Diverse Broadband Access Technologies

Broadband access technology is still quite commonly used. So I have studied the characteristics and advantages of different broadband access technologies. I would like to share with you here, hoping to help you. Broadband access technology is currently one of the most active areas of communication technology. In a telecom network, the access network connects users and business nodes to solve transmission, re-connection, and resource sharing issues. With the increase in bandwidth requirements, optical fiber is constantly extended to users. FTTB fiber to the building), FTTC fiber to the roadside), FTTCab (fiber to the building) and FTTZ fiber to the residential area) are being implemented, but it is still difficult to implement FTTH optical fiber to households. Therefore, there are two technical problems to be solved: First, The ONU Optical Network Unit) and the OLT optical line terminal) which technology should be used for information transmission; the second is how the user terminal or local area network accesses the ONU. There are many technologies to solve these two problems, especially the latter. They have different transmission features, market positioning, physical location, and problems to be solved, in the future, many technologies may coexist in actual access networks. This article will introduce some major Wired Broadband Access Technologies.

At present, the main wired broadband access technologies include: ordinary Modem, N-ISDN narrowband integrated business Digital Network), Cable Modem and hfc-fiber coaxial Cable), HDSL high-speed digital user loop) symmetric digital user loop with SDSL), asymmetric digital user loop with ADSL) and G. lite (no-shard ADSL), VDSL very high-speed digital user loop), HomePNA home telephone line Network Alliance), Ethernet, SDH synchronous digital sequence), PONPassive Passive Optical Network) and APONATM Passive Optical Network), IM-DSL Reverse Multiplexing digital user loop. In general, any broadband access technology has corresponding CO terminal devices) and RT client devices), but the latter is more diverse.

1. common Modem
Common Modem is currently one of the main methods to achieve narrowband Internet access. It is mature in technology and has a maximum transmission rate of 56 kbps. Technically, it does not rely on the optical access network. The product includes the user's Modem and the Modem pool placed in the telecom data center. Due to its low rate, it is gradually being replaced by N-ISDN and other technologies.

2. N-ISDN
N-ISDN, also known as "one-wire" is also a mature, dependent on optical access network of Narrow Band Access copper technology, the current main use of 2B + D to achieve telephone and Internet access, the typical download speed is up to 64 kbps, which can basically meet the current needs of narrow-band browsing. It is an economical and effective choice for Internet users to increase their Internet access speed. Currently, it has been activated in various cities in China, and users have been well reflected, gradually replacing General Modom. ISDN devices include switches and terminal devices. There are many types of terminal devices, but in terms of functions, they are mainly the free combination of ISDN network terminals, terminal adapters, routers and videophone functions, it also provides different interfaces, such as ISA, PCI, RS232, USB, analog telephone port, and Ethernet port, to meet different requirements.

3. Cable Modem and HFCs
Cable Modem (Cable Modem) is a method for using a Cable TV network to achieve broadband data access for users. It is also one of the key technologies in a hybrid fiber-optic coaxial network. As one of the earliest mature and market-oriented Broadband Access Technologies, the product has the characteristics of broadband and relative economics. In a coverage area of around 500 optical nodes, the service can provide 60 analog radio and television channels, at least 2 telephones per household, and a data service with a speed of at least 10 Mbps. Currently, there is a mature 40 Mbps Cable Modem. ). Use its 550M ~ in the future ~ The 200 MHz spectrum also provides at least MPEG-2 of on-demand TV services and other two-way telecommunications services. In the long run, the entire Service Network (FSN) is planned to provide various types of simulation and digital services over a single Network, and gradually transition from multi-user sharing of the above bandwidth to a single user exclusive.

