CATV Network Development Direction - Summary of Broadband Commercial Network: This article describes how to enter the Internet network in the two-way CATV network, how to go to broadband commercial network and online e-commerce. Keywords: Internet Broadband Business Network E-commerce, 有 电据 电据 我据 地 依 地 地.. .为 .一.... 地 地. 地 位 地 地 位 位.......... This article will introduce how to achieve the Internet network and how to gradually implement commercial network in my country, become a cradle of e-commerce. 1 Bidirectional CATV network How to Internet Network internet is an "online Internet" -IP network or route network of subnet interconnects through TCP / IP communication protocols and routers. The high-speed data service is transmitted through the two-way CATV network, which is connected to the Internet, which is completed by the Cable Modem threading. CABLE MODEM has developed with the promotion of cable TV broadband data transmission services, which is a user-end device for connecting a PC into a cable TV. 下 Here, you will focus on the composition and working principle of Cable Modem; protocol and international standards.
1.1 Cable Modem (CM) system composition CM system composition block diagram is shown in Figure 1.
The CM system consists of a Cable Modem Termination System.cmts, a Cable Network CN, a user-part of the CM, network management, and security system. In most cases, CMTS needs to be equipped with 1 Cable Modem. The cm of the user (about 500 ~ 2000 households) contained in 1 light node, this point is different from the phone modem now using the phone modem, ISP or telephone company must use the Modem Pool (MODEM pool) to correspond Every one-to-one call is one-to-one, that is, point-to-point; and in the CM system, usually each 6MHz or 8MHz band can be supplied with a number of 500 to 1000 households, with a significant sharing feature. cmts CM and Cable routers are connected to external Internet networks via 10basc-t, 100basc-t, or ATM OC-3. 1.1.2 Network part According to the current international standard MCNS DOCSIS (MultiMedia Cable Network Service Data-over Cable Service Interface Specification) specification, Cable Modem's signal transmission must be based on the HFC network architecture. In the HFC network, the optical node is a very important concept in the network. The CM can provide a transmission rate of up to 30 Mbps, which is actually shared by hundreds of users under 1 optical node, rather than one user. If the user belongs to the same light node exceeds the number of original designs, it is necessary to increase the optical node, essentially the number of optical paths, which means that the design of the HFC network should have a considerable elasticity, with the number of optical paths at any time. 1.3 User parts By Figure 1 shows that the user line is divided into two, all the way to pick up the TV program, and the other will pick up the Cable Modem for receiving normal TV programs. The CM automatically demodulates the corresponding digital channel and then uses the Internet to connect to the computer through the 10BASE-T Ethernet card. The transmission range of the local area network based on the 10BASE-T Ethernet card is generally only 300m, while the distance from the cable network user to the front end is usually tens of kilometers, so that the signal transmission delay of the user terminal to the front end is very large. Obviously, the network communication of computer users and front-end cannot adopt a normal LAN protocol. In order to solve this problem, CM can use universal network protocols, such as IP protocols; cable segments of data link layer protocols use DOCCSIS, IEEE802.14 protocol or with Compatible with other protocols. The data on the 1.2 Internet is how to transfer to the user PC via CATV HFC? In order to achieve high-speed access to the Internet, the user first sends a request command URL by analog MODEM or CABLE MODEM (two-way way). With the PPP point-to-point protocol, the transaction process is finally served in the Internet Service Provider ISP. Then, by dynamic allocation, users get the IP address in this transaction and send the requested information to the Internet. When the information requested by the user request, it will be sent to the Internet ISP, and then the ISP's router is responsible for sending the user cm through the cable television network. The data of the 1.2.2 cable segment is submitted to the network layer IP layer after layer layer, and then forward to the computer network interface after the Ethernet protocol layer package is processed. From the computer from the computer, submit the network layer after unpacking the Ethernet protocol layer, then press the IEEE 802.14 protocol layer layer to be packed to the HFC network. 1.2.3 CMTS Complete a gateway between IP networks and cable television networks, with communication traffic to manage IP, controls users to enter and exit networks.
