CA code for GPS PRN-1

Hello

1-Does anyone know how to generate the CA code for GPS

PRN_6_CA=dec2base(1455,2);
PRN_16_CA=dec2base(1776,2);
PRN_26_CA=dec2base(1761,2);

x=1;

G_1=1+x^3+x^10;



j=1;
k=10;
for i=1:1023
    
   for j=1:10;
   x(j)=
    ca_1(i,:)=[x1 x2 x3 x4 x5 x6 x7 x8 x9 x10];

 y=x3+x5;
    end
  
  if  y==2
      x1=0;
    else x1=1
  end
        
 if G_1==(G_1/2)

  
  y=x3+x5;
  if  y==2
      x2=0;
    else x2=1
       
 
  
  end
  
 
        
        
  i=i+1;
  
 
  k=k+1;
   
 
  end
  
  
end

I want to know how to shift the first value to right side if we have 10 value in the one row. So new data is entering at 1st place is sum of the 3rd and 10th place then convert it into binary form which is new value at 1st position. Hence we have to do till 1023 times.

One can see the video to know more what we have to do in the exercise.

https://www.youtube.com/watch?v=F0RRQ6eJVJQ&t=2s

Answer 1

[Kaashyap Pappu]

You can use the comm.PNSequence object to generate the gold code for both generators. For the second generator, you will have to set the mask property to the appropriate phase delay polynomial, and number of bits out as 1023.

chips = 1023;
genG1 = [10 7 0]; % 1 + x^3 + x^10
initVector =[1 1 1 1 1 1 1 1 1 1];
generator = comm.PNSequence('Polynomial',genG1,...
'InitialConditions',initVector,'SamplesPerFrame',chips);

Generate similarly for generator G2 using the phase delay polynomial as the mask, add both sequences using Modulo-2 addition using xor and you will have your sequence.

Hope this helps!

[vimal kumar chawda]

Hello Sir

I have tried on matlab example but my file is showning that class is not define. May i know why? As matlab example should be workout but why it is not working out? What maybe the rasons.

[Kaashyap Pappu]

The comm.PNSequence object works only if the Communications Toolbox is installed.

[vimal kumar chawda]

Hello Sir

1-In this mask is our initial vector. What does mask means ? for every respective satellite i have to set up the data or algorithm such set up is known as mask?

2- What should be Genpoly?

3-what is InitialStates? What type of value does it take like chip is 1023.

4-CurrentStates means ?

5- What does ... means ?

As per my understanding the blue data is reference and i have to substitute the value or data at beside that in black color like genG1,initVector..

[Kaashyap Pappu]

1. The mask would be the phase selection polynomial for each satellite vehicle. You can use a switch case setup for each satellite separately.
2. Generator polynomial is given the in the technical specification. Specify powers of X as a vector.
3. Initial states is a binary vector indication the starting state of the Linear Feedback Shift Register setup.
4. Current state is the current output values for each the registers.
5. ... is basically to inform the MATLAB compiler that the command is continued on the next line. This is used for readability.

The Blue data indicate properties of the specific object. The black highlighted variables are the user defined property values.

[ScubaNinjaDog]

But the ouput of the second generator is not directly used like with the first generator.

Answer 2

[Rajkumar Mishra]

Hello,

in the solution above is not the second term be '3' inplace of '7' as mentioned in this line

genG1 = [10 7 0]; % 1 + x^3 + x^10

Answer 3

[Markandeya Janaswamy]

From R2021b, Satellite Communications Toolbox supports generating C/A-codes. Use the function gnssCACode. See https://mathworks.com/help/satcom/ref/gnsscacode.html