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The passive optical network (pon) technology has been drastically improved in recent years. In spite of using the optical technology, the utilization of the entire bandwidth is a very challenging task
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| bet | 2/3 | | Sana | 16.05.2024 | | Hajmi | 198,66 Kb. | | #237287 |
Bog'liq The passive optical network ефкошьф (2)1.2. GPON
The GPON standard is defined in ITU-T G.984.x [14]. The data rates for downstream and upstream are 2.488 Gbps and 1.244 Gbps, respectively. The split ratio using a single fiber is 1:32 or 1:64 or sometimes 1:128, which means every fiber can serve up to 32, 64, or 128 users. In the data format, the GPON packets have 53 bytes in which 48 bytes are used for data and 5 bytes for overhead. GPON using a generic encapsulation method (GEM) to handle the other protocol like Ethernet, IP, transmission control protocol (TCP), user datagram protocol (UDP), T1/E1, video, VoIP, and other protocols for the data transmission. The GPON packet size ranges from 53 bytes to 1518 bytes [15].
In the 10-gigabit passive optical network (XGPON or 10GPON), the maximum downstreamrate is 10 Gbps and that of upstream is 2.5 Gbps [16]. The downstream wavelength is 1577 nm and the upstream wavelength is 1270 nm. It can serve up to 256 connections. The latest version is 10-gigabit symmetrical passive optical network (10 XGSPON) which provides downstream and upstream with a same data rate of 10 Gbps. The next generation passive optical networks (NG-PON1 and NG-PON2) fulfill the need of the wide bandwidth from end users. NG-PON1 was developed to achieve a data rate up to 10 Gbps/2.5Gbps and NG-PON2 was developed to achieve that of 40 Gbps/10 Gbps.
1.2. GPON
GPON standarti ITU-T G.984.x [14] da belgilangan. Pastki va yuqori oqim uchun ma'lumot uzatish tezligi mos ravishda 2,488 Gbit / s va 1,244 Gbit / s ni tashkil qiladi. Bitta tola yordamida bo'linish nisbati 1:32 yoki 1:64 yoki ba'zan 1:128 ni tashkil qiladi, ya'ni har bir tola 32, 64 yoki 128 foydalanuvchiga xizmat qilishi mumkin. Ma'lumotlar formatida GPON paketlari 53 baytga ega bo'lib, ularda 48 bayt ma'lumotlar uchun va 5 bayt yuk uchun ishlatiladi. Ethernet, IP, uzatishni boshqarish protokoli (TCP), foydalanuvchi datagram protokoli (UDP), T1/E1, video, VoIP va maʼlumotlarni uzatish uchun boshqa protokollar kabi boshqa protokollarni boshqarish uchun umumiy inkapsulyatsiya usuli (GEM) yordamida GPON. GPON paket hajmi 53 baytdan 1518 baytgacha [15].
10 gigabitli passiv optik tarmoqda (XGPON yoki 10GPON) maksimal pastga oqim tezligi 10 Gbit / s, yuqori oqim esa 2,5 Gbit / s ni tashkil qiladi [16]. Pastki oqimdagi to'lqin uzunligi 1577 nm, yuqoridagi to'lqin uzunligi esa 1270 nm. U 256 tagacha ulanishga xizmat qilishi mumkin. Eng so'nggi versiya 10 gigabitli nosimmetrik passiv optik tarmoq (10 XGSPON) bo'lib, u 10 Gbit / s bir xil ma'lumot tezligi bilan quyi va yuqori oqimni ta'minlaydi. Keyingi avlod passiv optik tarmoqlari (NG-PON1 va NG-PON2) oxirgi foydalanuvchilarning keng tarmoqni o’tkazish qobiliyati talablarini qondiradi. NG-PON1 10 Gbit/s/2,5 Gbit/s gacha ma’lumot uzatish tezligiga erishish uchun, NG-PON2 esa 40 Gbit/s/10 Gbit/s tezlikka erishish uchun ishlab chiqilgan.
