frame

by gowtham 2010-02-18 19:15:14

In computer networking and telecommunication, a frame is a digital data transmission unit or data packet that includes frame synchronization, i.e. a sequence of bits or symbols making it possible for the receiver to detect the beginning and end of the packet in the stream of symbols or bits. If a receiver is connected to the system in the middle of a frame tranmission, it ignores the data until it detects a new frame synchronization sequence.

In computer networking, a frame is a data packet on the Layer 2 of the OSI model.[1] A frame is "the unit of transmission in a link layer protocol, and consists of a link-layer header followed by a packet."[2] Examples are Ethernet frames (maximum 1500 byte plus overhead), PPP frames and V.42 modem frames.

In telecommunications, specifically time-division multiplex (TDM) and time-division multiple access (TDMA), a frame is a cyclically repeated data block that consists of a fixed number of time slots, one for each logical TDM channel or TDMA transmitter. In this consist, a frame is typically an entity at the physical layer. TDM application examples are SONET/SDH and the ISDN circuit switched B-channel. TDMA examples are the 2G and 3G circuit switched cellular voice services. The frame is also an entity for time-division duplex, where the mobile terminal may transmit during some timeslots and receive during others.


In video coding, a frame is an image. Examples are MPEG I frames, B frames and P frames.

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