| Term |
Definition |
| U Interface |
User interface - the final reference point in the ISDN network. Describes the full-duplex data signal on the local loop. |
| UADSL |
Universal Asymmetrical Digital Subscriber Line. Universal ADSL is a proposed specification that is intended to ensure global acceptance and interoperability of ANSI standard T1.413 ADSL based on DMT. UADSL promises a single standard supported by industrial partners, accelerating the development of ADSL specific chipsets, software and equipment. |
| UART |
Universal synchronous receiver-transmitter - Integrated circuit that converts computer data into asynchronous signals suitable for transmission via a telephone line, and vice versa. UARTs combine a transmitter (parallel-to-serial converter) and a receiver (serial-to-parallel converter) to provide a 'bridge' between the parallel signals used by the computer and the serial signals used by communications networks. |
| UDP |
User Datagram Protocol - A transport layer, UDP provides a protocol for applications to communicate with a minimum of overhead. UDP does not guarantee packet delivery or ordering. UDP runs on top of IP. Defined in IETF RFC768 & STD6. |
| UDT |
Unstructured Data Transfer - Transmission of ATM cells without regard for structure boundaries. |
| UHF |
Ultra high frequency - Transmission frequencies in the range 300 to 3,000 megahertz. |
| u-Law |
Companding/encoding law commonly used in North America. |
| Ultra wideband radio |
Ultra wideband radio - Also known as digital pulse wireless is a revolutionary wireless technology for transmitting large amounts of digital data over a wide spectrum of frequency bands with very low power. Ultra wideband radio not only can carry a huge amount of data over a short distance (up to 230 feet) at very low power (less than 0.5 milliwatts), but has the ability to carry signals through doors and other obstacles that tend to reflect signals at more limited bandwidths and a higher power. |
| UMTS |
Universal Mobile Telecommunications System. |
| UNI |
User Network Interface - The interface, defined as a set of protocols and traffic characteristics, between the CPE and the ATM network. |
| Unnumbered Information Frame |
A data transmission frame generated by the HDLC data link level protocol where no flow control and no error control is implemented. |
| Up-link |
The ground (up) to satellite transmission link. |
| Upstream |
The direction of information flow on a data communications link. The faster the upstream speed, the faster data can move from your local network or PC to the Internet. |
| USART |
Universal Synchronous-Asynchronous Receiver/Transmitter. |
| UTOPIA |
Universal Test and OPerations Interface for ATM) - The electrical interface on which ATM cells are passed. |