2. EPON and GPON standards and comparison
EPON carries naturally Ethernet frames, thus there is no need for extra adaptation methods or encapsulation [17]. In GPON Ethernet, the frame is encapsulated into the GEM frame and then it is modified into the SONET/synchronous digital hierarchy (SDH) frame, in the upstream and downstream directions. The EPON frame is either synchronous or fixed length or commonly normal operation using two messages: GATE and REPORT. In the same format of GPON for the upstream and downstream operations, GPON upstream and downstream frames are synchronized with the length of 125 ms. In EPON, ONU is addressed by the logical link identifier (LLID) during the transmission from OLT to ONU, OLT adds the preamble at the starting of the frame to identify destined ONU among multiple ONUs, but in the GPON traffic container (T-Cont) it is virtually connected to OLT and ONU. T-Cont has PORT IDs to identify proper ONU, which is assigned to ONU during the initialization by OLT. Both EPON and GPON support ONU discovery, initialization techniques and dynamic bandwidth allocation (DBA) methods. The EPON DBA algorithm is not suitable for GPON, because the frame structure of GPON is entirely different due to the significant difference of the MAC layer.
EPON and GPON standards have different guard time, overhead, and parameters which influence the bandwidth utilization. Both EPON and GPON standards define a) ONUs to convey the current buffer size to OLT by the REPORT message and b) OLT to convey bandwidth information back to ONUs by the GRANT message [18]. This communications mechanism is vibrant for the operation of DBA. EPON messages have larger overhead associated with them compared with GPON messages. The EPON standard provides more flexibility in the design of the DBA algorithm than GPON. The comparison between EPON and GPON is tabulated in Table 1 [19].
2. EPON va GPON standartlari va taqqoslash
EPON tabiiy ravishda Ethernet ramkalarini olib yuradi, shuning uchun qo'shimcha moslashish usullari yoki inkapsulyatsiyaga ehtiyoj qolmaydi [17]. GPON Ethernet-da freym GEM ramkasiga inkapsullanadi va keyin u yuqori va quyi oqim yo'nalishlarida SONET/sinxron raqamli ierarxiya (SDH) ramkasiga o'zgartiriladi. EPON ramkasi sinxron yoki belgilangan uzunlikdagi yoki odatda ikkita xabardan foydalangan holda normal ishlaydi: GATE va report. Yuqori va quyi oqim operatsiyalari uchun bir xil GPON formatida GPON yuqori va quyi oqim kadrlari 125 ms uzunlikda sinxronlashtiriladi. EPON-da ONU OLT dan ONU ga uzatishda mantiqiy havola identifikatori (LLID) bilan murojaat qiladi, OLT bir nechta ONUlar orasidan, lekin GPON trafik konteynerida (T-Cont) belgilangan ONUni identifikatsiyalash uchun ramkaning boshida kirishni qo'shadi. ) OLT va ONUga deyarli ulangan. T-Cont to'g'ri ONU ni aniqlash uchun PORT identifikatorlariga ega bo'lib, OLT tomonidan ishga tushirish vaqtida ONUga tayinlanadi. EPON ham, GPON ham ONU kashfiyoti, ishga tushirish usullari va dinamik tarmoqni o’tkazish qobiliyati ajratish (DBA) usullarini qo'llab-quvvatlaydi. EPON DBA algoritmi GPON uchun mos emas, chunki MAC qatlamining sezilarli farqi tufayli GPON ramka tuzilishi butunlay boshqacha.
EPON va GPON standartlari tarmoqni o’tkazish qobiliyatidan foydalanishga ta'sir qiluvchi turli xil qo'riqlash vaqti, qo'shimcha yuk va parametrlarga ega. EPON va GPON standartlari a) HESOBAT xabari orqali joriy bufer hajmini OLT ga etkazish uchun ONUlarni va b) GRANT xabari orqali tarmoqni o’tkazish qobiliyati ma'lumotlarini ONU ga qaytarish uchun OLTni belgilaydi [18]. Ushbu aloqa mexanizmi DBA ishlashi uchun jonli. EPON xabarlari GPON xabarlari bilan solishtirganda ular bilan bog'langan kattaroq yukga ega. EPON standarti DBA algoritmini loyihalashda GPONga qaraganda ko'proq moslashuvchanlikni ta'minlaydi. EPON va GPON o'rtasidagi taqqoslash 1-jadvalda keltirilgan [19].
