xuclock.m

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%                                    xuclock.m
%  Scope:   This MATLAB program generates and saves the user clock bias and drift
%           for a specified number of time steps and number of users (receivers), by 
%           using a simplified second order model [1]. WGS-84 constants are used.
%  Usage:   xuclock
%  Inputs:  - from keyboard the user should enter the following data: 
%             - maximum number of users (receivers), nru (default is 6)
%             - number of time steps to be generated, nrsteps (default is 1800)
%             - time step value, in seconds (default is 1 second)
%             - white noise spectral density amplitude (Sb) for the first component 
%               corresponding to clock bias, in seconds
%             - white noise spectral density amplitude (Sd) for the second component 
%               corresponding to clock drift, in second/second
%             - random number seed value (default is 0)
%           - selection of the storage data file
%             - mat-files: ucbfile.mat and ucdfile.mat
%             - selected name for two ASCII data files
%             - none, no storage (default)
%           - selection of user clock bias and drift plots from generated data
%           - some application specific parameters are initialized by default (see Sb 
%             and Sd for a clock with crystal oscillator)
%  Outputs: - output file storing the generated user clock bias and drift,
%             mat-files ucbfile.mat and ucdfile.mat, or two selected ASCII data file; 
%             each output array has nrsteps rows and nru columns
%           - plot of clock bias and drift versus time step 
%  External Matlab macros used:  uclock, rms, wgs84con
%  References:  [1] Brown, Grover R., Hwang, P.Y.C., Introduction to random signals 
%                   and applied Kalman filtering. Third Edition. John Wiley $ Sons,
%                   New York, 1997, pp. 428-431
%  Last update:  01/17/01
%  Copyright (C) 1999-01 by LL Consulting. All Rights Reserved.

clear
close all
yes = 'y';

disp('  ');
nru = input('Enter maximum number of users (receivers), nru (default is 6) -- >  ');
if isempty(nru)
   nru = 6;
end   
disp('  ');
nrsteps = input('Enter number of steps to be generated, nrsteps (default is 1800) -- >  ');
if isempty(nrsteps)
   nrsteps = 1800;
end   
ucerror = zeros(nrsteps,2);

disp('  ');
dt = input('Enter time step value, in seconds (default is 1 second) -- >  ');
if isempty(dt)
   dt = 1.;
end   
disp('  ');

%  Selection of clock moodel parameters

sb = 4.e-19;              % in seconds , for a clock with crystal oscillator
sf = 1.5791e-18;          % in second/second, for a clock with crystal oscillator

%  Selection of random number seed

iseed = input('Enter random number seed value (default is 0.)  -- >  ');
if isempty(iseed)
   iseed = 0.;
end   
randn('seed',iseed);
disp('  ');

%  Determine user clock bias and drift errors for all users

for kk = 1:nru
   [cbias,cdrift] = uclock(nrsteps,sb,sf,dt);
   ucbias(:,kk) = cbias;
   ucdrift(:,kk) = cdrift;
end   

%  Store the multipath generated data into ucfile.mat or selected ASCII data file

disp('Specify where you want to save the generated data ');
disp('     Enter  1   for the file ucfile.mat');
disp('     Enter  2   for the ASCII data files to be selected');
disp('     Enter  3   for NOT saving');
answer1 = input('Enter your selection  (default is 3) -- >  ');
if isempty(answer1)
   answer1 = 3;
end   
if  (answer1 == 1)
   save   ucbfile  ucbias
   save   ucdfile  ucdrift
elseif  (answer1 == 2)
   f2 = input('Enter the user clock bias ASCII data file (with extension) -- > ','s');
   for k = 1:nrstep
      for kk = 1:nru
         fprintf(f2,'%14.7e   %14.7e',ucbias(k,kk));
      end
      fprintf(f2,'\n');   
   end
   f3 = input('Enter the user clock drift ASCII data file (with extension) -- > ','s');
   for k = 1:nrstep
      for kk = 1:nru
         fprintf(f3,'%14.7e   %14.7e',ucdrift(k,kk));
      end
      fprintf(f3,'\n');   
   end
else
    fprintf('\nThe generated data is NOT saved\n');
end
 
 %  Execute user clock bias and drift plots
 
disp('  ');
answer2 = input('Execute user clock plots? (y/n)[y] ','s');
disp('  ');
if isempty(answer2)
   answer2 = yes;
end   

kfig = 1;
while strcmp(answer2,yes)
   usel = input('Select the user (receiver) number (1 to nru) --> ');
   xucbias = ucbias(:,usel);
   xucdrift = ucdrift(:,usel);
	x = 1:nrsteps;
	xmean_b = mean(xucbias);
	xstd_b = std(xucbias);
	xrms_b = rms(xucbias);
	temp1 = ['mean = ',num2str(xmean_b)];
	temp2 = ['st.dev. = ',num2str(xstd_b)];
	temp3 = ['rms = ',num2str(xrms_b)];
	gb = [temp1,' ;   ',temp2,' ;   ',temp3];
	xmean_d = mean(xucdrift);
	xstd_d = std(xucdrift);
	xrms_d = rms(xucdrift);
	temp1 = ['mean = ',num2str(xmean_d)];
	temp2 = ['st.dev. = ',num2str(xstd_d)];
	temp3 = ['rms = ',num2str(xrms_d)];
	gd = [temp1,' ;   ',temp2,' ;   ',temp3];

	figure(kfig)

	subplot(2,1,1)
	plot(x,xucbias), grid
	ylabel('User clock bias, in meters');
	title(['User clock bias  versus  Time step, for user ' num2str(usel) ]); 
	disp('Select the mouse position to insert statistics for clock bias');
	disp('Press a key to continue...');
	pause
	gtext(gb);          %  mouse placement of the text on a graph
	disp('  ');

	subplot(2,1,2)
	plot(x,xucdrift), grid
	xlabel(['Time step number (time step = ' num2str(dt) 'second(s))']);
	ylabel('User clock drift, in meters/second');
	title(['User clock drift  versus  Time step, for user ' num2str(usel) ]); 
	disp('Select the mouse position to insert statistics for clock drift');
	disp('Press a key to continue...');
	pause
	gtext(gd);          %  mouse placement of the text on a graph
   disp('  ');
   answer2 = input('Do you want to execute another plot? (y/n)[n] --> ','s');
   if isempty(answer2)
      answer2 = 'n';
   end
   kfig = kfig + 1;
   disp('  ');
end

disp('End of the program  XUCLOCK ');
disp('  ');