36 Ad ances in Elec ical and Elec onic Enginee ing
ALGORITHM DESIGN FOR ASSIGNMENT FREQUENCY CHANNELS FOR
SERVICES IN CATV NETWORK
J. Hlubík
Uni e si y o Zilina, Facul y o Elec ical Enginee ing, Depa men o Telecommunica ions and Mul imedia
Uni e zi na 1, 010 26 Zilina, Slo ak Republic, el.: +421 41 513 2252, mail: hlubik@ el.u c.sk
Summa y This a icle desc ibes algo i hm design o assignmen equency channels o se ices in CATV ne wo k. QAM
modula ed channels in designed sys em a e dynamically swi ched and equency adap ed. On in oduc ion, he e is sho ly
desc ibed p inciple o p o iding analog ideo, digi al ideo and da a se ices in CATV ne wo k. Objec o he a icle is
ocused on me hod o alloca ion indi idual TV and da a channels on he equency band. The conclusion compa es
ad an ages and disad an ages p esen and design sys em.
1. INTRODUCTION
Cable ele ision is a dis ibu ion sys em ha uses
a ne wo k o coax cables o deli e mul iple ideo
and audio channels. CATV sys ems can ha e up o
hund ed and wen y 6 MHz RF ansmission
channels o app oxima ely one hund ed 8 MHz RF
channels. Fo analog cable sys ems, each
ansmission channel p o ides one ideo p og am.
Fo digi al cable sys ems, each ansmission
channel can p o ide 4 o 10 ele ision channels.
When using he la ge a ailable bandwid h o coax
cable, his can p o ide mo e han 1,000 digi al
ideo channels o consume s.
Fig. 1. Dis ibu ion CATV sys em
Video b oadcas ing is he p ocess o ansmi ing
ideo images o a plu ali y o ecei e s. The
b oadcas ing medium may be ia adio wa es,
h ough wi ed sys ems (such as CATV), o h ough
packe da a sys ems (such as he In e ne ).
Tele ision in ol es he ansmission and ecep ion
o isual images ia elec ical signals. Video is an
elec ical signal ha ca ies TV pic u e in o ma ion.
Da a RF channels a e designed o e icien ly
ans e use da a (such as In e ne da a) be ween
use s and he cable sys em. Da a RF channels can
use a e y e icien o m o modula ion (such as
QAM) om he sys em o he end use allowing he
cable sys em o p o ide high speed da a om he
sys em o he ecei e (up o 30 Mbps o 40 Mbps)
pe RF channel. Because signals om mul iple
use s a e combined when hey a e sending da a o
he cable sys em, his inc eases he amoun o noise
le el so a mo e obus (less e icien ) modula ion
o m is used (such as QPSK), which can p o ide
medium speed da a om he use s o he sys em (up
o 2 o 5 Mbps) pe RF channel. Da a channels a e
de ined in he DOCSIS speci ica ion a ailable om
CableLabs. [4]
Fig. 2. Downs eam signals: anges o ope a ing
equencies and channels [1]
Fig. 3. F equency band o coax cable [1]
2. CHANNEL BONDING
The DOCSIS sys em allows anspa en bi-
di ec ional ans e o In e ne P o ocol (IP) a ic,
be ween he cable sys em head-end and cus ome
loca ions, o e an all-coaxial o hyb id- ibe /coax
(HFC) cable ne wo k.
The main ad an age o DOCSIS 3.0 s anda d
is no able inc eased ans e a e. One o he ways
o inc ease ans e a e is possibili y o usage o
mul iple downs eam channels ins ead o single
downs eam channel. The e a e mos o he
Algo i hm design o assignmen equency channels o se ices in CATV ne wo k 37
downs eam channels used o TV signal
dis ibu ion and only one downs eam channel is
used o in e ne access in p esen days. Bu , he e
is possibili y o me ge mul iple channels o inc ease
ans e a e o he in e ne access pu pose. As a
good example can be conside ed ha , one can
me ge ou downs eam channels 30Mbps each, o
achie e ans e a e o 120Mbps. [3]
Fig. 4. Channel bonding in DOCSIS 3.0
This way is p ope i s ly because, we i
doesn’ need any big in e posi ion o he
in as uc u e CATV ne wo k. Ope a o has o
ins all only new ac i e elemen s o CMTS and use s
will also need new cable modems. [3]
3. ALLOCATION FREQUENCY CHANNELS
FOR VIDEO AND DATA SERVICES
Designed algo i hm allows mo e e ec i ely
p o ocol DOCSIS 3.0 u iliza ion. TV se ices a e
ansmi ed on demand o cus ome s. On he base
bandwid h capaci y u iliza ion o coaxial cable can
by CMTS (cable modem e mina ion sys em) allo
one un il six een equency channels o each cable
modem.