3. DBA
In earlier days, the bandwidth is allocated to a user at a constant rate. If the user needs more bandwidth, it will not be feasible. Then most of the bandwidth will be wasted because of non-usage. This is usually said to be static bandwidth allocation, later several developments occurred in the evolution of optical fibers, which increased the speed of the network. DBA is the latest technique where the bandwidth allocated for the user can be varied according to the usage of the user. In DBA, each user buys fixed bandwidth, if the user needs more than the existing, it will be allocated. If any user is not using the allocated bandwidth, the excess bandwidth will be taken and allocated to the needed user. So many techniques and algorithms have been introduced based on DBA and each of them has its own advantage. However, the main motive of any of these algorithms is the same, which is the sharing of bandwidth. The heavily loaded units have to be allocated bandwidth as soon as possible by collecting the excess bandwidth from the lightly loaded units. The classification of the DBA algorithm is shown in Fig. 1 [20,21].
3. DBA
Avvalgi kunlarda tarmoqni o’tkazish qobiliyati foydalanuvchiga doimiy tezlikda taqsimlanadi. Agar foydalanuvchiga ko'proq tarmoqni o’tkazish qobiliyati kerak bo'lsa, bu amalga oshirilmaydi. Keyin tarmoqni o’tkazish qobiliyatining katta qismi foydalanilmaganligi sababli behuda ketadi. Bu odatda statik tarmoqni o’tkazish qobiliyati taqsimoti deb ataladi, keyinchalik optik tolalar evolyutsiyasida bir nechta o'zgarishlar ro'y berdi, bu esa tarmoq tezligini oshirdi. DBA - bu foydalanuvchi uchun ajratilgan tarmoqni o’tkazish qobiliyati foydalanuvchining foydalanishiga qarab o'zgarishi mumkin bo'lgan eng yangi texnika. DBA-da har bir foydalanuvchi belgilangan tarmoqni o’tkazish qobiliyati sotib oladi, agar foydalanuvchi mavjud bo'lganidan ko'proq kerak bo'lsa, u ajratiladi. Agar biron bir foydalanuvchi ajratilgan tarmoqni o’tkazish qobiliyatidan foydalanmasa, ortiqcha tarmoqni o’tkazish qobiliyati olinadi va kerakli foydalanuvchiga ajratiladi. DBA asosida juda ko'p texnika va algoritmlar kiritilgan va ularning har biri o'ziga xos afzalliklarga ega. Biroq, ushbu algoritmlarning har qandayining asosiy maqsadi bir xil, ya'ni o'tkazish qobiliyatini taqsimlash. Og'ir yuklangan birliklarga o'tkazish qobiliyatini imkon qadar tezroq ajratish kerak, bu esa engil yuklangan bloklardan ortiqcha o'tkazish qobiliyatini yig'ish orqali amalga oshirilishi kerak. DBA algoritmining tasnifi 1-rasmda keltirilgan [20,21].
ABSTRACT
Taking in consideration two leading high capacity optical access technologies, this paper presents a simple cost comparison between GPON and EPON platforms, exposing their major characteristics, making a comparative analysis to find the advantages and disadvantages between these two technologies. The work includes studies on the economic and technical feasibility of implementing a passive optical network; and the choice of valid economic and technical arguments when establishing, planning, or expanding such networks in a given region. The techno economic balance today clearly points to GPON technology, despite the high volume of IP-Ethernet data traffic which favors EPON.