In CMTS, IP package information content is intercepted and individually accepts sorting; CMTS assigns a new header to the wired television system in the selected sub-channel. 1.2.4 When IP data is in the Cable network, the broadcast IP package will look for a suitable Cable Modem. The cm listened to the same address as the IP address it issued in advance; once found, the CM receives the IP package, and then translates the digital signal by separating the video signal with the digital signal. Code and other processing, finally send it to the PC via the browser. The composition block diagram of Cable Modem cm is shown in Figure 2, the 1.3.1 tuner is the same as the digital top box, and the input RF signal is changed to the signal of IF (6 ~ 40MHz), and is usually Set the duplexer in the tuner to achieve the separation of the downlink signal. 1.3.2 demodulator For the input IF signals, 64 / 256QAM demodulation, Reed-Solomon error correction and MPEG synchronization operations. 1.3.3 Pulse Modulator It functions is the processing of the uplink return signal, which includes Reed-Solomon encoding, 16QAM / QPSK modulation, frequency conversion, D / A conversion, and the like. The modulation mode uses QPSK with strong anti-interference ability. 1.3.4 Processor The processor needs to process the string / and conversion of the signal, the frame flag identification, or insertion, the data signal in the MPEG frame, the filtering of the NPT, and the media access control MAC protocol is executed. Various soft and hardware operations. 1.3.5 Interface The meaning of the interface is the conversion of the necessary communication protocols, and communicates with the PC through the PCI bus interface, USB (Universal Series Bus) or the Ethernet interface. In general, the underlying protocol of the network communication of CM faces the cable TV network usually uses the IEEE802.4 token bus communication protocol to accommodate the long transmission line and star-tree network topology of cable television network; facing PC The end-to-end Ethernet protocol is converted by Ethernet-token converter.
1.4 Characteristics of Cable Modem 1.4.1 Features of the downlink signal stream According to the MCNS DOCSIS standard, the CM downlink uses 64 or 256QAM modulation mode, the band width is 6MHz (NTSC system), or 8MHz (PAL system), downward The transmission rate is determined in the width of the modulation and bandwidth. When the bandwidth is 6MHz, the 64QAM modulation rate is 31.2Mb / s, and the 256QAM modulation time is 41.6Mb / s. Two-way CATV HFC, the key is the return signal. The QPSK or 16QAM modulation method is generally used, and its band width is within 200kHz to 3.2 MHz, and the transmission rate can reach 320 kb / s ~ 10Mb / s. The uplink signal, such as VOD, etc., is always emitted in a pulse, and the uplink signal of multiple CMs can transmit in the same frequency through a split slot. The marked time slot has three, reserved time slots, contention time slots and distance scales. Time slot. a) Reserved time slot: also known as a dedicated time slot, is exclusive for a particular CM, and information is not allowed within the time slot. Reserved time slots are typically used for longer data transmission. b) Strong time slot: also known as competitive time slots, it is characterized by sharing all CMs, using competitive ways, when conflicting and cause data loss, system front end CMTS requires CM to resend at other times. Strong time slots are usually used for very short data transmission. c) Time slots: Since the physical distances of each CM and the front end CMTs are different from each other, there is far apart, it can cause the signal to extend the relative delay of milliseconds, in order to eliminate this difference, each CM is based The range adjustment protocol, moving the "clock" of the unit forward or backward, in order to prepare the delay, that is, the time extension is extensive. How to share the information of 1.4.2 cm, a) The bandwidth allocated by a single user is different from the number of networked users: the number of people who can be used on each 6MHz or 8MHz channel each 6MHz or 8MHz channel is set to maximum. In 2000, most of the actual applications are 500 to 1000, considering the reasons of return noise, the best user number is 500 corresponding to 1 optical node, each of which can generate 30 ~ 40Mb / s bandwidth transmission rate, when 500 people At the same time, when Internet access, each person-assigned transmission rate is 64 to 128kb / s. b) Bandwidth is dynamic allocation: The transmission rate of shared technology allocation in the surface is similar to ISDN (128kb / s) on the surface, and it seems that CM has no superiority; it is different, because the CM network connection is different from The connection of the telephone network line, the telephone network line connection is a swap-oriented call connection. It is the point-to-point occupancy bandwidth is fixed; the bandwidth actually occupying the CM connection is not fixed, only in the user's transmission, the instant to receive data, other Time does not take up network resources. It is because of bandwidth sharing, and the system can realize dynamic allocation of transmission bandwidth; for example, a few instantaneous use users, with a bandwidth, which can be much greater than 64 to 128kb / s transmission rate. When the network uses the peak period of the network, the system can also solve the bandwidth insufficient by flexible allocation of additional bandwidth. For example, one 6MHz or 8MHz band can double the downline rate, or to re-divide the physical network at the user segment, provide a line if necessary. Functions in 1.4.3MAC (Media Access Control) Media Access Control Protocol MAC usually completed by hardware or hardware.
