Refers to Ethernet versions that provide 100 Mbps data rate. The most popular is 100BaseT that runs over twisted pair cable.
Also see Ethernet.

Frequency Division Duplex. A duplexing technique which uses two separate channels on the same time slot for downlink and uplink transmission. FDD is suitable for full duplex voice conversation. FDD is mostly deployed in licensed spectrum due to the requirement for the availability of a pair of channels for transmitting and receiving.
Compare with TDD.

Fiber Distributed Data Interface. A LAN technology that employs token-passing access method and runs over fiber optic cable. FDDI provide data rate of 100 Mbps.
Also see token passing.

Frequency Division Multiplexing. A multiplexing technique in which signals are put in different portions of bandwidth and transmitted simultaneously.
Also see multiplexing. Compare with TDM.

Frequency Division Multiple Access. A multiple access technique in which signals from multiple stations are transmitted simultaneously but each signal must be allocated a portion of total bandwidth.
Also see multiple access. Compare with TDMA.

Forward Error Correction. A method of correcting errors in a message that is done by a receiver based on the correction bits added to the message by the transmitter.
Also see CRC.

Far End Crosstalk. Crosstalk that is caused by the coupling of signals traveling in the same direction.
Also see crosstalk. Contrast with NEXT.

Full Function Device. A ZigBee device with full functionality that can act as a master (controller) in a network.
Also see ZigBee. Contrast with RFD.

Frequency Hopping Spread Spectrum. FHSS is a spread spectrum technique in which the frequency of an already modulated signal is modulated again.
FHSS is used in Bluetooth with GFSK (Gaussian Frequency Shift Keying) as its modulation technique. Bluetooth signal hops from one frequency channel to another within the specified spectrum 1600 times per second to avoid interference from other wireless systems. Therefore, each Bluetooth time slot is 1/1600 second or 625 μs long.
Compare with DSSS. Also see spread spectrum and Bluetooth.

Fiber optic is a thin glass or plastic strand in the core which is surrounded by a cladding and a protective coat and is used to carry information in optical (light) pulses. Because information is not carried as electrical signals, fiber optic cable is not sensitive to noise, crosstalk, and interference from nearby cables or the environment.
Two types of fiber optic are used in telecom and networking. They are single-mode fiber and multimode fiber. Single-mode fiber is used for longer distance, such as in CATV network, FTTB, and backbone network while multimode fiber is used for shorter distance, such as in high speed LAN.
See fiber optic structure. Also see single-mode and multimode.

Fast IrDA. An IrDA standard for short-range, point-to-point, and half-duplex communication using infrared that provides maximum data rate of 4 Mbps.
Also see IrDA and infrared.

Hardware or software that functions to block access by applications or services to a computer or LAN from public network like the Internet except for applications that are allowed by the client (user).

A high speed computer port that is used for transferring large files such as video files that was first developed by Apple, then became an IEEE standard, i.e. IEEE 1394.
IEEE 1394a that is ubiquitous today has maximum transfer rate of 400 Mbps over STP cable with maximum reach of 4.5 meters. The newer version, IEEE 1394b has maximum speed of 800 Mbps over Cat 5 or fiber optic cable with longer reach.
i.Link is another name of FireWire, coined by Sony.

A unique program that is installed in device's ROM (read-only memory) or PROM (Programmable ROM) that functions as the OS (Operating System) of the device. Updates for firmware are usually provided by the device manufacturer.

A modulation technique in which the carrier frequency varies in accordance with the information (baseband signal) amplitude variations.
The most familiar application is in FM radio broadcast. FM radio stations broadcast at frequencies ranging from 88 to 108 MHz.
Also see modulation.

Fixed Mobile Convergence. Refers to interoperability between fixed and mobile telecommunication networks. FMC may include integration in the core network and network management, single phone number across diverse networks, seamless handoff from fixed network to mobile network and vice versa, one multi-service billing, and multi-mode handset.
Several protocols/technologies considered as FMC enablers are UMA, SIP and IMS.

Fiber Optic Inter Repeater Link. Obsolete IEEE 802.3 Ethernet cabling standard for transmission over fiber optic cable with data rate of 10 Mbps.

A data structure which usually contains overhead (i.e. control bits, addresses, error-checking bits) and payload (message). Frame is the data unit handled by the Data Link Layer.
Frame composition depends on the type of network. In Ethernet, a frame consists of several fields as follows:
- Preamble  (8 bytes)
- Destination Address (6 bytes)
- Source Address (6 bytes)
- Type (2 bytes)
- Data (46 - 1500 bytes)
- CRC (4 bytes)
Therefore the maximum size of an Ethernet data frame is 1,582 bytes.
Also see Ethernet.

A layer 2 packet switching protocol that are widely used in corporate networks for LAN-to-LAN connection. Frame relay is modeled after the older X.25, but it gives higher data rate.
Also see X.25.

The number of wave cycles in the period of one second. Its notation is f. It is the inverse of Period (T), " f=1/T". 1 Hz (Hertz) is one cycle per second.

Frequency Shift Keying. A frequency modulation technique in which the frequency of a carrier is shifted (changed) by the baseband signal (information).
Also see modulation and FM.

File Transfer Protocol. An Application Layer protocol that functions to transfer files from a client (user) computer to an FTP server over the Internet.
Also see Application Layer.

Fiber To The Building or Fiber To The Business. An access network that runs over fiber optic cable all the way down to buildings. In a high rise building, there is usually a telecom room that contains fiber optic cable terminations for distribution by any type of cables to its tenants.

Fiber To The Curb. Most modern access networks uses FTTC. Fiber optic cables are terminated in an access node (curbside distribution cabinet) that usually serves a neighborhood area. From the access node, twisted pair cables are pulled to subscribers' homes.

Fiber To The Home. An access network that uses fiber optic cable all the way down to subscribers' homes. FTTH offers the fastest Internet connection compared with other broadband technologies, such as ADSL, VDSL, and cable modem. But FTTH is the most expensive and even in developed countries, its deployment is still limited.

Fiber To The Node. A fiber optic access network where fiber optic cable is terminated at an access node. From this node, usually services are delivered to customer premises via twisted pair cable using some sorts of xDSL or in some cases a wireless technology.

Fiber To The Premise. A broader term that covers both FTTB and FTTH, bringing fiber optic to customer premises.

Refers to all fiber optic access network where x is the latest (farthest) fiber termination point.

Simultaneous communication in both directions (transmit and receive).
Also see duplex. Compare with half duplex.