Laboratory of Physical Layer MuxDemux Physical Layer Physical
Laboratory of Physical Layer Mux/Demux
Physical Layer Physical layer includes transmission media that is connected to the physical layer. • The first introduces the entities involved in the physical layer. • Transmission method consists of digital and analog. • Bandwidth Utilization: How to use the available bandwidth by using Multiplexing and Spectrum Spreading. • Switching can occur in any layer.
Intro. Of Physical Layer Physical layer moves data in the form of electromagnetic signals across a transmission medium. • Data and signals can be either analog or digital. – Analog refers to an entity that is continuous; – digital refers to an entity that is discrete.
Intro. Of Physical Layer • Periodic analog signals can be used in data communication. – simple and – composite signals. • The attributes of analog signals consist of: • period, • frequency, and • phase.
Intro. Of Physical Layer Nonperiodic digital signals can be used in data communication. • The attributes of a digital signal such as: – bit rate and bit length • How digital data can be sent using analog signals. • Baseband broadband transmission.
Intro. Of Physical Layer Transmission impairment. 1. attenuation, 2. distortion, and 3. noise How they can impair a signal?
Intro. Of Physical Layer How many bits per second we can send with the available channel. Data rate depends on three factors: • The bandwidth available • The level of the signals we use • The quality of the channel (the level of noise) Two theoretical formulas were developed to calculate the data rate: 1. Nyquist for a noiseless channel, 2. Shannon for a noisy channel.
Multiplexing Data link with limited bandwidths. Bandwidth utilization: • multiplexing and • spectrum spreading Link = physical path Channel = the portion of a link that carries a transmission between a given pair of lines (One link can have many n channels) N lines share one link Multiplexing 8
Multiplexing Techniques
FDM – Example
Wavelength-Division Multiplexing
Time-Division Multiplexing The link is shown sectioned by time rather than by frequency. In the figure, portions of signals 1, 2, 3, and 4 occupy the link sequentially.
Multiplexer (Mux) • Selects between one of N inputs to connect to output • log 2 N-bit select input – control input • Example: 2: 1 multiplexer symbol 2: 1 Mux Select input S Truth table
Multiplexer Implementations • Logic gates – Sum-of-products form
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