Both CMTS and CM execute this protocol, the purpose is to reasonably share media, and its main functions are as follows: a) Level correction: Correct compensation for loss of different cables, the purpose is to make all CM's uplink signals at the front end The level is the same. b) Time base correction: Correct compensation for the delay of different cables. C) Frequency configuration: Dynamically assign frequencies to Cable Modem, and CM communicate with the system by allocation, downlink frequency. D) Time slot configuration: assign time slots to the uplink signal flow. 1.4.4 Transport Features The basic function of the user-end Cable Modem is to send the uplink digital signal to the RF (Radio Frequency) signal, demodulate the received downlink RF signal as a digital signal, (CMTS received from the external network) Frame package In MPEG-TS, extract data from the MPEG-TS frame to form an Ethernet data, output to the computer through 10Base-T port. Although the HFC network is also multiplexed, the data channel on a certain frequency is shared by multiple users, and the system controls the allocation and resource contention of the user channel through the MAC layer, and also supports different levels of business. . How to go to the commercial network The cable TV industry is carrying out industrial transformation, ranking among IT industry, she is going to a baby, who is needed to support, and the country office [1999] 82 It is a powerful arm. Established an enterprise-wide radio and television network transmission company, which is a wise choice for national assets, which is a wise choice for market regulations. She will build in China's information technology, in the construction of China's characteristic information. The framework of China's e-commerce plays an important role. Our idea is to plan into a network unit in each province, planning into provincial-oriented broadband integrated business network, carrying out e-commerce, video on demand VOD, online teaching, online medical, online banking and other services. The national CATV network has constituted a national universal commercial network. At that time, one of the information expressways with Chinese characteristics, one of the e-commerce networks, one of the national education networks, one of the national medical networks. 〖JP2〗 is "one of the networks", is because the demand of the global diversified market determines the network diversified pattern, which attempts to play the best in the world is not in line with market requirements. 2.1 in provincial units, build broadband multimedia integrated data network Construct the provincial broadband multimedia data network can be divided into 3 layers: its network topology is shown in Figure 3. Its network structure is divided into 3 floors, backbone network, metro network and access network, and different levels of different network technologies. Currently, the SDH transport system having a good transmission performance can be used. It is compatible with high compatibility and high reliability. It provides high quality TV signals to meet the needs of current cable TV and communication, 〖JP2 〗 Is one of the best transmission technology. Best Program The future can use IP Over WDM.
2.1.2 Multi-ring fiber physics networks in the city of the city, can be constructed of a network data platform, transmit analog TV signals and digital signals to accommodate the current needs by using the same cable heterogeneous. In the city, the user's business project demand will increasing, the business form will be a collection of various services such as sound, image, data, only 1 HFC network, one data front, two-way data services, I am afraid it will produce Optical fiber, frequency of frequency resources, management and maintenance also take care of it, it is difficult to provide quality service, so the data and TV score front end, one ring is the ring network of transmission module TV signals, one ring is a network of networks connected to each data ATM / IP Data Backbone City Network. 2.1.3 Access Network The best choice of the current access network. At present, there are two ways for HFC's broadband access: (1) Cable MODEM, (2) Set-top box "STB TV". 2. Two-way CATV HFC network will gradually go to commercial networks 2.2.1 Currently available broadband network service business in 2.2.1.1 VOD service A network can provide high quality real video on demand service vod, which is the two-way CATV HFC An important logo for item function is also an important logo to meet the information highway. Because the VOD business set sound, image, data is integrated, the network bandwidth, storage space, and return performance requirements are higher. It can be said that the implementation of the VOD service is marked with the arrival of the information highway. A) VOD system networking mode as shown in Figure 4: This mode is downgrade DVB-C, DVB (Digital Video Broadcast) code stream to ensure image transmission quality; Upstream use IP mode, users are connected through special set top boxes.
b) VOD system application prospect - reasonable planning, carefully design backbone network and HFC access network frequency band, establish video on-demand network, using mature special set-top box products that meet MCNS DOCSIS OPEN TV standards, build DVB-C front end, only 1 The top box can use the TV to implement VOD, VEB browsing, play digital phones, etc.
