NR modulation 1

Preface

          When testing throughput, the terminal mainly depends on two parameters , Network assigned RB, as well as Modulation

This series mainly refers to the courses of some overseas experts for sharing

            The main reference here is cisco Of tutorangel

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1.  summary
2.  RF Encoding and modulation Mechanisms
3. BPSK
4. QPSK
5. QAM

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One   summary

          After the coding , What we get is still digital signal 0,1 , As mentioned earlier, I will QPSK Will be able to 0

Modulation into 1,1 Modulation into -1 Simulation information of , Corresponding to one waveform.

          How to distinguish between wavefrom（symbol） , Mainly through amplitude , frequency , phase

        Why modulate :

          Finally, the signal should be transmitted through the antenna  

        The length of the antenna is proportional to the wavelength , So it is inversely proportional to the frequency , The higher the frequency is. , Shorter wavelength , The shorter the antenna can be . The length of the antenna is not equal to one wavelength , Tend to be 1/4 Wavelength or 5/8 wavelength .

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Two  RF Encoding and modulation Mechanisms

    After modulation ,0,1 Corresponding to one symbol( or waveform）, We can distinguish in three ways 0,1

      Amplitude, frequency, phase

    2.1 Amplitude distinguish

        

 

            The above can be distinguished by amplitude 1,0

     2.2 Frequency  distinguish

         

      Pictured , The frequency of the second half is higher , Low frequency is thought to be 1, High frequency thinks so 0.

2.3  phase distinguish

    0,1 Phase difference

 

 2.4  Modulation algorithm

    Corresponding to a time domain waveform

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 3: BPSK(Binary phase shift keying)  Binary phase shift keying

     

          According to the two levels of digital baseband signal , A phase modulation method that makes the carrier phase switch between two different values . Usually the two phases are different , It is sometimes called inverse keying PSK

      Take binary phase modulation as an example , The symbol is 0 when , The modulated carrier is in phase with the modulated carrier

      The symbol is 1, The modulated carrier is in inverse phase with the modulated carrier .

   

      One for each symbol bit, Or a waveform Corresponding to one bit

# -*- coding: utf-8 -*-
"""
Created on Mon Jul  4 15:06:27 2022

@author: chengxf2
"""
import numpy as np
import matplotlib.pyplot as plt


    
def bpsk(bit):
    
    a = 1.0
    w = 2.0
    
    if bit ==0:
        p  = -np.math.pi/2.0
    else:
        p = np.math.pi/2.0
    
    x = np.linspace(0, 2*np.math.pi,1000)
    y = []
    for t in x:
        v = a*np.cos(w*t+p)
        y.append(v)
    
    if 0 ==bit:
        plt.plot(x, y, color='g',linewidth=2.0,linestyle="-.") # plot Methods drawing points 
    else:
        plt.plot(x, y, color='r',linewidth=2.0,linestyle="-.") # plot Methods drawing points 
    plt.xlabel("x")
    plt.ylabel("y")
    plt.show()
        
    
  

bpsk(0)
    

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4: QPSK(Quadrature phase shift key Quadrature phase shift keying )

     BPSK yes 1bit/symbol

     QPSK yes 2bit/symbol

      Equivalent to doubling the rate

    

 

# -*- coding: utf-8 -*-
"""
Created on Mon Jul  4 15:06:27 2022

@author: chengxf2
"""
import numpy as np
import matplotlib.pyplot as plt
from enum import Enum

class QPSK_PHASE(Enum):
    ONE = 1
    TWO = 2
    THREE =3
    FOUR =4


    
def qpsk(phase):
    
    a = 1.0
    w = 2.0
    
    if phase is QPSK_PHASE.ONE:
        p = np.math.pi/2*0
    
    elif phase is QPSK_PHASE.TWO:
        p = np.math.pi/2
    elif phase is QPSK_PHASE.THREE:
        p = np.math.pi
    else:
        p = np.math.pi*3/2
    
    x = np.linspace(0, 2*np.math.pi,1000)
    y = []
    for t in x:
        v = a*np.cos(w*t+p)
        y.append(v)
    
    if phase is QPSK_PHASE.ONE:
        plt.plot(x, y, color='g',linewidth=2.0,linestyle="-.") # plot Methods drawing points 
    elif phase is QPSK_PHASE.TWO:
        plt.plot(x, y, color='r',linewidth=2.0,linestyle="-.") # plot Methods drawing points 
    elif phase is QPSK_PHASE.THREE:
        plt.plot(x, y, color='b',linewidth=2.0,linestyle="-.") # plot Methods drawing points 
    else :
        plt.plot(x, y, color='y',linewidth=2.0,linestyle="-.") # plot Methods drawing points 
    plt.xlabel("x")
    plt.ylabel("y")
    plt.show()
        
    
  

qpsk(QPSK_PHASE.FOUR)
    

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5： Quadrature Amplitude Modulation( Quadrature amplitude modulation ）

  The front is all adjusted phase, It has been said that it can be distinguished by increasing the range bit 0,1

  Such as 16QAM  

      One symbol It can transmit 4bit

   64AQM

      One symbol It can transmit 6bit

        The higher the modulation mode , The distance between points is getting closer , If in a noisy environment

The multipath transmission of signals affects , Signal attenuation and other effects , The obtained symbols will produce deviation , There is an error

At this time, the modulation mode needs to be gradually reduced 64QAM-16QAM-QPSK-BPSK, The speed will gradually decrease