protocol

Television (IPTV) becomes one of the most popular

multimedia applications in recent years[1][2]. It can

deliver the multimedia data to thousands of consumers at

the same time over IP-based network. The IPTV supports

not only the traditional voice and data services but also

the new services such as Video on Demand(VoD),

broadcast TV, live TV and so on. However, because of

limited bandwidth, unstable network and different

compression coding standards, the qulity of these kinds

of multimedia services cannot be guaranteed when they

are transmitted. So in order to guarantee the required

*Corresponding author

level of the QoS of theses multimedia services, IPTV is

facing many challenges[3].

In this paper, we mainly study on the overlay

multicast-based IPTV and design a scheme based on

multi-channel and overlay network for improving IPTV

transmission quality. Then we design the whole testbed

for this scheme and do the experiments with Thailand,

Vietnam, Indonesia and Taiwan.

The rest of this paper is structured as follows. The

overlay multicast for IPTV and some related work are

introduced in section 2. Section 3 analyses the decline of

the IPTV quality and presents the scheme based on

multi-channel and overlay network. Then section 4

presents the whole testbed architecture and the

experimental process. Finally, we summarize our work

and outline items for future work in section 5.

2. RELATED WORK

2.1. Multicast for IPTV

As we know, the delivery of multimedia data of IPTV

will push network infrastructures to the limit and require

very high levels of QoS [4][5]. There are two dominant

technologies for the delivery of packetized IPTV to

multiple recipients over Internet: peer-to-peer technology

and IP multicast tree technology. The use of packet-

switched IP multicast trees to deliver the content is a

well-established technology. It's the most efficient

delivery mechanism to support a tremendous number of

users at one time.

A Scheme Based on Multi-channel and

Overlay Technology for Improving IPTV

Transmission Quality

373

2.2 Overlay network technology

An overlay network is a virtual network of nodes and

logical links that is built on top of an existing network

with the purpose to implement some special network

services. In our research, it is responsible for handling

stream transmission of IPTV applications and operated

in an organized and coherent way. We do the experiment

on the overlay network named Trans-Eurasia

Information Network 3(TEIN3). TEIN3 is a huge

network with high speed for scientific research. Our

testbed contains Korea, Thailand, Vietnam, Indonesia

and Taiwan five countries who are connected by TEIN3.

2.3 Compression method for multimedia data

In order to guarantee QoS of IPTV service and satisfy

consumers' requirements for various multimedia data, we

need different video compression methods to support

high quality IPTV services.

1) H.264[6] is an advanced video coding for generic

audiovisual services. This video format has a very broad

application range that covers all forms of digital

compressed video from low bit-rate Internet streaming

applications to HDTV broadcast and digital cinema

applications with nearly lossless coding[7]. 2) MPEG-

2[8] is widely used as the format of digital television

signals that are broadcasted over the air, cable, and direct

broadcast satellite TV systems. It also specifies the

format of movies and other programs that are distributed

on DVD and similar discs. 3) Audio Video Interleave

(AVI) is a multimedia container format introduced by

Microsoft. AVI files can contain both audio and video

data in a file container that allows synchronous audio-

with-video playback. 4) Windows Media Video (WMV)

is a video compression format for several proprietary

codecs developed by Microsoft. It was originally

designed for Internet streaming applications, and now

WMV 9 has gained adoption for physical-delivery

formats such as HD DVD and Blu-ray Disc.

2.4 Multi-channel for IPTV

Fig. 1. Multi-channel for multimedia services

As shown in Fig. 1, the multimedia service can be

designed as multiple virtual channels. Various service

contents(such as video streaming, data, wireless) can be

deliveried into different channels with different

bandwidth, which can make full use of the limited

bandwidth resource and guarantee a required QoS level

of different service contents.

2.5 Overlay multicast testbed between Korea and

Thailand[9]

Before this work, we already established a testbed

over KOREN, THaiREN and TEIN2 for the

measurement of overlay multicast traffic. We did lots of

experiments on that testbed to analyze the speed of

stream transmission and tranmission security when the

stream is forwarded to various international networks.

Fig. 2. Overlay multicast testbed between KU and PSU

As shown in Fig. 2, the stream encoding was done in

KU, and the streaming was forwarded over KOREN,

TEIN2 and THaiREN. After receiving the video

streaming, the Edge OMR delivered it to local users by

using multicast.

