Experimental Characterisation of the Impact of IP-based Distribution Network QoS on the QoE of DVB-H...

8/9/2019 Experimental Characterisation of the Impact of IP-based Distribution Network QoS on the QoE of DVB-H Mobile Broadcast Video Services-2009

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P

MPEG 2

TS

IP Multicast

IP Network IPMPEG 2

TS

Modulator

EncodersIP

Encapsulator

ESG Server IP Modulator

CONTENT

PROVIDER Flute Server HEADEND

DISTRIBUTION

NETWORK

ANTENNA SITE USER

%i,! 1! +etwork architecture of a DVB-H mobile serice!

the QoE of the mobile ideo serice! In the domain of DVB-

H# this paper distin,uishes from former research as focus is

on the effects of errors that occur in the distribution network

instead of errors that occur between the antenna and the mobile

terminal =/>! &his paper also differs from other distribution

networks centric papers as in this research the effects of usin,

a DVB-IPD* compliant PE'-/ &S is used! &he use of QoE

as a @ualit) reference instead of packet-leel metrics# is also

an additional alue and ,ood reference indication for DVB-H

broadcast operators!

&his paper is structured as follows4 section / explains the

speci?cations and techni@ues that are of main importance for

the experiments and their results ! &he test setup and QoE

related concepts that are used for the experiments are described

in section 6! Section 7 explains the main results of these tests

%i,! /! IP Datacast oer DVB-H protocol stack!

which are discussed in section 3# to,ether with future work!

%inall) section J states our conclusions!%i,! 6! 9&P oer IP encapsulation of PE'-/ &S packets!

II! DVB-H 9E"&EDSPE*I%I*&I:+S

In this section# some technolo,ies that are of main impor-

tance for this paper are introduced! %irst DVB-IPD* will be

explained as this set of speci?cations de?nes the protocols

that are used on top of DVB-H! Second# we detail how the

DVB-IPD* compliant PE'-/ &S is sent oer an IP based

distribution network! &his section ends with an introduction

to two error correction techni@ues4 PE-%E* and Pro-PE'

*:PK6! &he former is used at the data link la)er of DVB-H

while the latter is speci?call) used to optimise the transport

of PE'-/ &S oer IP networks!

A. IP Datacast

an) commercial mobile &V networks are likel) to be h)-

brid networks combinin, a uni-directional broadcast network

with a bi-directional mobile telecommunications network! &he

set of DVB speci?cations for IP Datacastin, ;DVB-IPD*< =/>

are the ,lue that bind these two networks to,ether so that the)

can co-operate effectiel) in offerin, a seamless serice to the

consumer! DVB-IPD* is ori,inall) desi,ned for use with the

DVB-H ph)sical la)er# but can ultimatel) be used as a hi,her

la)er for all DVB mobile &V s)stems!

&he protocol stack of an IP Datacast oer DVB-H s)stem is

shown in %i,ure /! &he inte,ration of an IP la)er in the broad-

cast stack is one of the ke) concepts of an IPD* s)stem! &hese

IP data,rams are encapsulated inside the PE' &ransport

Stream ;&S< usin, PE ;ulti Protocol Encapsulation

the delier) of streamin, media# IP Datacast speci?es the use

of the 9eal-time &ransport Protocol ;9&P< and ?le delier) is

performed b) usin, %ile Delier) oer unidirectional &ransport

;%"(&E< =6># a protocol for unidirectional delier) of ?lesoer the Internet! &he use of these protocols is also clearl)

isible in the head-end of %i,ure 1! t the encoders# the

ideo data is encoded ;t)picall) usin, the H!/J7 codec< and

then encapsulated into 9&P packets! &hese 9&P-streams are

multicasted into the ulticast IP +etwork where ?nall)# the

IP Encapsulator will encapsulate all these IP packets into an

PE'/ &S!

