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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The passive optical network ефкошьф (2)

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. The main categories of PON are the Ethernet passive optical network (EPON) and gigabit passive optical network (GPON). These two networks use the dynamic bandwidth allocation (DBA) algorithm to attain the maximum usage of bandwidth, which is provided in the network dynamically according to the need of the customers with the support of the service level agreement (SLA). This paper will provide a clear review about the DBA algorithm of both technologies as well as the comparison.
Passiv optik tarmoq (PON) texnologiyasi so'nggi yillarda keskin yaxshilandi. Optik texnologiyadan foydalanishga qaramay, butun tarmoqdan samarali foydalanish juda qiyin vazifadir. PONning Ethernet passiv optik tarmog'i (EPON) va gigabit passiv optik tarmog'i (GPON) turlari mavjud. Ushbu ikki tarmoq xizmat ko'rsatish darajasi to'g'risidagi kelishuv (SLA) ko'magida mijozlarning ehtiyojlariga muvofiq tarmoqda dinamik ravishda taqdim etiladigan tarmoqni o’tkazish qobiliyatidan maksimal foydalanishga erishish uchun dinamik tarmoqni o’tkazish qobiliyati ajratish (DBA) algoritmidan foydalanadi. Ushbu BMIda ikkala texnologiyaning DBA algoritmi va taqqoslash haqida aniq sharh beradi.
The information and communications network technology is fast growing nowadays. Due to the gradual growth in the cellular mobile subscription and the usage of online video streaming services like Netflix, video conferencing, online high definition television (HDTV), video games, and cloud computing trends, the bandwidth requirement is continuously increasing [1]. According to the latest International Telecommunication Union (ITU) statistics, the fixed broadband usage is increased by 13.1% while mobile service subscriptions by 52.2% and the individuals accessing the Internet have been raised by 46%. An ITU report states that 53.6% of people worldwide access the Internet from their homes and this rate in developed countries increases to 84.4% [2]. Due to such extensive usage of the Internet, the demand for high-speed broadband services has increased drastically [3]. The extensive increase in network traffic and applications has caused a delay between end users and the central office [4]. The passive optical network (PON), which was used earlier, had this problem, so nowadays fiber-to-the-home (FTTH) or fiber-to-the-premises (FTTP) is used effectively [5]. PONs only have passive components but no active components in the transmission path. The passive components are combiners, couplers, and splitters. Since PON has no active components, there is no need of the optical to electrical conversion [6]. The only demerit of PON is the small coverage area, which depends on the signal strength. In an active optical network, the network coverage range is around 100 km, but that in PON is only 20 km. PON mainly has three sections: The optical line terminal (OLT), splitter/combiner, and optical network unit (ONU).
Axborot-kommunikatsiya tarmoqlari texnologiyalari bugungi kunda jadal rivojlanmoqda. Uyali mobil obunaning bosqichma-bosqich o'sishi va Netflix, video konferentsiya, onlayn yuqori aniqlikdagi televizor (HDTV), video o'yinlar va bulutli hisoblash tendentsiyalari kabi onlayn video oqim xizmatlaridan foydalanish tufayli tarmoqni o’tkazish qobiliyati talabi doimiy ravishda oshib bormoqda [1]. Xalqaro elektraloqa ittifoqining (XEI) soʻnggi statistik maʼlumotlariga koʻra, statsionar keng polosali ulanishdan foydalanish 13,1 foizga, uyali aloqa xizmatlariga obuna boʻlish 52,2 foizga, internetga ulangan shaxslar soni esa 46 foizga oshgan. XEI hisobotida aytilishicha, butun dunyo bo'ylab odamlarning 53,6 foizi Internetga o'z uylaridan kirishadi va rivojlangan mamlakatlarda bu ko'rsatkich 84,4 foizgacha oshadi [2]. Internetdan bunday keng foydalanish tufayli yuqori tezlikdagi keng polosali xizmatlarga talab keskin oshdi [3]. Tarmoq trafigining va ilovalarning keng ko'lamli o'sishi oxirgi foydalanuvchilar va markaziy ofis o'rtasida kechikishga olib keldi [4]. Ilgari ishlatilgan passiv optik tarmoq (PON) bu muammoga duch keldi, shuning uchun bugungi kunda uyga tolali (FTTH) yoki tolali tolali (FTTP) samarali qo'llaniladi [5]. PON-larda faqat passiv komponentlar mavjud, lekin uzatish yo'lida faol komponentlar yo'q. Passiv komponentlar birlashtiruvchi, ulash va ajratgichlardir. PON faol komponentlarga ega emasligi sababli, optikni elektrga aylantirishga hojat yo'q [6]. PON ning yagona kamchiliklari signal kuchiga bog'liq bo'lgan kichik qamrov maydonidir. Faol optik tarmoqda tarmoq qamrovi diapazoni 100 km atrofida, PONda esa atigi 20 km. PON asosan uchta bo'limga ega: optik liniya terminali (OLT), ajratuvchi/kombinator va optik tarmoq bloki (ONU).
