A modem used to connect a computer to a cable TV service that provides Internet access. Cable modems can dramatically increase the bandwidth between the user's computer and the Internet service provider. Download speeds have reached 6 Mbps and beyond, but the connection is asynchronous. In order to prevent users with lower-cost cable access from hosting high-traffic Web servers, the upload speed is considerably slower, from 10 to 20 times slower. Cable operators also routinely change IP addresses assigned to users to prevent Web hosting .
Cable modems connect to the computer via an Ethernet port, which is an always-on connection. Ethernet is a shared medium, and the individual user's speed will vary depending on how many customers are sending or receiving data on that cable segment at the same time. For example, when the kids come home from school around 3pm, many cable users experience a corresponding slowdown. See DOCSIS, cable Internet, Internet appliance and MSN TV.
A cable modem is a special type of modem that is designed to modulate a data signal over cable television infrastructure. Cable modems are primarily used to deliver broadband Internet access, taking advantage of unused bandwidth on a cable television network. There were 22.5 million cable modem users in the United States during Q1 2005. That's up from 17.4 million in Q1 2004. It is also commonly found in Canada and Latin America.
Cable Modems are latest tools used for high-speed data access. They provide a fast communication channel for computers on wide area networks such as the Internet and many company intranet. They make use of existing cable wire network already present in most cities. They are able to run ata higher speed of data communication. The term cable modem refers to a modem that operates over the ordinary cable TV network cables. Basically just connect the cable modem to the TV outlet for the cable TV and the cable TV operator connects a cable modem termination system(CMTS)in his end(The Head End)
Cable modems allow PC users to download information from online services up to 1000 times faster than today’s fastest telephone modems .Cable modem speeds range from 500 kbps to 30mbps, while a traditional V.90 56k modem tops at just 56kbps.This new breed of high speed devices is classified as broad band devices and includes cable modems as well as DSL and ISDN connection
The cable modem can take up the challenge offered by the emergence and popularity of broadband connections.Speed is so much better;we can easily make video calls,send and receive e –mails as well as clear and high-quality still and moving images over the internet while the TV remains tune to favorite channel on your PC.
Internet is the network of all networks, which connects various computers to one another throughout the world. It has gone through radical change since the public in general started5 years ago. During this period dial up modems became very common. Now even a 56.6kb/s modem is no longer able to offer the speed users require offering the full benefit s. besides the speed considerations, there are three problems with dial up connections. First depending upon the number of subscribers dial ling into the same central office at the same time, it can take a significant time to connect to Internet. This can be frustrating to a subscriber who wants to buy a stock pm, a situation where every second counts. Second unless the subscriber has an alternative phone line dedicated to Internet connection he or she cannot make or receive phone calls during online time. This obviously has serious disadvantage especially in emergencies. Third, if too many subscribers are online at the same time, it can put a load on the central switches.
These problems highlighted the need for access technologies, that could offer higher speeds of connection, leave the telephone line free for voice calls, be reasonably priced and preferably utilize an existing physical communication link. An obvious choice of medium was the coaxial cable bringing hoe TV programs. Necessity is the mother of invention. In addition, this germinated to a modem that could use the coaxial cable to simulateneously carry high-speed Internet data, TV programs, and perhaps voice calls. It is a modem in the true sense of the world. It modulates and de modulates signals and delivers Internet data to the desktop at blazing speeds. This lightning speed is because of the wide bandwidth available in the CATV network and innovative technology in the cable modem.
This seminars explores the high-speed capability of cable modem technology in detail, with emphasis on the mode of operation, network architecture, alternative technologies, and security issues.
CABLE MODEM TECHNOLOGY
A cable modem connection is something in between modem and Ethernet in terms of speed. For connecting a cable modem, we need a CATV network. CATV network is used for cable TV distribution. With an upgrade of the system, it is possible to allow signals to flow in both directions. Higher frequencies flow towards the subscriber and the lower frequencies go in the other directions. Most CATTV networks are Hybrid Fiber Coax network. The signals of fiber-optical cables from the Head-End center to location near the location near the subscriber. At that point, the signals are converted to coaxial cables that run to subscriber premises.