The Cable Center

This glossary of cable and telecommunications terms is intended to enhance your understanding of this dynamic industry. We are able to present this information with the generous help of CableLabs - consult their website for the most up-to-date information about cable technology.

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Ultra High Frequency (UHF)
Channels above channel 13 (or from 470 MHz to 806 MHz).

Unbound application
An unbound application is not associated with a broadcast service.

Unbundling
The separation and discrete offering of the components of the local telephone service. Unbundling of network components facilitates the provision of pieces of the local network, such as local switching and transport, by telephone company competitors.

Unidirectional Hypertext Transport Protocol (UHTTP)
A broadcast transfer protocol, suitable for delivery of content using IP multicast.

Uniform Resource Locator (URL)
The address of an Internet site. The URL contains the protocol used for the site (e.g., http, ftp), the domain name or IP address of the site (e.g., and, optionally, the folder or page on the site where specific information is stored.

Universal Asynchronous Receiver Transmitter (UART)
A computer’s UART chip dictates the maximum rate a computer can send and receive data over its serial ports.

Universal Serial Bus (USB)
A plug-n-play standard for connecting multiple (up to 127) input/output devices to a single high-bandwidth port. The design of the bus allows hot-swapping of the devices (disconnection and reconnection without powering the computer off) and automatic configuration. The USB peripheral bus standard was developed by Compaq, IBM, DEC, Intel, Microsoft, NEC, and Northern Telecom. The original version of USB (USB1.1) supports a data rate of 12Mbps, while the second version (USB2.0) supports a data rate of 480 Mbps.

Unspecified Bit Rate (UBR)
The UBR service class is intended for delay-tolerant or non-real-time applications, or those which do not require tightly constrained delay and delay variation.

Upconverter
A device used to add a lower frequency to a microwave frequency.

Uplink
The return signal from the user to the base station.

Uploading
The transfer of files from a local computer “up” to a remote computer.

Upstream
The term used to describe traffic and paths that go from the subscriber to the headend. Also known as Reverse Path or Return Path.

Upstream Channel Descriptor (UCD)
The MAC Management Message used to communicate the characteristics of the upstream physical layer to the cable modems.

User Datagram Protocol (UDP)
A protocol residing on top of IP that is used for end-to-end transmission of user messages. Unlike TCP, UDP is an unreliable protocol, which means that it does not contain any retransmission mechanisms. Thus, UDP packets are not guaranteed to make it through the network.

User Interface (UI)
A user interface is the sensory and behavioral aspects of a program that are presented to a user. The term is generally used to denote the menuing and navigational constructs of a program.