The central office has OLT, which links the optical network to the Internet protocol (IP), asynchronous transfer mode (ATM), or synchronous optical network (SONET) background. The optical splitter is a passive device that splits the single optical signal from OLT into multiple equal but low power signals to ONUs located at the customer premises. The upstream direction is from multiple ONUs to OLT and the downstream direction is from OLT to ONUs [7]. PON has various types, of which the Ethernet passive optical network (EPON) and gigabit passive optical network (GPON) are the latest and familiar ones [8]. EPON and GPON are used for the Internet access, voice over Internet protocol (VoIP), digital TV, teleconferencing, collaborative gaming, and some applications used as backhaul connections for cellular base stations, Wi-Fi hot spots, and distributed antenna systems. The only difference is the protocol used for its upstream and downstream. The main challenges in the upstream transmission are the separation of signals from multiple ONUs which transmit the signals simultaneously to the combiner, so it must use the multiplexing technique to avoid collision between these ONUs signals.
Markaziy ofisda optik tarmoqni Internet protokoli (IP), asinxron uzatish rejimi (ATM) yoki sinxron optik tarmoq (SONET) foniga bog'laydigan OLT mavjud. Optik ajratuvchi passiv qurilma bo'lib, bitta optik signalni OLT dan bir nechta teng, lekin past quvvatli signallarga mijozning binolarida joylashgan ONUlarga ajratadi. Yuqori oqim yo'nalishi bir nechta ONU dan OLT ga va quyi oqim yo'nalishi OLT dan ONU ga [7]. PON turli xil turlariga ega, ulardan Ethernet passiv optik tarmog'i (EPON) va gigabit passiv optik tarmog'i (GPON) eng yangi va tanishlaridir [8]. EPON va GPON Internetga kirish, ovozli Internet protokoli (VoIP), raqamli televidenie, telekonferentsiya, hamkorlikdagi o'yinlar va ba'zi ilovalar uyali tayanch stantsiyalar, Wi-Fi ulanish nuqtalari va taqsimlangan antenna tizimlari uchun qayta ulanish sifatida ishlatiladi. Yagona farq uning yuqori va quyi oqimi uchun ishlatiladigan protokoldir. Yuqori oqim uzatishdagi asosiy qiyinchiliklar signallarni bir vaqtning o'zida birlashtiruvchiga uzatadigan bir nechta ONU dan signallarni ajratishdir, shuning uchun bu ONU signallari o'rtasidagi to'qnashuvni oldini olish uchun multiplekslash texnikasidan foydalanish kerak.
