Cable Broadband

Basic overview

Introduction

The development momentum of CableModem access technology in the world, especially in North America, is very strong. Guangdong, Zhejiang, Sichuan, Guangxi, Shenzhen, Nanjing and other provinces and cities have opened CableModem access. It is the biggest competitor of the telecommunication company's xDSL technology. In the future, the xDSL access technology based on the traditional telephone network developed vigorously by the telecommunication company camp and the CableModem technology promoted by the broadcasting system and cable TV manufacturers will compete in the access network market (especially the high-speed Internet access market).

China

In China, the broadband access technology developed by the radio and television department on the cable television (CATV) network has matured and entered the market. The CATV network has a wide coverage area and a large number of users (according to statistics, the number of cable TV users nationwide has exceeded 100 million in January 1999); the network has a wide spectrum range and a high starting point. Most newly-built CATV networks use optical fiber coaxial Hybrid network (HFC network), using adjacent frequency transmission system with bandwidth above 550MHZ, is very suitable for providing broadband functional services. Cable Modem (CableModem) technology is a network access technology based on CATV (HFC) network.

Technical introduction

CableModem and the previous Modem are in principle that the data is modulated and then transmitted in a frequency range of the Cable (cable), demodulated and transmitted during reception The mechanism is the same as that of ordinary Modem, but the difference is that it modulates and demodulates through a certain transmission frequency band of CATV. The transmission medium of the ordinary Modem is independent between the user and the switch, that is, the communication medium is exclusive to the user. CableModem is a shared medium system, and other idle frequency bands can still be used for the transmission of cable TV signals.

Feature introduction

CableModem completely solves the congestion caused by the transmission of sound and image, and its rate has reached more than 10Mbps, and the downstream rate is even higher. Although the traditional modem has developed a product with a rate of 56Kbps, its theoretical transmission limit is 64Kbps, and it is impossible to increase it. Cable Modem is also a key equipment for building a metropolitan area network. Hybrid optical fiber coaxial network (HFC) backbone uses optical fiber, and tree-type bus coaxial cable network is used to connect users in optical node communities. The transmission frequency can be as high as 550/750MHz. It is necessary to use CableModem to transmit data in HFC network.

Technical Principles

This is the necessary magic weapon for cable TV to enter the Internet access market. Since the successful two-way transmission experiment of analog and digital TV and data on the cable television network of Orlando, Florida by Time Warner in December 1993, Cable technology has become the most promising access technology. On the one hand, it can theoretically provide extremely fast access speeds and relatively low access fees. On the other hand, cable TV has a huge user base. Cable TV stations generally separate a 6MHZ channel from the TV channels between 42MHZ and 750MHZ for downlink transmission of data. Usually the downlink data adopts 64QAM (quadrature amplitude modulation) modulation mode, the highest rate can reach 27Mbps, if adopts 256QAM, the highest rate can reach 36Mbps. Uplink data is generally transmitted through a section of frequency spectrum between 5 and 42 MHz. In order to effectively suppress the accumulation of uplink noise, QPSK modulation is generally used. QPSK is more suitable for noise environments than 64QAM, but the rate is lower. Uplink speed can reach up to 10Mbps.

CableModem itself is not just a modem, it integrates the functions of MODEM, tuner, encryption/decryption device, bridge, network interface card, virtual VLAN proxy and Ethernet hub. It does not require dial-up Internet access, does not occupy a telephone line, and can provide a permanent connection online at any time. A VPN (virtual private network) connection is established between the service provider's equipment and the user's Modem. CableModem provides a standard 10BaseT Ethernet interface to connect to the user's PC device or local area network hub. In addition to the two-way CableModem access solution, COM21 also supports the one-way CableModem access solution. Its uplink channel adopts telephone MODEM backhaul, which saves the huge cost required for two-way transformation of the current CATV network, saves operating costs, and can immediately launch high-speed Internet access services; but it also loses the greatest advantage of CableModem technology: no Occupy the phone line, no dialing and permanent connection.

With the rapid development of science and technology, especially Internet technology, and the opening of the telecommunications market, a situation where the three major networks of telecommunications network, cable television network and computer network coexist and merge with each other has gradually formed. China Telecom has realized the transmission and switching of the backbone network and the digitization of the relay and switching of the local network, but the user access network still uses analog copper wire as the main transmission medium, which has become the bottleneck of the modern telecommunications network. The explosive development of Internet technology has caused more and more multimedia data such as video, audio and high-definition images to be transmitted on the network. This information is swallowing limited channel bandwidth resources at a terrible speed. The traditional access network must develop towards high bandwidth. Using the existing HFC network, local cable TV stations can quickly transform into TV program providers and broadband Internet data service providers, thereby winning new money-making opportunities and sharing the promising broadband data service market.