2.2.1.2 E-commerce and family bank E-commerce as an advanced trading method in the field of commercial trade has swept around the world. E-commerce has quickly entered China, especially China's upcoming WTO, and the WTO will mean e-commerce from the sense of network economy. In 2000 China's e-commerce year, e-commerce has been mature. The first step in achieving e-commerce is broadband data integrated information network and banking network, first can use this to carry out a home banking business.
a) Family banking system networking is shown in Figure 5: Bank and the Provincial Broadband Network Control Center are connected by fiber optic lines, enabling users to visit the bank's home banking server through Cable Modem or set-top box, visible multi-level firewall guarantee family bank Safety, prevent foreign illegal intrusion, so users can handle access to the deposit in home, convenient and safe. b) E-commerce: Windows 2000 operating system and Site sever tools and other powerful features, broke through the technology "bottleneck" of e-commerce, for Chinese users, e-commerce no longer "far in the sky" is already "near In front of you. What is urgent needs to be solved is that it is possible to organize the e-commerce laws and regulations of my country's specific national conditions as soon as possible. The three big problems of e-commerce are, CA argumentation systems, payment systems, and logistics distribution systems. The current progress is: About the CA demonstration system, the People's Bank of China will start building a financial CA center last year. In the first quarter of this year, the initial line is investigated, and the interconnection and intersection of other CA systems at home and abroad. Certification, system localization and localization, etc., have a long way. In terms of payment systems, China Merchants Bank, Bank of China, and Construction Banks have opened online banking, but only two ways of special accounts and SET protocols. Logistics distribution system, currently national organized large-scale distribution system is still established. With the development of my country's e-commerce, the above three puzzles, the introduction of the laws and regulations of e-commerce, and the family bank will be very convenient to transition to e-commerce, and use the household through broadband data integrated information network to complete commercial trade. Various activities. 2.2.1.3 Distance Education Distance Education is a multimedia business integrating data, sound, and images. It is very high for bandwidth requirements. It is another important sign of the quality of data broadband network. It is also another characteristic of broadband network applications. Accessing the distance education system through the broadband network at home (the system can be universities, each company training system, each test point), accept the teacher's treated, distance education system networking method as shown in Figure 6: 2.2 .2 long-term planning, comprehensive supporting; people-oriented, online trade in 2.2.2.1 long-term planning, comprehensive support: After completing an interactive network equipment system, it is not commercial services, which is only to carry out business services. The first step, to make the cable TV industry to the market, among the IT industry, become one of the protagonists, will also have long-term planning, integrated, and establish a corresponding management system. First of all, a comprehensive network management system fully managed network resources, equipment, users, and charges is to run a good foundation for commercial network. Secondly, in the establishment of the provincial broadband data integrated information network, the provincial capital is the center of all localities, the county division center, and constitute a comprehensive coverage of network platforms in the province. Mature 1 province networking, gradually, 2 provinces, two provinces, multiple provinces, until the national large network. 2.2.2.2 People-oriented, online business a) Bidirectional cable TV user group will come to life: Provide users with Internet access as an entry point for multi-functional services, and quickly start the market. b) In order to start the market, let users buy the price of cheap and beautiful CM and set-top boxes, to encourage manufacturers to develop better terminal equipment, reduce user networked costs, and improve after-sales service. c) In addition to providing a variety of services in addition to home users, providing a data transmission platform for unit users, providing a variety of line access services to enterprising technology and network foundations for enterprise e-commerce.
2.3INTERNET / INTRANET / CATV HFC online e-commerce in 2.3.1 online e-commerce characteristics Global Internet / Intranet is increasingly popular and developed, promoting the development of online e-commerce, plus CATV HFC is connected to Internet / Intranet, will form E - commerce characteristics with Chinese characteristics. a) Online e-commerce systems use Internet technology to facilitate connection and expansion, and provide general information platforms for interactive multimedia, which is easy to popularize and apply. b) Online e-commerce system due to the national network of CATV.com, more determines that it is facing the whole society, and its users are very broad, including not only enterprises and government departments, but also all institutions and families, individuals. c) Investment in online e-commerce system, short development time, low operating cost, users do not need to be found, so you don't need special training, easy to use. d) Online e-commerce systems can provide various application services for users, providing various application services to enterprises, reduce costs, and improve efficiency services. 2.3.2 Online e-commerce system framework A complete online e-commerce system consists of three parts of the network platform, system software platform, and e-commerce applications. A browser, web server, database server 3 layer structure that is popular with the current Internet is consistent. 2.3.3 Software platform for online e-commerce: Software platform contains the basic service platform and the business development platform 2. The subsystem of the service and business development platform provided by the underlying service platform is Table 1: 3 Conclusion Face the challenges and opportunities in the new century, cable TV network will usher in the opportunities of history, and the two-way interactive cable TV network will become a development. Mainstream, and will provoke the heavy responsibility of building information expressions with Chinese characteristics. In the next 10 years, the two-way CATV HFC will also go to the market and become the draft soldiers in my country. ▲
