Data Communications Systems: ATM 25, Phoneline Networking, Universal Serial Bus (USB),

Asynchronous Transfer Mode 25 (ATM 25)
ATM 25 is a 25 Mbps version of the asynchronous transfer mode (ATM) system. ATM technology is relatively complex when compared to Ethernet and token ring systems. As a result, the use of standard ATM technology in LAN systems has been limited. However, a 25 Mbps version of the ATM standard was developed for PDN LANs. The capability of ATM systems to simultaneously provide multiple communication channels with varying levels of quality of service (QoS) make it advantageous for use in multimedia systems. ATM 25 technology is used to provide digital video and Internet access through the use of ATM in digital subscriber line (DSL) and cable modem systems.

Phoneline Networking
In the late 1990’s, the home phoneline network alliance (HomePNA) developed a specification that allows home computers and data devices (such as network printers) to interconnect via standard home telephone wiring. In the first generation of phoneline networking, data rates of 1 Mbps were achieved but recently data transmission rates of 10 Mbps have been demonstrated. The Phoneline Network uses special NIC’s that send and receive high frequency signals that do not interfere with standard telephone service. To connect a phoneline network to a DSL connection, a phoneline bridge must be used.

Universal Serial Bus (USB)
Universal serial bus (USB) is a short distance data communication interface (typically, only a few meters) that now comes standard on most personal computers. The USB was designed to replace the older slower UART data communications port. USB ports permit data transmission speeds up to 12 Mbps. Most computers that were manufactured in 2001 included a universal serial bus (USB) connector. The USB data bus can also connect up to 10 devices to the same bus using a low cost hub device. USB lines can only extend for a few feet from the computer.

FireWire is a short distance data communications interface (up to approximately 5 meters) that is based on industry standard IEEE-1394. FireWire can transmit at speeds up to 400 Mbps and can support up to 63 devices per bus. Firewire provides for isochronous (repetitive streaming data format) that allows it to transfer audio and video signals.

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