3. PROPOSED SCHEME BASED ON MULTI-

CHANNEL AND OVERLAY TECHNOLOGY

3.1. Overview of the scheme and architecture

For maintaining the level of multimedia service

quality and supporting multi-channel and overlay well,

we need a stable and effective network environment. So

as shown in Fig. 3, in order to obtain more exhaustive

and accurate experimental data and result, we design this

whole testbed and do the experiments with Thailand,

Vietnam, Indonesia and Taiwan.

Fig. 3. Architecture of the scheme based on overlay

network

The core network of this test bed is TEIN3, and five

high speed research networks in different countries

connect to TEIN3 to support multimedia data

transmission based on multi-channel. In this scheme,

Konkuk University in Korea establishes different

channels to transmit multimedia streams with other test

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points in other countries. In order to support multicast

IPTV, Overlay Multicast Relay (OMR) device is set up

in every test point. It consists of server and client

terminal which are called Root and Edge in this scheme.

The Root can capture the local multimedia stream from

video server, and then transmit it by unicast through

overlay network. And the use of Edge is to receive the

multimedia stream from overlay network and implement

the local multicast.

3.2. Evaluation and analysis about QoS of IPTV

multimedia streams

In this scheme, we plan two phases for the

implementation and experiment. First one is evaluation

and analysis about QoS of IPTV multimedia streams.

Through this phase, we can get evaluation about QoS of

various multimedia data and find the problem when

transmitting streams by using multi-channel and overlay

technology.

Fig. 4. Overlay multicasting architecture in the first

phase

Fig. 4 shows us the test bed architecture of the first

phase. For more exhaustive evaluation data, various

multimedia formats should be considered in this scheme.

First we transmit multimeida streams with other 4

countries respectively, and the condition is as followings:

Table 1. QoS of IPTV based on single channel

Thailand Vietnam Indonesia Taiwan

Stream

format

AVI H.264 Live

stream

MPEG-

2

QoS Good Good Good Good

As shown in Table 1, when we transmit video stream

with just one country at one time, the QoS of IPTV is

good for different stream formats. Because it is single

channel and network resource (like bandwidth) is enough

for high quality video stream transmission.

Then a group experiment is implemented. We adopt

two single channels to transmit different video formats to

Thailand and Vietnam simultaneously, and the same

work is done with Indonesia and Taiwan simultaneously.

The former result is still good but the QoS of both live

stream and MPEG-2 goes down obviously. At last, when

we adopt four single channels to transmit different video

formats to four countries simultaneously, the QoS of

each channel arises obvious decline.

This decline results from live stream. Because the

real-time video stream demands a high and stable

bandwidth to maintain the real-timing and uncompressed

video stream transmission, the QoS of other channels is

also influenced.

3.3. Multimedia data transmission scheme based on

multi-channel

The second phase is to utilize multi-channel and

overlay technology to implement IPTV multimedia data

transmission with four countries simultaneously.

In order to implement multicast and multi-channel

IPTV services, we need a protocol which can support

video stream transmission of various formats and real-

time QoS control. Real-time Transport Protocol (RTP) is

a good choice to do this job. RTP defines a standardized

packet format for delivering audio and video over IP

networks. This standard defines a pair of protocols, RTP

and Real-time Transport Control Protocol (RTCP). RTP

is used for transfer of multimedia data, and RTCP is used

to monitor transmission statistics and QoS, and it’s also

used to aid synchronization of multiple streams.

One of the design considerations of RTP is to support

a range of multimedia formats (such as H.264, MPEG,

MJPEG, etc.) and allow new formats to be added without

revising the RTP standard. So in this scheme, we can use

RTP to implement multi-channel. When the streaming

server in Konkuk University of Korea sends streams of

various formats including real-time streaming, the

enormous video stream is delivered to different channels

by using RTP and VLC multimedia framework.

Fig. 5. Multi-channel for IPTV stream transmission with

4 countries

As shown in Fig. 5, four different video streams are

delivered into four channels and sent to Taiwan,

Vietnam, Thailand and Indonesia respectively. Every

channel has its own destination, so the unicast is used for

stream transmission on overlay network. When streams

arrive at each test point, the Edge OMR in local area can

relay the stream by using multicast for local users.

As we know, RTCP provides out-of-band statistics

and control information for an RTP flow. The primary

function of RTCP is to provide feedback on the QoS in

media distribution by periodically sending statistics

information to participants in a streaming multimedia

session. In this scheme, because of different stream

fomats, these channels have different requirements about

bandwidth and the level of QoS. So according to the

feedback information (such as lost packet counts, jitter,

round-trip delay time, etc.) of RTCP, the stream server

can adjust encoding parameters timely to guarantee QoS

of IPTV multimedia transmission.

