MindMap Gallery physical layer
Physical layer mind map, including an overview of the physical layer, Basic knowledge of data communication, transmission media, Channel multiplexing technology, etc.
Edited at 2024-04-02 20:37:46This infographic, created using EdrawMax, outlines the pivotal moments in African American history from 1619 to the present. It highlights significant events such as emancipation, key civil rights legislation, and notable achievements that have shaped the social and political landscape. The timeline serves as a visual representation of the struggle for equality and justice, emphasizing the resilience and contributions of African Americans throughout history.
This infographic, designed with EdrawMax, presents a detailed timeline of the evolution of voting rights and citizenship in the U.S. from 1870 to the present. It highlights key legislative milestones, court decisions, and societal changes that have expanded or challenged voting access. The timeline underscores the ongoing struggle for equality and the continuous efforts to secure voting rights for all citizens, reflecting the dynamic nature of democracy in America.
This infographic, created using EdrawMax, highlights the rich cultural heritage and outstanding contributions of African Americans. It covers key areas such as STEM innovations, literature and thought, global influence of music and arts, and historical preservation. The document showcases influential figures and institutions that have played pivotal roles in shaping science, medicine, literature, and public memory, underscoring the integral role of African American contributions to society.
This infographic, created using EdrawMax, outlines the pivotal moments in African American history from 1619 to the present. It highlights significant events such as emancipation, key civil rights legislation, and notable achievements that have shaped the social and political landscape. The timeline serves as a visual representation of the struggle for equality and justice, emphasizing the resilience and contributions of African Americans throughout history.
This infographic, designed with EdrawMax, presents a detailed timeline of the evolution of voting rights and citizenship in the U.S. from 1870 to the present. It highlights key legislative milestones, court decisions, and societal changes that have expanded or challenged voting access. The timeline underscores the ongoing struggle for equality and the continuous efforts to secure voting rights for all citizens, reflecting the dynamic nature of democracy in America.
This infographic, created using EdrawMax, highlights the rich cultural heritage and outstanding contributions of African Americans. It covers key areas such as STEM innovations, literature and thought, global influence of music and arts, and historical preservation. The document showcases influential figures and institutions that have played pivotal roles in shaping science, medicine, literature, and public memory, underscoring the integral role of African American contributions to society.
physical layer
Physical layer overview
characteristic
Mechanical properties
Electrical characteristics
Features
Procedure characteristics
four Q
Choice of physical transmission media
information encoding problem
Performance analysis (transmission speed)
Channel multiplexing
Basic knowledge of data communications
data and signals
Classification
Analog: Continuous
digital: discrete
data to signal
Analog data to analog signal (amplifier, modulator):
Analog data to digital signal (PCM encoder): sampling, quantization, encoding
Digital data to analog signal (modulator): can be through amplitude modulation, frequency modulation or phase modulation
Digital data to analog signal (digital transmitter)
non-return-to-zero encoding
1=-5V, 0=5V
Disadvantage: Transformer cannot be used during the process
Manchester encoding
1=low to high potential jump, 0=high to low potential jump
Disadvantage: The signal rate is twice the data rate (two potentials in one time interval)
Differential Manchester encoding
1=No transition, 0=There is a transition
Data communication system model
Communication Systems
Types of communication
According to the type of signal transmitted: analog, digital
According to transmission media: wired, wireless
According to the way of information exchange: simplex, half-duplex, duplex
Basic parameters of communication system performance
Data rate (bit rate)
Unit: bps
C (data rate) = B (baud rate) log₂V (voltage level)
Symbol rate (baud rate)
Unit: baud
Is the basic unit of the signal. The symbol for the signal is equal to the bit for the data.
Code element length: Use symbols with the same time interval to represent a number, so that the time interval
Code element: Use symbols with the same time interval to represent a number, so that the signals within the time interval
Channel capacity
Maximum data rate of the channel
signal-to-noise ratio
=S (signal power)/N (noise power)
Usually expressed in logarithmic form: 10lg (S/N)
Unit: 10lg (signal-to-noise ratio) dB
Signal-to-noise ratio 1000 is 30dB
Channel bandwidth
The frequency range that the channel can pass
low pass, band pass, high pass
limited bandwidth signal
Signal bandwidth: Any signal can be transformed into the sum of multiple sine waves through Fourier transform
Channel bandwidth
The ultimate capacity of the channel
Nye's criterion
The maximum symbol rate for a low-pass noiseless channel is equal to twice the channel bandwidth
The maximum symbol rate of a bandpass noiseless channel is equal to the channel bandwidth
Shannon's theorem: C=Wlog₂(1 S/N) bps
C: The limit information transmission rate of the channel, W: Bandwidth
Transmission medium
Wired (guided)
Twisted pair: UTP (unshielded), STP (shielded), RJ connector
coaxial cable
Optical cable: single-mode optical fiber, multi-mode optical fiber, electrical signal-optical signal
Magnetic media
power line
Wireless (non-guided)
Shortwave: reflection from the ionosphere
Terrestrial microwave: transmission in a straight line (large bowl)
Satellite Communications
infrared
Channel multiplexing technology
Signal time domain and frequency domain
FDM (Frequency Division Multiplexing)
TDM (Time Division Multiplexing)
STDM (statistical time division multiplexing)
WDM (Wavelength Division Multiplexing)
CDM (Code Division Multiplexing)