4. HDSL and SDSL
HDSL uses a non-relay user ring road network to transmit information at a Symmetric high speed using a non-load telephone line. The typical speed is 2 Mbps, and the distance is 3 ~ 5 km. Two or three pairs of twisted-pair copper wires are used. line pairs, low bit error rate, and line codes are not required, which provides good spectrum compatibility. At present, HDSL Technology has developed relatively mature, mainly used to replace the traditional T1/E1, to solve the Broadband Access Technology for scattered users, renting lines for users, and transmitting multiple channels of voice, video and data. SDSL is a simplified HDSL version. It uses a single twisted pair wire to provide bidirectional high-speed variable bit rate connections. The speed ranges from 2.084 Kbps to 4mm Mbps. The maximum transmission distance is 3 kilometers on twisted pair wires. HDSL/SDSL can be combined with FTTB/FTTC. In terms of functions, there are not many types of HDSL devices, and the compatibility between devices of various manufacturers is poor. SDSL is mature later, and the product types are not rich.

5. ADSL and G. lite
ADSL uses load telephone lines for Asymmetric high-speed transmission of information on a non-relay user Ring Road Network. Compared with HDSL/SDSL, it avoids user-side interference and improves the transmission rate, extended transmission distance. ADSL uses DMTDiscrete Multitone (discrete multiple audios) line codes. The downlink communication supports a speed of Mbps ~ 8 Mbps or higher, the uplink communication rate is 16 KB ~ 640Kbps or higher, simulating independent user traffic. At present, it can transmit 6 Mbps signals over 0.5 km on 3.6-core twisted pair wires. G. lite is a simplified ADSL to reduce costs and facilitate the installation of client devices. The downlink speed is up to 1.5 Mbps, And the uplink speed is up to 512 Kbps. No telephone splitter is required. The maximum transmission distance is 5 kilometers.

ADSL includes G. (lite) the CO-end device DSLAM digital user loop multiplexing) is mainly used to achieve the function of re-connection and sub-connection, which can be placed in the local office or residential area, the purpose of putting it in a residential area is to increase the transmission rate and enable more common users to use ADSL. In this case, the combination of optical access networks is required. There are many client devices, including: ADSL Modem with different interfaces PCI, USB, and Ethernet, ADSL routers that meet different needs, and Integrated Gateway, splitter, or low-pass filter for data and voice at the same time. Currently, G. the difference between lite and ADSL is not too large, mainly because of the difference in DSLAM prices. However, due to the fact that telecom operators are more interested in full-speed adsl dslam, the current ADSL chips and devices support both full-speed ADSL and G. lite, so in reality pure G. lite products are rare. In China, the ADSL lab network has been activated in Guangdong, Shanghai, Fujian, Wuhan and other places. However, family users are hard to afford to pay expensive installation fees and usage fees.

6. VDSL
In the development of ADSL, it is found that the transmission rate will be greatly improved by appropriately reducing the distance, which leads to VDSL. In the VDSL system, the uplink and downlink channels are separated by the frequency division multiplexing technology. The encoding methods include CAP no-carrier amplitude and phase modulation), DMT, and DWMT Discrete Wavelet Multi-audio. The upstream and downstream speeds of VDSL are also asymmetric. the downlink speeds include 13 Mbps, 26 Mbps, and 52 Mbips. The transmission distance is 1500 m, 300 m, and m; generally, the uplink speed is 3 Mbps: 1.6 Mbps, 19.2 Mbps, and Mbps. VDSL must be used in combination with FTTB, FTTC, FTTCab, and FTTZ. In terms of products, VDSL is similar to ADSL, but due to the late appearance of VDSL technology, there are not many formal products.

7. HomePNA
HomePNA is a technology that uses telephone lines to establish a LAN. It solves the connection problem between multiple devices of home users and cannot be viewed as an independent broadband access technology. From the spectrum perspective, the physical layer signals of HomePNA are distributed between 5.5MHz and 9.5MHz. The center frequency is 7.5 MHz, and the data transmission rate is 1 Mbps. On the media access control layer, HomePNA uses the existing Ethernet protocol; in connection mode, the HomePNA technology enables all nodes in the network to be connected in a chrysanthemum chain without central convergence or exchange. This connection method helps simplify installation, it can also cleverly change the random topology of home phone cabling.

From the product perspective, the end devices of HomePNA are developing from an independent network interface card and an embedded network card on the PC motherboard to a 10/100 M fast Ethernet card. To solve the Internet access problem, homePNA is combined with xDSL and common Modem to form a smart home gateway.

