Frequently Asked Questions About 56K Modems
How does 56K work?
56Kbps modems rely on a 100% digital telephone network except for the local loop, which is the last connection from the telephone company to the user location. The telephone company's digital network lines usually have a bearer capacity of 56Kbps. The conversion from analog to digital information is limited to a range of analog frequencies combined with noise, limits bandwidth to about 35Kbps.
56Kbps modems require a 100% digital connection from the modem being dialed to the local loop of the dialing modem, meaning only one digital-to-analog conversion at the local loop. Taking into account noise distortions introduced by the conversion, the modem can achieve 56Kbps. If there was no noise and everything could be done perfectly, it would allow communications at 64 Kbps.
What kind of technology is 56K?
56K modem technology is an asymmetrical modem modulation scheme that provides for data transmission speeds up to 56Kbps upstream from a central site to a remote site over the public switched telephone network. The return path will be at V.34 speeds initially but may go higher depending on developments in the 56K standard.
The 56K path requires digital connectivity at the central site (ISDN, T1). The 56K signal is transmitted over the digital network to the central office closest to the remote site. From the central office the high speed signal is sent over the analog local loop to the remote site. The return path is traditional analog.
What type of users will benefit from 56k technology?
Internet access users, telecomuters, and home office users will all benefit from 56K technology. 56K will provide full support of multimedia applications on the Internet and private LANs which often require the high bandwidth capability of 56K. The 56K technology depends on central site support from the service provider (ie. Internet Service Provider or corporate LAN access provider). These 56K modems are designed for Internet use, telecomuters and home office users who want to download files, graphics and games from the Internet and private networks faster than ever before with an analog modem.
There is a lot of hype about 56K delivery rates. What can a user realistically expect to achieve?
56K performance is dependent on the quality of the telephone line and the performance enhancing features of the modem. There are some lines where performance at 56K, or very close to 56K, can be achieved all the time. There are other lines where the performance will never reach 56K. Based on network testing, Shiva believes that 56K technology can be fine tuned to allow users to expect close to 56K performance 60-70 percent of the time. However that level of performance will require a standard, which will be achieved only through further development.
What is happening with the standards body? When do you expect to see a standard?
The 56k standard is moving steadily but slowly to date. We would expect a TIA interim U.S. standard later this year and a formal ITU standard in the second half of 1998. Shiva's Rockwell-based modem will be compatible with or easily upgradeable to the ITU standard.
Why are the speeds different between uploading and downloading files?
The 56K technology requires a digital connection to the analog local loop in order to run 56K to the remote site. Users with dial-up connections to a service provider in most metropolitan areas can be expected to have access to a digital connection. Users with dial-up connections to a private LAN can increasingly expect digital connections, however this depends upon the central-site concentrator the enterprise has installed. Assuming the connection is digital, it is the path from the service provider to the remote site where the high bandwidth pipe is needed and adds value. For example, an Internet user downloading the multimedia data from a web site or a telecomuter downloading a large document from the corporate LAN. The return path from the remote user to the service provider/private LAN is general keystroke type data which does not require as high a bandwidth.