B. Transport of MPEG-2 TS over IP

PE'-/ &ransport Streams are composed of 1 b)te &S

Packets# each with a 7 b)te header! &here are two methods

currentl) utilised for the carria,e of PE'-/ &S oer IP of

which one is mandator)! &his method# speci?ed b) the IE&%

in =7> and b) the DVB-IPI ,roup in =3># uses 9&P to carr)

PE'-/ &S packets! In this case# the 9&P pa)load carries an

inte,ral number of &S packets# which is L for Ethernet based

networks ;as the) hae a aximum &ransmission (nit of 1300

b)tes

test set-up we used 9&P encapsulation oer an Ethernet based

network with L PE'-/ &S packets per IP data,ram!

264 2009 IFIP/IEEE Intl. Symposium on Integrated Network Management orks!ops

C. MPE-FEC&he obectie of PE-%E* is to improe the *.+ and


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Doppler performance in mobile channels and to improe

the tolerance to impulse interference! Gith PE-%E*# the

IP data,rams of each time sliced burst are protected b)

9eed-Solomon parit) data ;9S datadistributed all oer the burst! Each IP data,ram is transmittedin an PE section and each column of the 9S data table is

transmitted in an PE-%E* section! &he receier reconstructs

the PE and PE-%E* sections from the receied &S packets!

Decapsulation is performed b) insertin, IP data,rams and

redundanc) columns to correct locations in the PE-%E*

frame! &he 9S decodin, is then performed row-wise!

lthou,h# in a DVB-H architecture# PE-%E* is used

to improe the delier) performance between the antenna

site and the user# the redundanc) is inserted at the head-

end for performance reasons! In this case# the *P( intensie

%E* encodin, can be done centralised instead of distributed

amon,st the different antennas! &herefore# PE-%E* can also

be used to cope with data loss between the head-end and the

antenna site!

D. Pro-MPEG COP#3

Pro-PE' *ode of Practice K6 describes a %orward Error

*orrection ;%E*< method for protection a,ainst errors in de-

lierin, professional PE'-/ &S data oer IP networks! Gith

that method implemented in IP adapters# packet errors# out of

order packets# network itter and dela) can be compensated!

%E* data insertion is done in real-time alon, with &S oer IP

encapsulation! Protection data is calculated and embedded in

re,ular 9&P packets with a speci?c pa)load t)pe!

&he mechanism is based on the insertion of additional data

containin, the result of an M:9 ;exclusie :9


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%i,! 7!

:ur practical test bed!

In order to iterate oer the same tests and calculate the

PS+9# each media stream was encoded in adance as opposed

to a real-time broadcast! &he ideo encodin, parameters are4

"Video *odec4 H!/J7

"%rame 9ate4 /3 fps

"9esolution4 QV' 6/0x/70

"&ar,et Video Bit 9ate4 /30 kbps

%i,! 3! QoE impact of PE-%E* with 10C column *:PK6 %E*!

"aximum Video Bit 9ate4 300 kbps

Different ideos were encoded# representin, different content

t)pes ;@ui show# sports# music ideo# news# etc!< resultin, in

a realistic bou@uet of content streamed! Ge focused on the

QoE of one speci?c ideo channel but also streamed other

ideos in accompan)in, channels! &he V"* media pla)er

was used in order to stream the channels that were used

as accompan)in, channel! Ge used / laptops simultaneousl)

as client deices and on each laptop a different channel

was recorded! :ne channel contained an action scene while

the second measurement channel contained a @ui show! :n

both the encodin, side and the client side we used the in-

house xstreamer for streamin, and decodin, of the measured

channels! V"* was not appropriate for this task as some issues

occurred when usin, V"* for capturin, H!/J7 oer 9&P data!

%or the IP encapsulator we used the DIP010 from 9ohde N

Schwar! &he modulator at the antenna site was the DV 3000

DVB-&.H modulator from (BS =/> and on the two laptops an

en,ineerin, sample of :ptions DVB-H.HSDP =/> combo-

card was used for capturin, the broadcasted DVB-H stream!

&he laptops were positioned close to the antenna# resultin, in

a perfect wireless channel @ualit)!