8. Ethernet
Due to the popularity of 10 M/M Ethernet, the maturity and low cost of M Ethernet technology, and the fact that people only need IP services and do not require QOS, the full Ethernet Access solution has been widely used. Its basic concept is to establish a M Ethernet backbone network to achieve M Ethernet to the building, roadside, residential area, then, M Ethernet is used to access the floor of the building, small buildings and residential buildings, and 10 M Ethernet is used to access the semi-public room and desktop. Currently, the user uses the ethernet card and Category 5 lines to connect to the devices on the floor. The switches on the second floor use VLAN Technology). The out-of-band management is implemented through common Modem, remote power supply is adopted, while VLAN technology is used for the second-level switches with higher throughput.) hybrid optical cables and Modem are used to manage and power switches on the floor; multiple cells share a gigabit router and NAT network address ing through optical fiber cables). The backbone network connects multiple routers to form a broadband ip man. The access between users should be through the vro, and user management should also be completed at the node where the vro is located.

9. SDH
SDH is suitable for access networks with high reliability, flexibility, high compact, low power consumption and low cost. Generally, when the bandwidth is 155Mbps or higher, the SDH system can be directly connected to the user in the form of a point-to-point or ring topology. When the bandwidth is greater than 34Mbps, directly set sdh adm (Add/Drop Multiplexer, plug-in Multiplexing) to connect the user with a STM-1 channel to the STM-N service node, which can be point-to-point, you can also use a ring structure. If the bandwidth requirement is far less than 34Mbps, a lower-speed multiplexing or shared ADM is more cost-effective, the end multiplexing based on the roadside (DP point) can be used to provide a large number of users with 2 mbps bandwidth as the basic unit. Users with bandwidth less than 2 Mbps can rely on business multiplexing or post-PON to solve the problem. Using STM-0 Sub-rate connections (Sub STM-0) is a cost-effective solution for small bandwidth users, while maintaining all SDH management capabilities and functions, ITU-T G.708 specifies such an interface.

Although SDH can allocate different bandwidths for different nodes during construction, it cannot dynamically adjust the Total node rate. Many SDH devices, especially sdh adm, are applicable to access networks.

10. PON and APON
Passive Optical Network (PON) includes narrowband Passive Optical Networks and ATM-based Broadband Passive Optical Networks-APON. The former is used to provide data transmission channels at 2 Mbps and below, the latter can provide up to 622Mbps downstream transmission channels. APON mostly uses passive double stars or tree structures, and uses special point-to-multiple-point multi-access protocols, so that many ONU/ONTOptical Network termination, optical Network terminals) share OLT, many users share ONU to reduce the initial construction cost. Currently, APON products have been officially launched, but the variety is limited, and the integration of components needs to be further improved.

11. IM-DSL
The basic idea of IM-DSL is to establish multiple xDSL links, and form a high-speed physical link through Reverse Multiplexing Technology. Then, using the statistical multiplexing technology of ATM, many users can share this physical channel. Apparently, the IM-DSL transmission distance is limited to 2 kilometers, to solve the contradiction between the current broadband DSL technology and the wide implementation of FTTB, FTTC and FTTZ due to limited transmission distance. IM-DSL technology makes full use of existing telephone lines, small projects, good capacity scalability, less investment, but there is a lack of industrial standards at present, at the same time by the pressure from the user to extend the and optical fiber. At present, it is difficult to see mature and formal products of this technology.

Summary
With the development of data and multimedia services, broadband and optical fiber networks become more and more obvious. The research and development of broadband access technology has become a hot topic in the current communication field. From the current development perspective, there are three different systems of broadband access technology: xDSL, especially ADSL), Cable Modem, HFCs, and Ethernet, as a broadband access technology, APON and SDH will also develop in the corresponding fields.

1. How wireless access network technology works
2. IP access network technology is under pressure
3. Future Development Trend of Access Network Technology
4. Practical application of Broadband Access Network
5. Full explanation of Broadband Access Network Technology