ANTRACT
Ikki etakchi yuqori sig'imli optik kirish texnologiyasini hisobga olgan holda, ushbu maqola GPON va EPON platformalari o'rtasidagi oddiy narxlarni taqqoslashni taqdim etadi, ularning asosiy xususiyatlarini ochib beradi, bu ikki texnologiya o'rtasidagi afzallik va kamchiliklarni topish uchun qiyosiy tahlil qiladi. Ish passiv optik tarmoqni amalga oshirishning iqtisodiy va texnik maqsadga muvofiqligi bo'yicha tadqiqotlarni o'z ichiga oladi; va ma'lum bir mintaqada bunday tarmoqlarni o'rnatish, rejalashtirish yoki kengaytirishda haqiqiy iqtisodiy va texnik dalillarni tanlash. Bugungi kunda texnoiqtisodiy muvozanat EPON-ni qo'llab-quvvatlaydigan IP-Ethernet ma'lumotlar trafigining yuqori hajmiga qaramay, GPON texnologiyasiga aniq ishora qiladi.
Today the optical fiber is the only medium of transmission capable of supporting speed rates above 1 Gbit/s over metropolitan area distances (notwithstanding the long-haul high capacity systems, which are not within the scope of this work), thus the fiber is playing a vital role becoming the right technology solution and giving way to the near future of the metropolitan access and local loop telecommunications through the Passive Optical Networks (PONs) [ 2]. The two prevailing and competing technologies being the gigabit PON (GPON), established under the ITUT framework, and the Ethernet PON (EPON), established under the IEEE 802.3 framework. Further details will be given ahead.
Bugungi kunda optik tola metropoliten masofalarida 1 Gbit/s dan yuqori tezlikni qo'llab-quvvatlashga qodir bo'lgan yagona uzatish tizimidir. Ikkita yetakchi tashkilot va raqobatchi texnologiyalar ITUT tizimi doirasida yaratilgan gigabit PON (GPON) va IEEE 802.3 doirasida yaratilgan Ethernet PON (EPON) hisoblanadi.
2. GPON AND EPON WORLD MARKET
The deployment of PON networks in the world is growing every day, mostly in Japan, Korea, USA and Europe. As seen above, PONs are divided into two major types: the EPON, preferred in the region of Asia-Pacific, and GPON in North America and Europe. In all these areas, companies that offer PON networks are aggressively pursuing their deployment.
According to a study made by the FTTH Council [3], 14 countries have a percentage over 1% of homes with optical fiber connections. Among those 14 countries, the top 3 are in Asia (South Korea, Hong Kong and Japan).
The first, South Korea, has 31.4% of homes connected by optical fiber, followed by Hong Kong 23.4%, Japan with 21.3% and Sweden with 7.1%. The other 10 countries are: Taiwan, Norway, Denmark, Slovenia, Iceland, China, Holland, Italy and Singapore.
In Latin America, GPON networks are coming to the market; cities such as Bogota, Sao Paulo, Buenos Aires and Santiago already have the service of such networks in selected areas. In Colombia there is a platform developed by a foreign company that offers transmission rates at 10Mbit/s. Brazil is the only South American country that developed a GPON platform itself, with a local industry supplying [ 4].
2. GPON VA EPON JAHON BOZORI
Dunyoda PON-tarmoqlarining tarqalishi kun sayin ortib bormoqda, asosan Yaponiya, Koreya, AQSh va Yevropada. Yuqorida ko'rinib turibdiki, PONlar ikkita asosiy turga bo'lingan: Osiyo-Tinch okeani mintaqasida afzal ko'rilgan EPON va Shimoliy Amerika va Evropada GPON. Ushbu sohalarning barchasida PON tarmoqlarini taklif qiluvchi kompaniyalar o'zlarining joylashishini agressiv ravishda davom ettirmoqdalar.
FTTH Kengashi [3] tomonidan o'tkazilgan tadqiqotga ko'ra, 14 mamlakatda optik tolali ulanishga ega uylarning 1% dan ortig'i bor. O'sha 14 davlat orasida birinchi 3 ta o'rin Osiyoda joylashgan (Janubiy Koreya, Gonkong va Yaponiya).
Birinchisi, Janubiy Koreyada uylarning 31,4 foizi optik tolaga ulangan, keyin Gonkong 23,4 foiz, Yaponiya 21,3 foiz va Shvetsiya 7,1 foizga ega. Qolgan 10 ta davlat: Tayvan, Norvegiya, Daniya, Sloveniya, Islandiya, Xitoy, Gollandiya, Italiya va Singapur.