In order to proide a brid,e between the output of the

IP encapsulator and the IP based distribution network we

used two commerciall) aailable SI to IP and IP to SI

,atewa)s! &hese units proide an interface between PE'-/

transport streams# ia a DVB-SI interface# to the IP based

network! t the reception site# a second unit de-concentrates

the PE'-/ transport streams from the IP network# back

to indiidual PE'-/ transport streams and out throu,h the

DVB-SI connections! &he PE'-/ transport stream packets

are encapsulated as described in section II-B with L PE'-/

packers per IP packet! In order to cope with packet losses# the

units hae implemented Pro-PE' %E* accordin, to Pro-

PE' *ode of Practice K6 re! / as described in section

II-D! Durin, our experiments# we extensiel) experimented

with different con?,urations of this t)pe of %E*!

%inall)# we used a *lick Impairment +ode in order to induce

random packet loss in the distribution network ;i!e! between

the two SI to IP ,atewa)s

re,ular "inux based P*# where an implementation of the *lick

odular 9outer proect => is runnin, in kernel mode! &he*lick implementation allows capturin, each packet passin,

throu,h the router and manipulatin, it when necessar)! &)pical

packet manipulations include discardin, a packet# reschedulin,

the delier)# etc!

IV! DES*9IP&I:+ :% 9ES("&S

&o inesti,ate the impact on the QoE# measured throu,h the

PS+9 ideo @ualit) metric# we introduced random packet loss

between the IP encapsulator and IP decapsulator! B) usin, the

*lick impairment node# we introduced a random packet loss

alue from 0C to 10C with steps of 0!/3C! &he al,orithm is

stateless which means that each packet has the same chance of

,ettin, lost! Ghile# a packet loss ratio of 10C is er) hi,h# and

possibl) extremel) rare# we inesti,ated these hi,h alues in

order to show a trend between con?,urations and their PS+9

alue!

s discussed in Section II# a DVB-H architecture usin, an

IP-based distribution network has two forms of redundanc)

incorporated4 the PE-%E*# encoded at the ideo head-end#

and the PE' *:PK 6 error correction techni@ue# encoded

at the IP encapsulator! Ge inesti,ated the impact of both

techni@ues b) ar)in, the amount of redundanc) introduced

in the network! Each test was repeated /0 times4 we present

aera,e alues to,ether with their statistical ariance!

%i,ure 3 illustrates the impact of different PE-%E* alues

for a ?xed *:PK6 redundanc) of 10C and an increasin,

packet loss ratio! Here# we clearl) see how an PE-%E*

techni@ue is needed to cope with packet loss! t an PE-%E*

of 1!3C# which is a ne,li,ible redundanc)# the ?xed *:PK6

%E* redundanc) cannot tolerate an) packet loss! packet

loss ratio of 0!3C alread) results in a drop in PS+9 of 1LdB#

which results to a bad ideo @ualit)! lthou,h# PE-%E* is

used to cope with wireless errors between the antenna site and

the receiers# it also has a bene?cial effect on errors in the



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&B"E I

S&+D9D DEVI&I:+ V"(ES;I+ DB

IP ,atewa)# seeral PE'-&S packets are in turn ,rouped into

one IP packet! &his causes the ori,inal parts of the IP packet

to be scattered amon,st seeral IP packets! If one packet ,oes

lost in the IP based distribution network seeral IP packets in

the hi,her IP la)er are affected! &herefore# the *:PK6 %E*

onl) has a limited performance when no other error correction

2009 IFIP/IEEE Intl. Symposium on Integrated Network Management orks!ops 267


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In this paper# we focused on a random loss model and

assumed that no packet loss was introduced between antenna

and deice! In future work# we plan to inesti,ate other QoS

deterioration aspects such as a burst) loss model and itter!

%urthermore# we also plan to inesti,ate the combined effect

of QoS deterioration in the distribution network and errors

between antenna and deice!

VI! *:+*"(SI:+In this paper# we inesti,ated the mutual inFuence of two

%E* mechanisms ;PE-%E* and PE' *:PK6< that are

present in a DVB-H serice that is distributed oer an IP

based primar) distribution network! Based on the @ualit) of

the ideo# as perceied b) the user# it is shown that the

con?,uration of PE-%E* will hae a maor impact on the

tolerance of the s)stem with respect to random packet loss

that is introduced in the primar) distribution link! &he results

also indicated that due to the nature of the s)stem# a certain

%i,! ! Spread of :S Score for 1!3C PE-%E* column *:PK6 %E* and

ariable PE-%E*!

techni@ues exist!

