Algorithm design for assignment frequency channels for services in CATV network

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