(Source Section: System Integration
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Detailed description: In order to meet the requirements of network and business broadbandization, the broadbandization of access network is accelerating. The mainstream of wired access technology is digital subscriber line (DSL) based on telephone line and broadband optical access technology based on optical fiber, while wireless access technology has developed from narrowband wireless access to broadband wireless access.
In the development process of wired access network, ADSL, which currently occupies the dominant position in the broadband access market, has been stretched, and optical access is in copper. The new generation of optical access will replace the copper-based xDSL technology and will become the last km of mainstream technology.
From DSL to ADSL2 : Bidirectional symmetry
DSL technology has been used for 8 years since its earliest use, and it has been continuously improved with the development of network services. In 1999, ITU-T (International Telecommunication Union) promulgated the first-generation ADSL standard. In the following two or three years, ADSL gradually matured and entered a period of rapid development. However, the first-generation ADSL technology still exposed many insurmountable failures in terms of business development, operation and maintenance. In order to overcome these failures, ITU-T adopted a new generation of ADSL standards - G.992.3 and G.992.4 in May 2002, and on this basis, the spread spectrum G.992.5 standard was also adopted in January 2003. . People usually refer to the G.992.3, G.992.4 and G.992.5 standards as the second generation of ADSL2 technology. Because of solving the problem of interoperability, ADSL entered a period of rapid development again in 2006.
While ADSL2 technology is widely used, ITU-T has also rapidly promoted the formulation of VDSL2 standards. When the frequency of VDSL2 is 30MHz, the transmission performance can achieve symmetrical 100Mbit/s. Although people have questions about the prospects for the use of VDSL2 technology, its high-bandwidth performance in two-way symmetry and short-distance range has made people look forward to it.
From BPON to GPON: The High Bandwidth Choice
In recent years, the growth rate of fixed-line operators' revenue from voice and pure broadband services has been declining. and attract more users. Therefore, increasing broadband speed is an inevitable strategic choice for operators.
PON (Passive Optical Network) technology is the mainstream technology of broadband optical access technology. At present, the representative technologies of PON are EPON (Ethernet Passive Optical Network) and GPON (Gigabit Passive Optical Network) technology, APON (ATM-based Passive Optical Network) and BPON (Broadband Passive Optical Network) technology due to high cost , low bandwidth, has been basically eliminated by the market.
APON and BPON refer to ATM-based passive optical networks. These two technologies can utilize the centralized and statistical multiplexing of ATM, combined with the sharing effect of passive splitters on optical fibers and optical line terminals, so that the performance-price ratio can be significantly improved. Improve. However, the actual service adaptation of APON/BPON is very complicated, the service provision capability is limited, the data transmission rate and efficiency are not high, and the cost is high, and its market prospect is bleak due to the decline of ATM. Finally, from the perspective of business development trends, the available bandwidth of APON is still insufficient to meet the development needs of networks and services.
EPONEPON technology is mainly based on the IEEE802.3ah standard, which is a point-to-multipoint communication method. From the structure of EPON, its key advantage is that it simplifies the traditional multi-layer overlapping network structure. EPON can provide a rate of 2.5Gbit/s, which can reduce the equipment cost by about 30 ompared with the 1.25Gbit/s system.
The main fault of EPON is that IEEE802.3ah only stipulates the MAC layer and the physical layer, and the standards above the MAC layer are developed by the manufacturers themselves, which brings flexibility and also causes the failure of poor equipment interoperability. Secondly, the overall efficiency of EPON is low, mainly due to the use of 8B/10B line coding, which introduces a 20 andwidth loss, plus other extra overhead, the available load is only about 50%. Third, because EPON is mainly a standard driven by Ethernet equipment manufacturers, it does not fully consider the operation needs of network operators, and the management functions are not rich enough.)
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