&he latter is also illustrated in %i,ure # which shows the

spread of the :S for a packet loss ratio of 0!3# 1# 1!3 and /C

a ?xed PE-%E* of 1!3C and a ariable *:PK6 redundanc)!

Here# we see that an *:PK6 %E* of 10C and /0C is not

able to support an) packet loss in the IP based distribution

network! In the 10C case# all ideos had a bad ideo @ualit)#

while for a redundanc) of /0C# 1 out of 6 ideos had a poor

or moderate ideo @ualit)! *:PK6 redundanc) of 60C is

able to support a packet loss ratio of 0!3C but not more! %or

a packet loss ratio of 1C alread) 1 out of 3 ideos results in

a moderate or bad ideo @ualit)! Hence# for a low PE-%E*

redundanc)# the *:PK6 mechanism has a low performance4addin, redundanc) onl) leads to a mar,inal improement in

ideo @ualit)!

V! DIS*(SSI:+N %(&(9E G:9A

&he results that are presented in this paper onl) show a small

part of all the tests that were conducted for this research! fter

anal)sin, all the results# some relationships or effects hae

been proed but contrar) to earlier research =2># no formula

can be formed for calculatin, the ideal %E* redundanc)! &his

is mainl) due to the burst) behaiour of a DVB-H serice

as the probabilit) that a fault occurs in a speci?c channel

is dependent on the number of channels the DVB-H serice

consists of! lthou,h QoE is a er) ,ood indicator for the

perceied ideo @ualit) b) the user# it is also er) dependent

on which data is corrupt! ore precisel) the loss of an I frame

in a DVB-H serice# will hae more impact than the loss of a B

frame! lso# the encapsulation of seeral PE'/-&S packets

into one IP packet# introduces an additional random factor as

the loss of such an IP packet ma) affect more than one H!/J7

frame or ideo stream! &hese introduced random factors are

responsible for the hi,h statistical ariance that was measured

durin, our experiments!

unpredictabilit) should be taken account# resultin, in a hi,h

statistical ariance! Gith respect to recommendations for the

addition of PE' *:PK6 %E* in the transmission network#

this hi,h ariance incorporates that not the aera,e alues

but the PS+9 results of the most affected ideos are of

main importance! &herefore# the :S scores proide a ,ood

indication of possible ,ood con?,urations! In ,eneral# the

results indicate that the addition of *:PK6 %E* has onl) an

added alue ;with respect to the band width cost< when a er)

low PE-%E* redundanc) ;e!,! 1!3C< is used! %or the most

common PE-%E* con?,urations ;ar)in, between /0C to

66C redundanc)*A+:G"ED'E+&

&he authors would like to thank %rank eert and Aoen De&ro)er from Bel,acom for proidin, us with some e@uipment

and useful information! Steen "atr$e is funded b) Ph!D ,rant

of the %und for Scienti?c 9esearch# %landers ;%G:-V

9E%E9E+*ES

=1> E&SI E+ 60/607 1!1!14Di,ital Video Broadcastin, ;DVB ! Gebster# Video Qualit) Experts 'roup - ultimedia 9eport# /00!

=L> 9! Prieset a'.# Qos traf?c in wireless "+ oerlappin, cells# in

E(ropean ,re'ess 2**# thens# 'reece# 7 /00J!

=> &he *lick odular 9outer proect# =online>

http4..www!read!cs!ucla!edu.click.!

=2> S! "atr$e# P! Simoens# B! D e Vleeschauwer# G! Van de eerssche#

%! De &urck# B! Dhoedt# P! Demeester# S! Van den Ber,he# and E! 'ilon de

"umle)# n autonomic architecture for optimiin, @oe in multimedia

access networks#o(rna' of Co"p(ter Net/or0s# /002!


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