So this scheme can not only evaluate the performance

of multiple video streams and QoS of IPTV multimedia

data transmission, but also guarantee QoS of IPTV when

multiple video streams of different formats are

transmitted simultaneously.

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4. EXPERIMENTS AND DISCUSSION

In this section, first we carry out the whole test bed

including multimedia stream server, the Root OMR and

Edge OMRs in other 4 countries. Table 2 shows the

device information about Root and Edge OMRs.

Table 2. Device information about Root and Edge OMRs

CPU Hard

disk

Network

interface

mem

ory

Korea

OMR

Intel(R)

Celeron(R)

2.00GHz

100G 100baseT

x-FD

2474

76

KB

Thailand

OMR

Intel(R)

Core(TM)2

Quad Q6600

2.40GHz

250G 100baseT

x-FD

3635

736

KB

Indonesia

OMR

Intel(R)

Pentium(R)D

3.00GHz

80G 100baseT

x-FD

5141

96

KB

Vietnam

OMR

Intel(R)

Pentium(R)D

3.00GHz

80G 100baseT

x-FD

5141

96

KB

Taiwan

OMR

Intel(R)

Pentium(R)D

3.00GHz

80G 100baseT

x-FD

5141

96

KB

Fig. 6 shows the actual test bed architecture for

multimedia IPTV service in this scheme. The connection

from KOREN to TEIN3 has a high bandwidth as

2.5Gbps, and other connections from other countries to

TEIN3 have the bandwidth of 622Mbps or 155Mbps. So

we choose Konkuk University in Korea as the server

point which is responsible for multimedia stream

encoding and transmission by multi-channel.

Fig. 6. The actual test bed architecture for multi-channel

IPTV service

In the first phase, we test the single channel stream

transmission with other four countries respectively. The

live streaming case between Korea and Indonesia is

shown in Fig. 7. The real-time streaming source goes

into overlay network through Root OMR. Then the Edge

OMR in Indonesia can receive this stream and transmit it

to local users by using multicast. Through this process,

we evaluate the QoS of multimedia streams of various

formats and the result shows the QoS is good enough for

users when only one stream is transmitted. But when

multiple streams are transmitted simultaneously, the QoS

of each stream gets influenced since the real-time

streaming case demands a very high and stable

bandwidth.

Fig. 7. Live streaming test architecture between Korea

and Indonesia

By using VLC framework, we can monitor each

stream bit rate and packet losting condition on real time

when playing test video. So we record each bit rate at

intervals of one minute and draw the Fig. 8. As shown in

Fig.8, from the beginning to the 10th minute, the stream

bit rates of four different videos get a similar trend. Even

the real-time streaming to Indonesia also doesn't occupy

too much bandwidth since we just record the static image

for real-time streaming. So the QoS of these four videos

can be maintained at a relatively good level. But after 10

minutes, we start moving the camera and recording

something moving. As a result, the bit rate of the real-

time streaming to Indonesia goes up obviously while the

bit rates of the other three streams get decreased.

Because the real-time stream occupies a great amount of

bandwidth unexpectedly, packet-lost of the other three

streams becomes more serious and the QoS also get

worse at the same time. So if we transmit these streams

in different channels, this kind of influence can be

reduced to minimum and the QoS of other streams can

be guaranteed well.

Fig. 8. Stream bit rate of four countries' test video

The second phase is the multi-channel test between

five countries. We use RTP based on VLC framework to

support multi-channel stream transmission. And OMR is

used for overlay multicasting. When multimedia streams

of different formats are transmitted in different channels,

the feedback information about streams can be sent back

to the stream server. Then according to this information,

the server can adjust values of stream encoding

parameters to reduce lost-packet rate and delay time.

Although the definition of real-time streaming frames

may decline, the QoS of the other streams can reach to

the requaired level while the fluency of streams also can

be guaranteed well.

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5. CONCLUSION

This paper firstly introduces the current development

of IPTV and stduies some related technologies about

QoS of IPTV. Secondly we design and build a multi-

channel test bed with four other countries for evaluating

and improving QoS of multimedia IPTV. Finally we do

some experiments on this test bed to discuss the reasons

which result in the decline of QoS of IPTV and the

solution based on multi-channel and overlay network.

Our future work will address how to improve the

accuracy of QoS evaluation and how to make streams

from different channels be received in each local area.

We hope this scheme and test bed can do more work for

improving QoS of IPTV.

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