Lotin Amerikasida GPON tarmoqlari bozorga chiqmoqda; Bogota, San-Paulu, Buenos-Ayres va Santyago kabi shaharlarda allaqachon tanlangan hududlarda bunday tarmoqlar xizmati mavjud. Kolumbiyada 10Mbit/s tezlikda uzatish tezligini taklif qiluvchi xorijiy kompaniya tomonidan ishlab chiqilgan platforma mavjud. Braziliya GPON platformasini ishlab chiqqan yagona Janubiy Amerika davlati boʻlib, uni mahalliy sanoat yetkazib beradi [4].
3. TECHNICAL COMPARISON BETWEEN GPON AND EPON
Finding the right technology to cover the last mile of any network has always been a challenge for the telecommunication companies. Find an optimal solution can be a complex process with many factors involved and that should be taken with caution. A determining factor in the cost of an FTTH network is to understand the characteristics of the PON technology (EPON, GPON), such as available bandwidth, network efficiency, and allowed split-ratio. The two technologies have a wellmarked difference in the aspect of architecture. GPON offers a complex network of layer 2 in a tree structure, based on the ATM protocol and multiple protocols that enable the support structure platform [5]. EPON uses simple 2-layer networks using IP for data, voice and video.
The structure of GPON network is supported by a transport solution using different layer 2 protocols of the OSI model. Using ATM technology, which generates virtual circuits that are provided by different types of services that are transported from the CO (Central Office) to corporate users generally. This type of transport offers a high quality service. The Virtual Circuits are generated for each type of service offered on the network. Additionally, equipments of GPON networks need conversions protocols, segmentation, termination of virtual channel (VC) and point-to-point protocol (PPP). In short, the structure of the GPON consists of multiple layer 2 networks on the same physical layer. Each network has a different protocol [6].
EPON on the other hand, provides Ethernet connectivity to any IP-based networks, via the use of routers and gateways connected by optical fibers. Although Ethernet networks have expanded around the world, from local, national, even to international backbone networks [ 7], our focus here is on the protocols that allow the passive optical tree/star to reach the final users from a single head-end.
There are also differences in terms of range, bandwidth efficiency, cost per user, management, and protection [ 12].
3. GPON VA EPON O'RTASIDA TEXNIK TAQQOSLASH
Охирги мил абонентларига юқори сифатли сигналларни етказиб беришда to'g'ri texnologiyani танлаш telekommunikatsiya kompaniyalari учун doimo qiyin bo'lgan.
Optimal yechimni topish juda ko'p omillarni o'z ichiga oladi va bu murakkab jarayondir. FTTH tarmog'i narxining hal qiluvchi omili PON texnologiyasining (EPON, GPON) xususiyatlarini, masalan, mavjud trafik, tarmoq samaradorligi va ruxsat etilgan bo'linish nisbatlarini tushunishdir. Ikkila texnologiya arxitektura jihatidan sezilarli farqga ega. GPON ATM protokoli va qo'llab-quvvatlovchi tuzilma platformasini ta'minlaydigan bir nechta protokollarga asoslangan daraxt tuzilmasida 2 qatlamli murakkab tarmog'ini taklif qiladi [5]. EPON ma'lumotlar, ovoz va video uchun IP-dan foydalangan holda oddiy 2 qatlamli tarmoqlardan foydalanadi.
GPON tarmog'ining tuzilishi OSI modelining turli darajadagi 2 protokollaridan foydalangan holda transport yechimi bilan quvvatlanadi. Odatda CO (Markaziy ofis) dan korporativ foydalanuvchilarga uzatiladigan turli xil xizmatlar tomonidan taqdim etiladigan virtual sxemalarni yaratadigan ATM texnologiyasidan foydalanish. Ushbu turdagi transport yuqori sifatli xizmatni taklif qiladi. Virtual sxemalar tarmoqda taklif qilinadigan har bir xizmat turi uchun yaratiladi. Bundan tashqari, GPON tarmoqlarining uskunalari konvertatsiya protokollari, segmentatsiya, virtual kanalni tugatish (VC) va nuqtadan nuqta protokoliga (PPP) muhtoj. Muxtasar qilib aytganda, GPON strukturasi bir xil jismoniy qatlamdagi bir nechta 2-qavatli tarmoqlardan iborat. Har bir tarmoq turli xil protokollarga ega [6].