Prospects

According to the forecast in 1999, the population of the United States using CableModem to access the Internet through the cable television broadband data network will soon exceed 3 million, and it is predicted that the population using CableModem will grow rapidly. Well-known technology and entertainment multinational companies such as Cisio, 3com, Nortel, General Telecommunications, AT&T, and Time Warner have invested in the industry of cable TV broadband Internet access, which is equivalent to setting the best guarantee for cable TV broadband Internet services. . In our country, the number of people going online through the cable TV broadband data network is increasing exponentially. There are dozens of domestic listed companies, dozens of cable TV stations or cable TV network companies, including well-known domestic high-tech listed companies and provincial cable TV stations. : ZTE, Shanghai Bell, SVA, Oriental Pearl TV, Guangdong Cable TV, etc. have all invested in the cable TV broadband network industry. If the cable TV broadband network does not have broad development prospects, these companies will invest heavily in this industry. NS? Why can cable broadband Internet services grow to such an astonishing number? Let’s make a simple comparison between broadband Internet access and telephone Internet access: dial-up Internet access, the Internet speed is generally 33.6Kbps/56.6Kbps, while the ISDN dedicated line Internet service generally provided by local telephone companies, the connection speed is 128Kbps, if you use ADSL The data dedicated line is used to access the Internet, and the connection speed is about 1.8Mbps, but the transmission distance cannot exceed 5 kilometers, and the equipment is very expensive. Internet access through cable TV broadband, using CableModem, the data transmission speed can reach between 10M-36Mbps, through the optical fiber backbone network transmission, the distance can "cross continents and provinces", through the HFC network to transmit data, can cover the entire large and medium-sized cities; if In the future, the cable television broadband network will reach the level of fiber-to-the-building after the transformation in the future, realizing a full data network, and the transmission speed can reach more than 1000Mbps. This is the real information highway. In addition to achieving high-speed Internet access, it can also achieve visualization High-speed data transmission services such as telephone, video conferencing, multimedia distance learning, telemedicine, online games, IP telephony, high-speed digital broadcasting, VPN, and video-on-demand.

Speed

Many people worry that the bandwidth of CableModem is shared. If there are more people on the Internet, the speed will decrease. Here we explain from different perspectives such as technology and trend to help you understand how big the bandwidth of CableModem is. It has been mentioned earlier that CableModem can generate 27M/36Mbps bandwidth on a single cable TV channel with different modulation techniques, which is equivalent to the bandwidth of 16-22 ADSL dedicated lines. Based on the bandwidth of each Cable channel and the number of users who are online at the same time on this channel, we can calculate the average bandwidth per person. The "feeling" is used here because the bandwidth of CableModem, like Ethernet0, is shared by all users. Regarding the estimation method of bandwidth available to each person on a shared media (SharedMedia), it is estimated using a model called "statistical multiplexing". When other users are not carrying out a large number of transmissions, users almost Can enjoy all the bandwidth exclusively. This is the reason why cablemodem users can often enjoy ultra-high speed. According to estimates, each broadband Internet user can enjoy an average speed of 200-500Kbps, the fastest 1500Kbps (equivalent to an ADSL dedicated line) In the future network development, when the transmission speed reaches 1Gbps or more, the average speed that each user can enjoy will be more than 2Mpbs.

The areas where the Shanghai Cable Link did not open:

Shanghai City: Baoshan District, Beicai, Chuansha, Cao Road, Gong Road, Waigaoqiao, Zhangjiang, Pudong District, Tang Town and Sanlin Town.

Shanghai suburbs and counties: Songjiang District, Nanhui District, Fengxian District, Jinshan District, Chongming District, Jiading District, Qingpu District

Price

·Wired broadband Monthly subscription of 220 yuan for initial installation + 120 yuan/month

·Wired broadband package of 1200 yuan per year (one year) (free of initial installation fee) + no account restrictions + free relocation

·Wired broadband package for two years and 25 months, 2400 yuan / 25 months (free of initial installation fee) + no account restrictions + free transfer.

Other fees for wired broadband:

Suspend fee: 50 yuan/time

Insurance fee: 20 yuan/month, charged after three months of suspension

Equipment testing: free

Relocation: free

Termination of service: free