A cable modem uses the existing TV cable network for data transfers, for Internet applications, for example.
Via a 10 Mbps Ethernet connection to the PC.
The maximum downstream (i.e. receiving) speed is 30 Mbps. 10 Mbps can be achieved in the upstream (transmitting) direction. As the cable network is a shared medium with several receivers connected to a channel simultaneously, the effective available bandwidth depends on a number of factors such as the number of connected cable modems, the services provided, network traffic volume, etc. The cable network operator can make several channels available, however, to scale the available bandwidth within the available free channels as required.
All data is encrypted between the modem of the provider and that of the end user. DES encryption (Data Encryption Standard) with a key length of 56 bits is used for this purpose. In addition, the key is repeatedly changed during the course of data transmission. It thus fulfills the highest possible security requirements.
That depends on the pricing models of the individual service providers. The prices will certainly vary in accordance with the bandwidth, quality of the Internet connection and a number of other factors.
Initially, it will be possible to buy or rent cable modems via the service providers. In the course of time, cable modems will also be available from computer retailers. According to forecasts by leading market research institutes, the prices will be slightly higher than today's prices for high-end analog modems by the turn of the century.
The first pilot projects are currently taking place, but in most cases the technology has not yet been standardized. The debut of broadly-based commercial solutions with standardized modems will take place around the middle of 1999.
The MCNS/DOCSIS (Multimedia Cable Network System / Data Over Cable System Interface Specification) standard is currently available and has been ratified by the ITU (ITU-T J.112). This will ensure compatibility and the availability of equipment at market-oriented prices.
Internet access will certainly be available initially. However, other applications can also be realized as a result of the available bandwidth, such as video and audio streaming, videoconferencing, virtual private networks, multimedia, e-mail, etc.
Cable telephony will be realized via the VoIP (Voice over IP) protocol. Telephone conversations will then be directed to the "normal" telephone network via so-called gateways.
It's already possible today to view one television program, record another on a different station and listen to the radio using the same cable channel. In the future, Internet data will also be continuously available via the cable network. This data can then be accessed parallel to TV and radio reception.