Boshqa tomondan, EPON optik tolalar orqali ulangan marshrutizatorlar va shlyuzlardan foydalanish orqali har qanday IP-ga asoslangan tarmoqlarga Ethernet ulanishini ta'minlaydi. Garchi Ethernet tarmoqlari butun dunyo boʻylab mahalliy, milliy, hatto xalqaro magistral tarmoqlargacha kengaygan boʻlsa-da [7], bu yerda asosiy eʼtiborimiz passiv optik daraxt/yulduzning yakuniy foydalanuvchilarga bir nuqtadan yetib borishiga imkon beruvchi protokollarga qaratilgan.
Shuningdek, diapazon, tarmoqni o’tkazish qobiliyati samaradorligi, har bir foydalanuvchi uchun xarajat, boshqaruv va himoya jihatidan farqlar mavjud [12].
Bandwidth
Different offers of bandwidth are available between the two protocols; GPON promised rates of 1.25 Gbit/s or 2.5 Gbit/s of downstream and upstream rates scalable from 155 Mbit/s to 2.5 Gbit/s [ 5]. EPON offers a symmetrical rate of 1.25 Gbit/s. The EPON system efficiency is poor compared with GPON. EPON technology is characterized by extensive headers in the frame, causing low efficiency and consequently, fewer bits of payload (payload) against GPON solutions [ 7]. The two technologies support cable TV (CATV), which demand high rates in the downstream direction for the video service.
3.2. Range of Service
For both technologies, the practical limitation depends on the budget provisions for the optical link. The range specified for the two networks is approximately 20 km, the difference in the rate of division of the optical splitters and the number of optical network units (ONU) supported by each OLT, are two factors that make a point of difference for the two technologies [10]. GPON offers support up until 128 ONUs. With the EPON standard, depending on the kind of lasers, the technology typically can accommodate up to 32 users per OLT or 64 in some cases using Forward Error Correction (FEC) protocols.
3.3. System Management
EPON requires a simple system management, while GPON demands systems for the three Layer 2 network protocols that need. This factor means a lower cost for EPON in the network. Besides, EPON does not require conversion multiple protocols, becoming another factor of cost reduction in the Network.
3.4. Safety and Security
The AES encryption (Advanced Encryption Standard) is part of the standard ITU-T GPON. In EPON networks, the encryption mechanism is not defined in the standard. Some vendors of EPON also use AES, EPON realize the process of encryption in both directions of transmission; upstream and downstream. The OAM service (Operation,
Administration and Maintenance) is also present in the two technologies. GPON uses PLOAM+OMCI (Physical Layer Operations, Administration and Maintenance + Open Manage Client Instrumentation). EPON uses Ethernet OAM.
Tarmoqni o’tkazish qobiliyati
Uzatuvchi va qabul qiluvchilar o'rtasida tarmoq trafiklari bo'yicha turli xil takliflar mavjud; GPON 1,25 Gbit/s yoki 2,5 Gbit/s quyi va yuqori oqim tezligini 155 Mbit/s dan 2,5 Gbit/s gacha kengaytirilishini va’da qildi [5]. EPON 1,25 Gbit/s simmetrik tezlikni taklif qiladi. EPON tizimining samaradorligi GPON bilan solishtirganda yomon. EPON texnologiyasi framedagi keng sarlavhalar bilan tavsiflanadi, bu past samaradorlikka olib keladi. Ikki texnologiya kabel televideniyasini (CATV) qo'llab-quvvatlaydi, bu esa video xizmati uchun quyi oqim yo'nalishida yuqori tariflarni talab qiladi.
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Bosh sahifa
Aloqalar
Bosh sahifa
The passive optical network (pon) technology has been drastically improved in recent years. In spite of using the optical technology, the utilization of the entire bandwidth is a very challenging task
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