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 20:37:46One Hundred Years of Solitude is the masterpiece of Gabriel Garcia Marquez. Reading this book begins with making sense of the characters' relationships, which are centered on the Buendía family and tells the story of the family's prosperity and decline, internal relationships and political struggles, self-mixing and rebirth over the course of a hundred years.
One Hundred Years of Solitude is the masterpiece of Gabriel Garcia Marquez. Reading this book begins with making sense of the characters' relationships, which are centered on the Buendía family and tells the story of the family's prosperity and decline, internal relationships and political struggles, self-mixing and rebirth over the course of a hundred years.
Project management is the process of applying specialized knowledge, skills, tools, and methods to project activities so that the project can achieve or exceed the set needs and expectations within the constraints of limited resources. This diagram provides a comprehensive overview of the 8 components of the project management process and can be used as a generic template for direct application.
One Hundred Years of Solitude is the masterpiece of Gabriel Garcia Marquez. Reading this book begins with making sense of the characters' relationships, which are centered on the Buendía family and tells the story of the family's prosperity and decline, internal relationships and political struggles, self-mixing and rebirth over the course of a hundred years.
One Hundred Years of Solitude is the masterpiece of Gabriel Garcia Marquez. Reading this book begins with making sense of the characters' relationships, which are centered on the Buendía family and tells the story of the family's prosperity and decline, internal relationships and political struggles, self-mixing and rebirth over the course of a hundred years.
Project management is the process of applying specialized knowledge, skills, tools, and methods to project activities so that the project can achieve or exceed the set needs and expectations within the constraints of limited resources. This diagram provides a comprehensive overview of the 8 components of the project management process and can be used as a generic template for direct application.
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)