physical_layer.pptx - The physical Layer The physical layer...

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The physical layer is responsible for movements of individual bits from one hop (node) to the next. 6-1 Link Layer and LANs The physical Layer
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Physical Layer is concerned with the following: Physical characteristics of interfaces and medium . It defines the characteristic of the interface between devices and medium. It also define the type of transmission medium (wired and wirless). Representation of bits. The physical layer bit stream must be encoded into signals (electrical or optical). It defines the type of encoding( how 0, 1 are changed to signal). Data rate. It defines the number of bits sent per second. Synchronization of bits. The sender and receiver must use the same bit rate. Their clocks must be synchronized. Line configuration. Physical layer is concerned with the connection of devices to the media ( point-to point or multipoint). 6-2 Link Layer and LANs
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(simplex, half-duplex, or full duplex Data Link Layer 5-3
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Representation of bits One of the major functions of the physical layer is to move data in the form of electro-magnetic signals across a transmission medium. To be transmitted, data must be transformed to electromagnetic signals. 6-4 Link Layer and LANs
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Data types Data could be analog or digital. Analog data take on continuous values. Sound made by human voice Digital data take on discrete values. Data stored in computer memory in forms of 1s and 0s 6-5 Link Layer and LANs
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Conversion of data to signals Analog data can be represented by: analog signal or digital signal (after sampling). Digital data can be represented to digital signal or analog signal (after modulation) . 6-6 Link Layer and LANs
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Types of signals Analog signal: has infinitely many levels of intensity over a period of time. Digital signal: can have a limited numbers of defined values. It 6-7 Link Layer and LANs
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Sine Wave A sine wave can be represented by three parameters: Peak amplitude the absolute value of its highest intensity, proportional to the energy it carries. The peak amplitude of electric signals is measured in volts.
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