Unit wiring diagram (unit wiring rules)

At present, most residential wiring uses HFC.

The so-called last mile wiring.

Details are as follows:

As the goal pursued by people, intelligent community and intelligent residence will inevitably increase the complexity and difficulty of network wiring in the whole community. Therefore, the optimization of network wiring is imminent. With the acceleration of global informatization, broadband multimedia services are becoming the key development direction of communication networks and telecom operators. How to transmit broadband integrated multimedia information including video, voice and data in the same network is a central topic in the current communication network industry. The key to realize broadband multimedia service data transmission lies in the network? Quot the last mile ",that is, from the multimedia backbone network to the broadband access network of every household.

Broadband access technology based on HFC makes full use of existing HFC network resources, avoids repeated construction of the network, effectively solves the difficulty of network wiring, and reduces the overall investment cost of the community. Cable TV network has a bandwidth of up to 860MHz and two-way transmission capability. In addition to using CATV to transmit a large number of TV programs, there are enough bandwidth resources to provide various business applications. According to their types, these services can be divided into audio, video and digital, which is one of the best ways to develop the information superhighway. At the same time, the network can also provide data channels for various intelligent subsystems (such as three-meter remote transmission, security and other systems), and realize the optimization and integration of network wiring in the whole community.

Introduction of 1 HFC

Characteristics and frequency band division of 1. 1 HFC

HFC (Hybrid Fiber Coaxial Cable) is a hybrid fiber coaxial cable network. The network is a two-way media sharing system, including the optical fiber trunk between the front end and the optical fiber nodes, and the coaxial distribution network from the optical fiber nodes to the user premises. The video signal is transmitted on the optical fiber in an analog way. Optical fiber nodes connect optical fiber trunk lines and coaxial distribution lines. Is the optical fiber node dizzy through the lower lead of coaxial cable? 00 to 500 user services. These connected users share the same cable, so * * * can enjoy its available capacity and bandwidth at the same time. Compared with the traditional tree and branch cable networks, HFC greatly reduces the number of amplifiers between the front-end and the households, thus improving the signal quality and reliability (amplifier failure is the main reason for business interruption on CATV networks). There are several other advantages to adopting this HFC topology. The fiber backbone no longer needs an amplifier. The noise interference of optical fiber is small and its signal attenuation is also small. When the amplifier does fail, only a few users are affected, and fault location is relatively easy.

At present, traditional cable TV networks are mostly 300MHz, 450MHz or 550MHz systems. HFC adopts 860MHz coaxial network, which must support both broadcast information transmission and two-way information transmission. According to the latest regulations of gy/t 106- 1999, the frequency bands of HFC are divided as follows (as shown in figure 1).

Figure 1 HFC coaxial cable frequency band division

○ 5mhz ~ 65mhz is used for uplink transmission of analog, data and control signals.

χ 87mhz ~ 108mhz is used for FM broadcasting.

χ 108 MHz ~ 550 MHz is used for downlink transmission of analog, data and control signals.

○ 550 MHz ~ 860 MHz is used for digital signal downlink (such as VOD and HDTV). ).

1.2 service functions of HFC broadband access network system

1. Analog radio and television, FM broadcasting and other traditional services.

2. High-speed data services such as high-speed Internet access based on IP technology;

3.IP voice /IP video service;

4. Other value-added services, such as distance education, telemedicine, virtual private network (VPN), video on demand (VOD), video conference, telecommuting, digital TV, access channel for providing comprehensive information resources in the community, peripheral alarm information transmission, closed-circuit TV monitoring system image transmission, visitor intercom system networking information transmission, burglar alarm information transmission, public equipment information transmission, etc. Take it? /p & gt；

2 HFC network scheme

2. 1 system framework

The system architecture of HFC is shown in Figure 2. The management center is equipped with data front-end equipment (INA), network management system, local server and cable TV program source. After the output of each INA is mixed with the TV signal, the optical distributor can serve multiple optical nodes, and each optical node can serve about 300 to 500 users, which can provide sufficient bandwidth for each user.

Figure 2 System Frame Diagram

2.2 Client System Framework

The schematic diagram of the client system is shown in Figure 3. On the client side, Cable Modem is configured to provide users with high-speed data services, and HomeGateway is configured as a data acquisition terminal for security, remote meter reading and public equipment monitoring. Cable Modem is used as the data transmission terminal of IP, and a data information channel is built on HFC broadband communication network.