1.1. EPON
EPON is a kind of PON that carries Ethernet traffic. EPON is a combination of Ethernet and time division multiplexing (TDM) [9]. Ethernet is perfectly accepted in EPON because of its broadcasting nature. Ethernet packets from OLT are broadcasted to proper ONUs by using the media access control (MAC) address, which is attached in the Ethernet packets in the downstream transmission. In the upstream direction, the TDM technology is used. If we consider N ONUs in the design model, the non-overlapping timeslot assigned to every ONU and the N ONUs’ timeslots can be combined together to make a frame, which has small overhead for synchronizing the OLT and ONUs clocks. The traffic reaches ONU either from the single user or local area network (LAN). Packets are buffered in ONU until ONU gets its timeslot from OLT, and once it gets its timeslot all the buffered packets will be transmitted in the upstream direction.
The multi-point control protocol (MPCP) arbitration is a mechanism that supports the timeslot management of OLT [10]. Various kinds of dynamic allocation in EPON are serviced by MPCP, although it does not have any direct relations with the bandwidth. MPCP performs two-way communications between OLT and ONUs along with the simultaneous transmission of multiple ONUs to OLT [11]. MPCP is composed of five messages: GATE, REPORT, REGISTER REQUEST, REGISTER, and REGISTER_AC [12]. The functions of the GATE and REPORT messages are to carry out normal operations during the normal mode. The GATE message is sent to proper ONU along with starting transmission time and length after receiving the data request. The auto discovery mode uses the remaining three-message frame to identify recently connected ONUs, round trip time, and MAC address, respectively [13].
1.1. EPON
EPON Ethernet trafigini tashuvchi PON turidir. EPON Ethernet va vaqtni taqsimlash multipleksiyasining (TDM) birikmasidir [9]. Ethernet o'zining eshittirish xususiyati tufayli EPON-da mukammal qabul qilinadi. OLT dan Ethernet paketlari quyi oqimdagi Ethernet paketlariga biriktirilgan media kirishni boshqarish (MAC) manzili yordamida tegishli ONUlarga uzatiladi. Yuqori oqim yo'nalishida TDM texnologiyasi qo'llaniladi. Dizayn modelida N ONU ni ko'rib chiqsak, har bir ONU va N ONU vaqt oralig'iga tayinlangan bir-biriga mos kelmaydigan vaqt oralig'i OLT va ONU soatlarini sinxronlashtirish uchun kichik yuk bo'lgan ramka yaratish uchun birlashtirilishi mumkin. Trafik ONUga bitta foydalanuvchi yoki mahalliy tarmoqdan (LAN) yetib boradi. ONU o'z vaqt oralig'ini OLT dan olmaguncha paketlar ONU da buferlanadi va u o'z vaqt oralig'ini olgandan keyin barcha buferlangan paketlar yuqori oqim yo'nalishida uzatiladi.
Ko'p nuqtali nazorat protokoli (MPCP) arbitraj OLT vaqt oralig'ini boshqarishni qo'llab-quvvatlaydigan mexanizmdir [10]. EPON-da dinamik taqsimotning har xil turlari MPCP tomonidan xizmat ko'rsatadi, garchi u tarmoqni o’tkazish qobiliyati bilan to'g'ridan-to'g'ri aloqaga ega emas. MPCP bir vaqtning o'zida bir nechta ONU ni OLT ga uzatish bilan bir vaqtda OLT va ONU o'rtasida ikki tomonlama aloqani amalga oshiradi [11]. MPCP beshta xabardan iborat: GATE, Report, REGISTER REQUEST, REGISTER va REGISTER_AC [12]. GATE va Report xabarlarining vazifalari oddiy rejimda normal operatsiyalarni bajarishdir. GATE xabari ma'lumotlar so'rovini olgandan so'ng, uzatish vaqti va uzunligi bilan birga tegishli ONUga yuboriladi. Avtomatik kashfiyot rejimi mos ravishda yaqinda ulangan ONUlarni, aylanma safar vaqtini va MAC manzilini aniqlash uchun qolgan uchta xabarli kadrdan foydalanadi [13].

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