Indi idual equency channels a e occupied on
he basis o eques in his design me hod.
F equency band is di ided in o wo segmen s. Fi s
equency segmen is gi en o TVoD o VoD
se ices. In op ical node a e TV p og ams swi ched
and inse in o i s segmen . Second segmen is
gi en o da a se ices ha a e ansmission o e
DOCSIS 3.0. These segmen s can be assigned o
ups eam and downs eam oo.
P ocess o indi idual channel alloca ion is
showed on ig. 5. Random numbe gene a o s
gene a es a i al ime and depa u e ime i and o
o indi idual se ice. Ma ix C is c ea ed om
ec o s i and o. E e y elemen o un-pai column
is a i al ime and e e y elemen o pai column is
depa u e ime. Ma ix ows a e indi idual
equency channels.
Example o i e se ices in i s segmen :
Gene a ed ec o s:
[
]
9192,03061,14176,04478,04692,2= in
[
]
0309,22110,13766,07322,04652,4= ou
[
]
5598,56406,43346,39170,24692,2= i
[
]
5907,78517,57111,36492,39344,6= o
Final ma ix:








=
5907,7 8517,5
0
5598,5 6406,4
0
7111,36492,3
9344,6
3346,3 9170,2
4692,2
C
Fig. 5. Alloca ion i e se ices in i s segmen
Algo i hm occupied o equency band is
showed on ig 6. Fi s s ep in algo i hm is
ini ializa ion o simula ion ime and numbe o
equency canal. On he basis o a i al in ensi y 
and depa u e in ensi y  i s gene a o gene a e
a i al ime and depa u e ime o se ice o i s
segmen . Second gene a o is gene a ed a i al ime
and depa u e ime o second segmen . These
imes a e w i en in o single elemen s o ma ix A
and B on he basis o condi ions in algo i hm co e.
Ma ix o a i al imes is ma ix A and ma ix o
depa u e imes is ma ix B. Ma ix C is c ea ed
om ma ix A and B ha is g aphic showed a he
end o algo i hm.
Time gene a o s gene a es exponen ial di ided
a i al ime and se ice ime dis ibu ions, each
wi h he espec i e pa ame e s  and . F equency
band in CATV ne wo k is sys em MM100 in
queueing heo y. The M/M/100-Queue has he
same di ided a i al ime and se ice ime
dis ibu ions as he M/M/1queue, howe e , he e
a e 100 se e s in he sys em and he wai ing line is
in ini ely long [2]. As in he M/M/1 case a comple e
desc ip ion o he sys em s a e is gi en by he
numbe o cus ome s in he sys em (due o he
memo y less p ope y).
38 Ad ances in Elec ical and Elec onic Enginee ing
Fig. 6. Design algo i hm o assignmen equency channels o se ices in CATV ne wo k
Algo i hm design o assignmen equency channels o se ices in CATV ne wo k 39
Fig. 7. A i al in ensi y o i s segmen
Fig. 8. A i al in ensi y o second segmen
Fig. 9. Assignmen equency channels o se ices in CATV ne wo k
In he simula ion has been se ed 7982 eques s
in simula ion ime 400. I equency band is ull
sys em e uses nex eques s.
4. CONCLUSION
The main ad an age o his sys em is lexibili y
o assigning equency channels. Sys em is based
on eques o assign single equency channel. F ee
equency band can be used o DOCSIS 3.0 da a
se ices. Cable ele ision ope a o s wi h his HFC
ne wo k sys em should be able o compe e wi h
FTTH echnology.
Acknowledgemen
The au ho s g a e ully acknowledge suppo
om he VEGA 1/0375/08, Analy ický model
domácej p ís upo ej sie e no ej gene ácie p e
audio, ideo a dá o é služby. 1/2008 – 12/2010.
REFERENCES
[1] CICIORA, W., FARMER,J., LARGE, D.:
Mode n Cable Tele ision Technology: Video,
Voice, & Da a Communica ions; Mo gan
Kau mann Publishe s; 1s edi ion, 1999.
[2] ADAN, I., RESING, J.: Queueing Theo y,
Depa men o Ma hema ics and Compu ing
Science Eindho en Uni e si y o Technology,
2001
[3] DOCSIS 3.0: MAC and Uppe Laye
P o ocols In e ace Speci ica ion, © Copy igh
2006 Cable Tele ision Labo a o ies, Inc., 3s
[4] HOTTMAR, V., SCHWARTZ, L,
TRSTENSKÝ, D.: End Use Box o
In e ac i e Cable Tele ision. IEEE
T ansac ion on Consume Elec onics, MAY
2007, Vol. 53, No. 2, ISSN 0098-3063