Figure 3 Client System Diagram

2.3 Physical expansion between cable modem and optical fiber node

The main function of cable modem is to transmit high-speed digital data from network to users and from users to network on cable network. Fig. 4 depicts the physical topology and interface between the cable modem and the optical fiber node. The "X" here represents the number of cable modems connected to the subnet. Depending on the traffic situation, this topology can usually support 300 to 500 families. At the channel layer, in order to receive digital data signals, the downlink cable modem must tune the receiver to the 6MHz band between 550 and 860MHz. Here, it is assumed that there are "m" downlink paths in the cable subsystem. The industry chooses QAM modulation as the downlink modulation technology. In the upstream direction, Cable Modem realizes the transmitter function, and uses the 6MHz frequency band between 5MHz and 65MHz to transmit information to the front end. It is assumed here that "n" uplink paths are used to transmit uplink data. Burst QPSK modulation technology is used to modulate data and put it into 6MHz channel.

Fig. 4 Physical structure of cable modem/optical fiber node

3 Advantages of HFC system

The establishment of HFC broadband access system is equivalent to the establishment of an information "highway" in the whole residential area. Residents can ride on this "highway" and get the maximum amount of information with less cost and shorter time. The network center is quite? Quot "Expressway" toll stations and management stations, the property management office can formulate the property management system in combination with the relevant rules and regulations and the characteristics of the residential area. Through the maintenance and suggestions of the community, we can provide all kinds of information services and management for residents, provide the required living and living environment for all kinds of houses, and collect the necessary management fees to achieve the purpose of value-added property management.

1. Advantages of high-speed Internet access. Domestic home Internet access mainly adopts the Modem mode of ordinary telephone line, that is, access to the Internet backbone network through the PSTN of the telecommunications department. Limited by the 64kb/s voice path of PSTN switch, the highest Internet access rate is only 56 KB/s. Even if the 2B+D terminal mode of narrow-band ISDN is adopted, it can only reach128 KB/s/s. The support for broadband multimedia services is still unsatisfactory. The downlink rate of cable modem is as high as 46Mb/s, which can fully meet the needs of broadband multimedia services. The IP router is located at the front end. For the media sharing structure, the front end concentrates all IP traffic and sends it to the IP router. Proxy server or cache is optional and can be set at the front end. They have copies of popular web pages and texts. These copies can be sent to the requesting cable modem users at a faster speed as needed.

2. Bandwidth advantage: Generally, 500 households can enjoy 40M bandwidth, which can ensure users' high-speed access.

3. Using HFC technology, the information transmission distance is far, and there is no strict transmission distance limit.

4. Using HFC network resources to solve the problems of transmission media such as safety and remote transmission of three meters, which saves investment and is convenient for construction.

Four engineering examples

HFC broadband access project of an intelligent community in Chongqing is located in Yuzhong District, Chongqing. The first phase covers an area of 80,000 square meters and consists of two 29-story commercial and residential buildings. In order to build an information superhighway in the community, save investment and facilitate construction management, it is decided to implement HFC broadband access in the community. CableStream, a product of Hughes Company, USA, is selected for this project. The front office of the residential area is located on the 8th floor of Building A. The front-end equipment is CSH3000 of cable modem of CableStream, which is compatible with DVB2.0 and European MODEM 1.0. Based on the fast IP technology, the bandwidth is used efficiently, and it can be extended to 2 downlink (10 Mbps) and 16 uplink (/. The equipment adopts advanced QOS management to adapt to different users and services, and its hot exchange and real-time download technology make online configuration flexible. The terminal equipment is CableStream's high-speed European cable modem CSR3000, which is compatible with European modem standard 1.0, fully compatible with DVB's MAC layer standard, and can be upgraded on site. Through a powerful software download mechanism, business services can be continuously strengthened in the future. The device can connect as many as 12 home network PCs, and integrates IP routing function. Its optimized European RF interface ensures the maximum efficiency of spectrum utilization and minimizes noise and distortion. The network management software CSM 1000 is a cable modem with CableStream for system management. The software supports the remote management of the set-top box system of cable modem system, and automatically configures the system, user categories and services through the modular StreamPloit architecture mechanism. Its advanced QOS management has brought flexible and diverse business models. Through the implementation of HFC broadband access, the intelligent requirements of the community are met and the investment is saved.

5 concluding remarks

In the long run, HFC plans to provide a so-called full service network (FSN), that is, a single network provides various types.

Analog and digital communication services, including wired and wireless, voice and data, image information services, multimedia and transaction processing services. This full-service network will connect the front end of CATV network, traditional telephone exchange, other image and information service facilities (such as VOD server), cellular mobile exchange, personal communication exchange and so on. Many information and entertainment services will be provided through gateways, and today's front-end will develop into an important gateway for users to access the open bandwidth information superhighway. Users will be able to access various services from various servers and enjoy expensive service resources, such as VOD center and ATM switching resources. In a word, this full-service network provided by HFC will be a new type of broadband service network, which provides us with a good way to realize broadband communication.